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Mutations in Lung Adenosquamous Carcinomas

Journal of Thoracic Oncology just issued a published ahead-of-print article that examined mutations of most frequent driver mutations seen in pulmonary adenocarcinomas in a series of 76 resected adenosquamous carcinomas of the lung.

This is an important study to note because it supports the recommendation by IASLC/ERS/ATS to send these tumors for molecular testing.  Another interesting finding for pathologists is the finding of excess ALK mutations associated with those tumors with a solid pattern histologic subtype in the adenocarcinoma component.

 

Analysis of Major Known Driver Mutations and Prognosis in Resected Adenosquamous Lung Carcinomas

Wang, Rui MD; Pan, Yunjian MD; Li, Chenguang MD,PhD; Zhang, Huibiao MD; Garfield, David MD; Li, Yuan MD; Ye, Ting MD; Hu, Haichuan MD; Luo, Xiaoyang MD; Li, Hang MD; Zhang, Yang MD; Zhang, Jie MD; Zhou, Xiaoyan MD; Shen, Lei MD; Pao, William MD,PhD; Sun, Yihua MD; Chen, Haiquan MD

Published Ahead-of-Print

 

Abstract

 

Introduction: Genotyping for driver mutations is now routinely used to guide clinical care of patients with lung cancer. Adenosquamous lung carcinoma (AdSqLC) is a subtype of cancer that contains both adenocarcinoma and squamous cell carcinoma. However, the incidence, clinicopathologic characteristics, and prognostic implications of major driver mutations in AdSqLCs are not well established.

Methods: Seventy-six resected AdSqLCs and 646 lung adenocarcinomas were screened for known genetic alterations involving EGFR, ERBB2, KRAS, BRAF, PIK3CA, AKT1, RET, and ALK. Tumors showing acinar, lepidic, micropapillary, or papillary growth in glandular component were classified as classical AdSqLC.

Results: Of the 76 AdSqLCs, 43 (56.6%) harbored known mutant kinases, including 24 (31.6%) with EGFR mutations, eight (10.5%) with KRAS mutations, two (2.6%) with AKT1 (2.6%) mutations, one (1.3%) with ERBB2 insertion mutation, one (1.3%) with PIK3CA mutation, four (5.3%) with ALK fusions, and three (4%) with KIF5B-RET fusions. No mutation was found in BRAF. The mutational profiles and clinicopathologic characteristics of classical AdSqLC were strikingly similar to that of poorly differentiated adenocarcinoma. However, AdSqLCs with solid growth pattern in glandular component had high frequency of ALK or RET fusions and low EGFR mutation rate.

Conclusions: To our knowledge, this is the first comprehensive study investigating major oncogenic driver mutations in a large cohort of AdSqLC patients in a Chinese population. The findings suggest that it will be clinically valuable to investigate the growth pattern of glandular component in AdSqLCs.

ETS2 mediates tumor suppressor function and MET inhibition in lung adenocarcinoma

There was a very intriguing paper published online by Clinical Cancer Research on May 9 last week that should be of interest for those involved in lung cancer research.  The authors are Mohamed Kabbout, Melinda Garcia, Junya Fujimoto, et al. from M.D. Ancerson Cancer Center in Houston and the title of the article is "ETS2 mediated tumor suppressive function and MET oncogene inhibition in
human non-small cell lung cancer." 

In brief, the authors find that there is significant downregulation of the ETS2 transcription factor in lung adenocarcinomas compared to normal lung tissues.  ETS2 expression is linked to various canonical cancer-associated pathways in lung cancer cells, in particular the HGF pathway.  Moreover, knockdown of ETS2 is associated with up-regulation of the ZEB1, SNAI2, RAB3B, SERPINB5 and SPDEF genes
with concomitant with elevated cell migration and invasion.  Last, low ETS2 protein is predictive of shorter time-to-recurrence in NSCLC and lung adenocarcinoma.  These data suggest that ETS2 functions as a tumor-suppressor in lung cancer cells by, at least in part, regulation of the migration- and invasion-promoting transcriptome.

