Frequent and Persistent PLCG1 Mutations in Sézary Cells Directly Enhance PLCγ1 Activity and Stimulate NFκB, AP-1, and NFAT Signaling

Intron retention in PI-PLC γ1 mRNA as a key mechanism affecting MMP expression in human primary fibroblast-like synovial cells

The intron retention (IR) is a phenomenon utilized by cells to allow diverse fates at the same mRNA, leading to a different pattern of synthesis of the same protein. In this study, we analyzed the modulation of phosphoinositide-specific phospholipase C (PI-PLC) enzymes by Harpagophytum procumbens extract (HPE) in synoviocytes from joins of osteoarthritis (OA) patients. In some samples, the PI-PLC γ1 isoform mature mRNA showed the IR and, in these synoviocytes, the HPE treatment increased the phenomenon. Moreover, we highlighted that as a consequence of IR, a lower amount of PI-PLC γ1 was produced. The decrease of PI-PLC γ1 was associated with the decrease of metalloprotease-3 (MMP-3), and MMP-13, and ADAMTS-5 after HPE treatment. The altered expression of MMPs is a hallmark of the onset and progression of OA, thus substances able to decrease their expression are very desirable. The interesting outcomes of this study are that 35% of analyzed synovial tissues showed the IR phenomenon in the PI-PLC γ1 mRNA and that the HPE treatment increased this phenomenon. For the first time, we found that the decrease of PI-PLC γ1 protein in synoviocytes interferes with MMP production, thus affecting the pathways involved in the MMP expression. This finding was validated by the silencing of PI-PLC γ1 in synoviocytes where the IR phenomenon was not present. Our results shed new light on the biochemical mechanisms involved in the degrading enzyme production in the joint of OA patients, suggesting a new therapeutic target and highlighting the importance of personalized medicine.

Genomic profiling of mycosis fungoides identifies patients at high risk of disease progression

ABSTRACT

Mycosis fungoides (MF) is the most prevalent primary cutaneous T-cell lymphoma, with an indolent or aggressive course and poor survival. The pathogenesis of MF remains unclear, and prognostic factors in the early stages are not well established. Here, we characterized the most recurrent genomic alterations using whole-exome sequencing of 67 samples from 48 patients from Lille University Hospital (France), including 18 sequential samples drawn across stages of the malignancy. Genomic data were analyzed on the Broad Institute's Terra bioinformatics platform. We found that gain7q, gain10p15.1 (IL2RA and IL15RA), del10p11.22 (ZEB1), or mutations in JUNB and TET2 are associated with high-risk disease stages. Furthermore, gain7q, gain10p15.1 (IL2RA and IL15RA), del10p11.22 (ZEB1), and del6q16.3 (TNFAIP3) are coupled with shorter survival. Del6q16.3 (TNFAIP3) was a risk factor for progression in patients at low risk. By analyzing the clonal heterogeneity and the clonal evolution of the cohort, we defined different phylogenetic pathways of the disease with acquisition of JUNB, gain10p15.1 (IL2RA and IL15RA), or del12p13.1 (CDKN1B) at progression. These results establish the genomics and clonality of MF and identify potential patients at risk of progression, independent of their clinical stage.

Staphylococcus aureus induces drug resistance in cancer T cells in Sézary syndrome

