Dihydroartemisinin (DHA) has recently attracted increasing attention for its low toxicity and high antitumor activity. DHA has been reported to have synergistic anticancer effects with a variety of drugs in the clinic; however, the molecular mechanism by which DHA inhibits tumorigenesis and improves oxaliplatin cytotoxicity in colon cancer cells is still not well understood. In this study, we found that DHA can inhibit cell proliferation and colony formation in a dose-dependent manner. Prohibitin 2 (PHB2) is a potential target by which DHA exerts its antitumor and cytotoxic effects.The function and molecular mechanism of PHB2 in colon cancer tumorigenesis were fully studied to determine the regulatory mechanism between DHA and PHB2. We found that PHB2, a mitochondrial inner membrane scaffold protein, has a higher expression level in colon cancer tissues than in adjacent nontumor tissues and is mainly localized in mitochondria. Overexpression of PHB2 can promote cell proliferation and colony formation in vitro and accelerate tumor growth in vivo. We also found that the expression level of PHB2 was inversely related to the cytotoxicity of DHA and oxaliplatin in colon cancer cells. The molecular mechanism of PHB2 in tumorigenesis and cancer therapy was further studied. The results showed that 20 μM DHA can downregulate PHB2 expression in a ubiquitylation-dependent manner and subsequently block PHB2-induced RCHY1 upregulation and p53 and p21 downregulation. In this process, RCHY1 is necessary for PHB2 to play a tumor-promoting role. Thus,

Objective As a member of the peptidyl arginine deiminase (PAD) family, PADI3 is weakly expressed in colon cancer tissues and highly expressed in adjacent colon cancer tissues. However, the role of PADI3 in colon cancer is unclear. In this study, we investigated the function and molecular mechanism of PADI3 in colon cancer tumorigenesis. Methods Western blot and real-time PCR were used to detect the expression levels of several genes. CCK-8, flow cytometry (FCM) and colony formation assays were used to examine cell proliferation, the cell cycle and colony formation ability. RNA-sequencing analysis was used to study the molecular mechanism of PADI3 in tumorigenesis. A truncation mutation experiment was performed to determine the key functional domain of PADI3. Results PADI3 overexpression inhibited cell proliferation and colony formation and led to G1 phase arrest in both HCT116 (originating from primary colon cancer) and LoVo (originating from metastatic tumor nodules of colon cancer) cells. PADI3-expressing HCT116 cells had a lower tumor formation rate and produced smaller tumors than control cells. PADI3 significantly decreased Sirtuin2 (Sirt2) and Snail expression and AKT phosphorylation and increased p21 expression, and Sirt2 overexpression partly reversed the effects induced by PADI3 overexpression. Immunocytochemistry showed that PADI3 is mainly localized in the cytoplasm. Truncation mutation experiments showed that the C-domain is the key domain involved in the antitumor activity of PADI3. Conclusions PADI3 suppresses Snail expression and AKT phosphorylation and promotes p21 expression by downregulating Sirt2 expression in the cytoplasm, and the C-domain is the key domain for its antitumor activity.

Sirtuin 2 (SIRT2), as a member of the sirtuin family, has representative features of evolutionarily highly conserved nicotinamide adenine dinucleotide (NAD+)-dependent deacetylase activity. In addition, SIRT2, as the only sirtuin protein colocalized with tubulin in the cytoplasm, has its own functions and characteristics. In recent years, studies have increasingly shown that SIRT2 can participate in the regulation of gene expression and regulate signal transduction in the metabolic pathway mainly through its post-translational modification of target genes; thus, SIRT2 has become a key centre in the metabolic pathway and participates in the pathological process of metabolic disorder-related diseases. In this paper, it is discussed that SIRT2 can regulate all aspects of gene expression, including epigenetic modification, replication, transcription and translation, and post-translational modification, which enables SIRT2 to participate in energy metabolism in life activities, and it is clarified that SIRT2 is involved in metabolic process-specific signal transduction mechanisms. Therefore, SIRT2 can be involved in metabolic disorder-related inflammation and oxidative stress, thereby triggering the occurrence of metabolic disorder-related diseases, such as neurodegenerative diseases, tumours, diabetes, and cardiovascular diseases. Currently, although the role of SIRT2 in some diseases is still controversial, given the multiple roles of SIRT2 in regulating physiological and pathological signal transduction, SIRT2 has become a key target for disease treatment. It is believed that with increasing research, the clinical application of SIRT2 will be promoted.