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Exosomes and nanoscale messenging

This month's Laboratory Investigation has an interesting free article by Hood et al. exploring exosomes--nanoparticles formed by inward budding of microvesiclar bodies and released into the extracellular matrix as part of a nanoscale messenger system.  The size of these particles (30-100nm) facilitates their penetration into cells at the invasive tumor front and they have been shown to participate in cell to cell communication such as morphogen and RNA transport between cells.

The authors' hypothesis is that melanoma exosomes act as "nanovehicles" (I love this term!) to prepare the microenvironment for tumor cell implantation.  This article describes a unique in vitro angiogenesis assay system to study exosomes and their influence on endothelial cell tubulogenesis (i.e., early anagiogenic changes) and spheroid sprouting (a later stage of angiogenesis).  This system also incorporates a novel method of tracking the trafficking of exosomes.

I know this is "out there" but I was not familiar with this topic at all and thought it fascinating.

P.S. Sorry for my recent prolonged absence from posting--teaching the second-year medical students some lung pathology.

New CAP Today online version available!

If you haven't done so, check out the new CAP Today online edition.  Although I try to read as much as I can in an electronic or online format, sometimes I fatigue trying to navigate through things since I find that I don't necessarily read things in a front-to-back manner.  The new CAP Today version is wonderfully easy to navigate and you can customize a comfortable size to read.  It is also pretty intuitive to use (you don't need an instruction manual).  Definitely a score for CAP!  And it takes up less shelf-space than the ledger size print edition.

Dark Daily offers free report on changing your lab's culture

The Dark Daily is offering another free report about strategies for changing your laboratory's "culture," that is fostering within the lab a sense of successful problem-solving skills and self-directed pursuit of excellence.

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(URL FOR THIS ITEM: http://www.darkdaily.com/change-your-laboratory-working-culture )

Recent lecture on role of KRAS mutation in management of colorectal cancer

I recently gave a Tumor Board presentation on the role of KRAS mutation testing in the management of colorectal cancer.  The PowerPoint file is attached for educational purposes.  I hope you will find it of interest.

Download K-ras lecture upload

Dark Daily offers free report on increasing lab revenue

The Dark Daily is offering a free white paper on increasing laboratory reimbursement by focusing on revenue cycle management:

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FREE WHITE PAPER (42 pages)

There is no doubt that the complexity of laboratory revenue cycle management is unmatched in all of health care. With frequent regulatory and compliance rules changes, ever tightening margins, and a severely weakened economy, it is getting harder and harder for potentially acquirable independent labs to be sure they are not leaving potential profits on the table. The Dark Report is happy to offer our readers a chance to download our recently published White Paper “A CEO’s Guide to Increasing Laboratory Valuation: Effective Revenue Cycle and Compliance Management are Critical Success Factors” at absolutely no charge.

(URL FOR THIS ITEM: http://www.darkdaily.com/ceo-guide-to-increasing-laboratory-valuation-effective-revenue-cycle-and-compliance-management )

NIH State-of-the-Science Statement on Breast DCIS

The conference statement from the recent NIH "State-of-the-Science" conference on ductal carcinoma-in situ (held September 22-24, 2009) is available online.  You can download a pdf for free.

Some interesting findings:

1. While the incidence of "noncomedo" DCIS continues to increase, the incidence of the (to me, more biologically worrisome) comedo type peaked in 1995 and has been declining (through 2006).
2. MRI in DCIS?  Most studies show that MRI is more sensitive in detecting multicentric disease but is not specific.  MRI also reportedly over- and under-estimates the extent of DCIS compared to pathological exam.
3. Although the absolute numbers are small (due to the overall high survival rates in DCIS), there are higher breast cancer recurrence and mortality rates in Black women diagnosed with DCIS compared with White women.
4. No molecular markers have been identified to stratify prognostic groups.  High grade, comedo pattern, margin involvement and size have been related to increased risk of recurrent DCIS and progression to invasive carcinoma--but hard numbers are hard to come by.
5. DCIS is a heterogenous disease with a high probability of long-term disease-free survival--whatever therapy is received.