ABSTRACT

Patients with Sézary syndrome (SS), a leukemic variant of cutaneous T-cell lymphoma (CTCL), are prone to Staphylococcus aureus infections and have a poor prognosis due to treatment resistance. Here, we report that S aureus and staphylococcal enterotoxins (SE) induce drug resistance in malignant T cells against therapeutics commonly used in CTCL. Supernatant from patient-derived, SE-producing S aureus and recombinant SE significantly inhibit cell death induced by histone deacetylase (HDAC) inhibitor romidepsin in primary malignant T cells from patients with SS. Bacterial killing by engineered, bacteriophage-derived, S aureus-specific endolysin (XZ.700) abrogates the effect of S aureus supernatant. Similarly, mutations in major histocompatibility complex (MHC) class II binding sites of SE type A (SEA) and anti-SEA antibody block induction of resistance. Importantly, SE also triggers resistance to other HDAC inhibitors (vorinostat and resminostat) and chemotherapeutic drugs (doxorubicin and etoposide). Multimodal single-cell sequencing indicates T-cell receptor (TCR), NF-κB, and JAK/STAT signaling pathways (previously associated with drug resistance) as putative mediators of SE-induced drug resistance. In support, inhibition of TCR-signaling and Protein kinase C (upstream of NF-κB) counteracts SE-induced rescue from drug-induced cell death. Inversely, SE cannot rescue from cell death induced by the proteasome/NF-κB inhibitor bortezomib. Inhibition of JAK/STAT only blocks rescue in patients whose malignant T-cell survival is dependent on SE-induced cytokines, suggesting 2 distinct ways SE can induce drug resistance. In conclusion, we show that S aureus enterotoxins induce drug resistance in primary malignant T cells. These findings suggest that S aureus enterotoxins cause clinical treatment resistance in patients with SS, and antibacterial measures may improve the outcome of cancer-directed therapy in patients harboring S aureus.

Microneedle Patch Delivery of PLCG1-siRNA Efficient Enhanced Temozolomide Therapy for Glioblastoma

The blood-brain barrier (BBB) and drug resistance present challenges for chemotherapy of glioblastoma (GBM). A microneedle (MN) patch with excellent biocompatibility and biodegradability was designed to bypass the BBB and release temozolomide (TMZ) and PLCG1-siRNA directly into the tumor site for synergistic treatment of GBM. The codelivery of TMZ and PLCG1-siRNA enhanced DNA damage and apoptosis. The potential mechanism behind this enhancement is to knockdown of PLCG1 expression, which positively regulates the expression of signal transducer and activator of transcription 3 genes, thereby preventing DNA repair and enhancing the sensitivity of GBM to TMZ. The MN patch enables long-term sustainable drug release through in situ implantation and increases local drug concentrations in diseased areas, significantly extending mouse survival time compared to other drug treatment groups. MN drug delivery provides a platform for the combination treatment of GBM and other central nervous system diseases.

Membrane-bound Merkel cell polyomavirus middle T protein constitutively activates PLCγ1 signaling through Src-family kinases

Merkel cell polyomavirus (MCV or MCPyV) is an alphapolyomavirus causing human Merkel cell carcinoma and encodes four tumor (T) antigen proteins: large T (LT), small tumor (sT), 57 kT, and middle T (MT)/alternate LT open reading frame proteins. We show that MCV MT is generated as multiple isoforms through internal methionine translational initiation that insert into membrane lipid rafts. The membrane-localized MCV MT oligomerizes and promiscuously binds to lipid raft-associated Src family kinases (SFKs). MCV MT-SFK interaction is mediated by a Src homology (SH) 3 recognition motif as determined by surface plasmon resonance, coimmunoprecipitation, and bimolecular fluorescence complementation assays. SFK recruitment by MT leads to tyrosine phosphorylation at a SH2 recognition motif (pMTY114), allowing interaction with phospholipase C gamma 1 (PLCγ1). The secondary recruitment of PLCγ1 to the SFK-MT membrane complex promotes PLCγ1 tyrosine phosphorylation on Y783 and activates the NF-κB inflammatory signaling pathway. Mutations at either the MCV MT SH2 or SH3 recognition sites abrogate PLCγ1-dependent activation of NF-κB signaling and increase viral replication after MCV genome transfection into 293 cells. These findings reveal a conserved viral targeting of the SFK-PLCγ1 pathway by both MCV and murine polyomavirus (MuPyV) MT proteins. The molecular steps in how SFK-PLCγ1 activation is achieved, however, differ between these two viruses.

