Accelerating AXL targeting for TNBC therapy.

The tyrosine kinase receptor AXL of the TAM (TYRO3, AXL and MERTK) family is considered as a promising therapeutic target for different hematological cancers and solid tumors. AXL is involved in multiple pro-​tumorigenic processes including cell migration, invasion, epithelial-mesenchymal transition (EMT), and stemness, and recent studies demonstrated its impact on cancer metastasis and drug resistance. Extensive studies on AXL have highlighted its unique characteristics and physiological functions and suggest that targeting of AXL could be beneficial in combination with chemotherapy, radiotherapy, immunotherapy, and targeted therapy. In this mini review, we discuss possible outcomes of AXL targeting either alone or together with other therapeutic agents and emphasize its impact on triple negative breast cancer (TNBC).

The AXL-PYK2-PKCα axis as a nexus of stemness circuits in TNBC.

Cancer stem cells (CSCs) are implicated in tumor initiation, metastasis and drug resistance, and considered as attractive targets for cancer therapy. Here we identified a clinically relevant signaling nexus mediated by AXL receptor, PYK2 and PKCα and show its impact on stemness in TNBC. AXL, PYK2, and PKCα expression correlates with stemness signature in basal-like breast cancer patients, and their depletion in multiple mesenchymal TNBC cell lines markedly reduced the number of mammosphere-forming cells and cells harboring CSCs characteristic markers. Knockdown of PYK2 reduced the levels of AXL, PKCα, FRA1, and PYK2 proteins, and similar trend was obtained upon PKCα depletion. PYK2 depletion decreased AXL transcription through feedback loops mediated by FRA1 and TAZ, whereas PKCα inhibition induced redistribution of AXL to endosomal/lysosomal compartment and enhanced its degradation. PYK2 and PKCα cooperate at a convergence point of multiple stemness-inducing pathways to regulate AXL levels and concomitantly the levels/activation of STAT3, TAZ, FRA1, and SMAD3 as well as the pluripotent transcription factors Nanog and Oct4. Induction of stemness in TNBC sensitized cells to PYK2 and PKCα inhibition suggesting that targeting the AXL-PYK2-PKCα circuit could be an efficient strategy to eliminate CSCs in TNBC.

Synthetic lethal combination targeting BET uncovered intrinsic susceptibility of TNBC to ferroptosis.

Identification of targeted therapies for TNBC is an urgent medical need. Using a drug combination screen reliant on synthetic lethal interactions, we identified clinically relevant combination therapies for different TNBC subtypes. Two drug combinations targeting the BET family were further explored. The first, targeting BET and CXCR2, is specific for mesenchymal TNBC and induces apoptosis, whereas the second, targeting BET and the proteasome, is effective for major TNBC subtypes and triggers ferroptosis. Ferroptosis was induced at low drug doses and was associated with increased cellular iron and decreased glutathione levels, concomitant with reduced levels of GPX4 and key glutathione biosynthesis genes. Further functional studies, analysis of clinical datasets and breast cancer specimens revealed a unique vulnerability of TNBC to ferroptosis inducers, enrichment of ferroptosis gene signature, and differential expression of key proteins that increase labile iron and decrease glutathione levels. This study identified potent combination therapies for TNBC and unveiled ferroptosis as a promising therapeutic strategy.

Hepatitis C virus core protein interacts with cellular metastasis suppressor Nm23-H1 and promotes cell migration and invasion.

Hepatitis C virus (HCV) is the major etiological agent of hepatocellular carcinoma (HCC), which is the fourth most common cause of cancer-related deaths worldwide and second in terms of deaths of males (Bray et al. in CA Cancer J Clin 68(6):394-424, 2018). HCV-induced HCC is a multi-step process that involves alteration of several host regulatory pathways. One of the key features of HCV-associated hepatocellular carcinoma is the metastasis of cancer cells to different organs. Human Nm23-H1 is one of the best-studied metastasis suppressor proteins, and it has been shown to be modulated in many human cancers. Our study shows that the core protein of HCV genotype 2a can co-localize and interact directly with Nm23-H1 within cancer cells, resulting in modulation of the anti-metastasis properties of Nm23-H1. The HCV core protein promotes SUMOylation and degradation of the Nm23-H1 protein, as well as transcriptional downregulation. This study provides evidence that the HCV core protein is a pro-metastatic protein that can interact directly with and modulate the functions of cellular metastasis suppressor Nm23-H1.

Hepatitis C Virus Mediated Metastasis in Hepatocellular Carcinoma as a Therapeutic Target for Cancer Management.

BACKGROUND: Hepatocellular carcinoma (HCC) is one of the most common causes of cancer associated deaths. Prognosis is relatively poor in cases where Hepatitis C Virus (HCV) is associated as causative agent, mainly due to increased risk of metastasis. Metastasis is the major cause of all cancer related deaths. METHODS: We reviewed reports linking expression of HCV encoded proteins with changes in cellular functions. We also compared reports on HCV-induced HCC with those on non-viral and Hepatitis B Virus (HBV) induced HCC. Novel therapeutic approaches for handling metastatic HCC were also reviewed. RESULTS: HCV infection is associated with expression of multiple pro-metastatic factors in HCC patients. HCV encoded proteins can directly induce pro-metastasis cellular functions. HCV-induced HCC has a greater chance of recurrence than any non-viral and Hepatitis B Virus (HBV) induced HCC. Recent advances in understanding of evolutionary dynamics of tumor argue that trying to prevent spreading of cancer may ultimately prove to be a better approach than striving to cure it. Inhibiting the metastasis can thereby substantially increase the survival period in patients. Host cell protein Nm23-H1 is a known suppressor of tumor metastasis and has been shown to be modulated by proteins encoded by different viruses associated with cancers. CONCLUSION: Nm23-H1 is an important therapeutic target for virus mediated malignancies. This review is an attempt to summarize the current state of understanding of cancer cell metastasis in HCV induced tumors, and argues for approaches based on targeting host and viral factors critical for cancer metastasis as therapeutic targets.

