Transcriptional analysis of estrogen receptor alpha variant mRNAs in colorectal cancers and their matched normal colorectal tissues

Estrogen is involved in suppression of colorectal cancer development and exerts its function via estrogen receptors α, β and their splicing variants. Whether the recently indentified ER-α splicing variants, ER-α36 and ER-α46, play a role in colorectal cancer development is unknown. In this study, we quantified the mRNA copy numbers of wild type ER-α (ER-α66), ER-α46 and ER-α36 in 35 colorectal cancers and their matched normal colorectal tissues by quantitative real-time PCR assay, and correlated their mRNA levels with the clinicopathological properties of the tumors. We found that ER-α66, ER-α46 and ER-α36 mRNAs were coexpressed in all colorectal cancers and their matched normal tissues. The decreased mRNA levels of ER-α36 and ER-α46 whereas no difference of ER-α66 mRNA was observed in colorectal cancers compared to their matched normal tissues. Moreover, change in the expression of ER-α36 mRNA level was correlated with Dukes’ stage of the tumor and the lymph node metastasis. ER-α36 mRNA was decreased significantly in Dukes’ C + D compared to Dukes’ A + B stage tumors (P = 0.017), and the expression of ER-α36 mRNA in N1/N2 was lower than that in N0 lymph node metastasis (P = 0.049). So ER-α36 and ER-α46 might be implicated in the development and progression of colorectal cancers.