TCR Pathway Mutations in Mature T Cell Lymphomas

Mature T cell lymphomas are heterogeneous neoplasms that are aggressive and resistant to treatment. Many of these cancers retain immunological properties of their cell of origin. They express cytokines, cytotoxic enzymes, and cell surface ligands normally induced by TCR signaling in untransformed T cells. Until recently, their molecular mechanisms were unclear. Recently, high-dimensional studies have transformed our understanding of their cellular and genetic characteristics. Somatic mutations in the TCR signaling pathway drive lymphomagenesis by disrupting autoinhibitory domains, increasing affinity to ligands, and/or inducing TCR-independent signaling. Collectively, most of these mutations augment signaling pathways downstream of the TCR. Emerging data suggest that these mutations not only drive proliferation but also determine lymphoma immunophenotypes. For example, RHOA mutations are sufficient to induce disease-relevant CD4+ T follicular helper cell phenotypes. In this review, we describe how mutations in the TCR signaling pathway elucidate lymphoma pathophysiology but also provide insights into broader T cell biology.

A gain-of-function variation in PLCG1 causes a new immune dysregulation disease

BACKGROUND

Phospholipase C (PLC) γ1 is a critical enzyme regulating nuclear factor-κB (NF-κB), extracellular signal-related kinase, mitogen-activated protein kinase, and nuclear factor of activated T cells signaling pathways, yet germline PLCG1 mutation in human disease has not been reported.

OBJECTIVE

We aimed to investigate the molecular pathogenesis of a PLCG1 activating variant in a patient with immune dysregulation.

METHODS

Whole exome sequencing was used to identify the patient's pathogenic variants. Bulk RNA sequencing, single-cell RNA sequencing, quantitative PCR, cytometry by time of flight, immunoblotting, flow cytometry, luciferase assay, IP-One ELISA, calcium flux assay, and cytokine measurements in patient PBMCs and T cells and COS-7 and Jurkat cell lines were used to define inflammatory signatures and assess the impact of the PLCG1 variant on protein function and immune signaling.

RESULTS

We identified a novel and de novo heterozygous PLCG1 variant, p.S1021F, in a patient presenting with early-onset immune dysregulation disease. We demonstrated that the S1021F variant is a gain-of-function variant, leading to increased inositol-1,4,5-trisphosphate production, intracellular Ca2+ release, and increased phosphorylation of extracellular signal-related kinase, p65, and p38. The transcriptome and protein expression at the single-cell level revealed exacerbated inflammatory responses in the patient's T cells and monocytes. The PLCG1 activating variant resulted in enhanced NF-κB and type II interferon pathways in T cells, and hyperactivated NF-κB and type I interferon pathways in monocytes. Treatment with either PLCγ1 inhibitor or Janus kinase inhibitor reversed the upregulated gene expression profile in vitro.

CONCLUSIONS

Our study highlights the critical role of PLCγ1 in maintaining immune homeostasis. We illustrate immune dysregulation as a consequence of PLCγ1 activation and provide insight into therapeutic targeting of PLCγ1.

A Systematic Compilation of Human SH3 Domains: A Versatile Superfamily in Cellular Signaling

SRC homology 3 (SH3) domains are fundamental modules that enable the assembly of protein complexes through physical interactions with a pool of proline-rich/noncanonical motifs from partner proteins. They are widely studied modular building blocks across all five kingdoms of life and viruses, mediating various biological processes. The SH3 domains are also implicated in the development of human diseases, such as cancer, leukemia, osteoporosis, Alzheimer's disease, and various infections. A database search of the human proteome reveals the existence of 298 SH3 domains in 221 SH3 domain-containing proteins (SH3DCPs), ranging from 13 to 720 kilodaltons. A phylogenetic analysis of human SH3DCPs based on their multi-domain architecture seems to be the most practical way to classify them functionally, with regard to various physiological pathways. This review further summarizes the achievements made in the classification of SH3 domain functions, their binding specificity, and their significance for various diseases when exploiting SH3 protein modular interactions as drug targets.

