Molecular Regulation of Breast Cancer Progression

背景：乳腺癌（BrCa）是女性中最常见的肿瘤，黑人女性发病率最高

Background: Cancer of the breast (BrCa) is the most frequent tumor in women, affecting black women most severely; BrCa is also more prevalent and morbid in military women. Localized primary carcinomas are often found and removed, curing up to 80% of the women and few men afflicted. Once the cancer has disseminated, current therapies, even newer biologics and immunotherapies, prolong life for just a few years. Signals and cell behaviors that enable metastatic survival and outgrowth of disseminated tumors are critical transition points. Our investigations during the present and previous Award periods demonstrated that upon dissemination to the ectopic microenvironment, the parenchymal cells direct the tumor cells to re-express epithelial markers including the defining E-cadherin. This cell-cell cohesion marker forms heterotypic binding that renders the tumor cells more resistant to killing by chemotherapies and death cytokines and down-regulate targets of immunotherapy. This protection from death signals proceeds through E-cadherin-triggered signaling involving at least the PI3 kinase-AKT pathway with the specific pathways being targeted herein. We also investigate that this epithelial reversion also likely leads to tumor cell dormancy, a complication of tumor dissemination. We have modeled this to demonstrate that quiescence of the entire organ underlies the dormancy, but that this non-proliferative state is plastic with stimulated cells being `awakened' and regaining an aggressive mesenchymal phenotype secondary to activation of the supporting nonparenchymal cells by specific stressors leads to inflammation-triggered outgrowth that will be investigated herein. Hypothesis: Our foundational model posits that E-cadherin-ligandation signals promote tumor cell dormancy and survival via select signaling pathways that can be targeted to reverse the chemo-resistance and possibly immune-escape. By discerning the operative signals and pathways we can develop novel approaches to micrometastases in targeting the emergent breast cancer cells. The interplay of tumor cells with cells of the metastatic microenvironment dictates both responsiveness to tumor-targeted therapies and dormancy/ outgrowth. This hypothesis leads to two linked questions – what are the mechanisms that confer the resistance of metastasis, and why do the tumor cells then later emerge from this dormant stage to grow as lethal tumors. These topics will lead to novel approaches by which these emergent carcinoma cells will be targeted. Specific Aims: Two linked but independent aims will be pursued simultaneously: I. Define the key tumor cell mechanisms that provide for resistance to killing in the micrometastatic niche and determine if targeting them can enhance chemosensitivity. E-cadherin promotes survival, at least in part, by signaling via the canonical AKT pathway, with our preliminary data supporting that targeting these intermediary kinases can abrogate the chemoresistance of metastasis. However, different AKT isoforms confound the efficacy. Enhanced chemo-sensitization will be established in a combination of preclinical models in culture, and innovative ex vivo microphysiological systems/bioreactor, and then validated in animal models. II. Determine the cues that activate the micrometastatic niche to trigger emergence from dormancy. Emergence from dormancy heralds the lethal stage of disseminated breast cancer. We found that the micro- metastatic niche both reflects and supports the quiescent during dormancy and activation driving outgrowth. We will determine critical signals in inflammatory response/tumor growth event for biomarker development and intervention using patient-derived tumor cells and serum specimens, validating in preclinical models. The successful completion of these experiments will shed new light on how to manipulate molecular controls of cell behavior that are subverted in breast carcinoma to promote progression. Validation of even components of our foundational model and our initial translational effort would highlight future avenues for rational interventions for the therapeutically refractory stage of cancer, clinically undetectable micrometastases.