Biomarkers of metastatic tumor microenvironment induced drug resistance

B59

Metastasis and drug resistance are major hurdles in curative cancer treatment. More attention is needed in decoding these aspects of cancer in order to develop more effective therapies. Recently we have discovered that the invasive mammary cancer cells in rodent models are resistant to chemotherapeutic drugs. Identification of molecular markers for both invasive and drug resistant cells from within the primary tumor would open a new vista in cancer molecular diagnosis. These would also potentially identify new pathways for therapeutic intervention which will be a useful adjunct to conventional therapies, interfering with tumor progression at several pivotal points.
 We have developed an in vivo invasion assay, which provides an opportunity to collect primary tumor cells that are actively in the process of invasion. The in vivo invasion assay has been combined with array-based gene expression analyses to investigate the gene expression patterns of carcinoma cells in primary mammary tumors during invasion. The expression of genes involved in cell division and survival, and cell motility were most dramatically changed in invasive cells indicating a population that is neither dividing nor apoptotic but intensely motile. We have performed biological assays to show in two different rodent models that the invasive carcinoma cells are hypoproliferative and drug resistant even before any therapeutic intervention is done on them. This invasion signature provides a general resource of possible targets for future anti-invasion and drug resistance therapy. Currently we are identifying biomarkers that can predict the potentially invasive and drug resistant cells in the primary tumor. We are utilizing unique RNA amplification methods along with in situ amplification and detection methods to detect the biomarker RNA either from or in the tissue.
 We have also performed florescence microscopy on the invasive mammary cancer cells to determine their cell surface marker expression. Work is in progress to perform fluorescence microscopy and flowcytometry on the invasive cells to identify selective expression and stability of expression of different protein biomarkers belonging to the invasion signature as well as the drug resistance pathways. We have also been successful in isolating the cancer cells at different steps of the metastatic process and studied their gene expression pattern and have identified a set of genes whose expression is altered transiently due to the tumor microenvironment.