A frequent PLCγ1 mutation in adult T-cell leukemia/lymphoma determines functional properties of the malignant cells

BACKGROUND

Development of adult T-cell leukemia/lymphoma (ATL) involves human T-cell leukemia virus type 1 (HTLV-1) infection and accumulation of somatic mutations. The most frequently mutated gene in ATL (36 % of cases) is phospholipase C gamma1 (PLCG1). PLCG1 is also frequently mutated in other T-cell lymphomas. However, the functional consequences of the PLCG1 mutations in cancer cells have not been characterized.

METHODS

We compared the activity of the wild-type PLCγ1 with that of a mutant carrying a hot-spot mutation of PLCγ1 (S345F) observed in ATL, both in cells and in cell-free assays. To analyse the impact of the mutation on cellular properties, we quantified cellular proliferation, aggregation, chemotaxis and apoptosis by live cell-imaging in an S345F+ ATL-derived cell line (KK1) and a KK1 cell line in which we reverted the mutation to the wild-type sequence using CRISPR/Cas9 and homology-directed repair.

FINDINGS

The PLCγ1 S345F mutation results in an increase of basal PLC activity in vitro and in different cell types. This higher basal activity is further enhanced by upstream signalling. Reversion of the S345F mutation in the KK1 cell line resulted in reduction of the PLC activity, lower rates of proliferation and aggregation, and a marked reduction in chemotaxis towards CCL22. The PLCγ1-pathway inhibitors ibrutinib and ritonavir reduced both the PLC activity and the tested functions of KK1 cells.

INTERPRETATION

Consistent with observations from clinical studies, our data provide direct evidence that activated variants of the PLCγ1 enzyme contribute to the properties of the malignant T-cell clone in ATL.

FUNDING

MRC (UK) Project Grant (P028160).

Targeting oncogenic transcription factors in skin malignancies: An update on cancer stemness and therapeutic outcomes

The skin is the largest organ of the human body and prone to various diseases, including cancer; thus, provides the first line of defense against exogenous biological and non-biological agents. Skin cancer, a complex and heterogenic process, with steep incidence rate often metastasizes due to poor understanding of the underlying mechanisms of pathogenesis and clinical challenges. Indeed, accumulating evidence indicates that deregulation of transcription factors (TFs) due to genetic, epigenetic and signaling distortions plays essential role in the development of cutaneous malignancies and therapeutic challenges including cancer stemness features and reprogramming. This review highlights the recent developments exploring underlying mechanisms how deregulated TFs (e.g., NF-κB, AP-1, STAT etc.,) orchestrates cutaneous onco-pathogenesis, reprogramming, stemness and poor clinical outcomes. Along this line, bioactive drugs, and their derivatives from natural and or synthetic origin has gained attention due to their multitargeting potential, potentially safer and effective therapeutic outcome for human malignancies. We also discussed therapeutic importance of targeting aberrantly expressed TFs in skin cancers with bioactive natural products and or synthetic agents.

Advances in the understanding and treatment of Cutaneous T-cell Lymphoma

Cutaneous T-cell lymphomas (CTCL) are a heterogeneous group of non-Hodgkin's lymphomas (NHL) characterised by the clonal proliferation of malignant, skin homing T-cells. Recent advances have been made in understanding the molecular pathogenesis of CTCL. Multiple deep sequencing studies have revealed a complex genomic landscape with large numbers of novel single nucleotide variants (SNVs) and copy number variations (CNVs). Commonly perturbed genes include those involved in T-cell receptor signalling, T-cell proliferation, differentiation and survival, epigenetic regulators as well as genes involved in genome maintenance and DNA repair. In addition, studies in CTCL have identified a dominant UV mutational signature in contrast to systemic T-cell lymphomas and this likely contributes to the high tumour mutational burden. As current treatment options for advanced stages of CTCL are associated with short-lived responses, targeting these deregulated pathways could provide novel therapeutic approaches for patients. In this review article we summarise the key pathways disrupted in CTCL and discuss the potential therapeutic implications of these findings.

