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Abstract Background Ufm1-specific ligase 1 (Ufl1) and Ufm1-binding protein 1 (Ufbp1), as putative targets of ubiquitin-fold modifier 1 (Ufm1), have been implicated in several pathogenesis-related signaling pathways. However, little is known about their functional roles in liver disease. Methods Hepatocyte-specific Ufl1 Δ/Δhep and Ufbp1 Δ/Δhep mice were used to study their role in liver injury. Fatty liver disease and liver cancer were induced by high-fat diet (HFD) and diethylnitrosamine (DEN) administration, respectively. iTRAQ analysis was employed to screen for downstream targets affected by Ufbp1 deletion. Co-immunoprecipitation was used to determine the interactions between the Ufl1/Ufbp1 complex and the mTOR/GβL complex. Results Ufl1 Δ/Δhep or Ufbp1 Δ/Δhep mice exhibited hepatocyte apoptosis and mild steatosis at 2 months of age and hepatocellular ballooning, extensive fibrosis, and steatohepatitis at 6–8 months of age. More than 50% of Ufl1 Δ/Δhep and Ufbp1 Δ/Δhep mice developed spontaneous hepatocellular carcinoma (HCC) by 14 months of age. Moreover, Ufl1 Δ/Δhep and Ufbp1 Δ/Δhep mice were more susceptible to HFD-induced fatty liver and DEN-induced HCC. Mechanistically, the Ufl1/Ufbp1 complex directly interacts with the mTOR/GβL complex and attenuates mTORC1 activity. Ablation of Ufl1 or Ufbp1 in hepatocytes dissociates them from the mTOR/GβL complex and activates oncogenic mTOR signaling to drive HCC development. Conclusions These findings reveal the potential role of Ufl1 and Ufbp1 as gatekeepers to prevent liver fibrosis and subsequent steatohepatitis and HCC development by inhibiting the mTOR pathway.

Abstract Background Targeting mitochondrial oncoproteins presents a new concept in the development of effective cancer therapeutics. ATAD3A is a nuclear-encoded mitochondrial enzyme contributing to mitochondrial dynamics, cholesterol metabolism, and signal transduction. However, its impact and underlying regulatory mechanisms in cancers remain ill-defined. Methods We used head and neck squamous cell carcinoma (HNSCC) as a research platform and achieved gene depletion by lentiviral shRNA and CRISPR/Cas9. Molecular alterations were examined by RNA-sequencing, phospho-kinase profiling, Western blotting, RT-qPCR, immunohistochemistry, and immunoprecipitation. Cancer cell growth was assessed by MTT, colony formation, soft agar, and 3D cultures. The therapeutic efficacy in tumor development was evaluated in orthotopic tongue tumor NSG mice. Results ATAD3A is highly expressed in HNSCC tissues and cell lines. Loss of ATAD3A expression suppresses HNSCC cell growth and elicits tumor regression in orthotopic tumor-bearing mice, whereas gain of ATAD3A expression produces the opposite effects. From a mechanistic perspective, the tumor suppression induced by the overexpression of the Walker A dead mutant of ATAD3A (K358) produces a potent dominant-negative effect due to defective ATP-binding. Moreover, ATAD3A binds to ERK1/2 in the mitochondria of HNSCC cells in the presence of VDAC1, and this interaction is essential for the activation of mitochondrial ERK1/2 signaling. Most importantly, the ATAD3A-ERK1/2 signaling axis drives HNSCC development in a RAS-independent fashion and, thus, tumor suppression is more effectively achieved when ATAD3A knockout is combined with RAS inhibitor treatment. Conclusions These findings highlight the novel function of ATAD3A in regulating mitochondrial ERK1/2 activation that favors HNSCC development. Combined targeting of ATAD3A and RAS signaling may potentiate anticancer activity for HNSCC therapeutics.

