Sequestsome-1/p62-targeted small molecules for pancreatic cancer therapy

Investigating synthetic lethality and PARP inhibitor resistance in pancreatic cancer through enantiomer differential activity

The RAD51-BRCA2 interaction is central to DNA repair through homologous recombination. Emerging evidence indicates RAD51 overexpression and its correlation with chemoresistance in various cancers, suggesting RAD51-BRCA2 inhibition as a compelling avenue for intervention. We previously showed that combining olaparib (a PARP inhibitor (PARPi)) with RS-35d (a BRCA2-RAD51 inhibitor) was efficient in killing pancreatic ductal adenocarcinoma (PDAC) cells. However, RS-35d impaired cell viability even when administered alone, suggesting potential off-target effects. Here, through multiple, integrated orthogonal biological approaches in different 2D and 3D PDAC cultures, we characterised RS-35d enantiomers, in terms of mode of action and single contributions. By differentially inhibiting both RAD51-BRCA2 interaction and sensor kinases ATM, ATR and DNA-PK, RS-35d enantiomers exhibit a 'within-pathway synthetic lethality' profile. To the best of our knowledge, this is the first reported proof-of-concept single small molecule capable of demonstrating this built-in synergism. In addition, RS-35d effect on BRCA2-mutated, olaparib-resistant PDAC cells suggests that this compound may be effective as an anticancer agent possibly capable of overcoming PARPi resistance. Our results demonstrate the potential of synthetic lethality, with its diversified applications, to propose new and concrete opportunities to effectively kill cancer cells while limiting side effects and potentially overcoming emerging drug resistance.

Exploring the Enigma: The Role of the Epithelial Protein Lost in Neoplasm in Normal Physiology and Cancer Pathogenesis

The cytoskeleton plays a pivotal role in maintaining the epithelial phenotype and is vital to several hallmark processes of cancer. Over the past decades, researchers have identified the epithelial protein lost in neoplasm (EPLIN, also known as LIMA1) as a key regulator of cytoskeletal dynamics, cytoskeletal organization, motility, as well as cell growth and metabolism. Dysregulation of EPLIN is implicated in various aspects of cancer progression, such as tumor growth, invasion, metastasis, and therapeutic resistance. Its altered expression levels or activity can disrupt cytoskeletal dynamics, leading to aberrant cell motility and invasiveness characteristic of malignant cells. Moreover, the involvement of EPLIN in cell growth and metabolism underscores its significance in orchestrating key processes essential for cancer cell survival and proliferation. This review provides a comprehensive exploration of the intricate roles of EPLIN across diverse cellular processes in both normal physiology and cancer pathogenesis. Additionally, this review discusses the possibility of EPLIN as a potential target for anticancer therapy in future studies.

SQSTM1/p62 promotes the progression of gastric cancer through epithelial-mesenchymal transition

Background

SQSTM1/p62 is an autophagy-related receptor protein that participates in regulating tumorigenesis and multiple signaling pathways. Gastric cancer (GC) is a common tumor in the digestive tract and continues to pose a significant threat to human health. Therefore, this study aims to investigate the impact of p62 on gastric cancer.

Methods

Immunohistochemistry and Western blotting were employed to assess the expression level of the p62 protein in gastric cancer tissues and its correlation with prognosis. Subsequently, in vitro cell experiments were conducted to determine the role of p62 in gastric cancer cell proliferation, migration, and metastasis.

Result

The expression of p62 in gastric cancer tissues was significantly higher than in normal tissues. The expression of p62 was positively correlated with poor prognosis in gastric cancer patients. In vitro cell experiments indicated that p62 promotes gastric cancer cell proliferation and migration. Mechanistically, elevated p62 expression induced epithelial-mesenchymal transition (EMT), leading to upregulation of E-cadherin and downregulation of N-cadherin and vimentin.

Conclusion

This study provides novel and robust evidence for the mechanism by which elevated p62 expression promotes the progression of gastric cancer. It offers promising therapeutic targets for anti-tumor treatment strategies in gastric cancer patients.

Nuclear-cytoplasmic translocation of SQSTM1/p62 protein enhances ESCC cell migration and invasion by stabilizing EPLIN expression