Mutations Affecting Genes in the Proximal T-Cell Receptor Signaling Pathway in Peripheral T-Cell Lymphoma

Simple Summary

The advent of next-generation sequencing (NGS) has allowed rapid advances in genomic studies on the pathogenesis and biology of peripheral T-cell lymphoma (PTCL). Recurrent mutations and fusions in genes related to the proximal TCR signaling pathway have been identified and show an important pathogenic role in PTCL. In this review, we summarize the genomic alterations in TCR signaling identified in different subgroups of PTCL patients and the functional impact of these alterations on TCR signaling and downstream pathways. We also discuss novel agents that could target TCR-related mutations and may hold promise for improving the treatment of PTCL.

Abstract

Peripheral T-cell lymphoma (PTCL) comprises a heterogeneous group of mature T-cell malignancies. Recurrent activating mutations and fusions in genes related to the proximal TCR signaling pathway have been identified in preclinical and clinical studies. This review summarizes the genetic alterations affecting proximal TCR signaling identified from different subgroups of PTCL and the functional impact on TCR signaling and downstream pathways. These genetic abnormalities include mostly missense mutations, occasional indels, and gene fusions involving CD28, CARD11, the GTPase RHOA, the guanine nucleotide exchange factor VAV1, and kinases including FYN, ITK, PLCG1, PKCB, and PI3K subunits. Most of these aberrations are activating mutations that can potentially be targeted by inhibitors, some of which are being tested in clinical trials that are briefly outlined in this review. Finally, we focus on the molecular pathology of recently identified subgroups of PTCL-NOS and highlight the unique genetic profiles associated with PTCL-GATA3.

Characterization of the membrane interactions of phospholipase Cγ reveals key features of the active enzyme

PLCγ enzymes are autoinhibited in resting cells and form key components of intracellular signaling that are also linked to disease development. Insights into physiological and aberrant activation of PLCγ require understanding of an active, membrane-bound form, which can hydrolyze inositol-lipid substrates. Here, we demonstrate that PLCγ1 cannot bind membranes unless the autoinhibition is disrupted. Through extensive molecular dynamics simulations and experimental evidence, we characterize membrane binding by the catalytic core domains and reveal previously unknown sites of lipid interaction. The identified sites act in synergy, overlap with autoinhibitory interfaces, and are shown to be critical for the phospholipase activity in cells. This work provides direct evidence that PLCγ1 is inhibited through obstruction of its membrane-binding surfaces by the regulatory region and that activation must shift PLCγ1 to a conformation competent for membrane binding. Knowledge of the critical sites of membrane interaction extends the mechanistic framework for activation, dysregulation, and therapeutic intervention.

Dynamics of allosteric regulation of the phospholipase C-γ isozymes upon recruitment to membranes

Numerous receptor tyrosine kinases and immune receptors activate phospholipase C-γ (PLC-γ) isozymes at membranes to control diverse cellular processes including phagocytosis, migration, proliferation, and differentiation. The molecular details of this process are not well understood. Using hydrogen-deuterium exchange mass spectrometry, we show that PLC-γ1 is relatively inert to lipid vesicles that contain its substrate, phosphatidylinositol 4,5-bisphosphate (PIP₂), unless first bound to the kinase domain of the fibroblast growth factor receptor (FGFR1). Exchange occurs throughout PLC-γ1 and is exaggerated in PLC-γ1 containing an oncogenic substitution (D1165H) that allosterically activates the lipase. These data support a model whereby initial complex formation shifts the conformational equilibrium of PLC-γ1 to favor activation. This receptor-induced priming of PLC-γ1 also explains the capacity of a kinase-inactive fragment of FGFR1 to modestly enhance the lipase activity of PLC-γ1 operating on lipid vesicles but not a soluble analog of PIP₂ and highlights potential cooperativity between receptor engagement and membrane proximity. Priming is expected to be greatly enhanced for receptors embedded in membranes and nearly universal for the myriad of receptors and co-receptors that bind the PLC-γ isozymes.