Abstract Background Alterations in metabolism are one of the emerging hallmarks of cancer cells and targeting dysregulated cancer metabolism provides a new approach to developing more selective therapeutics. However, insufficient blockade critical metabolic dependencies of cancer allows the development of metabolic bypasses, thus limiting therapeutic benefits. Methods A series of head and neck squamous cell carcinoma (HNSCC) cell lines and animal models were used to determine the efficacy of CPI-613 and CB-839 when given alone or in combination. Glutaminase 1 (GLS1) depletion was achieved by lentiviral shRNAs. Cell viability and apoptosis were determined in HNSCC cells cultured in 2D culture dish and SeedEZ™ 3D scaffold. Molecular alterations were examined by Western blotting and immunohistochemistry. Metabolic changes were assessed by glucose uptake, lactate production, glutathione levels, and oxygen consumption rate. Results We show here that HNSCC cells display strong addiction to glutamine. CPI-613, a novel lipoate analog, redirects cellular activity towards tumor-promoting glutaminolysis, leading to low anticancer efficacy in HNSCC cells. Mechanistically, CPI-613 inhibits the tricarboxylic acid cycle by blocking the enzyme activities of pyruvate dehydrogenase and alpha-ketoglutarate dehydrogenase, which upregulates GLS1 and eventually promotes the compensatory role of glutaminolysis in cancer cell survival. Most importantly, the addition of a GLS1 inhibitor CB-839 to CPI-613 treatment abrogates the metabolic dependency of HNSCC cells on glutamine, achieving a synergistic anticancer effect in glutamine-addicted HNSCC. Conclusions These findings uncover the critical role of GLS1-mediated glutaminolysis in CPI-613 treatment and suggest that the CB-839 and CPI-613 combination may potentiate synergistic anticancer activity for HNSCC therapeutic gain.

Abstract Tumor resistance to apoptosis and the immunosuppressive tumor microenvironment are two major contributors to poor therapeutic responses during cancer intervention. Pyroptosis, a lytic and inflammatory programmed cell death pathway distinct from apoptosis, has subsequently sparked notable interest among cancer researchers for its potential to be clinically harnessed and to address these problems. Recent evidence indicates that pyroptosis induction in tumor cells leads to a robust inflammatory response and marked tumor regression. Underlying its antitumor effect, pyroptosis is mediated by pore-forming gasdermin proteins that facilitate immune cell activation and infiltration through their release of pro-inflammatory cytokines and immunogenic material following cell rupture. Considering its inflammatory nature, however, aberrant pyroptosis may also be implicated in the formation of a tumor supportive microenvironment, as evidenced by the upregulation of gasdermin proteins in certain cancers. In this review, the molecular pathways leading to pyroptosis are introduced, followed by an overview of the seemingly entangled links between pyroptosis and cancer. We describe what is known regarding the impact of pyroptosis on anticancer immunity and give insight into the potential of harnessing pyroptosis as a tool and applying it to novel or existing anticancer strategies.

Abstract Background Metastasis is most often the root cause of cancer-related death. Human short stature homeobox 2 (SHOX2), a homeodomain transcription factor, is a novel inducer of epithelial-to-mesenchymal transition in breast cancer cells, though its exact role and underlying mechanisms in metastasis are not well understood. Methods TCGA analysis was performed to identify the clinical relevance of SHOX2 in breast cancer. Gene depletion was achieved by short hairpin RNA and small interfering RNA. Molecular regulations and alterations were assessed by Western blotting, immunoprecipitation, immunohistochemistry, qRT-PCR, chromatin immunoprecipitation coupled with qPCR (ChIP-qPCR), and ChIP/re-ChIP. The impact of SHOX2 signaling on tumor growth and metastasis was evaluated in orthotopic breast tumor mice. Results The expression level of SHOX2 is strongly associated with poor distant metastasis-free survival in breast cancer patients and inactivation of SHOX2 suppresses breast tumor growth and metastasis in mice. In breast cancer cells, SHOX2 directly activates Wiskott-Aldridge syndrome protein family member 3 (WASF3), a metastasis-promoting gene, at the transcriptional level, leading to a significant increase in metastatic potential. Mechanistically, SHOX2 activates signal transducer and activator of transcription 3 (STAT3) and recruits it to the WASF3 promoter, where STAT3 cooperates with SHOX2 to form a functional immunocomplex to promote WASF3 transcriptional activity in breast cancer cells. WASF3 knockdown abrogates SHOX2-induced metastasis, but not SHOX2-dependent tumorigenesis. Conclusions These findings provide a critical link between the SHOX2-STAT3-WASF3 signaling axis and metastasis and suggest that the targeting of this signaling node may represent a valuable alternative strategy for combating breast cancer metastasis.

