Expression of the Microtubule-Associated Protein MAP9/ASAP and Its Partners AURKA and PLK1 in Colorectal and Breast Cancers

Background. Colorectal and breast cancers are among the most common cancers worldwide. They result from a conjugated deficiency of gene maintenance and cell cycle control. Objective. We investigate the expression of the microtubule-associated protein MAP9/ASAP and its two partners AURKA and PLK1 in colorectal tumors as well as in ductal breast cancers. Materials and Methods. 26 colorectal cancer samples and adjacent normal tissues and 77 ductal breast cancer samples from grade I to grade III were collected. Real-time quantitative PCR was used to analyse the expression of MAP9, AURKA, and PLK1. Results. Expression of MAP9 is downregulated in colorectal cancer compared to normal tissues (P > 10(-3)), whereas those of AURKA and PLK1 are upregulated (P > 10(-4)). In ductal breast cancer, we found a grade-dependent increase of AURKA expression (P > 10(-3)), while the variations of expression of MAP9 and PLK1 are not significant (P > 0.2). Conclusions. MAP9 downregulation is associated with colorectal malignancy and could be used as a disease marker and a new drug target, while AURKA and PLK1 are upregulated. In ductal breast cancer, AURKA overexpression is strongly associated with the tumor grade and is therefore of prognostic value for the progression of the disease.