Proteomic analysis reveals dual requirement for Grb2 and PLCγ1 interactions for BCR-FGFR1-Driven 8p11 cell proliferation

Translocation of Fibroblast Growth Factor Receptors (FGFRs) often leads to aberrant cell proliferation and cancer. The BCR-FGFR1 fusion protein, created by chromosomal translocation t(8;22)(p11;q11), contains Breakpoint Cluster Region (BCR) joined to Fibroblast Growth Factor Receptor 1 (FGFR1). BCR-FGFR1 represents a significant driver of 8p11 myeloproliferative syndrome, or stem cell leukemia/lymphoma, which progresses to acute myeloid leukemia or T-cell lymphoblastic leukemia/lymphoma. Mutations were introduced at Y177F, the binding site for adapter protein Grb2 within BCR; and at Y766F, the binding site for the membrane associated enzyme PLCγ1 within FGFR1. We examined anchorage-independent cell growth, overall cell proliferation using hematopoietic cells, and activation of downstream signaling pathways. BCR-FGFR1-induced changes in protein phosphorylation, binding partners, and signaling pathways were dissected using quantitative proteomics to interrogate the protein interactome, the phosphoproteome, and the interactome of BCR-FGFR1. The effects on BCR-FGFR1-stimulated cell proliferation were examined using the PLCγ1 inhibitor U73122, and the irreversible FGFR inhibitor futibatinib (TAS-120), both of which demonstrated efficacy. An absolute requirement is demonstrated for the dual binding partners Grb2 and PLCγ1 in BCR-FGFR1-driven cell proliferation, and new proteins such as ECSIT, USP15, GPR89, GAB1, and PTPN11 are identified as key effectors for hematopoietic transformation by BCR-FGFR1.

Overarching roles of diacylglycerol signaling in cancer development and antitumor immunity

Diacylglycerol (DAG) is a lipid second messenger that is generated in response to extracellular stimuli and channels intracellular signals that affect mammalian cell proliferation, survival, and motility. DAG exerts a myriad of biological functions through protein kinase C (PKC) and other effectors, such as protein kinase D (PKD) isozymes and small GTPase-regulating proteins (such as RasGRPs). Imbalances in the fine-tuned homeostasis between DAG generation by phospholipase C (PLC) enzymes and termination by DAG kinases (DGKs), as well as dysregulation in the activity or abundance of DAG effectors, have been widely associated with tumor initiation, progression, and metastasis. DAG is also a key orchestrator of T cell function and thus plays a major role in tumor immunosurveillance. In addition, DAG pathways shape the tumor ecosystem by arbitrating the complex, dynamic interaction between cancer cells and the immune landscape, hence representing powerful modifiers of immune checkpoint and adoptive T cell-directed immunotherapy. Exploiting the wide spectrum of DAG signals from an integrated perspective could underscore meaningful advances in targeted cancer therapy.

PLCγ1/PKCθ Downstream Signaling Controls Cutaneous T-Cell Lymphoma Development And Progression

Developing mechanistic rationales can improve the clinical management of cutaneous T-cell lymphomas (CTCL). There is considerable genetic and biological evidence of a malignant network of signaling mechanisms, highly influenced by deregulated TCR/PLCγ1 activity, controlling the biology of these lesions. In addition, activated STAT3 is associated with clinical progression, although the alterations responsible for this have not been fully elucidated. Here we studied PLCγ1-dependent mechanisms that can mediate STAT3 activation and control tumor growth and progression. Downstream of PLCγ1, the pharmacological inhibition and genetic knockdown of PKCθ inhibited STAT3 activation, impaired proliferation, and promoted apoptosis in CTCL cells. A PKCθ-dependent transcriptome in MF/SS cells revealed potential effector genes controlling cytokine signaling, TP53, and actin cytoskeleton dynamics. Consistently, an in vivo chicken embryo model xenografted with MF cells showed that PKCθ blockage abrogates tumor growth and spread to distant organs. Finally, the expression of a number of PKCθ target genes, found in MF cells, significantly correlated with that of PRKCQ (PKCθ) in 81 human MF samples. In summary, PKCθ can play a central role in the activation of malignant CTCL mechanisms via multiple routes, including, but not restricted to, STAT3. These mechanisms may, in turn, serve as targets for specific therapies.

