Vitamin D and Breast Cancer: Does Weight Make a Difference?

Vitamin D3 (cholecalciferol, colecalciferol) is one of type of vitamin D which is made by the skin when exposed to sunlight; it is also found in some foods and can be taken as a dietary supplement. It is used to treat and prevent vitamin D deficiency and associated diseases, including rickets. Vitamin D3 may have a role obesity and cancer biology. In the body, Vitamin D3 is metabolized to the active form 1,25-dihydroxycholecalciferol (calcitriol, 1,25-(OH)2vitamin D3).

This protocol is a randomized, controlled, and blinded clinical trial in obese and non-obese breast cancer patients in whom the effects of vitamin D supplementation will be evaluated in the neoadjuvant setting. Changes in biomarker expression levels in blood will be assessed from baseline to post-treatment (post-surgery).

Per protocol (see title), the treatment groups are defined as those participants with body mass index (BMI) ≤ 25 ("non-obese") and > 25 ("obese"). Within each treatment group, dose of Vitamin D3 was stratified between 400 IU/day (control) and 10,000 IU/day (experimental). All analyses were typically conducted between BMI cohorts stratified by Vitamin D3 dose.

Protocol Primary Objective: "To determine whether dietary vitamin D can reverse the negative effects of obesity and insulin resistance as reflected by changes in breast cancer gene expression patterns in obese and non obese subjects diagnosed with breast cancer."

Protocol Secondary Objectives: "To determine whether dietary vitamin D can reverse the negative effects of obesity and insulin resistance as reflected by serum biomarkers of insulin resistance and adipokine secretion in obese and non obese subjects diagnosed with breast cancer."

The following markers will be part of this study.

• Insulin-like growth factor-binding protein 3 (IGFBP-3) is a Vitamin D target, and the most abundant of 6 different IGFBPs. The insulin-like growth factors 1 and 2 (IGF-1 and IGF-2) binds to IGFBP-3 with high affinity, which helps lengthen the half-life of circulating IGFs in all tissues. Through this binding action, IGFBP-3 exerts anti-proliferative effects by blocking the ability of IGFs to activate the IGF-1 receptor (IGF1R, which stimulates cell proliferation). IGFBP-3 levels were assessed on the basis of mRNA levels.
• p21 [also known as p21Cip1; p21Waf1, cyclin-dependent kinase inhibitor 1 (CDKI1) or cyclin-dependent kinase (CDK)-interacting protein 1 (CDKIP1)] is the primary mediator of p53-dependent cell cycle arrest in response to DNA damage, and is a proliferation; apoptosis; and invasion biomarker. p21 is primarily associated with inhibition of CDK2, but is capable of inhibiting all cyclin/CDK complexes. p21 3 levels were assessed on the basis of mRNA levels.
• Matrix metalloproteinase-11 (MMP-11), aka Stromelysin-3 (SL-3), is involved in the breakdown of extracellular matrix in the disease processes of metastasis and arthritis, as well as various normal physiological processes, such as embryonic development, reproduction, and tissue remodeling. MMP-11 levels were assessed on the basis of mRNA levels.
• Ki-67 ("Antigen Identified By Monoclonal Antibody Ki-67", Antigen Ki67) is the protein produced by the gene MKI67, and is a nuclear protein that is associated with cellular proliferation and ribosomal RNA transcription. Ki-67 is a recognized biomarker for mitotic rate and cellular, but is absent in resting (quiescent) cells (Stage G0). In breast cancer, Ki67 identifies a subset of patients with ER-positive breast cancer that is highly proliferative, and who derive greater benefit from adjuvant chemotherapy. MKI67 levels were assessed on the basis of mRNA levels.
• ESR1 is the gene encoding estrogen receptor alpha (ERα), also known as NR3A1 (nuclear receptor subfamily 3, group A, member 1), and is a nuclear receptor that is activated by the sex hormone estrogen. ERα plays a role in the physiological development and function of a variety of organ systems to varying degrees, including the reproductive, central nervous, skeletal, and cardiovascular systems. Genetic polymorphisms in ESR1 have been associated with breast cancer. ESR1 levels were assessed on the basis of mRNA levels.
• Leptin is a stimulator of adipose stromal cell estrogen synthesis and a breast cancer growth promoter. Serum levels of leptin correlate with body mass index (BMI, a measure of obesity) and breast cancer risk. Leptin receptors are expressed by breast cancer cells and leptin can promote (regulate) breast cancer cell proliferation. Leptin levels were measured by Western blot or immunohistochemical (IHC) methodology.
• Adiponectin inhibits breast cancer growth. Adiponectin receptors are expressed by breast cancer cells and adiponectin can inhibit (regulate) breast cancer cell proliferation by stimulating apoptosis in estrogen receptor (ER)+ Breast cancer cells and suppressing estrogen-stimulated cell growth. Adiponectin levels were measured by Western blot or immunohistochemical (IHC) methodology.
• Homeostasis Model of Assessment - Insulin Resistance (HOMA-IR) is a standard determination of insulin resistance based on fasting insulin and glucose levels.
• cRP (C-reactive protein) is an inflammation marker produced by the liver. High levels of CRP in the blood are indicative of a wide variety of conditions, including cancer. cRP levels were measured by Western blot or immunohistochemical (IHC) methodology.