The Daily Sign-Out

Evidence for tissue-specific differences in EMT

Remodeling of the extracellular matrix is a key process in cancer invasion.  Matrix metalloproteases (MMPs) have been shown to be important in ECM remodeling but identifying individual MMPs with specific roles in various cancers has been difficult due to functional overlap with other proteases.  The current Diseases Models and Mechanisms has an interesting article by Hald et al. in which they demonstrate that double-knockout mice lacking both plasmin and MMP-9 develop inflammatory colonic mass lesions that resemble mucosal prolapse lesions in humans.  In contrast, wound healing in skin in these mice is normal.  The findings indicate tissue-specific differences in ECM remodeling--and thus potential therapeutic targets. Further, this study demonstrates the potential utility of other mouse models for studying ECM remodeling in other tumors.  Provocative stuff and more of the EMT story unravels.

P53 in tumor-associated fibroblasts in invasive ductal carcinoma

Hasebe et al. have authored an interesting article in a recent Modern Pathology (2010;23:662-672) which builds on their earlier work that showed P53 expression in tumor-stromal fibroblasts (TSF) not forming fibrotic foci to be an important predictor of outcome in patients with invasive ductal carcinoma.

The fibrotic focus has been shown to be a prognostic factor in breast cancer.  Moreover, criteria for fibrotic foci proposed by Van den Eynden et al. in 2007 (Dr. Hasebe was a co-author) appear to both clinically significant and reproducible in daily practice.  I am surprised that the use of this feature has not been adopted for routine use since presenting breast cancer cases with prominent fibrotic foci never fails to elicit curiosity and questions in Tumor Board.  Further, a fibrotic focus has been proposed as a marker for tumor hypoxia and angiogenesis.

The purpose of the current study was to determine whether the combined assessment of P53 expression in tumor-stromal fibroblasts both forming and not forming fibrotic foci serves as a significant predictor of outcome in patients with invasive ductal carcinoma using multivariate analysis with well-established prognostic factors.

The authors studied 1,039 consecutive patients at a single Japanese institution who received surgery including axillary dissection; 873 also received conventional chemotherapy, endocrine therapy, or both.  Using FFPE serial sections of each tumor, the authors evaluated 8 different histological factors, including measuring the fibrotic focus using 8 mm as the cutoff per the Van den Eynden criteria.  Immunohistochemical staining for P53 was evaluated using the Dako mouse monoclonal antibody clone DO7 and staining of tumor-stromal fibroblasts was scored according to modified Allred scoring.  Furthermore, the authors stratified P53 staining in tumor-stromal fibroblasts into 3 groups each for those tumors with and without fibrotic foci.

373 out of 1,039 cases had fibrotic foci.  Notably, in 97 of these 373 (26%) P53 staining could not be evaluated because the tumor tissue sections examined by P53 IHC did not contain a fibrotic focus identified initially at routine examination.

The authors found significantly higher P53 Allred scores in TSFs not forming compared with TSFs forming fibrotic foci.  But P53 Allred scores >4 in TSFs forming fibrotic foci were also associated with fibrotic focus diameter > 8 mm: the size previously established as a cut-off for predicting adverse outcome independent of stage.

Based on Allred scores, the authors segregated P53 expression for TSFs forming and not forming fibrotic foci into risk classes.  Patients in pTNM stages I-III with intermediate to high risk classes of P53 expression showed a significantly higher tumor recurrence rate than patients in the low risk classes.  In addition, stage II and III patients with intermediate to high risk classes of P53 expression showed a significantly higher disease-related mortality rate.

By multivariate analysis, for stage I patients, intermediate to high risk classes of P53 expression in TSFs forming and not forming fibrotic foci and histological grade 3 were significantly associated with tumor recurrence (but not disease-specific death).  For stage II patients, intermediate to high risk classes of P53 expression in TSFs forming and not forming fibrotic foci were associated with increased tumor recurrence and tumor-related death.  Lymphovascular invasion and blood vessel invasion were significantly associated with increased tumor recurrence, whilst pT1 and fibrotic focus > 8 mm were significantly associated with increased tumor-related death.

(Next to) Bottom Line: P53-expression TSFs located both in the inner fibrotic foci an outer invasive front increase the malignant potential of invasive ductal carcinomas across stages I to III.

SO--should we start doing P53 IHC on all invasive ductal carcinomas?  Perhaps not ready yet for prime-time, but this study provides evidence that may, at least in part, explain the prognostic value of fibrotic focus diameter.  Measuring the fibrotic focus, however, may just be ready for prime-time and you may want to consider reviewing the original paper by Van den Eynden et al published in Histopathology 2007;51:440-451.

BUT I do have a few points to consider.  First, this is a single institution paper, so the methodology needs to be independently validated and a larger, multi-insitutional patient cohort needs to be studied to confirm the association between patient outcomes and P53 staining.  Second, other P53 antibodies should be evaluated to optimize the assay.  Third, the number of invasive ductal carcinomas with fibrotic foci that were excluded from the study is disquieting and may be a major source of observational bias.  Finally, the role of image analysis in providing quantitative P53 cut-offs may provide better discrimination between prognostically different groups.