Transcriptomic Changes During Stage Progression of Mycosis Fungoides

BACKGROUND

Mycosis fungoides (MF) is the most common cutaneous T cell lymphoma, which in the early patch/plaque stages runs an indolent course. However, ~25% of MF patients develop skin tumors, a hallmark of progression to the advanced stage and is associated with high mortality. The mechanisms involved in stage progression are poorly elucidated.

METHODS

We performed whole-transcriptome and whole-exome sequencing of malignant MF cells from skin biopsies obtained by laser-capture microdissection. We compared three types of MF lesions: early-stage plaques (ESP, n=12) as well as plaques and tumors from patients in late-stage disease (late-stage plaques [LSP], n=10, and tumors [TMR], n=15). Gene Ontology (GO) and KEGG analysis were used to determine pathway changes specific for different lesions which were linked to the recurrent somatic mutations overrepresented in MF tumors.

RESULTS

The key upregulated pathways during stage progression were those related to cell proliferation and survival (MEK/ERK, Akt-mTOR), Th2/Th9 signaling (IL4, STAT3, STAT5, STAT6), meiomitosis (CT45A1, CT45A3, STAG3, GTSF1, REC8) and DNA repair (PARP1, MYCN, OGG1). Principal coordinate clustering of the transcriptome revealed extensive gene expression differences between early (ESP) and advanced-stage lesions (LSP and TMR). LSP and TMR showed remarkable similarities at the level of the transcriptome, which we interpreted as evidence of cell percolation between lesions via hematogenous self-seeding.

CONCLUSION

Stage progression in MF is associated with Th2/Th9 polarization of malignant cells, activation of proliferation, survival, as well as increased genomic instability. Global transcriptomic changes in multiple lesions may be caused by hematogenous cell percolation between discrete skin lesions.

Recent advances in understanding the molecular role of phosphoinositide-specific phospholipase C gamma 1 as an emerging onco-driver and novel therapeutic target in human carcinogenesis

Phosphoinositide metabolism is crucial intracellular signaling system that regulates a plethora of biological functions including mitogenesis, cell proliferation and division. Phospholipase C gamma 1 (PLCγ1) which belongs to phosphoinositide-specific phospholipase C (PLC) family, is activated by many extracellular stimuli including hormones, neurotransmitters, growth factors and modulates several cellular and physiological functions necessary for tumorigenesis such as cell survival, migration, invasion and angiogenesis by generating inositol 1,4,5-triphosphate (IP3) and diacylglycerol (DAG) via hydrolysis of phosphatidylinositol 4,5-biphosphate (PIP2). Cancer remains as a leading cause of global mortality and aberrant expression and regulation of PLCγ1 is linked to a plethora of deadly human cancers including carcinomas of the breast, lung, pancreas, stomach, prostate and ovary. Although PLCγ1 cross-talks with many onco-drivers and signaling circuits including PI3K, AKT, HIF1-α and RAF/MEK/ERK cascade, its precise role in carcinogenesis is not completely understood. This review comprehensively discussed the status quo of this ubiquitously expressed phospholipase as a tumor driver and highlighted its significance as a novel therapeutic target in cancer. Furthermore, we have highlighted the significance of somatic driver mutations in PLCG1 gene and molecular roles of PLCγ1 in several major human cancers, a knowledgebase that can be utilized to develop novel, isoform-specific small molecule inhibitors of PLCγ1.

Mycosis Fungoides and Sézary Syndrome: An Integrative Review of the Pathophysiology, Molecular Drivers, and Targeted Therapy

Simple Summary

In the last few years, the field of cutaneous T-cell lymphomas has experienced major advances. In the context of an active translational and clinical research field, next-generation sequencing data have boosted our understanding of the main molecular mechanisms that govern the biology of these entities, thus enabling the development of novel tools for diagnosis and specific therapy. Here, we focus on mycosis fungoides and Sézary syndrome; we review essential aspects of their pathophysiology, provide a rational mechanistic interpretation of the genomic data, and discuss the current and upcoming therapies, including the potential crosstalk between genomic alterations and the microenvironment, offering opportunities for targeted therapies.