Too many SOX can be a bad thing

Nature Genetics published a fascinating article online on October 4 by Bass et al. identifying SOX2 amplification in lung and esophageal squamous cell carcinomas (SqCC).  It is refreshing to read a good study of squamous cell carcinomas since there has been so much published recently on lung adenocarcinomas.

This is a multi-institutional study that first examined 40 esophageal SqCC and 47 lung SqCC using SNP arrays to determine copy number changes and GISTIC (Genomic Identification of Significant Targets in Cancer) to score the significance of recurrent chromosomal gains and losses in order to identify peak regions likely to harbor tumor-driving genes.

The most significant amplified peak in lung SqCC was at chromosome 3q26.33, found in 11/47 lung SqCC and 6/40 esophageal SqCC.  In lung SqCC, the peak in this segment contained four genes, including SOX2; in esophageal SqCC, the peak only included SOX2.  Next, the authors measured SOX2 mRNA levels by RT-PCR in 27 lung SqCC with matched SNP data cases.  Cases with SOX2 amplification were found to have higher mRNA expression but they also found several cases without 3q26.33 amplification that had high SOX2 mRNA expression.  The authors made similar findings with esophageal SqCC.  The authors then performed an arrayed RNA interference screen targeting SOX2, neighboring genes, additional candidate genes and controls in 4 SqCC cell lines (2 lung, 2 esophageal) for differential effects on proliferation.  Suppression of SOX2 had the largest differential anti-proliferative effects on 3q26.33 amplified cell lines amongst all genes tested.  Further, they showed that SOX2 knockdown reduced anchorage-independent growth.  These findings were confirmed with rescue of the effects of SOX2 suppression by restoring wild-type SOX2 in a mutant cell line.

Additional work shows that SOX2 amplification and mRNA levels are significantly higher in lung SqCC compared with lung adenoca (which differentially showed NKX2-1 amplification and increased mRNA levels cf. to lung SqCC).  SOX2 alone could not transform immortalized tracheobronchial cells but could do so in cooperation with the epithelial isoform of FGFR2.

As it turns out SOX2 is an very interesting transcription factor intimately involved in forgut development and is required for proper differentiation of esophageal squamous mucosa and in multiple respiratory cell types.

This is a very dense paper presenting the results of multiple experiments of which I have summarized only a part.  What does all this mean for the practicing pathologist or oncologist?  The identification of SOX2-dependent pathways in lung squamous cell carcinomas is an exciting finding that may represent a novel therapeutic target--which has been conspicuously lacking so far in lung SqCC.

Novel classification for gastric cancer using pathways

A multi-institutional study published online on Oct. 1 in PLoS Genetics examined 301 gastric carcinomas using gene expression profiles and a pathway prediction model to identify major oncogenic pathways involved in gastric cancer and relate expression of these pathways to patient survival.  They found proliferation/stem cell-related, Wnt/beta-catenin, and NF-kappaB pathways are deregulated in over 70% of the gastric cancers they studied.  Furthermore, the found patterns of pathway co-activation associated with survival.  This is a free access paper so please download and read.

Reading the "Materials and Methods" of this paper is worthwhile in itself because the strategy the authors used is well-conceived and explained.  More importantly, this study demonstrates the feasibility of using gene expression profiles to perform in silico experiments to make pathway predictions as a basis for in vitro experiments--another example of "systems thinking" in pathology and oncology.

Micrometastases and ITCs in breast cancer: the controversy continues

This week's Journal of Clinical Oncology (October 1, 2009) has an article by Hansen et al (abstract) from the John Wayne Cancer Institute reporting a prospective study of invasive breast cancer patients with micrometastases in sentinel lymph node biopsies and its impact on survival.

They studied 790 patients with sentinel lymph nodes categorized as pN0(i-), pN0(i+), pN1mi, or pN1 and compared disease-free survival (DFS) and overall survival (OS).  Median follow-up was 72.5 months.

The results showed that pNO(i+) and pN1mi patients had a similar 8-year DFS and OS compared with pN0(i-) patients.  As expected, pN1 patients had significantly shorter 8-year DFS and OS compared with the other 3 groups.  Multivariate analysis showed macrometastases, tumor size and histologic type were predictive of shorter DFS, while OS was predicted by macrometastases, patient age, and ER status.

