Vitamin D Regulates CXCL12/CXCR4 and Epithelial-to-Mesenchymal Transition in a Model of Breast Cancer Metastasis to Lung

Abstract

Vitamin D deficiency is associated with poor cancer outcome in humans, and administration of vitamin D or its analogs decreases tumor progression and metastasis in animal models. Using the mouse MMTV-PyMT model of mammary cancer, we previously demonstrated a significant acceleration of carcinogenesis in animals on a low vitamin D diet and a reduction in spontaneous lung metastases when mice received vitamin D through perfusion. We investigate here the action mechanism for vitamin D in lung metastasis in the same non-immunodeficient model and demonstrate it involves the control of epithelial to mesenchymal transition as well as interactions between chemokine CXCL12 and its receptor CXCR4. In vitro, 10 -9M vitamin D treatment modifies the phenotype of MMTV-PyMT primary mammary tumor cells and significantly decreases their invasiveness and mammosphere formation capacity by 40 and 50% respectively. Vitamin D treatment also inhibits p-STAT3, Zeb1 and vimentin by 52%, 75% and 77% respectively, and increases E-cadherin by 87%. In vivo, dietary vitamin D deficiency maintains high levels of Zeb1 and p-STAT3 in cells from primary mammary tumors, and increases CXCL12 expression in lung stroma by 64%. In lung metastases, vitamin D deficiency increases CXCL12/CXCR4 co-localization by a factor of 2.5. These findings indicate an involvement of vitamin D in mammary cancer ”seed” (primary tumor cell) and ”soil” (metastatic site), and link vitamin D deficiency to epithelial-to-mesenchymal transition (EMT), CXCL12/CXCR4 signaling and accelerated metastasis, suggesting vitamin D-repleteness in breast cancer patients could enhance the efficacy of co-administered therapies in preventing spread to distant organs.

Vitamin D and Breast Cancer: Mechanistic Update

“…In vitro, 1,25D partially reversed the EMT phenotype (decreased invasion/motility) as evidenced by reduction in pSTAT3, ZEB1, and vimentin and increase in E-cadherin. (21,(95)(96)(97)(98) Furthermore, dietary vitamin D inhibited EMT and lung metastasis via reduction in ZEB1 and STAT3 expression in the MMTV-PyMT model of breast cancer. (21) In a xenograft model of human breast cancer, depletion of VDR promoted EMT and enhanced skeletal colonization.…”

“…(21,(95)(96)(97)(98) Furthermore, dietary vitamin D inhibited EMT and lung metastasis via reduction in ZEB1 and STAT3 expression in the MMTV-PyMT model of breast cancer. (21) In a xenograft model of human breast cancer, depletion of VDR promoted EMT and enhanced skeletal colonization. (23) Vitamin D signaling and stem cells One of the consequences of EMT is the emergence of cells that express markers and properties of mammary progenitor (stem) cells.…”

“…Indeed, it was rapidly established that 1,25D and a variety of synthetic VDR agonists exerted anticancer effects (including cell cycle arrest, (15) apoptosis, (16) and differentiation (17) ) in VDR-positive breast cancer cells in vitro as well as in some animal tumor models. (18)(19)(20) Other effects of 1,25D that were demonstrated in various breast cancer model systems included blockade of epithelial-mesenchymal transition (EMT), (21,22) invasion, (19) metastasis, (23)(24)(25) and energy metabolism, (25)(26)(27)(28)(29)(30) as well as induction of autophagy. (31)(32)(33)(34)(35) However, the specific mechanisms and pathways that link the 1,25D-VDR complex to the observed biological effects remain elusive and appear to be highly cell type specific based on mechanistic studies and genomic profiling as described below.…”

“…This research Tumor cells were studied ex vivo. (21) Vitamin D deficiency enhanced lung metastasis in vivo and markers of epithelial-mesenchymal transition (EMT) in vitro. Mechanisms identified included co-localization of chemokine CXCL12 and its receptor CXCR4 in the lung metastatic niche and increased expression of pSTAT3 and ZEB1 (EMT drivers).…”

Vitamin D as a Potential Preventive Agent For Young Women's Breast Cancer

“…In xenograft models of breast cancer, vitamin D deficiency (10,52) and loss of VDR expression (13,40) increase breast cancer metastasis, through promotion of angiogenesis and vascularization (66). In the MMTV-PyMT mouse model, dietary vitamin D deficiency increases metastatic burden in the lung (10,70), an effect likely mediated through increased CXCL12/CXCR4 signaling within the metastatic niche (70). Together, these observations suggest that vitamin D deficiency may establish a proangiogenic environment supportive of tumor cell dissemination, metastasis, and establishment at the secondary site; and implicate vitamin D as a potential therapeutic for the prevention and possible management of advanced, metastatic disease.…”