Role of Diacylglycerol Kinases in Acute Myeloid Leukemia.

Diacylglycerol kinases (DGKs) play dual roles in cell transformation and immunosurveillance. According to cancer expression databases, acute myeloid leukemia (AML) exhibits significant overexpression of multiple DGK isoforms, including DGKA, DGKD and DGKG, without a precise correlation with specific AML subtypes. In the TGCA database, high DGKA expression negatively correlates with survival, while high DGKG expression is associated with a more favorable prognosis. DGKA and DGKG also feature different patterns of co-expressed genes. Conversely, the BeatAML and TARGET databases show that high DGKH expression is correlated with shorter survival. To assess the suitability of DGKs as therapeutic targets, we treated HL-60 and HEL cells with DGK inhibitors and compared cell growth and survival with those of untransformed lymphocytes. We observed a specific sensitivity to R59022 and R59949, two poorly selective inhibitors, which promoted cytotoxicity and cell accumulation in the S phase in both cell lines. Conversely, the DGKA-specific inhibitors CU-3 and AMB639752 showed poor efficacy. These findings underscore the pivotal and isoform-specific involvement of DGKs in AML, offering a promising pathway for the identification of potential therapeutic targets. Notably, the DGKA and DGKH isoforms emerge as relevant players in AML pathogenesis, albeit DGKA inhibition alone seems insufficient to impair AML cell viability.

Wiskott-Aldrich syndrome protein interacts and inhibits diacylglycerol kinase alpha promoting IL-2 induction.

Background: Phosphorylation of diacylglycerol by diacylglycerol-kinases represents a major inhibitory event constraining T cell activation upon antigen engagement. Efficient TCR signalling requires the inhibition of the alpha isoform of diacylglycerol kinase, DGKα, by an unidentified signalling pathway triggered by the protein adaptor SAP. We previously demonstrated that, in SAP absence, excessive DGKα activity makes the T cells resistant to restimulation-induced cell death (RICD), an apoptotic program counteracting excessive T cell clonal expansion. Results: Herein, we report that the Wiskott-Aldrich syndrome protein (WASp) inhibits DGKα through a specific interaction of the DGKα recoverin homology domain with the WH1 domain of WASp. Indeed, WASp is necessary and sufficient for DGKα inhibition, and this WASp function is independent of ARP2/3 activity. The adaptor protein NCK-1 and the small G protein CDC42 connect WASp-mediated DGKα inhibition to SAP and the TCR signalosome. In primary human T cells, this new signalling pathway is necessary for a full response in terms of IL-2 production, while minimally affecting TCR signalling and restimulation-induced cell death. Conversely, in T cells made resistant to RICD by SAP silencing, the enhanced DAG signalling due to DGKα inhibition is sufficient to restore apoptosis sensitivity. Conclusion: We discover a novel signalling pathway where, upon strong TCR activation, the complex between WASp and DGKα blocks DGKα activity, allowing a full cytokine response.

Diacylglycerol Kinases in Signal Transduction.

In recent years, the significant research efforts put into the clarification of the PI3K/AKT/mTOR pathway resulted in the approval of the first targeted therapies based on lipid kinase inhibitors [...].

ROCK 'n TOR: An Outlook on Keratinocyte Stem Cell Expansion in Regenerative Medicine via Protein Kinase Inhibition.

Keratinocyte stem cells play a fundamental role in homeostasis and repair of stratified epithelial tissues. Transplantation of cultured keratinocytes autografts provides a landmark example of successful cellular therapies by restoring durable integrity in stratified epithelia lost to devastating tissue conditions. Despite the overall success of such procedures, failures still occur in case of paucity of cultured stem cells in therapeutic grafts. Strategies aiming at a further amplification of stem cells during keratinocyte ex vivo expansion may thus extend the applicability of these treatments to subjects in which endogenous stem cells pools are depauperated by aging, trauma, or disease. Pharmacological targeting of stem cell signaling pathways is recently emerging as a powerful strategy for improving stem cell maintenance and/or amplification. Recent experimental data indicate that pharmacological inhibition of two prominent keratinocyte signaling pathways governed by apical mTOR and ROCK protein kinases favor stem cell maintenance and/or amplification ex vivo and may improve the effectiveness of stem cell-based therapeutic procedures. In this review, we highlight the pathophysiological roles of mTOR and ROCK in keratinocyte biology and evaluate existing pre-clinical data on the effects of their inhibition in epithelial stem cell expansion for transplantation purposes.

