Anticancer bioactive peptide combined with docetaxel and its mechanism in the treatment of breast cancer.

Breast cancer remains a worldwide public-health issue. Novel drugs that increase the sensitivity and reduce the toxic side effects of chemotherapeutic agents are urgently required. The present study investigated the effect and mechanism of the short-term intermittent administration of an anticancer bioactive peptide (ACBP), docetaxel (DTX), ACBP combined with DTX (MIX) and ACBP combined with low dose DTX (L-MIX) to nude mice bearing human breast cancer tumors. The body weight, tumor length, tumor diameter, diet and water consumption of the tumor-bearing nude mice were calculated. The protein and mRNA expression levels of p53, p21 and Ki67 were detected via immunohistochemistry and reverse transcription-quantitative PCR, respectively. The results revealed that the activity level of each group of mice was consistent. However, the food and water consumption of the ACBP group was significantly increased compared with the NS group. Compared with the normal saline group, the tumor weights and volumes of the treatment groups were significantly decreased, indicating an inhibitory effect of the treatment. However, the MIX group exhibited lower tumor weights and volumes compared with the ACBP and DTX groups. Furthermore, no significant cell necrosis, edema or inflammatory cell infiltration was observed upon hematoxylin & eosin staining of the liver and spleen in all groups. The results also revealed that the p21, p53 and Ki67 protein and mRNA levels were decreased in the ACBP, DTX and MIX groups compared with the control group. Additionally, when compared with those in the MIX and L-MIX groups, the p21 and Ki67 protein, and p53 and Ki67 mRNA levels in the ACBP and DTX groups were significantly increased. The results suggested that the short-term intermittent use of ACBP alone had an inhibitory effect on tumor growth and improved the food and water consumption of tumor-bearing nude mice. Furthermore, the combination of ACBP and DTX reduced toxic side effects and the dosage requirement of drugs to achieve therapeutic effects on the tumor-bearing nude mice. Therefore, the antitumor effect of ACBP may be associated with the improvement of immune function in tumor-bearing nude mice and ACBP may serve an antitumor role via the p53-p21 signaling pathway in breast cancer.