More details. . .

Gene expression profiling showed significant decreased expression of ETS2 transcription factor transcripts in lung adenocarcinoma (ADC) compared to normal controls and quantitative RT-PCR confirmed decreased ETS2 expression.  Subset analysis should significantly decreased ETS2 expression in those ADCs from smokers compared to those from never-smokers.

They analyzed ETS2 expression by IHC in a microarray set of 201 NSCLC (135 ADC, 66 squamous cell carcinoma-SQC) tumors.  Low ETS2 expression was associated with shorter time-to-recurrence in stage I and all stages of patients.  Multivariate Cox proportional hazards analysis showed that, after adjusting for stage, low ETS2 expression was an independent predictor of shorter time-to-recurrence in NSCLC and ADC.

H441 human lung cancer cell lines transfected with small interfering RNA (siRNA) specific to ETS2 showed significantly reduced ETS2 transcript compared to controls.  ETS2 knockdown significantly increased cell growth, migration, and invasion.  Conversely, ETS2 overexpression in H1299 lung cancer cells showed significantly decreased cell migration and invasion.  Of interest, the magnitude of these changes following knockdown or overexpression of ETS2 was greater in measures of migration and invasion compared to cell growth--suggesting a tumor suppressor function for ETS2 at least in vitro.

Gene expression profiling of H441 lung cancer cell lines transfected with scrambled siRNA (control) versus ETS2-specific siRNA showed significant differential expression in 1,816 transcripts.  Functional analysis by Ingenuity Pathways Analysis (IPA) showed ETS2 knockdown modulated key oncogenic pathways, including HGF, integrin, tissue factor, semaphorin, and MAPK signaling.  Notably, HGF was the top modulated canonical pathway identified following knowdown, and further, an HGF-mediated gene-interaction network was among the among the top significant gene networks following topological arrangement of the genes found to be differentially expressed by IPA.

Western blot analysis and ELISA both showed increased phosphorylation MET following ETS2 knockdown.  Importantly, co-transfection of H441 lung cancer cells with MET-specific siRNA abrogated cell migration, invasion, and, to a lesser effect, cell growth mediated by knockdown of ETS2 expression alone.  Furthermore, co-transfection of cells with MET-specific siRNA significantly attenuated the induction of SNAI2, RAB3B, SPDEF and SERPINB5 mediated by knockdown of ETS2 alone as well as reduced expression of ZEB1. These data demonstrate that ETS2 suppresses key features of the lung cell malignant phenotype, at least in part, through inhibition of the MET oncogene. 

The authors also find that ETS2 suppresses EGF-mediated signaling in lung cancer cells.  HGF treatment increased ETS2 protein expression and phosphorylation of MET and ERK1/2 MAPK in H441 cells.  Conversely, expression of ETS2, phospho-MET, and phospho-ERK1/2 was attenuated by co-treatment of H441 cells with the MET TKI PHA-665752.  HGF treatment also significantly increased the expression of SNAI1, RAB3B, SPDEF, ZEB1, and SERPINB5 genes.  Moreover, the expression of these genes was significantly higher in HGF-treated cells transfected with ETS2-specific siRNA compared to similarly treated control cells.  Conversely, overexpression of ETS2 in H1299 cells decreased HGF-induced phosphorylated MET levels and decreased HGF-induced cell migration in the wound healing assay. 

Finally, NSCLC (p=0.01) or ADC (p=0.02) patients with relatively low ETS2 protein expression and higher phospho-MET membrane immunoreactivity showed shortest tiime-to-recurrence compared to other patient groups, specifically those with higher ETS2 and higher phospho-MET
expression.

Pathologists to Blame for Hindering Acquisition of Cancer Tissue for Genomic Testing?

