Loss of the vitamin D receptor in human breast and prostate cancers strongly induces cell apoptosis through downregulation of Wnt/β-catenin signaling

Abstract

Vitamin D co-regulates cell proliferation, differentiation and apoptosis in numerous tissues, including cancers. The known anti-proliferative and pro-apoptotic actions of the active metabolite of vitamin D, 1,25-dihydroxy-vitamin D [1,25(OH)2D] are mediated through binding to the vitamin D receptor (VDR). Here, we report on the unexpected finding that stable knockdown of VDR expression in the human breast and prostate cancer cell lines, MDA-MB-231 and PC3, strongly induces cell apoptosis and inhibits cell proliferation in vitro. Implantation of these VDR knockdown cells into the mammary fat pad (MDA-MB-231), subcutaneously (PC3) or intra-tibially (both cell lines) in immune-incompetent nude mice resulted in reduced tumor growth associated with increased apoptosis and reduced cell proliferation compared with controls. These growth-retarding effects of VDR knockdown occur in the presence and absence of vitamin D and are independent of whether cells were grown in bone or soft tissues. Transcriptome analysis of VDR knockdown and non-target control cell lines demonstrated that loss of the VDR was associated with significant attenuation in the Wnt/β-catenin signaling pathway. In particular, cytoplasmic and nuclear β-catenin protein levels were reduced with a corresponding downregulation of downstream genes such as Axin2, Cyclin D1, interleukin-6 (IL-6), and IL-8. Stabilization of β-catenin using the GSK-3β inhibitor BIO partly reversed the growth-retarding effects of VDR knockdown. Our results indicate that the unliganded VDR possesses hitherto unknown functions to promote breast and prostate cancer growth, which appear to be operational not only within but also outside the bone environment. These novel functions contrast with the known anti-proliferative nuclear actions of the liganded VDR and may represent targets for new diagnostic and therapeutic approaches in breast and prostate cancer.

Loss of the Vitamin D Receptor in Human Breast Cancer Cells Promotes Epithelial to Mesenchymal Cell Transition and Skeletal Colonization

“…For protein expression, cells were harvested at 24‐hours postplating. Western blot analysis was performed as described previously . Actin protein levels were used as loading controls.…”

“…We have recently demonstrated in mice that knockdown of the VDR in human breast (MDA‐MB‐231, MCF‐7) and prostate (PC3) cancer cell lines induces apoptosis and reduces tumor proliferation when cells are injected directly into the tissue. These effects were present both in vitro and in vivo, and independent of whether VDR knockdown cells were implanted orthotopically (ie, into the mammary fat pad/subcutaneous tissues) or at skeletal sites . However, although there is mounting evidence that VDR expression in malignant tumors is associated with neoplastic progression, the role of the VDR in the systemic metastatic spread of breast cancer cells to bone, and the molecular mechanisms involved in this process are unknown.…”

“…However, although there is mounting evidence that VDR expression in malignant tumors is associated with neoplastic progression, the role of the VDR in the systemic metastatic spread of breast cancer cells to bone, and the molecular mechanisms involved in this process are unknown. Notably, previous studies have not investigated VDR function in bone metastases despite the crucial role of vitamin D in bone metabolism . Employing an established rodent model of systemic cancer cell spread, the present study therefore aimed to define the role of the VDR in breast cancer metastasis to bone.…”

p62 functions as an oncogene in colorectal cancer through inhibiting apoptosis and promoting cell proliferation by interacting with the vitamin D receptor

“…12 Morphine-induced T-cell apoptosis is mediated through the downregulation of VDR and the activation of renin-angiotensin system (RAS). 18 In this study, we aimed to investigate the roles and molecular mechanisms of p62 in CRC. 14 Vitamin D is also important against bacterial infections.…”

Shiga‐like toxin I exerts specific and potent anti‐tumour efficacy against gastric cancer cell proliferation when driven by tumour‐preferential Frizzled‐7 promoter

“…[8][9][10] Among the 10 Frizzled family members, Frizzled-7 is the only evolutionarily conserved family member that regulates the development of the gastric system. [8][9][10] Among the 10 Frizzled family members, Frizzled-7 is the only evolutionarily conserved family member that regulates the development of the gastric system.…”