Targeting Post-Translational Regulation of p53 in Colorectal Cancer by Exploiting Vulnerabilities in the p53-MDM2 Axis

The role played by the key tumor suppressor gene p53 and the implications of p53 mutations for the development and progression of neoplasia continue to expand. This review focuses on colorectal cancer and the regulators of p53 expression and activity identified over the past decade. These newly recognized regulatory mechanisms include (1) direct regulation of mouse double minute 2 homolog (MDM2), an E3 ubiquitin-protein ligase; (2) modulation of the MDM2-p53 interaction; (3) MDM2-independent p53 degradation; and (4) inhibition of p53 nuclear translocation. We positioned these regulatory mechanisms in the context of p53 missense mutations, which not only evade canonical p53 degradation machinery but also exhibit gain-of-function phenotypes that enhance tumor survival and metastasis. Lastly, we discuss current and potential therapeutic strategies directed against p53 mutant-bearing tumors.

Nuclear NAD+ homeostasis is essential for naive and chemoresistant BRCA1/2-deficient tumor survival

Resistance to PARP inhibitors (PARPi) is emerging as the major obstacle to their effectiveness for the treatment of BRCA1/2-mutated, also referred as homologous recombination (HR)-deficient, tumors (HRD). Over the years, mechanistic studies gained insights on effectors acting downstream of PARP1, lagging behind the understanding of earlier events upstream - and thus independent - of PARP1. Here, we investigated the role of nuclear NAD+, an essential cofactor for the activity of key DNA repair proteins, including PARP1 and sirtuins. We show that NMNAT1- the enzyme synthesizing nuclear NAD+ - is synthetically lethal with BRCA1/2 in a PARP1-independent but SIRT6-dependent manner. Consequently, inhibition of NMNAT1/SIRT6 axis not only kills naive but also PARPi-resistant HRD cancer cells. Our results unravel a unique vulnerability of HRD tumors, therapeutically exploitable even upon PARPi resistance development.

Circulating Expressions of Gonadotropin Releasing Hormones and Risk of Ovarian Cancer

Background: Ovarian cancer (OC) is a worst type of malignancy in the field of gynecology. This is because ovarian tumors diagnosed at advanced stage of disease. The exact mechanism for its development is still unknown. Aim: The aim of this study is to measure the levels of steroidal hormones and their function in ovarian cancer progression. Methods: In the present study, fifty ovarian cancer patients and fifty control individuals were taken and serum was separated from their blood samples. The levels of steroid hormones were measured by ELISA kit methods. Results: Result of the current study determined the levels of E2, progesterone, testosterone, FSH, LH, 17-β-HSD-I, 17-β-HSD-II, cortisol and aromatase were extensively higher in patient group in comparison with healthy individuals. Conclusion: Current study concluded the Study concluded that overexpression of steroid hormones may lead to enhance tumor survival in ovarian cancer through various signaling mechanisms. Keywords: Ovarian cancer, Estradiol, FSH, LH, progesterone

The IL32/BAFF Axis Supports Prosurvival Dialog in the Lymphoma Ecosystem and Is Disrupted By NIK Inhibition

