Gastric cancer is one of the most common malignant solid tumors in the world, especially in Asia with high mortality due to a lack of effective treatment. The potential usage of the newly constructed arginine-depleting enzyme—mono-PEGylated Bacillus caldovelox arginase mutant (BCA-M-PEG20), an effective drug against multiple cancer cell lines such as cervical and lung cancers, for the treatment of gastric cancer was demonstrated. Our results indicated that BCA-M-PEG20 significantly inhibited argininosuccinate synthetase (ASS)-positive gastric cancer cells, MKN-45 and BGC-823, while another arginine-depleting enzyme, arginine deiminase (ADI, currently under Phase III clinical trial), failed to suppress the growth of gastric cancer cells. In vitro studies demonstrated that BCA-M-PEG20 inhibited MKN-45 cells by inducing autophagy and cell cycle arrest at the S phase under 0.58 U/mL (IC50 values). Significant caspase-dependent apoptosis was induced in MKN-45 after the treatment with 2.32 U/mL of BCA-M-PEG20. In vivo studies showed that administrations of BCA-M-PEG20 at 250 U/mouse twice per week significantly suppressed about 50% of tumor growth in the MKN-45 gastric cancer xenograft model. Taken together, BCA-M-PEG20 demonstrated a superior potential to be an anti-gastric cancer drug.

Gastric cancer is one of the most common malignant solid tumors in the world, especially in Asia with high mortality due to a lack of effective treatment. With our newly constructed arginine-depleting enzyme - mono-PEGlyated Bacillus caldovelox arginase mutant (BCA-M-PEG20) drug against multiple cancer cell lines such as cervical and lung cancers, we have explored the potential usage of BCA-M-PEG20 for the treatment of gastric cancer. Our results indicated that BCA-M-PEG20 significantly inhibited argininosuccinate synthetase (ASS) positive gastric cancer cells, MKN-45 and BGC-823, while another arginine-depleting enzyme - arginine deiminase (ADI, currently under Phase III clinical trial), failed to suppress the growth of gastric cancer cells. In vitro studies demonstrated that our BCA-M-PEG20 inhibited MKN-45 cells by inducing autophagy and cell cycle arrest at the S phase under 0.58 U/mL (IC50 values). Significant caspase-dependent apoptosis was induced in MKN-45 after the treatment of 1.16–2.32 U/mL of BCA-M-PEG20. Our in vivo studies showed that administrations of BCA-M-PEG20 with 250 U/mouse twice per week significantly suppressed about 50% of tumor growth in the MKN-45 gastric cancer xenograft model. Taken together, BCA-M-PEG20 demonstrates a superior potential to be an anti-gastric cancer drug.

Growing evidence proves that amino acid restriction can reverse obesity by reducing adipose tissue mass. Amino acids are not only the building blocks of proteins but also serve as signaling molecules in multiple biological pathways. The study of adipocytes’ response to amino acid level changes is crucial. It has been reported that a low concentration of lysine suppresses lipid accumulation and transcription of several adipogenic genes in 3T3-L1 preadipocytes. However, the detailed lysine-deprivation-induced cellular transcriptomic changes and the altered pathways have yet to be fully studied. Here, using 3T3-L1 cells, we performed RNA sequencing on undifferentiated and differentiated cells, and differentiated cells under a lysine-free environment, and the data were subjected to KEGG enrichment. We found that the differentiation process of 3T3-L1 cells to adipocytes required the large-scale upregulation of metabolic pathways, mainly on the mitochondrial TCA cycle, oxidative phosphorylation, and downregulation of the lysosomal pathway. Single amino acid lysine depletion suppressed differentiation dose dependently. It disrupted the metabolism of cellular amino acids, which could be partially reflected in the changes in amino acid levels in the culture medium. It inhibited the mitochondria respiratory chain and upregulated the lysosomal pathway, which are essential for adipocyte differentiation. We also noticed that cellular interleukin 6 (IL6) expression and medium IL6 level were dramatically increased, which was one of the targets for suppressing adipogenesis induced by lysine depletion. Moreover, we showed that the depletion of some essential amino acids such as methionine and cystine could induce similar phenomena. This suggests that individual amino acid deprivation may share some common pathways. This descriptive study dissects the pathways for adipogenesis and how the cellular transcriptome was altered under lysine depletion.