[Preliminary study on relationship between multi-drug resistance-associated protein 4 and radiosensitivity of rectal cancer].

Objective: To explore the correlation between multi-drug resistance-associated protein 4(MRP4) and the sensitivity of rectal cancer to radiation.

Methods: A total of 95 patients with advanced rectal cancer and received radiation therapy between January 2000 and January 2009. MRP4 and P53 protein expression in the paraffin-embedded specimen were detected by immunohistochemistry. Logistic regression analysis was used to evaluate factors associated with the sensitivity of rectal cancer to radiation.

Results: Forty patients(42%) were sensitive to radiation therapy, of whom 10(11%) achieved pathological complete remission. Fifty-five patients were (58%) not responsive to radiation. Patients with low expression of MRP4 had a 66.7%(24/36) response rate, significantly higher than that of patients with high MRP4 expression (29.1%,16/59)(P<0.05). Patients with low expression of P53 had a 63.9%(23/36) response rate, significantly higher than that of patients with high P53 expression(28.8%,17/59)(P<0.01). The response rate after long course radiation therapy was 83.3%(20/24), significantly higher than that of patients who underwent short and medium course radiation[(31.3%, 5/16) and(27.3%,15/55)](P<0.01). Multivariate Logistic regression analysis showed radiation regimen, the expression of P53 and MRP4 protein were independently associated with the sensitivity of rectal cancer to radiation(P<0.05).

Conclusion: MRP4 may serve as a predictive marker for the sensitivity of rectal cancer to preoperative radiation.