Diacylglycerol Kinase alpha in X Linked Lymphoproliferative Disease Type 1.

Diacylglycerol kinases are intracellular enzymes that control the balance between the secondary messengers diacylglycerol and phosphatidic acid. DGKα and DGKζ are the prominent isoforms that restrain the intensity of T cell receptor signalling by metabolizing PLCγ generated diacylglycerol. Thus, their activity must be tightly controlled to grant cellular homeostasis and refine immune responses. DGKα is specifically inhibited by strong T cell activating signals to allow for full diacylglycerol signalling which mediates T cell response. In X-linked lymphoproliferative disease 1, deficiency of the adaptor protein SAP results in altered T cell receptor signalling, due in part to persistent DGKα activity. This activity constrains diacylglycerol levels, attenuating downstream pathways such as PKCθ and Ras/MAPK and decreasing T cell restimulation induced cell death. This is a form of apoptosis triggered by prolonged T cell activation that is indeed defective in CD8+ cells of X-linked lymphoproliferative disease type 1 patients. Accordingly, inhibition or downregulation of DGKα activity restores in vitro a correct diacylglycerol dependent signal transduction, cytokines production and restimulation induced apoptosis. In animal disease models, DGKα inhibitors limit CD8+ expansion and immune-mediated tissue damage, suggesting the possibility of using inhibitors of diacylglycerol kinase as a new therapeutic approach.

Immunotherapy may protect cancer patients from SARS-CoV-2 infection: a single-center retrospective analysis.

Coronavirus disease 2019 (COVID-19) global pandemic has created unique challenges to healthcare systems throughout the world. Ensuring subjects' safety is mandatory especially in oncology, in consideration of cancer patients' particular frailty. We examined the proportion of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) IgM and/or IgG positive subjects in three different groups from Istituto Nazionale Tumori - IRCCS "Fondazione G. Pascale" in Naples (Campania region, Italy): cancer patients treated with Innovative Immunotherapy (Immune Checkpoint Inhibitors, ICIs), cancer patients undergoing standard Chemotherapies (CHTs) and healthcare providers. 9 out of 287 (3.1%) ICIs patients resulted positive, with a significant lower percentage in respect to CHTs patients (39 positive subjects out of 598, 6.5%) (p = 0.04). There was no statistically significant difference between ICIs cohort and healthcare providers, 48 out of 1050 resulting positive (4.6%). Performing a Propensity Score Matching based on gender and tumor stage, the effect of treatment on seropositivity was analyzed through a regression logistic model and the ICIs treatment resulted to be the only protective factor significantly (p = 0.03) associated with positivity (odds ratio-OR: 0.41; 95% confidence interval-CI 0.18-0.91). According to these preliminary data, ICIs would appear to be a protective factor against the onset of COVID-19 infection.

Identification of Key Phospholipids That Bind and Activate Atypical PKCs.

PKCζ and PKCι/λ form the atypical protein kinase C subgroup, characterised by a lack of regulation by calcium and the neutral lipid diacylglycerol. To better understand the regulation of these kinases, we systematically explored their interactions with various purified phospholipids using the lipid overlay assays, followed by kinase activity assays to evaluate the lipid effects on their enzymatic activity. We observed that both PKCζ and PKCι interact with phosphatidic acid and phosphatidylserine. Conversely, PKCι is unique in binding also to phosphatidylinositol-monophosphates (e.g., phosphatidylinositol 3-phosphate, 4-phosphate, and 5-phosphate). Moreover, we observed that phosphatidylinositol 4-phosphate specifically activates PKCι, while both isoforms are responsive to phosphatidic acid and phosphatidylserine. Overall, our results suggest that atypical Protein kinase C (PKC) localisation and activity are regulated by membrane lipids distinct from those involved in conventional PKCs and unveil a specific regulation of PKCι by phosphatidylinositol-monophosphates.

PARP Inhibitors in First-Line Therapy of Ovarian Cancer: Are There Any Doubts?