Medscape recently posted an article that discusses the need for standards for acquiring, preserving and storing cancer tissue, citing a recent Viewpoint article in JAMA by Drs. Laura Goetz, Kelly Bethel, and Eric Topol. If you have the chance, I highly recommend you pathologists read the full article as there is a valuable discussion of the need for appropriate specimens for next-generation cancer genomic testing.  Basically, we need to move beyond the idea that "diagnosis" just means having enough tissue or cells to make a morphological diagnosis (including immunohistochemical stains) to one where the "diagnosis" is extended to include molecular testing, even whole-genome sequencing.

I do admire Dr. Topol's principled stand to get patients to drive demand for obtaining appropriate tissue for genomic testing (a refreshing free market approach!).  However, I must take exception to comments made by Dr. Topol in the Medscape article where he states (bold is my emphasis):

Dr. Topol notes that there is much resistance from pathologists, in that it would be expensive to have fresh frozen specimens because it requires increased space, monitoring, and electricity for storage in freezers, there would be problems with reimbursement, and so on. "Basically, every excuse under the sun," he said. "But if it was one of them having a new diagnosis of cancer, they would probably like to have as much information as possible."

After having read the JAMA article, I have no idea why Dr. Topol takes such a gratuitous--and unnecessary swipe at pathologists.  His remarks and imputations are as ignorant as they are offensive.  While Dr. Topol correctly assesses the factors that are contributing to the slow development of processes, standards, and facilities to obtain, preserve, and maintain tumor specimens appropriate and optimal for molecular and genomic testing, resistance from pathologists is absolutely not one of the factors. In fact, the College of American Pathologists, our leading voice, has taken a lead role in developing such standards and educating pathologists in molecular and genomic oncology. See the CAP's resource page for molecular oncology.

Dr. Topol's assessment of the factors that are hindering the development of more widespread tissue procurement for genetic testing is solid--viz., trend of less tissue obtained for diagnosis, logistical issues with fresh frozen specimens, reimbursement--but his conclusion blaming pathologists is absolutely wrong.  The resistance that pathologists are putting forth has nothing to do with the concept of acquiring fresh frozen tissue (which we agree wholeheartedly with!) but with the facts that 1) we are responsible for establishing and maintaining an accredited facility for providing this service and 2) we are largely responsible for paying for this service which is neither reimbursed professionally or technically or adds to the "bottom line" of the institutions that we serve.  Since about 75% of cancer care is delivered at the community hospital level, perhaps Dr. Topol has some solutions for how these hospitals specifically are going to manage and pay for this--regardless if one of the pathologists (or even one of the administrators) has a new diagnosis of cancer.

Video: Dr. Jack West discusses changing views on molecular testing in NSCLC

The Lungevity blog features a video of Dr. Jack West from Swedish Cancer Institute in Seattle discussing his evolving views regarding molecular testing for actionable driver mutations in non-small-cell lung cancer (NSCLC). Dr. West is a thought-leader in lung oncology and I found this a tidy and brief summary of current issues and reasonable argument for expansion of such testing.

This is important for pathologists as we are often tasked with triaging testing as the time of diagnosis, managing results reporting, and driving testing. My own views as a pathologist with a concentration on lung cancer have changed over the last two years based on clinical practice, research meetings, recent publications, and listening to clinicians' views. Initially, it seemed to me that reflex testing of all advanced stage (stage 2B and up) lung adenocarcinomas and excluding tumors with squamous histology; since we generally are unaware of the smoking history, I ignored smoking history as a criterion for testing. I okayed this with the oncologists and off we went. Dr. West succinctly contrasts the two views concerning molecular testing in NSCLC: essentially testing all patients with advanced stage NSCLC versus testing focused on "enriched" populations, e.g. adenocarcinoma histology, never/light smokers.

My own views began to change as a result of one memorable lung cancer research meeting at Rush we had when one of the thoracic surgeons related how a patient grilled him on why he received an expensive bill for all this molecular testing without any discussion with the surgeon or oncologist and, moreover, when he had already expressed his preference to not receive any further treatment following biopsy and mediastinoscopy. These aren't cheap tests and someone (not the pathologist) must explain these results to the patient. I also reviewed our experience with molecular testing and found several instances where testing was sent on early-stage patients and squamous histology tumors, which I didn't think was appropriate. Based on another round of discussions with the oncologists, I decided that we should consult with the oncologist before ordering molecular testing.

