Abstract P6-01-03: Decreasing the metastatic potential in Triple Negative Breast Cancer through the miR-17 cluster

Background: In animal models of breast cancer, caloric restriction (CR), or a 25–30% reduction of calories, has decreased tumor initiation and progression. We sought to determine if CR could be used as a novel therapeutic intervention to enhance cytotoxic therapies such as radiation (RT) and alter the molecular profile of triple negative breast cancer (TNBC), which displays a poor prognosis. Methods/Results: In two murine models of TNBC (4T1 which is highly metastatic and 67NR which is locally aggressive), mice with palpable tumors were treated with radiation, caloric restriction (30% intake reduction) or both. 3 times per week measurements revealed significant tumor regression with RT or diet modification, and an even greater regression is observed combining diet modification with RT. Concurrently, many reports have shown that TNBC is most distinct from other breast tumor subtypes due to up-regulation of the miR-17-92 cluster which we have shown by RT-PCR is downregulated with both CR and radiation (RT) and even further decreased with the combination. cDNA arrays done on all conditions revealed that the top 5 statistically significant GO terms with high fold changes were all associated with extracellular matrix and metastases. In silico analysis demonstrated 5 ECM related genes that were targets of the miR-17 cluster: collagen 4 alpha 1 (COL4A1), collagen 4 alpha 3 (COL4A3), laminin alpha 3 (LAMA3), metallopeptidase inhibitor 2 and 3 (TIMP2 and TIMP3) and these were inversely correlated with the miRs. Conclusions: CR, or altering the metabolism of breast cancer, can be combined with RT to decrease progression of TNBC tumors and that the miR-17-92 cluster is also decreased with these conditions. cDNA arrays suggest that extracellular matrix (ECM) proteins play a large role in the mechanism of action of CR and RT combined. Combination therapy with CR and RT can decrease the metastatic potential in TNBC and in part does this through the miR-17-92 cluster by way of controlling ECM. Citation Information: Cancer Res 2012;72(24 Suppl):Abstract nr P6-01-03.