The standard of care for newly diagnosed advanced ovarian cancer (NADOC) is represented by surgical debulking followed by systemic platinum-taxanes combination chemotherapy. At the last European Society for Medical Oncology (ESMO) Congress, results from three trials testing three different poly-adenosine-diphosphate-ribose-polymerase (PARP) inhibitors (olaparib, niraparib, veliparib) in first-line therapy of OC have been presented. For the first time, these studies evaluated the efficacy of PARP inhibitors in this setting and the relative predictive biomarkers for patients' selection. The use of a PARP inhibitor is related with prolonged progression free survival (PFS) in the whole population of NADOC, although the magnitude of benefit varies widely among subgroups, highlighting the need to identify specific biological subtypes into clinical practice. In this minireview, we discuss the updated data available from clinical studies in this scenario.

Genomic Profile and BRCA-1 Promoter Methylation Status in BRCA Mutated Ovarian Cancer: New Insights in Predictive Biomarkers of Olaparib Response.

Objective: We assessed the genomic profile of four representative BRCA-mutated ovarian cancer (OC) patients treated with olaparib to investigate the relationship between intratumor heterogeneity and response to olaparib treatment. The main aim is to identify possible predictive biomarkers of response to olaparib through the analysis of HRD or not HRD genes and the definition of BRCA1 promoter methylation status. Methods: DNA, isolated from formalin-fixed, paraffin-embedded (FFPE) diagnostic OC tissues, was analyzed by FoundationOneCDx™. This assay detects alterations in a total panel of 324 genes, using the Illumina® HiSeq 4000 platform. Methylation analysis of the BRCA gene promoter was carried out by pyrosequencing with PyroMark Q24 platform (Qiagen), an in vitro nucleic acid sequence-based detection test based on pyrosequencing technology for quantitative measurements of methylation status. Results: Case #1 and #2 were defined Long-term responders since they received olaparib for 27 and 36 months, respectively. These remarkable results could be explained, at least in part, by the presence of somatic IDH1 mutation in case #1 and PI3K and SOX2 amplification in the case #2. In case #3, the somatic NF1 mutation appeared to be related to the short duration of response. In the case #4, in which the patients is on olaparib from 1 year achieving a stable disease, a somatic mutation of BRCA1 was recorded. Moreover, in all cases, levels of BRCA1 promoter were strictly related to olaparib response. Conclusions: Based on our experience, genomic analysis of tumor tissue at diagnosis might help to determine the future response to olaparib in advanced OC setting, revealing predictive biomarkers beyond BRCA 1-2 and HRD status.

PARP inhibitors in ovarian cancer.

Poly-ADP-ribosepolymerase inhibitors (PARPis) are the most active and interesting therapies approved for the treatment of epithelial ovarian cancer. They have changed the clinical management of a disease characterized, in almost half of cases, by extreme genetic complexity and alteration of DNA damage repair pathways, particularly homologous recombination (HR) deficiency. In this review, we provide an updated overview of the available results of recent clinical trials on the three Food and Drug Administrationand European Medicines Agency approved PARPis in ovarian cancer: olaparib, niraparib, and rucaparib. Furthermore, we anticipate the future perspective of combination regimens with antiangiogenic, immunocheckpoint inhibitors, and other biological agents as strategies to overcome resistance mechanisms, potentiate the therapeutic efficacy, and expand their clinical use in non-HR deficient tumors.

Triple-Negative Breast Cancers: Systematic Review of the Literature on Molecular and Clinical Features with a Focus on Treatment with Innovative Drugs.

PURPOSE OF REVIEW: Triple-negative breast cancer (TNBC) accounts for 15-20% of diagnosed breast tumours, with higher incidence in young and African-American women, and it is frequently associated with BRCA germline mutations. Chemotherapy is the only well-established therapeutic option in both early- and advanced-stages of the disease. TNBC tumours relapse earlier after standard anthracycline- and/or taxane-based chemotherapy treatments, generally within 1-3 years after the diagnosis, and often develop visceral metastases, representing the subtype with a worse prognosis among all breast cancers. In the present review, we will provide an updated overview of the available results of recent clinical trials for this disease and we will describe the implications of the known molecular pathways representing novel targets for development of future therapies for TNBC patients. RECENT FINDINGS: Over the past decade, the advent of gene expression micro-array technology has led to the identification of different actionable targets including various genomic alterations, androgen receptor, PARP, PI3K, VEGF and other proteins of the angiogenic pathway. Thus, novel targeted drugs have been tested in clinical trials reporting promising results in specific TNBC molecular subgroups. Although cytotoxic chemotherapy remains the mainstay of treatment for TNBC patients, the identification of novel 'drugable' targets and pathways for developing personalized treatments represents a promising investigational approach in the management of the TNBC subtype.