Abstract

Primary cutaneous T-cell lymphomas (CTCLs) constitute a heterogeneous group of diseases that affect the skin. Mycosis fungoides (MF) and Sézary syndrome (SS) account for the majority of these lesions and have recently been the focus of extensive translational research. This review describes and discusses the main pathobiological manifestations of MF/SS, the molecular and clinical features currently used for diagnosis and staging, and the different therapies already approved or under development. Furthermore, we highlight and discuss the main findings illuminating key molecular mechanisms that can act as drivers for the development and progression of MF/SS. These seem to make up an orchestrated constellation of genomic and environmental alterations generated around deregulated T-cell receptor (TCR)/phospholipase C, gamma 1, (PLCG1) and Janus kinase/ signal transducer and activator of transcription (JAK/STAT) activities that do indeed provide us with novel opportunities for diagnosis and therapy.

Phospholipase C families: Common themes and versatility in physiology and pathology

Phosphoinositide-specific phospholipase Cs (PLCs) are expressed in all mammalian cells and play critical roles in signal transduction. To obtain a comprehensive understanding of these enzymes in physiology and pathology, a detailed structural, biochemical, cell biological and genetic information is required. In this review, we cover all these aspects to summarize current knowledge of the entire superfamily. The families of PLCs have expanded from 13 enzymes to 16 with the identification of the atypical PLCs in the human genome. Recent structural insights highlight the common themes that cover not only the substrate catalysis but also the mechanisms of activation. This involves the release of autoinhibitory interactions that, in the absence of stimulation, maintain classical PLC enzymes in their inactive forms. Studies of individual PLCs provide a rich repertoire of PLC function in different physiologies. Furthermore, the genetic studies discovered numerous mutated and rare variants of PLC enzymes and their link to human disease development, greatly expanding our understanding of their roles in diverse pathologies. Notably, substantial evidence now supports involvement of different PLC isoforms in the development of specific cancer types, immune disorders and neurodegeneration. These advances will stimulate the generation of new drugs that target PLC enzymes, and will therefore open new possibilities for treatment of a number of diseases where current therapies remain ineffective.

Antineoplastic effect of a novel nanosized curcumin on cutaneous T cell lymphoma

Cutaneous T cell lymphomas (CTCLs) are a group of heterogeneous, life-threatening, extra-nodal and lymphoproliferative T cell neoplasms. Since chronic inflammation serves a key role in CTCL progression, curcumin, a natural pigment with proven anti-inflammatory and antineoplastic properties, as well as minimal toxicity, may be used as a therapeutic agent. In the present study, two formulations of curcumin (standard ethanolic and a Pluronic^®P-123/F-127 micellar solution) were compared regarding their cytotoxic efficacy and speed of internalization in three CTCL cell lines, namely HuT-78, HH and MJ. In addition, the modulating effect of curcumin on selected proteins involved in the proliferation and progression of the disease was determined. The results indicated the superiority of the Pluronic^®P-123/F-127 micellar curcumin over the standard ethanol solution in terms of cellular internalization efficiency as determined by spectrophotometric analysis. Notably, the presence of commonly used media components, such as phenol red, may interfere when interpreting the cytotoxicity of curcumin, due to their overlapping absorbance peaks. Therefore, it was concluded that phenol red-free media are superior over media with phenol red in order to correctly measure the cytotoxic efficacy and cell penetration of curcumin. Depending on the cell line, the IC₅₀ values of micellar curcumin varied from 29.76 to 1.24 µΜ, with HH cells demonstrating the highest sensitivity. This cell line had the lowest expression levels of the Wilms' tumor-1 transcription factor. Performing western blot analyses of treated and untreated CTCL cells, selective signal transduction changes were recorded for the first time, thus making curcumin nano-formulation an attractive and prospective option with therapeutic relevance for CTCL as a rare orphan disease.