Are there Relationships between the VDR-FokI Polymorphism and Vitamin D and the Insulin Resistance in Non-melanoma Skin Cancer (NMSC) Patients? A Protocol for Case-control Studies

Background and Objectives: Evidence indicate relationships between the sunlight exposure, vitamin D status and non-melanoma skin cancer (NMSC) risk. Vitamin D receptor (VDR) polymorphisms have been linked to metabolic changes in insulin resistance and various cancers. The purpose of this study is to investigate relationships between the sunlight exposure and the NMSC risk. Furthermore, relationships between the VDR FokI polymorphism and vitamin D status and the insulin resistance in NMSC patients will be assessed. Materials and Methods: A hospital-based case-control study is designed. Participants are randomly categorized into case and control groups. Eligible patients are adults who meet the inclusion criteria with verified diagnosis of NMSC with signed informed consents. Totally, 73 NMSC diagnosed cases and 72 healthy controls are recruited and their sunlight exposure data and genetic information are collected via interviews and high-resolution melting (HRM), respectively. Conclusions: There are controversial reports on the relevance of sunlight exposure to non-melanoma skin cancer risk due to the dual effect of UVB radiation on promoting vitamin D3 synthesis in the skin and increasing DNA damage leading to skin cancer. Results of this study provide data on how much sunlight exposure includes beneficial health effects with no skin cancer risks. Vitamin D status may affect risks of insulin resistance-linked diseases such as cancers. Findings will contribute to the current knowledge of the roles of vitamin D, insulin resistance and FokI polymorphism in skin cancer development.