But as Dr. West says, "Some patient's cancer don't read the books." He relates several recent experiences that have caused him to revise his views: squamous tumors that show driver mutations, including one tumor with both EGFR activating mutation and ALK rearrangement. He advocates broader, more expansive molecular testing as well as consideration of testing recurrences and re-biopsy of clinically stable lesions.

The bottom line is that this is still an evolving area--we must be aware of new data coming out and be prepared to modify our views and practices.

New directions for lung squamous cell carcinoma

For non-small cell lung cancer patients with localized or regional disease, treatment options vary little according to histology.  For metastatic NSCLC "targeted" therapies for patients with EGFR activating mutations or ALK translocations, pemetrexed, and the addition of bevacizumab to conventional chemotherapy have improved the treatment of metastatic NSCLC.  Unfortunately, all of these improvements apply almost exclusively to NSCLC adenocarcinoma histotype.

 For squamous cell carcinoma of the lung (SQC), the standard treatment remains cytotoxic chemotherapy, usually consisting of a platinum-containing doublet (carboplatin>US, cisplatin>Europe) with docetaxel or erlotinib used as second-line agents.

Similar to adenocarcinomas, squamous cell carcinomas are a heterogenous group of clinically, molecularly, and genetically different tumors.  Current work on SQCs is focused on identifying unique molecular patterns or driver mutations that may be therapeutic targets.  Kathryn Gold, Ignacio Wistuba and Edward Kim have published an excellent review of this recent work on SQC in Clinical Cancer Research 2012 18(11); 3002–7 that I recommend if you want a state-of-the-art update.

This review is more clinically oriented (for the pathologist) but provides connections between observed molecular abnormalities with drugs in various stages of development and current trials.  One interesting development is a phase II trial opening soon looking at the agent NCT01514864 for patients with squamous cell carcinoma with a mutation in discoidin domain receptor 2 kinase (DDR2).  I previously posted on a paper that identified DDR2 kinase mutations in lung squamous cell carcinoma about a year ago--so this is some exciting stuff! DDR2 kinase mutations occur in about 4% of SQC which doesn't seem like much until you input the denominator of the number of lung SQC diagnosed per year--this is analogous to EML-ALK translocations in lung ADC. 

Establishing clonality in multifocal nonsmall cell lung cancer

Up to 8% of nonsmall cell lung cancer (NSCLC) patients present with 2 or more anatomically separate lung tumors.  Distinguishing between synchronous primary tumors and intrapulmonary metastases is an important clinical question because this determination significantly changes tumor staging and subsequent therapeutic decisions.

Arne Warth et al. have published a single institution study from University Hospital Heidelberg in the current issue (1 June 2012) of European Respiratory Journal (abstract) that examines the clonal relationship in a series of patients with morphologically indistinguishable multifocal NSCLC.

The authors screened their archives for synchronous multifocal NSCLC in the same lobe (pT3), different ipsilateral lobes (pT4), and bilateral lobes (pM1a).  An important part of this study is that the authors only included those cases in which morphology between the tumors was indistinguishable using published criteria from the literature (Girard et al, Am J Surg Pathol 2009--actually a great reference).  They included 78 patients in this study.

The authors performed EGFR and KRAS mutation screening by using single-strand conformation polymorphism sensitive gel elctrophoresis and then subjected aberrently migrating bands to direct DNA Sanger sequencing.  The authors analyzed 14 polymorphic microsatellite markers for loss of heterozygosity. A clever part of the analysis of clonality in this study was the utilization of individual clonality scores for each tumor pair by multiplying the likelihood of the observed findings for each informative variable.  Thus, the clonality score defines the statistical error probability of a clonal or non-clonal relationship.

