Targeting ATR/CHK1 pathway in acute myeloid leukemia to overcome chemoresistance

Partners in crime: POPX2 phosphatase and its interacting proteins in cancer

Protein phosphorylation and dephosphorylation govern intracellular signal transduction and cellular functions. Kinases and phosphatases are involved in the regulation and development of many diseases such as Alzheimer’s, diabetes, and cancer. While the functions and roles of many kinases, as well as their substrates, are well understood, phosphatases are comparatively less well studied. Recent studies have shown that rather than acting on fewer and more distinct substrates like the kinases, phosphatases can recognize specific phosphorylation sites on many different proteins, making the study of phosphatases and their substrates challenging. One approach to understand the biological functions of phosphatases is through understanding their protein–protein interaction network. POPX2 (Partner of PIX 2; also known as PPM1F or CaMKP) is a serine/threonine phosphatase that belongs to the PP2C family. It has been implicated in cancer cell motility and invasiveness. This review aims to summarize the different binding partners of POPX2 phosphatase and explore the various functions of POPX2 through its interactome in the cell. In particular, we focus on the impact of POPX2 on cancer progression. Acting via its different substrates and interacting proteins, POPX2’s involvement in metastasis is multifaceted and varied according to the stages of metastasis.

Knockdown of DNA-binding protein A enhances the chemotherapy sensitivity of colorectal cancer via suppressing the Wnt/β-catenin/Chk1 pathway

DNA-binding protein A (dbpA) is reported to be upregulated in many cancers and associated with tumor progress. The present study aimed to investigate the role of dbpA in 5-fluorouracil (5-FU)-resistant and oxaliplatin (L-OHP)-resistant colorectal cancer (CRC) cells. We found that 5-FU and L-OPH treatment promoted the expression of dbpA. Enhanced dbpA promoted the drug resistance of SW620 cells to 5-FU and L-OHP. DbpA knockdown inhibited cell proliferation, induced cell apoptosis, and cell cycle arrested in SW620/5-FU and SW620/L-OHP cells. Besides, dbpA short hairpin RNA (shRNA) enhanced the cytotoxicity of 5-FU and L-OHP to SW620/5-FU and SW620/L-OHP cells. Meanwhile, dbpA shRNA inhibited the activation of the Wnt/β-catenin pathway that induced by 5-FU stimulation in SW620/5-FU cells. Activation of the Wnt/β-catenin pathway or overexpression of checkpoint kinase 1 (Chk1) abrogated the promoting effect of dbpA downregulation on 5-FU sensitivity of CRC cells. Importantly, downregulation of dbpA suppressed tumor growth and promoted CRC cells sensitivity to 5-FU in vivo. Our study indicated that the knockdown of dbpA enhanced the sensitivity of CRC cells to 5-FU via Wnt/β-catenin/Chk1 pathway, and DbpA may be a potential therapeutic target to sensitize drug resistance CRC to 5-FU and L-OHP.