Abstract
Tryptophan metabolism plays a role in the occurrence and development of hepatocellular carcinoma cells. By degrading certain amino acids, tumor growth can be limited while maintaining the body’s normal nutritional requirements. Tryptophan side-chain oxidase (TSO) enzyme can degrade tryptophan, and its inhibitory effect on hepatocellular carcinoma cells is worthy of further study. To investigate the degradation effect on tryptophan, TSO was isolated and purified from qq Pseudomonas. The reaction products were identified with high performance liquid chromatography (HPLC) and high-performance liquid chromatography tandem mass spectrometry (HPLC-MS). De novo sequencing provided the complete amino acid sequence of TSO. The results of CCK-8, colony formation, transwell, and qPCR confirmed that TSO had inhibitory effects on the proliferation and migration of HCCLM3 (human hepatocarcinoma cell line) and HepG2 cells. The results of flow cytometry confirmed its apoptotic activity. In animal experiments, we found that the tumor-suppressive effect was better in the oncotherapy group than the intraperitoneal injection group. The results of immunohistochemistry also suggested that TSO could inhibit proliferation and promote apoptosis. In conclusion, a specific enzyme that can degrade tryptophan and inhibit the growth of hepatoma cells was authenticated, and its basic information was obtained by extraction/purification and amino acid sequencing.
Highlights
Hepatocellular carcinoma (HCC) is one of the most common malignant tumors worldwide, with more than 800,000 new cases and deaths each year [1]
The results showed that Tryptophan side-chain oxidase (TSO) could promote the apoptosiscould promote the apoptosis of HCCLM3 and cells, and that at thethis endotoxin content concentration had no effect of HCCLM3 and HepG2 cells, and thatHepG2 the endotoxin content concentration hadat nothis effect on cell growth
We found that tryptophan was completely degraded in the TSO group and in the TDO2 inhibitor combined with TSO group, with almost no kynurenine production
Summary
Hepatocellular carcinoma (HCC) is one of the most common malignant tumors worldwide, with more than 800,000 new cases and deaths each year [1]. Recent studies have shown that certain amino acids play an important role in the occurrence and development of tumors. Tryptophan, first extracted from casein by Hokinst in 1902, is one of the eight essential amino acids that cannot be synthesized in the human body It is an indispensable component of proteins and plays an important role in maintaining the physiological activities of plants and animals [18]. The development of antitumor drugs targeting tryptophan metabolism has been primarily based on the tumor-promoting functions of IDO1 and TDO to develop smallmolecule inhibitors of these enzymes for cancer treatments [31,32,33,34]. HPLC-MS was used to verify that TSO degraded tryptophan in tumor cells and prevented tryptophan from being metabolized in accordance with the canine urine pathway, partially inhibiting the proliferation and growth of tumor cells. We sequenced the amino acids of TSO, laying a foundation for future investigations of its targets and its development as an anticancer drug
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