Results

1. The study included 58 adenocarcinomas (ADC) and 20 squamous cell carcinomas (SQC).  59 were pT3, 18 pT4, and 1 pM1a.  The mean follow up for all patients was 25.6 months. 97.4% of all specimens could be classified as clonal, likely clonal or nonclonal.
2. Tumors from 22 patients (28%) showed divergent LOH status indicative of non-clonal origin (14/58 ADC, 8/20 SQC).
3. Activating EGFR mutations were found in both synchronous tumors in 4/58 ADC and none of the SQC showed EGFR mutation.
4. KRAS mutations were found in 20 cases (17 ADC, 3 SQC), including in both synchronous tumors in 13 cases but in only 1 tumor in 6 cases. 1 patient had divergent EGFR and KRAS mutations in separate tumors.
5. Combined allelotyping of LOH and EGFR and KRAS mutational status showed that 36% of synchronous primary tumors were not clonally related.  Remember these were tumors that were determined to be morphologically indistinguishable.
6. Impact of clonality of multifocal NSCLC on overall survival: Kaplan-Meier curves show a trend that patients with 2 clonally unrelated tumors have a better outcome but this did not reach statistical significance by univariate analysis.

Conculsions

There is no objective, specific anatomical or morphological criteria that reliably indicate a clonal or non-clonal origin of multiple NSCLC tumors.  Therefore, the authors recommend performing predictive molecular testing (EGFR and KRAS) separately in all cases with synchronous tumor nodules or allelotyping to identifiy clonally related tumors.

This paper will influence the way I approach these situations.  First, I will specifically incorporate the Girard criteria to identify morphologically indistinguishable cases.  Second, I will send out separate tumor specimens for EGFR and KRAS mutation analysis before assigning my pathologic staging to the case.  A couple practical questions are not addressed by this study.  Given the remarkable morphological heterogeneity of lung ADC--and the high percentage of "mixed" subtype tumors, isn't it possible that morphological disparate tumors could still be clonally related?  The authors don't specifically address the issue of mixed subtype in relation to "morphologically indistinguishable" tumors--but this would be a major practical issue.  Should we simply assume that morphologically different-ish tumors are non-clonal or do the testing anyway?  A great complimentary study would test all synchronous tumors regardless of histology since this study showed that morphological criteria could not predict clonal origin even in a narrow series of synchronous tumors that looked alike in pairs.  An intriguing point of this study is the possible relationship between clonal relationship and OS.  The authors rightly conclude that this should be tested in larger cohorts of NSCLC patients to identify any statistically significance to the trend that they identified.  I am perplexed as to why clonally unrelated tumors should have better outcomes.  If any one has any thoughts, I'd love to hear them--please post a comment with your thoughts. 

Medscape Interview with NIH Director

Medscape recently produced a fascinating interview with Dr. Francis Collins, Director of the National Intitutes of Health that focuses on genomics but ranges broadly over several areas, including medical education and preventative medicine.  It's not that long and there is also a text format if you don't want to watch the interview.  Highly recommended.  This a thought-provoking interview.

I think Dr. Collins is overly optimistic about the impact of genomics on day-to-day patient care.  Pharmacogenomics, for one example he uses, has not made any impact thus far in my experience.  While it is a tool, perhaps, for demonstrating why a patient may not be responding to a particular drug, the use of pharmacogenomic testing before initiating treatment has not been prospectively studied to my knowledge in any trials, for any drug.  This leaves aside the further studies regarding cost-benefit analyses as well as the issue of payment/reimbursement.  Right now, it seems cheaper and tried to put a patient on a standard dose and see what happens.

Another example is the idea of genomic sequencing of cancers.  It sounds good because it provides a "personalized" profile of a cancer.  What about tumor heterogeneity?  Do we sequence the primary tumor or metastasis?  Which part of the primary tumor?  Which metastasis?  Finally, how does one compare "unique" tumor genotypes and develop groups to statistically compare treatment responses?  At some point, patients have to be lumped together (and thus muddying up personalized differences) in order to find appropriate guidelines for treatment and provide some prognostic information.

