Antitumor and antimetastatic effect of antimicrobial peptide conjugated with tumor homing peptide TMTP1 on the transplanted prostate cancer and gastric cancer in nude mice

Abstract

Due to their lower risk for induction of resistance, antimicrobial peptides with selective anticancer effect could be developed into a new generation of anticancer drugs. We conjugated an antimicrobial peptide with tumor-targeting peptides (TMTP1) to explore whether it has inhibiting effect on the progression and metastasis of transplanted prostate cancer and gastric cancer in nude mice. Subcutaneously transplanted human prostate cancer and orthotopically transplanted human gastric cancer in nude mice were prepared. 50 µmol/L PBS (control group), 50 µmol/L TMTP1 (TMTP1 group) or 50 µmol/L TMTP1-GG-D(KLAKLAK)(2) (treatment group) were injected i.p. to the three groups of nude mice, respectively. The binding ability of the novel fusion polypeptide TMTP1-GG-D(KLAKLAK)(2) to the tumors and its antitumor effect were assessed by measurement of tumor volume, histopathological examination of the tumor tissues, testing apoptosis index of tumor cells with TUNEL staining, and survival curve plotting of the mice. The median survival time of subcutaneous prostate cancer-bearing mice was 50 days in the control group, 55 days in the TMTP1 group, and 70 days in the TMTP1-GG-D(KLAKLAK)(2) group (P < 0.05). The median survival time of the subcutaneous gastric cancer-bearing mice was 25 days in the control group, 30 days in the TMTP1 group, and 45 days in the TMTP1-GG-D(KLAKLAK)(2) group (P < 0.01). The tumor volume in the subcutaneous prostate cancer-bearing mice was (2.5 ± 0.3)cm(3) in the control group, (1.8 ± 0.2) cm(3) in the TMTP1 group, and (0.3 ± 0.1)cm(3) in the TMTP1-GG-D(KLAKLAK)(2) group (P < 0.01). The tumor volume of the subcutaneous gastric cancer-bearing mice was (3.8 ± 0.4) cm(3) in the control group, (3.2 ± 0.2)cm(3) in the TMTP1 group, and (0.4 ± 0.1) cm(3) in the TMTP1-GG-D(KLAKLAK)(2) group (P < 0.01). Large tumors were observed in the stomach of the orthotopic gastric cancer-bearing mice of the control and TMTP1 groups. The tumor volume of the TMTP1-GG-D(KLAKLAK)(2) group was obviously reduced. White metastases in the liver, spleen and abdominal wall were observed in the control and TMTP1 groups (P < 0.01). TUNEL staining revealed that the apoptosis index of the control group was (31.9 ± 1.5)%, TMTP1 group (37.2 ± 2.3)% and TMTP1-GG-D(KLAKLAK)(2) group (69.7 ± 2.1)% (P < 0.01). The results of our study demonstrate that the novel fusion peptide of antimicriobial peptide conjugated with TMTP1 can effectively inhibit tumor progression and metastasis, therefore, is promising to be a novel effective anticancer drug.