Breast cancer is the most common cancer type and the second cause of cancer death in women. Different mechanisms are contributed to the initiation and progression of the breast cancer. OCC-1 and APPL2 neighboring genes located in 12q.23.3 human chromosome region are related to colorectal cancer. Here, we intended to investigate OCC-1 newly reported transcript variants and APPL2 gene expression alteration in breast cancer specimens and investigate OCC-1 variants overexpression effect on APPL2 and on cell cycle status. Rt-qPCR analysis indicated that the expression level of OCC-1A/B and OCC-1D (not OCC-1C) transcript variants has been increased while, APPL2 gene expression level has been decreased in breast cancer specimen, compared to their normal pairs. Therefore, a negative correlation of expression is evident between APPL2 and OCC-1 genes in breast cancer specimen. Unlike OCC-1A/B which encodes a small protein, OCC-1D noncoding RNA overexpression lead to APPL2 downregulation in MCF7 cells. Consistently, OCC-1D overexpression resulted in increased sub-G1 cell population in MCF7 cells, detected by flow cytometry. Altogether, these results suggest that OCC1-D variant have an inhibitory effect on APPL2 expression and may regulate the cell cycle status.
Keywords: APPL2; Breast cancer; OCC-1 gene.