Breast cancer heterogeneity and stromal alterations detected by LCM

This work was performed at Breast Cancer Research Laboratory, Fox Chase Cancer Center, Philadelphia, PA, USA. We employed the technique of laser capture microdissection to obtain selected chosen cells without contamination of other cells that could interfere with final results of molecular analysis. Results confirmed that genetic alterations at specific loci of 9p occur earlier than discernable morphological or histopathological alterations and the presence of genetic alterations within morphologically normal breast tissue adjacent to carcinoma foci was also assessed. These findings have significant practical implications for the evaluation of what has to be considered the "free margin" of a tumor when performing breast conserving surgical therapeutic procedures as molecular markers should be taken into consideration for their use in addition to the histopathological evaluation of the resected margins. Study also confirmed intralesional heterogeneity when comparing different foci within the same DCIS or IDC and the observation that different populations of cells exist within a single tumor, an indication that they do not share clonal origin. These observations remain of major interest on what concerns surgical conservative procedures and prevention strategies of breast cancer.

Authors and affiliations:
Margarida Figueiredo Dias (1), Robert Blumenstein (2), Jose Russo (3)

(1) Centro Hospitalar da Universidade de Coimbra, Faculdade de Medicina da Universidade de Coimbra, Coimbra, Portugal.

(2) DeSales University, Allentown, Center Valley, PA, USA.

(3) Breast Cancer Research Laboratory, Fox Chase Cancer Center, Philadelphia, PA, USA

Abstract:
The present study was designed for determining whether the p arm of chromosome 9 exhibited allelic losses in invasive ductal carcinomas of the breast, and if so, to determine when these lesions emerged during the process of neoplastic progression. For this purpose various foci of epithelial cells from 14 invasive ductal carcinomas (IDC), ductal carcinomas in situ (DCIS), normal mammary lobules, skin, and/or lymph nodes were obtained from tissue sections by laser capture microdissection technique. Microsatellite DNA polymorphism analysis of chromosome 9p was performed utilizing five highly informative microsatellite markers (D9S199, D9S157, D9S171, D9S265, and D9S270). The highest frequency of loss of heterozygosity (LOH) was observed in invasive ductal carcinomas, which was maximal at 9p22-23 (D9S157), with lower frequencies for markers D9S171, D9S199, D9S265, and D9S270. DCIS lesions presented LOH 9p22-23 (D9S157), which showed the highest frequency, followed by 9p21 (D9S171), D9S199, and D9S265, which were similar in frequency to those observed in IDC. An unexpected finding was the intralesional heterogeneity in allelic loss found by comparing different foci within the same DCIS or IDC, since LOH was observed in some but not in all the tumor foci studied, an indication that clones of cells that differ in genetic composition coexist in the same lesion. Interestingly, phenotypically normal breast tissues adjacent to IDC or DCIS exhibited LOH at D9S157 and/or D9S171. These findings indicated that LOH was an early event in breast cancer progression. These data are supportive of a model whereby LOH of chromosome arm 9p occurs very early in the progression of cancer, even when cells still are phenotypically normal. Furthermore, we observed that different populations of cells exist within a single tumor, an indication that they do not share clonal origin.

Journal: Oncology Letters

Link: https://doi.org/10.3892/ol.2017.5892