Abstract Background There is no consensus about the effective dosages of melatonin in cancer management, thus, it is imperative to fully understand the dose-dependent responsiveness of cancer cells to melatonin and the underlying mechanisms. Methods Head and neck squamous cell carcinoma (HNSCC) cells with or without melatonin treatment were used as a research platform. Gene depletion was achieved by short hairpin RNA, small interfering RNA, and CRISPR/Cas9. Molecular changes and regulations were assessed by Western blotting, quantitative RT-PCR (qRT-PCR), immunohistochemistry, and chromatin Immunoprecipitation coupled with qPCR (ChIP-qPCR). The therapeutic efficacy of FGF19/FGFR4 inhibition in melatonin-mediated tumor growth and metastasis was evaluated in orthotopic tongue tumor mice. Results The effect of melatonin on controlling cell motility and metastasis varies in HNSCC cells, which is dose-dependent. Mechanistically, high-dose melatonin facilitates the upregulation of FGF19 expression through activating endoplasmic stress (ER)-associated protein kinase RNA-like endoplasmic reticulum kinase (PERK)-Eukaryotic initiation factor 2 alpha (eIF2α)-activating transcription factor 4 (ATF4) pathway, which in turn promotes FGFR4-Vimentin invasive signaling and attenuates the role of melatonin in repressing metastasis. Intriguingly, following long-term exposure to high-dose melatonin, epithelial HNSCC cells revert the process towards mesenchymal transition and turn more aggressive, which is enabled by FGF19/FGFR4 upregulation and alleviated by genetic depletion of the FGF19 and FGFR4 genes or the treatment of FGFR4 inhibitor H3B-6527. Conclusions Our study gains novel mechanistic insights into melatonin-mediated modulation of FGF19/FGFR4 signaling in HNSCC, demonstrating that activating this molecular node confines the role of melatonin in suppressing metastasis and even triggers the switch of its function from anti-metastasis to metastasis promotion. The blockade of FGF19/FGFR4 signaling would have great potential in improving the efficacy of melatonin supplements in cancer treatment.

The tumor microenvironment (TME) is a rich and active arena that is strategically evolved overtime by tumors to promote their survival and dissemination. Over the years, attention has been focused to characterize and identify the tumor-supporting roles and subsequent targeting potentials of TME components. Nevertheless, recapitulating the human TME has proved inherently challenging, leaving much to be explored. In this regard, in vivo model systems like zebrafish, with its optical clarity, ease of genetic manipulation, and high engraftment, have proven to be indispensable for TME modeling and investigation. In this review, we discuss the recent ways by which zebrafish models have lent their utility to provide new insights into the various cellular and molecular mechanisms driving TME dynamics and tumor support. Specifically, we report on innate immune cell interactions, cytokine signaling, metastatic plasticity, and other processes within the metastatic cascade. In addition, we reflect on the arrival of adult zebrafish models and the potential of patient-derived xenografts.

Epidemiological and clinical studies over the past two decades have provided strong evidence that genetic elements interacting with environmental components can individually and collectively influence one’s susceptibility to cancer. In addition to tumorigenic properties, numerous environmental factors, such as nutrition, chemical carcinogens, and tobacco/alcohol consumption, possess pro-invasive and pro-metastatic cancer features. In contrast to traditional cancer treatment, modern therapeutics not only take into account an individual’s genetic makeup but also consider gene–environment interactions. The current review sharpens the focus by elaborating on the impact that environmental factors have on the pathogenesis and progression of head and neck cancer and the underlying molecular mechanisms involved. Recent advances, challenges, and future perspectives in this area of research are also discussed. Inhibiting key environmental drivers of tumor progression should yield survival benefits for patients at any stage of head and neck cancer.