Role of apoptosis associated genes in predicting clinical outcome of breast cancer

Introduction: Neoadjuvant chemotherapy, also called preoperative chemotherapy, is now widely used in the treatment of breast carcinoma. It has several potential advantages compared with the traditional strategy of surgery followed by adjuvant chemotherapy. Neoadjuvant chemotherapy substantially reduces the size of the primary tumor and lymph node metastasis in grater then 80% of cases, increasing the probability that breast-conserving surgery can be performed instead of mastectomy. Neoadjuvant chemotherapy is also a valuable research tool for discovery predictive markers of chemotherapy response.

Aim: The study is aimed at investigation of the biomarkers in predicting pathologic response to the therapy. We assume that regression of the tumors after neoadjuvant treatment is executed predominantly by apoptosis despite different chemotherapy agents.

Material and methods: The role of apoptosis in regression of the tumors after neoadjuvant chemotherapy was determined by two independent method: TUNEL and anti-active caspase 3 assay, respectively. The transcriptional profile of 84 key apoptosis genes was evaluated in both pre-therapeutically obtained tumor tissue by core needle biopsy and in speciemen removed by final surgery, using Real-Time PCR assay (SABiosciences).

Results: This study included 16 patients with histologically proven invasive breast cancer, that are primarily indicated to breast conserving surgery or mastectomy but that are treated by neoadjuvant chemotherapy. In each case, analysis of transcription profile was performed before and after the treatment, respectively. On the basis of hierarchical cluster analysis of 13 significantly changed genes, we divided patients into good and bad prognosis groups which good correlate with progression free survival. In the good prognosis group we found statistically significant downregulation of expression of MCL1 and IGF1R genes after neoadjuvant treatment. We also found statistically significant overexpression of BCL2L10, BCL2AF1, CASP8, CASP10, CASP14, CIDEB, FADD, HRK, TNFRSF25, TNFSF8 and TNFSF7 genes. In contrast, we found upregulation of IGF1R due to the treatment in the group of poor prognosis. The expression of remaining genes remained almost unchanged in this group of patients.

Conclusion: Unfortunately, little progress has been made with regards to new molecular prognostic/predictive markers that can assist oncologists in treatment decision-making for breast cancer. In this study, we verify our presumption that tumor regression after chemotherapy is caused by apoptosis despite the diverse schema of the treatment. Moreover, we develop the 13 apoptosis associated genes expression assay which may be heplful for stratification of the patients into groups with different response to chemotherapy. As we shown, gene expression profiling after neoadjuvant chemotherapy is a valuable research tool for investigation of molecular markers which may better reflect tumor biology and treatment response than standard prognostic and predictive factors.

This work was supported by Grant IGA MZ ČR No. NS10575-3.