Weiss, H. L. | bioRxiv Science

bioRxiv2019

Integrin α6β4 signaling switches DNA repair from homologous recombination to non-homologous end-joining pathway to sensitize breast cancer cells to cisplatin

Integrin 6{beta}4 is highly expressed in triple negative breast cancer (TNBC) and drives aggressiveness by stimulating proliferation, angiogenesis, cell migration, invasion and metastasis. Signaling from this integrin stimulates DNA repair and apoptosis resistance, suggesting that it could contribute to therapeutic resistance. Upon testing this hypothesis, we found that integrin 6{beta}4 signaling promoted a three-fold greater sensitivity to cisplatin but exhibited no difference in response to other chemotherapies tested. Mechanistic investigations revealed that integrin 6{beta}4 stimulated quicker and higher amplitude of activation of ATM, Chk2, p53, and 53BP1, which required the integrin {beta}4 signaling domain. Genetic manipulation of gene expression demonstrated that mutant p53 cooperated with integrin 6{beta}4 for cisplatin sensitivity and was necessary for downstream phosphorylation of 53BP1 and enhanced ATM activation. Additionally, we discovered that integrin 6{beta}4 preferentially activated DNA-PKc in response to cisplatin, which led to formation of DNA-PKc-p53 complexes and 53BP1 activation. As a result, integrin 6{beta}4 shifted double strand break repair from homologous recombination (HR) to non-homologous end joining (NHEJ). In summary, we discovered a novel function of integrin 6{beta}4 in switching DSB repair from HR to NHEJ that results in cisplatin sensitivity in TNBC.

cancer biology↗

bioRxiv2018

Induction of AMPK activation by N,N-Diarylurea FND-4b decreases growth and increases apoptosis in triple negative and estrogen-receptor positive breast cancers

PurposeTriple negative breast cancer (TNBC) is the most lethal and aggressive subtype of breast cancer. AMP-activated protein kinase (AMPK) is a major energy regulator that suppresses tumor growth, and 1-(3-chloro-4-((trifluoromethyl)thio)phenyl)-3-(4-(trifluoromethoxy)phenyl)urea (FND-4b) is a novel AMPK activator that inhibits growth and induces apoptosis in colon cancer. The purpose of this project was to test the effects of FND-4b on AMPK activation, proliferation, and apoptosis in breast cancer with a particular emphasis on TNBC.\n\nMaterials and methods(i) Estrogen-receptor positive breast cancer (ER+BC; MCF-7, and T-47D), TNBC (MDA-MB-231 and HCC-1806), and breast cancer stem cells were treated with FND-4b for 24h. Immunoblot analysis assessed AMPK, acetyl-CoA carboxylase (ACC), ribosomal protein S6, cyclin D1, and cleaved PARP. (ii) Sulforhodamine B growth assays were performed after treating ER+BC and TNBC cells with FND-4b for 72h. Proliferation was also assessed by counting cells after 72h of FND-4b treatment. (iii) Cell death ELISA assays were performed after treating ER+BC and TNBC cells with FND-4b for 72h.\n\nResults(i) FND-4b increased AMPK activation with concomitant decreases in ACC activity, phosphorylated S6, and cyclin D1 in all subtypes. (ii) FND-4b decreased proliferation in all cells, while dose-dependent growth decreases were found in ER+BC and TNBC. (iii) Increases in apoptosis were observed in ER+BC and the MDA-MB-231 cell line with FND-4b treatment.\n\nConclusionsOur findings indicate that FND-4b decreases proliferation for a variety of breast cancers by activating AMPK and has notable effects on TNBC. The growth reductions were mediated through decreases in fatty acid synthesis (ACC), mTOR signaling (S6), and cell cycle flux (cyclin D1). ER+BC cells were more susceptible to FND-4b-induced apoptosis, but MDA-MB-231 cells still underwent apoptosis with higher dose treatment. Further development of FND compounds could result in a novel therapeutic for TNBC.

cancer biology↗