Molecular markers reflecting malignant transformation and tumor progression

Abstract

The early detection of neoplastic lesions is most critical in the successful treatment of malignant disease. This thesis investigates molecular targets for an improved detection and diagnosis of cancer by exploring the value of interphase fluorescence in situ hybridization (FISH) to detect specific chromosomal aneuploidies and gene amplifications, and laminin-5 gamma2 chain expression detected by immunohistochemistry as a marker for invasiveness. The aim of this thesis is to establish a better understanding of malignant transformation and tumor progression on the molecular level, and translate this knowledge to relevant diagnostic applications.

We collected fine needle aspirates from breast lesions and applied FISH to the cytological samples. Based on extensive comparative genomic hybridization (CGH) analysis, we designed three probe cocktails that target specific genetic aberrations known to be frequently involved in breast tumorigenesis. We have shown that benign lesions maintain a stable genome, however, carcinomas carry genetic aberrations that could readily be visualized with the probe cocktails. We have designed a translational assay that allows one to objectively diagnose breast cancer in cytological samples independent of any other markers. This test strengthens diagnostic precision and stratifies patients for specific rational treatments.

The value of the laminin-5 gamma2 chain as a marker of invasiveness was explored for the early diagnosis of invasive disease in cervical lesions. We designed a pilot study to investigate whether cytoplasmic laminin-5 gamma2 chain is expressed in cervical lesions that progress to carcinoma. We analyzed archival biopsies of matched preinvasive and invasive lesions. Our findings suggest that cytoplasmic laminin-5 gamma2 chain immunostaining is closely associated with the transition of preinvasive lesions into invasive disease. This study helps to establish the laminin-5 gamma2 chain as a molecular marker for invasiveness in cervical carcinomas, and is useful in the diagnostic interpretation of early invasive lesions.

Inspired by the laminin-5 gamma2 chain as a marker for invasiveness, we were interested in investigating whether laminin-5 gamma2 chain expression can be used as a marker to predict clinical outcome. We analyzed uniformly treated early stage (T1) carcinomas of the mobile tongue, in which the biological aggressiveness is variable. We found laminin-5 gamma2 chain expression was significantly higher in the tongue lesions that had recurred. We conclude that the laminin 5 gamma2 chain predicts aggressiveness in early stage carcinomas of the mobile tongue, and could be useful as a marker in stratifying those patients who would benefit from additional treatment, i e. radiation or neck dissection.

Vulvar carcinoma is an human papilloma virus (HPV) related tumor, and follows a similar pattern of progression as cervical carcinoma. We applied interphase FISH to vulvar carcinomas and pre-cancerous lesions with a multicolor probe for a telomerase gene mapping to chromosome 3q, a molecular target of cervical cancer. Included was laminin-5 gamma2 chain analysis. We found 3q amplified in all vulvar carcinomas and in the majority of precancerous lesions. Laminin-5 gamma2 chain expression was present only in the carcinomas. The results indicate that gain of chromosome 3q precedes the acquisition of invasive capacity in vulvar lesions, and thus is an early aberration in vulvar carcinogenesis. The detection of genomic amplification of 3q in diagnostic samples could be an independent test for the diagnosis of vulvar carcinomas and precursor lesions.