Modulatory Effect of Curcumin on Expression of Methyltransferase/Demethylase in Colon Cancer Cells: Impact on wt p53, mutp53 and c-Myc.

Curcumin-mediated anti-cancer properties have been correlated with the inhibition of oncogenic molecules such as mutp53 and c-Myc. Their targeting is therapeutically significant, as p53, following point mutations, can acquire oncogenic functions, and c-Myc overexpression, due to translocations, point mutations, protein/protein interactions, or epigenetic modifications, plays a central role in cancer cell proliferation and metabolic reprogramming, particularly in colorectal cancer. In a previous study, we showed that curcumin strongly downregulated mutp53 while activating wtp53 and reduced the expression of methyltransferases such as EZH2, G9a, and MLL-1 in colon cancer cells.

Mutant p53 upregulates HDAC6 to resist ER stress and facilitates Ku70 deacetylation, which prevents its degradation and mitigates DNA damage in colon cancer cells.

Cancer cells employ interconnected mechanisms to withstand intrinsic and extrinsic stress, with mutant p53 (mutp53) playing a key role in bolstering resistance to endoplasmic reticulum (ER) stress. In this study, we further investigated this phenomenon, focusing on the DNA damage triggered by ER stress. Our findings indicate that mutp53 mitigates ER stress-induced DNA damage by sustaining high levels of Ku70, a critical protein in DNA repair via the non-homologous end joining (NHEJ) pathway, which functions alongside Ku80.

Changes in Lysine Methylation Contribute to the Cytotoxicity of Curcumin in Colon Cancer Cells.

Epigenetic abnormalities play a critical role in colon carcinogenesis, making them a promising target for therapeutic interventions. In this study, we demonstrated that curcumin reduces colon cancer cell survival and that a decrease in lysine methylation was involved in such an effect. This correlated with the downregulation of methyltransferases EZH2, MLL1, and G9a, in both wild-type p53 (wtp53) HCT116 cells and mutant p53 (mutp53) SW480 cells, as well as SET7/9 specifically in wtp53 HCT116 cells.

EZH2 Inhibition by DS3201 Triggers the Kaposi's Sarcoma-Associated Herpesvirus Lytic Cycle and Potentiates the Effects Induced by SAHA in Primary Effusion Lymphoma Cells.

Primary Effusion Lymphoma (PEL) cells carry Kaposi's sarcoma-associated herpesvirus (KSHV) in a latent state, except for a small number of cells in which the virus replicates to ensure its persistence into the infected host. However, the lytic cycle can be reactivated in vitro by exposing these lymphoma cells to various treatments, leading to cell lysis. To restrict viral antigen expression, KSHV induces repressive epigenetic changes, including DNA methylation and histone modifications.

Post-Translational Modifications (PTMs) of mutp53 and Epigenetic Changes Induced by mutp53.

Wild-type (wt) p53 and mutant forms (mutp53) play a key but opposite role in carcinogenesis. wtP53 acts as an oncosuppressor, preventing oncogenic transformation, while mutp53, which loses this property, may instead favor this process. This suggests that a better understanding of the mechanisms activating wtp53 while inhibiting mutp53 may help to design more effective anti-cancer treatments.

SAHA/5-AZA Enhances Acetylation and Degradation of mutp53, Upregulates p21 and Downregulates c-Myc and BRCA-1 in Pancreatic Cancer Cells.

Epigenetic changes are common in cancer and include aberrant DNA methylation and histone modifications, including both acetylation or methylation. DNA methylation in the promoter regions and histone deacetylation are usually accompanied by gene silencing, and may lead to the suppression of tumor suppressors in cancer cells. An interaction between epigenetic pathways has been reported that could be exploited to more efficiently target aggressive cancer cells, particularly those against which current treatments usually fail, such as pancreatic cancer.

5-AZA Upregulates SOCS3 and PTPN6/SHP1, Inhibiting STAT3 and Potentiating the Effects of AG490 against Primary Effusion Lymphoma Cells.

Epigenetic modifications, including aberrant DNA methylation occurring at the promoters of oncogenes and oncosuppressor genes and histone modifications, can contribute to carcinogenesis. Aberrant methylation mediated by histone methylatransferases, alongside histones, can affect methylation of proteins involved in the regulation of pro-survival pathways such as JAK/STAT and contribute to their activation. In this study, we used DNA or histone demethylating agents, 5-Azacytidine (5-AZA) or DS-3201 (valemetostat), respectively, to treat primary effusion lymphoma (PEL) cells, alone or in combination with AG490, a Signal transducer and activator of transcription 3 (STAT3) inhibitor.

HSP110 Inhibition in Primary Effusion Lymphoma Cells: One Molecule, Many Pro-Survival Targets.

Heat shock proteins (HSPs) are highly expressed in cancer cells and represent a promising target in anti-cancer therapy. In this study, we investigated for the first time the expression of high-molecular-weight HSP110, belonging to the HSP70 family of proteins, in Primary Effusion Lymphoma (PEL) and explored its role in their survival. This is a rare lymphoma associated with KSHV, for which an effective therapy remains to be discovered.

NFE2L2 and STAT3 Converge on Common Targets to Promote Survival of Primary Lymphoma Cells.

NFE2L2 and STAT3 are key pro-survival molecules, and thus, their targeting may represent a promising anti-cancer strategy. In this study, we found that a positive feedback loop occurred between them and provided evidence that their concomitant inhibition efficiently impaired the survival of PEL cells, a rare, aggressive B cell lymphoma associated with the gammaherpesvirus KSHV and often also EBV. At the molecular level, we found that NFE2L2 and STAT3 converged in the regulation of several pro-survival molecules and in the activation of processes essential for the adaption of lymphoma cells to stress.