This is a well-designed, prospective study and worth taking note and the accompanying editorial by Dr. Thomas Julian is also notable.

These findings are in contrast to a recently published NEJM article by a Dutch group from Maastricht University Medical Center (de Boer et al. NEJM 2009 Aug 13: 353-363).  This study was also prospective but studied non-sentinel pN0(i+) and pN1mi regional LN involvement in early-stage breast cancer patients.  It compared DFS in pNo(i+) and pN1mi patients who had not received adjuvant therapy with those pNo(i+) and pN1mi patients who did receive adjuvant therapy and with node-negative (pN0) patients.  The authors found that the pN0(i+)/N1mi, no adjuvant therapy group had a shorter 5-year DFS compared with those who did received adjuvant therapy.  This same Dutch group, furthermore, published a "scary" (to me!) meta-analysis study in JNCI in November 2008 examining the association of isolated tumor cells in sentinel LN with non-sentinel LN metastases.  The study included 29 studies and found an overall risk of non-sentinel lymph node metastases when there was ITCs in the sentinel node of 12.3% (95% C.I. 9.5% to 15.7%)--roughly one-and-a-half to two times the published false negative rate for SLN biopsy.  Here's the scary part: nearly two-thirds (64%) of patients with ITCs in their SLN also had non-sentinel LN macrometastases!

It seems that when the pN0(+) situation arises in my practice, there are multiple phone calls questioning the result, its meaning, and what to do next.  First, the designation of pN0(+) whether positive by H&E or IHC is confusing (at best) and basically, er, wrong--as it seems pathologically, clinically, and biologically.  Yet, it also appears that each patient's treatment plan must be evaluated individually.  The current evidence supports completion axillary dissection in these patients, although perhaps this just kicks the can down the street if those nodes are negative.  Two ongoing studies which have completed accrual, NSABP B-32 (retrospective IHC analysis) and ACOSOG Z0010 (prospective study), should help clarify this problem.

Intestinal metaplasia in Barrett's esophagus--RIP?

This is a follow-up to my post from last month regarding columnar metaplasia of the esophagus.  Dr. David Agbamu provided a reference to an article by renowned GI pathologists, Drs. Riddell and Odze, "Definition of Barrett's esophagus: time for a rethink--is intestinal metaplasia dead?" published online on July 21, 2009 in the Am J Gastroenterol.

I finally had a chance to read and digest this paper and heartily recommend practicing pathologist colleagues to do the same as I think it can inform (and reform?) our practices.  GEJ biopsies and esophagus biopsies "r/o Barrett's" are common specimens seen in both "community" and "academic" practice settings.

Drs. Riddell and Odze make a compelling argument challenging the American College of Gastroenterology 2008 definition of BE, i.e., columnar-type mucosa at endoscopy (of any length) PLUS the identification of "intestinal metaplasia" (=goblet cells) on biopsy of the tubular esophagus.  First, they contrast this definition with British and Japanese definitions of BE which do require any histologic confirmation.  In brief, these definitions equate endoscopically recognized columnar-lined esophagus (CLE) with BE.  Second, they outline evidence in support of dropping the requirement for goblet cells in the diagnosis of BE.  The absence of goblet cells on biopsy of CLE is not a matter of sampling error and does not account for the dynamics of goblet cell expression (waxing/waning, conversion to nongoblet cell phenotype).  Moreover, protein expression and molecular alterations are the same in CLE with and without goblet cells.  Finally, there appears to be an equal risk of neoplastic progression in CLE regardless of goblet cells.

The clinical implications for pathologists is that it shifts the purpose of the index endoscopic examination and biopsy of CLE from the diagnosis of BE (Is there goblet cells or not?) to an initial surveillance for dysplasia (which is even more challenging!).

Finally, the authors argue for the fallacy of "ultrashort" BE: most agree that the endoscopic diagnosis of BE cannot be made with certainty if the CLE segment is < 1 cm.  Of those biopsied, only a minority of these show histologic features that enable them to be differentiated as being of esophageal or gastric origin.  But even if the origin of the biopsy can be determined, the risk of malignant progression of a segment of columnar metaplasia < 1 cm is unknown.

Again, this a real thought-provoking and well-documented article.