PADI3 induces cell cycle arrest via the Sirt2/AKT/p21 pathway and acts as a tumor suppressor gene in colon cancer

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.RNAsequencing 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.

miR-573 is a negative regulator in the pathogenesis of rheumatoid arthritis

Rheumatoid arthritis （RA） is a chronic autoimmune disease characterized by abnormal inflammation, angiogenesis, and cartilage destruction. Our previous study demonstrated an increased expression of thioredoxin domain containing 5 （TXNDC5） in the synovial tissues of RA, and its overexpression was implicated in RA pathology. Although TXNDC5 variation is linked to genetic susceptibility to RA, the regulation of its abnormal expression has not been well defined. Here, we show that TXNDC5 is directly targeted by microRNA （miR）-573, and TXNDC5, in turn, mediates the suppressive effect of miR-573 on the invasion of synovial fibroblasts of RA （RASFs）. miR-573 overexpression suppressed the expression of interleukin 6 （I L-6） and cyclooxygenase 2 in RASFs, as well as the production of tumor necrosis factor-alpha and interleukin- 1 beta by activated THP-1 cells in response to lipopolysaccharide （LPS） stimulation. Moreover, treatment with conditioned medium of RASFs transfected with miR-573 mimic inhibited the angiogenic ability of human umbilical vein endothelial cells （HUVECs）. Of note, epidermal growth factor receptor and Toll-like receptor 2 were validated as new direct targets of miR-573, and mediate the regulation of miR-573 on IL-6 production as well as the angiogenesis of HUVECs. In addition, exogenous miR-573 expression suppressed the activation of mitogen-activated protein kinase （MAPK）, signal transducer and activator of transcription 3, and phosphatidylinositol-3 kinase/activate protein kinase B in RASFs in response to LPS. Indeed, MAPK signaling was essential to ensure the function of miR-573. Taken together, our study points toward the protective roles of miR-573 in the pathological process of RA and suggests a potential target in the treatment of RA.