Background Aggressive B-cell lymphomas, such as Mantle cell lymphoma (MCL), are microenvironment-dependent tumors but, in contrast to tumoral intrinsic anomalies, complex interplays within their ecosystems are largely ignored. A better understanding of these dialogs could provide new perspectives integrating the key role of the microenvironment to increase treatment efficiency of this hard to cure B-cell malignancy. Methods To identify novel molecular regulations occurring in lymphoma protective ecosystems, we performed a transcriptomic analysis based on the comparison of publicly available datasets from circulating (PB, n=77) versus MCL lymph nodes (LN, n=107) together with deep RNA sequencing of purified CD19+CD5+ MCL (n=8) versus normal B-cells (n=6). This integrated analysis led to the discovery of microenvironment-dependent and tumor-specific secretion of the cytokine IL32β by lymphoma cells. Using in situ multiplex immunohistochemistry , ex vivo models of primary MCL cells (n=23) and IL32 KO MCL cell lines (Crispr/Cas9), we studied the regulation and the functional impact of IL32β in the MCL context, especially in the dialog with tumor-associated macrophages. Results Among the 6887 genes differentially expressed in MCL LN compared to PB in vivo, 70% were confirmed in CD19+ MCL cells cocultured ex vivo and 39% were tumor-specific, that is to say not upregulated in cocultured normal B cells (NBC). Top-genes scoring revealed that IL32 was the most upregulated genes within the "Tumor-specific" transcriptional program. Using ex vivo models of primary MCL cells, we demonstrated that the microenvironment-dependent secretion of IL32β was controlled by the CD40/NFKB2 axis whereas its tumor specificity was the consequence of IL32 promoter hypomethylation in MCL compared to NBC. IL32 protein expression was confirmed in MCL LN in situ by multiplex IHC. The latter allowed the concurrent detection of MCL cells, T cells, macrophages and IL32. Consistently with the microenvironment-dependent induction of IL32 in MCL, we observed that IL32 expression was enriched in situ in tumor zones infiltrated with T cells, compared to tumor-exclusive zones. Based on in vitro experiments using IL32 KO MINO cells (Crispr/Cas9), we demonstrated that, through the secretion of IL32β, the tumor was able to corrupt its microenvironment by polarizing monocytes into specific protumoral CD163 mid MCL-associated macrophages, which secrete both pro- (e.g. IL6, OSM, IL1a/b) and anti- inflammatory (e.g. IL10, IDO, IL18, IL4L1) soluble factors. We next highlighted that IL32β-stimulated macrophages supported tumor survival mostly through a soluble dialog, which is driven by BAFF. Finally, we demonstrated the efficacy of selective NIK/alternative-NFkB inhibition to counteract both microenvironment-dependent induction of IL32β (RNA expression inhibition: 62 % ; n= 3) and BAFF-dependent survival of MCL cells (survival support inhibition : 47 % ; n=6). Conclusions In summary, our data uncovered the IL32β/BAFF axis as a previously undescribed pathway involved in MCL-associated macrophage polarization and tumor survival. Dependent on alternative-NFkB signaling, tumor-specific secretion of IL32β led to the corruption of the microenvironment through the polarization of monocytes into specific MCL-associated macrophages, which in turn favor tumor survival. While IL32β-stimulated macrophages secreted several protumoral factors, they supported MCL survival through BAFF and consequent alternative-NFkB activation in tumor cells. Our data shows that targeting IL32b, BAFF or the alternative NFkB pathway through NIK inhibition could also be of major interest for counteracting the multiple cross-talks that occur in the MCL microenvironment and, especially, the CD40L + T-cell / MCL / CD163 + MCL-associated macrophage triad. Figure 1 Figure 1. Disclosures No relevant conflicts of interest to declare.

Suppression of HSF1 activity by wildtype p53 creates a driving force for p53 loss-of-heterozygosity

The vast majority of human tumors with p53 mutations undergo loss of the remaining wildtype p53 allele (loss-of-heterozygosity, p53LOH). p53LOH has watershed significance in promoting tumor progression. However, driving forces for p53LOH are poorly understood. Here we identify the repressive WTp53–HSF1 axis as one driver of p53LOH. We find that the WTp53 allele in AOM/DSS chemically-induced colorectal tumors (CRC) of p53R248Q/+ mice retains partial activity and represses heat-shock factor 1 (HSF1), the master regulator of the proteotoxic stress response (HSR) that is ubiquitously activated in cancer. HSR is critical for stabilizing oncogenic proteins including mutp53. WTp53-retaining CRC tumors, tumor-derived organoids and human CRC cells all suppress the tumor-promoting HSF1 program. Mechanistically, retained WTp53 activates CDKN1A/p21, causing cell cycle inhibition and suppression of E2F target MLK3. MLK3 links cell cycle with the MAPK stress pathway to activate the HSR response. In p53R248Q/+ tumors WTp53 activation by constitutive stress represses MLK3, thereby weakening the MAPK-HSF1 response necessary for tumor survival. This creates selection pressure for p53LOH which eliminates the repressive WTp53-MAPK-HSF1 axis and unleashes tumor-promoting HSF1 functions, inducing mutp53 stabilization enabling invasion.

