Antitumor activity of recombinant antimicrobial peptide penaeidin-2 against kidney cancer cells.

Penaeidin-2 (Pen-2) is an important antimicrobial peptide derived from the Pacific white shrimp, Penaeus vannamei, and possesses both antibacterial and antifungal activities. Recent studies suggest that recombinant penaeidins show similar activities to the native Pen-2 protein. Previous researches have shown that some antimicrobial peptides (AMPs) exhibit cytotoxic activity against cancer cells. To date, there have been no studies on the antitumor effects of Pen-2. This study evaluated the potential of recombinant pen-2 (rPen-2) in the selective killing of kidney cancer cell lines ACHN and A498, and its action mechanism. MTT assays found the maximal growth inhibition of HK-2, ACHN and A498 cells treated with 100 µg/mL rPen-2 at 48 h was 13.2%, 62.4%, and 70.4%, respectively. DNA-specific fluorescent dye staining showed a high percentage of apoptosis on cancer cells. Flow cytometry revealed that the apoptosis rate of HK-2, ACHN and A498 cells was 15.2%, 55.2%, and 61.5% at 48 h respectively, suggesting that rPen-2 induced higher apoptosis rate in cancer cells than in HK-2 cells. Laser confocal scanning microscopy demonstrated that the plasma membrane was the key site where rPen-2 interacted with and destroyed tumor cells. Scanning electron microscopy showed the morphologic changes of the cell membranes of kidney cancer cells treated with rPen-2. These results suggest that rPen-2 is a novel potential therapeutic agent that may be useful in treating kidney cancers.

PcLT, a novel C-type lectin from Procambarus clarkii, is involved in the innate defense against Vibrio alginolyticus and WSSV.

Lectins play important roles in the innate immunity. In this work, a C-type lectin, PcLT, was obtained from Procambarus clarkii which contained a carbohydrate recognition domain (CRD) with the ability to bind to Vibrio alginolyticus and white spot syndrome virus (WSSV). RT-PCR and qRT-PCR analyses demonstrated PcLT was specifically expressed in the hepatopancreas and the mRNA was markedly upregulated by V. alginolyticus and WSSV challenge, although a slight difference in timing was observed. The study also revealed upregulation of the mRNA expression and activity of immunological factors, peroxinectin, phenoloxidase, and superoxide dismutase in hemolymph in response to recombinant PcLT (rPcLT). Moreover, rPcLT also enhanced the phagocytosis, facilitated the subsequent clearance of V. alginolyticus and prolonged the survival of WSSV-infected shrimp. These results suggested that PcLT not only served as a pathogen recognition receptor (PRR), but also functioned as an immune modulator, participating in host defense against invaders.