Strategies for successful primary treatment of HER2-positive breast cancer include use of the HER2 inhibitors trastuzumab or lapatinib in combination with standard chemotherapy. While successful, many patients develop resistance to these HER2 inhibitors indicating an unmet need. Consequently, current research efforts are geared toward understanding mechanisms of resistance and the signaling modalities that regulate these mechanisms. We have undertaken a study to examine whether signaling molecules downstream of epidermal growth factor receptor, which often act as compensatory signaling outlets to circumvent HER2 inhibition, can be co-targeted to overcome resistance. We identified JNK signaling as a potential area of intervention and now show that inhibiting JNK using the pan-JNK inhibitor, SP600125, is effective in the HER2-positive, resistant JIMT-1 xenograft mammary tumor model. We also investigate potential combination strategies to bolster the effects of JNK inhibition and find that co-targeting of JNK and the protein kinase HUNK can prohibit tumor growth of resistant HER2-positive mammary tumors in vivo.

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Tamoxifen is the most widely prescribed adjuvant therapy for estrogen receptor positive (ER+) breast cancer which comprises around 70% of all breast cancer cases. While many patients respond positively to tamoxifen treatment around 50% have de-novo resistance and approximately 30% of responsive tumors recur due to acquired drug resistance. Compared to European American women, African-American women with ER+ breast cancer, have worse progression-free and overall survival which coincides with increased resistance to anti-cancer therapies such as tamoxifen. Poor diet, low income, obesity and a lack of exercise are established lifestyle factors that are known to increase cancer burden and are often more prevalent in African American communities. Our research has identified a potential mechanistic link between sugar derived metabolites and estrogen receptor (ER) phosphorylation which provides a biological consequence of these established lifestyle factors which may directly impact tamoxifen therapy and minority health. Glycation is the non-enzymatic glycosylation of sugar moieties to biological macromolecules such as protein and DNA which produces reactive metabolites known as advanced glycation end products (AGE's). AGE's accumulate in our tissues as we grow older and drive many of the complications associated with diseases displaying health disparity including diabetes, metabolic syndrome, Alzheimer's and heart disease. Significantly, low income, obesity and an inactive lifestyle are established factors driving health disparity that also contribute to increased AGE accumulation levels in our bodies. In particular, AGE content in the Western Diet has consistently increased over the last 50 years due to increased consumption of sugar laden and cheap processed/manufactured foods which are high in reactive AGE metabolites and promote obesity. Due to the established links with lifestyle and cancer disparity we examined the biological effects of AGEs on tamoxifen therapy and found that elevated AGE levels can directly affect the response to tamoxifen treatment and promote tamoxifen resistance. AGE treatment in ER+ breast cancer cell models promoted tamoxifen resistance via the activation of the MAPK and AKT pathways leading to resistance associated changes in ERα phosphorylation. We also observed greater levels of AGE and its cognate receptor for AGE (RAGE) within breast cancer tumor and serum samples and showed a correlation between tumor progression and intra-tumoral AGE concentration. Strategies to eliminate or delay the occurrence of tamoxifen resistance would contribute to increasing overall survival in minority populations. By associating lifestyle-derived AGEs with tamoxifen resistance, opportunities exist for impacting cancer treatment initiatives arising through health and nutritional education and community outreach programs driven by basic, translational, epidemiological and cancer prevention research initiatives. Citation Format: Katherine R. Walter, Danzell M. Smith, Van Phan, Laura spruill, Marvella E. Ford, Victoria J. Findlay, David P. Turner. Defining the implications of sugar derived metabolites (AGEs) to tamoxifen resistance and breast cancer disparity: Is it a question of lifestyle? [abstract]. In: Proceedings of the Eighth AACR Conference on The Science of Health Disparities in Racial/Ethnic Minorities and the Medically Underserved; Nov 13-16, 2015; Atlanta, GA. Philadelphia (PA): AACR; Cancer Epidemiol Biomarkers Prev 2016;25(3 Suppl):Abstract nr C65.

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Poor diet, low income, obesity and a lack of exercise are established lifestyle factors that are known to increase cancer burden and are often more prevalent in African American communities. As our understanding of tumor biology advances, it is becoming increasingly clear that these inter-related lifestyle factors have distinct molecular consequences on the biological make-up of tumors, altering cell signaling events and gene expression profiles to contribute to cancer disparity outcomes such as its earlier development or its progression to more aggressive disease. Sparse information exists about the genetic and biological factors that contribute to differential cancer survival and mortality rates observed in minority populations. A greater understanding of the interplay between risk factors and the molecular mechanisms associated with cancer disparity will significantly impact minority health. Advanced glycation end products (AGEs) are reactive metabolites produced as a by-product of sugar metabolism. Failure to remove these highly reactive metabolites can lead to protein damage, aberrant cell signaling, increased stress responses, and decreased genetic fidelity. Critically, AGE accumulation is also directly affected by our lifestyle choices such as poor diet, low income, obesity and a lack of exercise. We recently reported a potential mechanistic link between AGEs and prostate cancer which may provide a molecular consequence of our lifestyle choices that can directly impact tumor biology and contribute to cancer disparity. We examined circulating and intra-tumoral AGE metabolite levels in clinical specimens and identified a race specific, tumor dependent pattern of accumulation in prostate cancer serum and tumor. Further mechanistic studies in immortalized prostate cancer cell lines show that AGE treatment increases the expression of the receptor for AGEs (RAGE) to activate cancer-associated signaling cascades. Loss of function studies show that AGE mediated increases in cancer associated processes was dependent upon RAGE expression. Significantly, we show that AGEs are secreted into the tumor microenvironment by cancer cells and may function as signaling molecules to promote immune cell recruitment. These data implicate the AGE-RAGE signaling axis as a potential biological mechanism promoting prostate cancer and may represent a biological mechanism promoting prostate cancer disparity. AGE metabolites may have high potential impact as prognostic/diagnostic markers and/or as a novel area of potential therapeutic intervention to reduce cancer disparity. Citation Format: Danzell M. Smith, Dion Foster, Van Phan, Victoria J. Findlay, Lourdes M. Nogueira, Laura Spruill, Mahtabuddin Ahmed, Judith D. Salley, Marvella E. Ford, David P. Turner. Mechanistic implications of advanced glycation end-products to prostate cancer and racial disparity. [abstract]. In: Proceedings of the Eighth AACR Conference on The Science of Health Disparities in Racial/Ethnic Minorities and the Medically Underserved; Nov 13-16, 2015; Atlanta, GA. Philadelphia (PA): AACR; Cancer Epidemiol Biomarkers Prev 2016;25(3 Suppl):Abstract nr C76.