RHEB methylation in white blood cell, a novel candidate marker for breast cancer screening

Aberrant DNA methylation of tumor surrounding stromal cells is one of epigenetic changes, partly caused by the secretion of tumor cells. Here, we searched the tumor-induced DNA methylation profile in white blood cells (WBCs) caused by the secretion of breast cancer cell, that will be possible marker for breast cancer screening. Using DNA methylation microarray, we identified aberrant DNA methylated genes from co-culture model between healthy controls peripheral blood mononuclear cells (PBMCs) with 3 breast cancer cell lines. From bioinformatics analysis, six methylated CpG sites in 3 validation genes were selected for preliminary test to determine the most effective CpG sites for detection in breast cancer patient WBCs using methylation-specific polymerase chain reaction (MSP). After test, the cg03998173 of RHEB was selected as a validation gene with the result of 100% sensitivity and 80% specificity. Later, this methylation marker determined in the WBCs from 200 breast cancer patients and 200 healthy controls by SYBR green-based real-time MSP (RT-MSP). The RHEB methylation were detected in WBCs from 188 (94%) breast cancer patients and 59 (29.50%) healthy controls with high sensitivity of 94% and specificity of 70.50% (P-value < 0.0001). In conclusion, tumor-induced DNA methylation in WBCs caused by the secretion of breast cancer cells can be effective tumor marker for breast cancer screening. The RHEB methylation is a new highly sensitive and specific tumor marker from DNA methylation change in white blood cells of breast cancer patient blood. Therefore, the RHEB methylation may be considered as a tumor marker for breast cancer screening.