Carboxypeptidase A4 promotes cell growth via activating STAT3 and ERK signaling pathways and predicts a poor prognosis in colorectal cancer.

Carboxypeptidase A4 (CPA4) is a novel cancer-related gene that is aberrantly expressed in various malignant tumors. However, the roles and mechanisms of CPA4 have not been explored in colorectal cancer (CRC). In this study, we investigated the functions and mechanisms by which CPA4 promotes CRC progression. Quantitative real-time PCR (qRT-PCR) and western blot showed that CPA4 mRNA and CPA4 protein levels were up-regulated in CRC compared to levels in adjacent normal tissue. Immunohistochemistry (IHC) results indicating high CPA4 levels were positively associated with poor prognoses. In addition, Cell Counting Kit-8 (CCK-8), colony formation, flow cytometry, and transwell assays demonstrated that CPA4 overexpression facilitated the growth of CRC cells, whereas CPA4 knockdown resulted in decreased proliferation, G1/S phase transition arrest, and apoptosis. Subcutaneous tumorigenesis was performed in nude mice to confirm the tumor-promoting effects of CPA4 in vivo. Western blot revealed that activation of the STAT3 and ERK pathways is one of the oncogenic functions of CPA4 in CRC. Accordingly, CPA4 promotes CRC cell growth via activating the STAT3 and ERK pathways and may be a prognostic factor or therapeutic target for CRC.

Carboxypeptidase A4 promotes proliferation and stem cell characteristics of hepatocellular carcinoma.

Carboxypeptidase A4 (CPA4), a member of the metallo-carboxypeptidase family, is overexpressed in liver cancer and is associated with cancer progression. The role of CPA4 in hepatocellular carcinoma (HCC) remains unclear. In this study, we aimed to evaluate the relevance of CPA4 to the proliferation and expression of stem cell characteristics of hepatocellular carcinoma cells. Western blot analysis showed high CPA4 expression in the liver cancer cell line Bel7402 and low expression in HepG2 cells. Knock-down of CPA4 decreased cancer cell proliferation as detected by MTT and clone formation assays. The serum-free culture system revealed that downregulated CPA4 suppressed the sphere formation capacities of tumour cells. However, upregulated CPA4 increased the proliferation and sphere formation capacity. In addition, the protein expression of CD133, ALDH1 and CD44 also increased in cells with upregulated CPA4. In vivo, the overexpression of CPA4 in tumour cells that were subcutaneously injected into nude mice markedly increased the growth of the tumours. These data suggest that CPA4 expression leads to poor prognoses by regulating tumour proliferation and the expression of stem cell characteristics and may therefore serve as a potential therapeutic target of HCC.

Mast cell chymase reduces the toxicity of Gila monster venom, scorpion venom, and vasoactive intestinal polypeptide in mice.

Mast cell degranulation is important in the pathogenesis of anaphylaxis and allergic disorders. Many animal venoms contain components that can induce mast cell degranulation, and this has been thought to contribute to the pathology and mortality caused by envenomation. However, we recently reported evidence that mast cells can enhance the resistance of mice to the venoms of certain snakes and that mouse mast cell-derived carboxypeptidase A3 (CPA3) can contribute to this effect. Here, we investigated whether mast cells can enhance resistance to the venom of the Gila monster, a toxic component of that venom (helodermin), and the structurally similar mammalian peptide, vasoactive intestinal polypeptide (VIP). Using 2 types of mast cell-deficient mice, as well as mice selectively lacking CPA3 activity or the chymase mouse mast cell protease-4 (MCPT4), we found that mast cells and MCPT4, which can degrade helodermin, can enhance host resistance to the toxicity of Gila monster venom. Mast cells and MCPT4 also can limit the toxicity associated with high concentrations of VIP and can reduce the morbidity and mortality induced by venoms from 2 species of scorpions. Our findings support the notion that mast cells can enhance innate defense by degradation of diverse animal toxins and that release of MCPT4, in addition to CPA3, can contribute to this mast cell function.