High-fat diet impairs ferroptosis and promotes cancer invasiveness via downregulating tumor suppressor ACSL4 in lung adenocarcinoma

Background Long-chain acyl-CoA synthetase-4 (ACSL4) is involved in fatty acid metabolism, and aberrant ACSL4 expression could be either tumorigenic or tumor-suppressive in different tumor types. However, the function and clinical significance of ACSL4 in lung adenocarcinoma remain elusive. Results ACSL4 was frequently downregulated in lung adenocarcinoma when analyzing both the TCGA database and the validation samples, and the lower ACSL4 expression was correlated with a worse prognosis. Using gene set enrichment analysis, we found that high ACSL4 expression was frequently associated with the oxidative stress pathway, especially ferroptosis-related proteins. In vitro functional studies showed that knockdown of ACSL4 increased tumor survival/invasiveness and inhibited ferroptosis, while ACSL4 overexpression exhibited the opposite effects. Moreover, high-fat treatment could also inhibit erastin-induced ferroptosis by affecting ACSL4 expression. The anti-tumor effects of ferroptosis inducers and the anti-ferroptosis effects of the high-fat diet were further validated using the mouse xenograft model. Conclusions ACSL4 plays a tumor-suppressive role in lung adenocarcinoma by suppressing tumor survival/invasiveness and promoting ferroptosis. Our study provided a theoretical reference for the application of ferroptotic inducers and dietary guidance for lung adenocarcinoma patients.

The Role of Tumor Microenvironment in Cancer Metastasis: Molecular Mechanisms and Therapeutic Opportunities

The tumor microenvironment (TME) regulates essential tumor survival and promotion functions. Interactions between the cellular and structural components of the TME allow cancer cells to become invasive and disseminate from the primary site to distant locations, through a complex and multistep metastatic cascade. Tumor-associated M2-type macrophages have growth-promoting and immunosuppressive functions; mesenchymal cells mass produce exosomes that increase the migratory ability of cancer cells; cancer associated fibroblasts (CAFs) reorganize the surrounding matrix creating migration-guiding tracks for cancer cells. In addition, the tumor extracellular matrix (ECM) exerts determinant roles in disease progression and cancer cell migration and regulates therapeutic responses. The hypoxic conditions generated at the primary tumor force cancer cells to genetically and/or epigenetically adapt in order to survive and metastasize. In the circulation, cancer cells encounter platelets, immune cells, and cytokines in the blood microenvironment that facilitate their survival and transit. This review discusses the roles of different cellular and structural tumor components in regulating the metastatic process, targeting approaches using small molecule inhibitors, nanoparticles, manipulated exosomes, and miRNAs to inhibit tumor invasion as well as current and future strategies to remodel the TME and enhance treatment efficacy to block the detrimental process of metastasis.

High Grade Glioma Surgery - Clinical Aspects and Prognosis

Introduction: High grade gliomas (HGG) are a group of tumors with infiltrative nature in general. Surgery is the first step in their treatment. It can be beneficial in two aspects: firstly, in establishing normal intracranial pressure and, secondly, in reducing the tumour volume. The choice of method depends on the location of the lesion, the expected grade of malignancy, and the general condition of the patient. Despite constant development of neuro-oncology and microsurgical techniques, the 5-year survival rate in patients with HGG remains less than 10% and the median survival is still less than 2 years.&nbsp; Aim: At present, there is no final therapeutic &ldquo;segment&rdquo; to provide a better outcome than the complex treatment of HGG. Moreover, the treatment&rsquo;s relative efficacy and recurrence of these tumours carry an additional problem. The aim of this study was to estimate the overall survival of patients with HGG operated in our clinic and compare it with literature data.&nbsp; Materials and methods: One hundred twenty-one cranial operations for HGG were reviewed (conducted between 2014 and 2019). Summary characteristics of the various parameters were presented in respect to the radical nature of the operative intervention using Kaplan-Meier analysis and chi square tests. All patients were followed up at regular check-ups. Results: HGGs were 103 or 85.12% of all gliomas operated for the 2014-2019 period. The most common cases were in the 51 to 60 age group. The cases in men were twice as common. The most common localization of the neoplasm is in the temporal region (36.36%) and the rarest was found in the occipital region (3.30%). It was estimated that our operated patients with HGG had 12.23 months over-all survival. Gross total resected patients had a median survival (OS) of 14.53 months, while subtotal resected patients had a median survival (OS) of 10.44 months. It is estimated 7.97 months free tumor survival period (time to relapse - FTS) for our operated patients with HGG. Gross total resected patients had a median FTS of 10.88 months, while subtotal resected patients had median FTS of 5.70 months. We noticed permanent new neurological deficit (NND) in 20 patients (19.45%) operated with GTR, and in 5 patients (4.85%) operated with STR.&nbsp; Conclusions: Median survival - OS, free tumor survival period - FTS and new neurological deficit - NND were statistically significant (p<0.05) with extent of resection &ndash; GTR or STR in our study. Maximal safe radical (total) or supratotal resection is preferred in treating HGG.&nbsp;