Lots more to think about!

Review of microsatellite instability (MSI) in colorectal cancer

Clinical Cancer Review just published an "OnlineFirst" article on February 2, 2012 (link to abstract) that reviews microsatellite instability (MSI) in colorectal cancer.  There have been several recent reviews on this topic in various journals, including Archives of Pathology and Laboratory Medicine in October 2011.  The review by Drs Geiersbach and Samowitz in Archives is excellent (and recommended too) but has a decidedly technical, lab-oriented focus. I recommend this one to pathologists looking for a more clinically-oriented review that especially addresses current and future studies looking at how the molecular heterogeneity of "MSI" tumors may have different chemosensitivity responses.  It is very readable and certainly is the most current.  If you're looking for an article that makes you look good in tumor board, this is it!

A couple of highlights:

• MSI as prognostic marker in CRC.  Observational studies, retrospective data from randomized clinical trials and meta-analyses have consistently shown that tumors that show MSI or deficient mismatch repair (MMR) are independently associated with improved survival and reduced recurrence rates compared with individuals with MSS tumors.
• ECOG 5202 is a ongoing trial of stage II CRC patients stratifying them into low-risk versus high-risk based on MSI and allelic loss of 18q.  Low-risk patients (MSI and intact 18q) are assigned to an observational arm post-op while high-risk patients (MSS and allelic loss of 18q) are assigned to standard post-op chemo for stage III patients (FOLFOX).  Unfortunately, this study will not address the use of MSI as a predictive marker for response to 5-FU therapy.
• MSI as predictive marker in CRC.  Mutliple studies, including RCTs, retrospective case series, in vitro cell line data, and a meta-analysis, have consistently shown that MSI is a negative predictive marker for response to 5-FU.  It has been recently recommended that patients with stage II colon cancer showing MSI not receive 5-FU as adjuvant therapy given their favorable prognosis and lack of benefit from 5-FU.  Incidentally, in discussing whether to routinely test for MSI in stage II and II patients with the oncologists, it was evident that there is a lot of "catch-up" and education that needs to be done here. 
• Currently, there are only limited data in MSI tumors from patients treated with oxaliplatin combined with 5-FU and predictive information is lacking.  This is an important confounding problem interpreting the literature since standard first-line treatment for CRC is 5-FU and oxaliplatin.  It appears, however, from in vitro studies that oxaliplatin sensitivity is independent of the MMR system.
• Since KRAS testing is becoming more routine for CRC, especially in high stage III/stage IV cancers, it is important also to note that sporadic MSI CRCs (with epigenetic inactivation of hMLH1) show frequent (~50%) co-occurrence of BRAFV600E mutations (compared to an overall BRAF mutation frequency of about 10% among all CRCs).  Note: The presence of a BRAF mutation indicates a sporadic MSI CRC and essentially excludes a diagnosis of Lynch syndrome.
• There's a lot of interesting stuff on possible additional targets for therapy you should check out.

WCLC 2011 Oral Presentations: (More) Genomics

Continuing posts summarizing my highlights from the oral presentations from WCLC 2011.

The Biomarkers V presentation highlight (O39.01) was a retrospective analysis of the CALGB 30406 study looking at the impact of specific EGFR mutations on outcomes.  CALGB 30406 was a prospective trial in never/light smokers, previously untreated patients with advanced lung adenocarcinoma randomized to receive erlotinib (ERL) or ERL plus carboplatin and paclitaxel (C/P) as first-line therapy.  Patients with EGFR mutations had similar outcomes (RR, PFS, OS) in both arms of the study vs. EGFR-wild type  patients but no significant difference was seen in outcomes in exon 19 deletion vs. L858R mutation, irregardless of treatment arm.  Good evidence to address a certainly relevant question.