Modulation of cyclic nucleotide-mediated cellular signaling and gene expression using photoactivated adenylyl cyclase as an optogenetic tool.

Cyclic nucleotide signaling pathway plays a significant role in various biological processes such as cell growth, transcription, inflammation, in microbial pathogenesis, etc. Modulation of cyclic nucleotide levels by optogenetic tools has overcome certain limitations of studying transduction cascade by pharmacological agents and has allowed several ways to modulate biological processes in a spatiotemporal manner. Here, we have shown the optogenetic modulation of the cyclooxygenase 2 (Cox-2) gene expression and their downstream effector molecule (PGE2) in HEK-293T cells and the development process of Dictyostelium discoideum via modulating the cyclic nucleotide (cAMP) signaling pathway utilizing photoactivated adenylyl cyclases (PACs) as an optogenetic tool. Light-induced activation of PACs in HEK-293T cells increases the cAMP level that leads to activation of cAMP response element-binding protein (CREB) transcription factor and further upregulates downstream Cox-2 gene expression and their downstream effector molecule prostaglandin E2. In D. discoideum, the light-regulated increase in cAMP level affects the starvation-induced developmental process. These PACs could modulate the cAMP levels in a light-dependent manner and have a potential to control gene expression and their downstream effector molecules with varying magnitude. It would enable one to utilize PAC as a tool to decipher cyclic nucleotide mediated signaling pathway regulations and their mechanism.

Role of Modulator of Inflammation Cyclooxygenase-2 in Gammaherpesvirus Mediated Tumorigenesis.

Chronic inflammation is recognized as a threat factor for cancer progression. Release of inflammatory molecules generates microenvironment which is highly favorable for development of tumor, cancer progression and metastasis. In cases of latent viral infections, generation of such a microenvironment is one of the major predisposing factors related to virus mediated tumorigenesis. Among various inflammatory mediators implicated in pathological process associated with cancer, the cyclooxygenase (COX) and its downstream effector molecules are of greater significance. Though the role of infectious agents in causing inflammation leading to transformation of cells has been more or less well established, however, the mechanism by which inflammation in itself modulates the events in life cycle of infectious agent is not very much clear. This is specifically important for gammaherpesviruses infections where viral life cycle is characterized by prolonged periods of latency when the virus remains hidden, immunologically undetectable and expresses only a very limited set of genes. Therefore, it is important to understand the mechanisms for role of inflammation in virus life cycle and tumorigenesis. This review is an attempt to summarize the latest findings highlighting the significance of COX-2 and its downstream signaling effectors role in life cycle events of gammaherpesviruses leading to progression of cancer.

Hepatitis C Virus E1 protein promotes cell migration and invasion by modulating cellular metastasis suppressor Nm23-H1.

Hepatocellular carcinoma (HCC) is the most prevalent primary liver cancer and its incidence is on the rise largely attributed to Hepatitis C virus (HCV) related liver cancer. A distinct feature of HCV associated HCC is the substantially increased incidence of metastasis compared to non-viral or HBV associated HCC. Nm23-H1 is the first reported human metastasis suppressor down-regulated in many human metastatic cancers. Nm23-H1 functions are modulated in several virus associated cancers. Our study now shows that HCV E1 protein expression as well as HCV infection induces pro-metastatic effect on cancer cells which is simultaneous to Nm23-H1 transcriptional down-regulation and Nm23-H1 protein degradation. Moreover, Nm23-H1 intracellular localization is significantly altered in cells expressing HCV E1 protein. Importantly, overexpression of Nm23-H1 can rescue the cancer cells from pro-metastatic effects of HCV E1 and HCV infection. Our limited study provides evidence for role for Nm23-H1 in HCV mediated cancer metastasis.

COX-2 induces lytic reactivation of EBV through PGE2 by modulating the EP receptor signaling pathway.

Inflammation is one of the predisposing factors known to be associated with Epstein Barr Virus (EBV) mediated tumorigenesis. However it is not well understood whether inflammation in itself plays a role in regulating the life cycle of this infectious agent. COX-2, a key mediator of the inflammatory processes is frequently over-expressed in EBV positive cancer cells. In various tumors, PGE2 is the principle COX-2 regulated downstream product which exerts its effects on cellular processes through the EP1-4 receptors. In this study, we further elucidated how upregulated COX-2 levels can modulate the events in EBV life cycle related to latency-lytic reactivation. Our data suggest a role for upregulated COX-2 on modulation of EBV latency through its downstream effector PGE2. This study demonstrates a role for increased COX-2 levels in modulation of EBV latency. This is important for understanding the pathogenesis of EBV-associated cancers in people with chronic inflammatory conditions.

Host proteins associated with Hepatitis C virus encoded NS4A.

Virus-associated cancers account for more than 12 % of all the cancers. Hepatitis C virus (HCV) infects nearly 3 % of the population worldwide and has emerged as a major causative agent of liver disease with a big impact on public health. The HCV non-structural protein NS4A is a 54-amino-acid polypeptide that serves as an essential co-factor for the NS3 serine protease. We report here on a proteomic study to identify cellular proteins associated with NS4A. The results of this study show an association of three host cellular proteins with NS4A including two novel NS4A interacting partners. Our data provide evidence for complex involving NS4A with previously unreported cellular proteins including housekeeping protein GAPDH, and PI3P-5 K which is involved in cellular protein trafficking to nucleus. These novel associations add to the diversity of NS4A functions in relation to the virus infection and subsequent pathogenesis.