Decreased expression of Rab27A and Rab27B correlates with metastasis and poor prognosis in colorectal cancer.

The Rab27 subfamily of secretory small GTPase plays a vital role in vesicle trafficking and regulates tumor growth and metastasis in several cancer types. Thus, this research was designed to explore the clinical and prognostic significance of Rab27A and Rab27B in colorectal cancer (CRC) patients. Reverse transcription-polymerase chain reaction (RT-PCR), western blot, and immunohistochemistry (IHC) analysis were used to examine Rab27A and Rab27B expression in human CRC cell lines and primary tumors. The correlation of gene expression with clinicopathological features and prognosis was also evaluated. Our results indicated that Rab27A expression was down-regulated in primary tumors compared with matched adjacent tissues (100%, 8/8), as detected by western blot. IHC analysis revealed that the positive expression rate of Rab27A in primary CRC tissues was lower than in adjacent normal tissues (P = 0.005). Negative expression of Rab27A and Rab27B significantly correlated with poor tumor differentiation (both P < 0.001) and positive vascular invasion (P = 0.005, P = 0.021, respectively). Moreover, absence of Rab27A was associated with advanced tumor node metastasis (TNM) stage (P = 0.006), distant metastasis (P = 0.002), and local recurrence (P = 0.038). Survival analysis also showed a significant correlation between unfavorable survival and negative expression of Rab27A (P = 0.002). In addition, positive expression of both Rab27A and Rab27B was a protective factor in CRC. In conclusion, decreased expression of Rab27A and Rab27B, especially Rab27A, closely correlated with tumor progression and are valuable prognostic indicators in CRC patients.