Recent studies have shown that NSCLC can be differentiated into "epithelial-like" and "mesenchymal-like" tumors based on gene expression and EMT biomarkers have been associated with erlotinib activity in both in vitro and clinical specimens.  Increasing evidence also suggests that changes in DNA methylation also are associated with the phenotypic EMT transition in lung cancer cells.  MO16.02, presented in the Biomarkers VII session, is a proof-of-principle study by Genentech researchers using an integrated genomics approach combining gene expression profiling and methylated DNA immunopecipitation (meDIP) to define phenotypic subsets of NSCLC by their DNA methylation patterns.  They further developed quantitative methylation-specific PCR assays for 14 markers identified by meDIP and pyrosequencing assays for another 5 markers.  They tested a panel of NSCLC cell lines with defined responses to erlotinib by these assays and showed good correlation with erlotinib activity or EL/ML status.  This study showed the potential for using DNA methylation profiles in targeted therapy profiles.  This seemed like a lot of fancy razzle-dazzle in this context and I'm unclear what it would really add in a practical sense; it seems to me most of the work on DNA methylation patterns in lung cancer has been focused on identifying markers for early diagnosis in serum.

WCLC 2011 Oral Presentations: Squamous Cell Carcinoma

There were several interesting presentations regarding squamous cell lung carcinoma that are worthy of attention.

O06.02 presented in the Biomarkers I session by Selinger et al. was a study of a possible prognostic marker for SQC called Special AT-rich Binding Protein-1 (SATB1).  SATB1 is a global genome organizer that recruits chromatin remodeling proteins for epigenetic regulation of multiple genes in a tissue-specific manner.  SATB1 is normally expressed in normal respiratory ciliated columnar epithelium in bronchi and terminal bronchioles but the authors observed loss of this protein by IHC expression in preinvasive squamous lesions and in NSCLC.

In their cohort of 243 NSCLC patients, the authors found that loss of SATB1 was an independent predictor of decreased cancer-specific survival in SQC patients (HR 2.06, P=0.016).  The authors suppose that loss of SATB1, which can act as a transcriptional activator or repressor, in early lung lesions results in widespread disruption of tissue-specific epigenetic modifications, leading to activation or repression of key cancer genes and promotion of lung tumorigenesis.

This provocative study raises more questions than it can answer but is worthy of notice because of its identification of a possible prognostic marker for SQC (as opposed to ADC) but also the interesting mechanistic questions it raises with regard to changes in tissue-specific epigenetic regulation for the development of or progression of cancer.

 

O037.07 by Savic et al. was presented in the Biomarkers IV session and adds to the growing number of studies on Sex Determining Region Y-box 2 protein (SOX2) in NSCLC.  SOX2 is located on the long arm of chromosome 3, an area that has been previously identified as being associated with loss of 3q in early stages of SCQ carcinogenesis.  This study involved a tissue microarray constructed from 568 patients with stage 1 NSCLC with detailed histopathological and clinical data.  SOX2 gene data was determined by FISH and SOX2 protein expression was assessed by IHC.  This data was correlated then with clinicopathological findings and OS and cancer-specific survival.

Increased SOX2 gene amplification or polysomy was found in 4% of (17/429) evaluable samples but 16/17 (94%) were associated with non-ADC histology.  SOX2 protein expression was found in 48% of NSCLC and was associated with non-ADC histology (P<0.001): SOX2 expression was identified in 78% of SQC specimens (178/227) but only in 15% of ADC (29/191).  Further, SOX2 protein expression was significantly associated with high grade tumors, patients >50 years, and male gender.  Finally, they noted a significant association between increased SOX2 gene number and protein expression (P<0.001).

While these are some intriguing findings, this presentation doesn’t quite deliver. Unfortunately, the authors did not report any correlation data with survival (and this is a glaring deficiency) nor do they offer any speculation on the discrepancy between the few cases that show increased SOX2 gene copy number and the frequent observation of SOX2 protein expression in SQC.  Further work on SOX2 definitely seems warrented, especially because of this association with SQC histology and its location in a chromosome region frequently lost in early stages of squamous carcinogenesis.