Esophageal squamous cell carcinoma (ESCC) is an aggressive malignant disease with a poor prognosis. We previously found that p62 presented a marked nuclear-cytoplasmic translocation in ESCC cells as compared that in normal esophageal epithelial cells, but its effects on ESCC cells remain unclear. This study aims to clarify the impacts of different cellular localization of p62 on the function of ESCC cells and the underlying molecular mechanisms. We here demonstrated that cytoplasmic p62 enhances the migration and invasion abilities of esophageal cancer cells, whereas nuclear p62 has no effect. We further explored the interaction protein of p62 by using GST pull-down experiment and identified EPLIN as a potential protein interacting with p62. In addition, reducing EPLIN expression significantly inhibited the migration and invasion of ESCC cells, which were rescued when EPLIN expression was restored after the p62 knockdown. At a molecular level, p62 in cytoplasm positively regulated the expression of EPLIN via enhancing its protein stability. Data from the TCGA and GEO database displayed a significant up-regulation of EPLIN mRNA expression in ESCC tissues compared with corresponding paired esophageal epithelial samples. Our findings present evidence that the nuclear-cytoplasmic translocation of p62 protein contributes to an aggressive malignancy phenotype, providing candidate molecular biomarkers and potential molecular targets for the diagnosis and treatment of ESCC.

p62 Is a Potential Biomarker for Risk of Malignant Transformation of Oral Potentially Malignant Disorders (OPMDs)

To determine the intracellular behavior of p62, a marker of selective autophagy, in oral potentially malignant disorders (OPMDs). This retrospective study includes 70 patients who underwent biopsy or surgical resection and were definitively diagnosed with OPMDs. Immunohistochemical staining for p62, XPO1, p53, and ki67 was performed on all samples and positive cell occupancy was calculated. We statistically investigated the correlation between protein expression in OPMDs and the association between malignant transformation, clinicopathological characteristics, and occupancy. ki67 expression was negatively correlated with p62 expression in the nucleus (p < 0.01) and positively correlated with p62 expression in the cytoplasm (p < 0.01). For malignant transformation, the expression of p62 in the nucleus (p = 0.03) was significantly lower in malignant transformation cases, whereas the expression of p62 in the cytoplasm (p = 0.03) and the aggregation expression (p < 0.01) were significantly higher. Our results suggest that the function of p62 is altered by its subcellular localization. In addition, defects in selective autophagy occur in cases of malignant transformation, suggesting that p62 is a potential biomarker of the risk of malignant transformation of OPMDs.

The emerging potential role of p62 in cancer treatment by regulating metabolism

p62 is an important multifunctional adaptor protein participating in autophagy and many other activities. Many studies have revealed that p62 is highly expressed in multiple cancers and decreasing its level can effectively lower the proliferation ability of cancer cells. Moreover, much research has highlighted the significant role of the regulation of cancer cell metabolism in helping to treat tumors. Recent reports demonstrate that p62 could regulate cancer cell metabolism through various mechanisms. However, the relationship between p62 and cancer cell metabolism as well as the related mechanisms has not been fully elucidated. In this review, we describe glucose, glutamine, and fatty acid metabolism in tumor cells and some signaling pathways that can regulate cancer metabolism and are mediated by p62.

Establishment of a Necroptosis-Related Prognostic Signature to Reveal Immune Infiltration and Predict Drug Sensitivity in Hepatocellular Carcinoma

Background: Hepatocellular carcinoma (HCC) is a common type of primary liver cancer and has a poor prognosis. In recent times, necroptosis has been reported to be involved in the progression of multiple cancers. However, the role of necroptosis in HCC prognosis remains elusive.

Methods: The RNA-seq data and clinical information of HCC patients were downloaded from The Cancer Genome Atlas (TCGA) and International Cancer Genome Consortium (ICGC) databases. Differentially expressed genes (DEGs) and prognosis-related genes were explored, and the nonnegative matrix factorization (NMF) clustering algorithm was applied to divide HCC patients into different subtypes. Based on the prognosis-related DEGs, univariate Cox and LASSO Cox regression analyses were used to construct a necroptosis-related prognostic model. The relationship between the prognostic model and immune cell infiltration, tumor mutational burden (TMB), and drug response were explored.

Results: In this study, 13 prognosis-related DEGs were confirmed from 18 DEGs and 24 prognostic-related genes. Based on the prognosis-related DEGs, patients in the TCGA cohort were clustered into three subtypes by the NMF algorithm, and patients in C3 had better survival. A necroptosis-related prognostic model was established according to LASSO analysis, and HCC patients in TCGA and ICGC were divided into high- and low-risk groups. Kaplan–Meier (K–M) survival analysis revealed that patients in the high-risk group had a shorter survival time compared to those in the low-risk group. Using univariate and multivariate Cox analyses, the prognostic model was identified as an independent prognostic factor and had better survival predictive ability in HCC patients compared with other clinical biomarkers. Furthermore, the results revealed that the high-risk patients had higher stromal, immune, and ESTIMATE scores; higher TP53 mutation rate; higher TMB; and lower tumor purities compared to those in the low-risk group. In addition, there were significant differences in predicting the drug response between the high- and low-risk groups. The protein and mRNA levels of these prognostic genes were upregulated in HCC tissues compared to normal liver tissues.

Conclusion: We established a necroptosis-related prognostic signature that may provide guidance for individualized drug therapy in HCC patients; however, further experimentation is needed to validate our results.