ALK inhibitors suppress HCC and synergize with anti-PD-1 therapy and ABT-263 in preclinical models.

Hepatocellular carcinoma (HCC) currently lacks effective therapies, leaving a critical need for new treatment options. A previous study identified the anaplastic lymphoma kinase (ALK) amplification in HCC patients, raising the question of whether ALK inhibitors could be a viable treatment. Here, we showed that both ALK inhibitors and ALK knockout effectively halted HCC growth in cell cultures. Lorlatinib, a potent ALK inhibitor, suppressed HCC tumor growth and metastasis across various mouse models. Additionally, in an advanced immunocompetent humanized mouse model, when combined with an anti-PD-1 antibody, lorlatinib more potently suppressed HCC tumor growth, surpassing individual drug efficacy. Lorlatinib induced apoptosis and senescence in HCC cells, and the senolytic agent ABT-263 enhanced the efficacy of lorlatinib. Additional studies identified that the apoptosis-inducing effect of lorlatinib was mediated via GGN and NRG4. These findings establish ALK inhibitors as promising HCC treatments, either alone or in combination with immunotherapies or senolytic agents.

HOXC6 drives a therapeutically targetable pancreatic cancer growth and metastasis pathway by regulating MSK1 and PPP2R2B.

Pancreatic ductal adenocarcinoma (PDAC) is one of the deadliest cancers, which lacks effective therapies. Here, we demonstrate that the transcription factor, homeobox C6 (HOXC6), is overexpressed in most PDACs, and its inhibition blocks PDAC tumor growth and metastasis. HOXC6 transcriptionally activates tumor-promoting kinase MSK1 and suppresses tumor-inhibitory protein PPP2R2B in PDAC. HOXC6-induced PPP2R2B suppression causes mammalian target of rapamycin (mTOR) pathway activation, which facilitates PDAC growth. Also, MSK1 upregulation by HOXC6 is necessary for PDAC growth because of its ability to suppress apoptosis via its substrate DDX17. Combinatorial pharmacological inhibition of MSK1 and mTOR potently suppressed PDAC tumor growth and metastasis in PDAC mouse models. PDAC cells with acquired resistance to MSK1/mTOR-inhibitors displayed activated insulin-like growth factor 1 receptor (IGF1R) signaling and were successfully eradicated by IGF1R inhibitor. Furthermore, MEK inhibitor trametinib enhanced the efficacy of dual MSK1 and mTOR inhibition. Collectively, these results identify therapeutic vulnerabilities of PDAC and an approach to overcome acquired drug resistance to prolong therapeutic benefit.

LIMK2 promotes melanoma tumor growth and metastasis through G3BP1-ESM1 pathway-mediated apoptosis inhibition.

Melanoma is the leading cause of skin cancer-related deaths, and current melanoma therapies, including targeted therapies and immunotherapies, benefit only a subset of metastatic melanoma patients due to either intrinsic or acquired resistance. LIM domain kinase 2 (LIMK2) is a serine/threonine kinase that plays an important role in the regulation of actin filament dynamics. Here, we show that LIMK2 is overexpressed in melanoma, and its genetic or pharmacological inhibition impairs melanoma tumor growth and metastasis in both cell culture and mice. To determine the mechanism by which LIMK2 promotes melanoma tumor growth and metastatic progression, we performed a phosphoproteomics analysis and identified G3BP1 as a key LIMK2 target, which mirrored the effects of LIMK2 inhibition when inhibited. To further determine the role of G3BP1 downstream of LIMK2, we knocked down the expression of G3BP1, performed RNA-seq analysis, and identified ESM1 as a downstream target of G3BP1. G3BP1 was required for ESM1 mRNA stability, and ESM1 ectopic expression rescued LIMK2 or G3BP1 inhibition-induced suppression of melanoma growth and metastatic attributes. These results collectively identify the LIMK2→G3BP1→ESM1 pathway as a facilitator of melanoma tumor growth and metastasis and document that LIMK2 is a therapeutically tractable target for melanoma therapy.

Transcriptional, chromatin, and metabolic landscapes of LDHA inhibitor-resistant pancreatic ductal adenocarcinoma.

Metabolic reprogramming, due in part to the overexpression of metabolic enzymes, is a key hallmark of cancer cells. Lactate dehydrogenase (LDHA), a metabolic enzyme that catalyzes the interconversion of lactate and pyruvate, is overexpressed in a wide variety of cancer types, including pancreatic ductal adenocarcinoma (PDAC). Furthermore, the genetic or pharmacological inhibition of LDHA suppresses cancer growth, demonstrating a cancer-promoting role for this enzyme. Therefore, several pharmacological LDHA inhibitors are being developed and tested as potential anti-cancer therapeutic agents. Because cancer cells are known to rapidly adapt and become resistant to anti-cancer therapies, in this study, we modeled the adaptation of cancer cells to LDHA inhibition. Using PDAC as a model system, we studied the molecular aspects of cells resistant to the competitive LDHA inhibitor sodium oxamate. We performed unbiased RNA-sequencing (RNA-seq), assay for transposase-accessible chromatin with sequencing (ATAC-seq), and metabolomics analyses of parental and oxamate-resistant PDAC cells treated with and without oxamate to identify the transcriptional, chromatin, and metabolic landscapes of these cells. We found that oxamate-resistant PDAC cells were significantly different from parental cells at the levels of mRNA expression, chromatin accessibility, and metabolites. Additionally, an integrative analysis combining the RNA-seq and ATAC-seq datasets identified a subset of differentially expressed mRNAs that directly correlated with changes in chromatin accessibility. Finally, functional analysis of differentially expressed metabolic genes in parental and oxamate-resistant PDAC cells treated with and without oxamate, together with an integrative analysis of RNA-seq and metabolomics data, revealed changes in metabolic enzymes that might explain the changes in metabolite levels observed in these cells. Collectively, these studies identify the transcriptional, chromatin, and metabolic landscapes of LDHA inhibitor resistance in PDAC cells. Future functional studies related to these changes remain necessary to reveal the direct roles played by these changes in the development of LDHA inhibitor resistance and uncover approaches for more effective use of LDHA inhibitors in cancer therapy.

Co-targeting of specific epigenetic regulators in combination with CDC7 potently inhibit melanoma growth.

Melanoma is a highly aggressive skin cancer that frequently metastasizes, but current therapies only benefit some patients. Here, we demonstrate that the serine/threonine kinase cell division cycle 7 (CDC7) is overexpressed in melanoma, and patients with higher expression have shorter survival. Transcription factor ELK1 regulates CDC7 expression, and CDC7 inhibition promotes cell cycle arrest, senescence, and apoptosis, leading to inhibition of melanoma tumor growth and metastasis. Our chemical genetics screen with epigenetic inhibitors revealed stronger melanoma tumor growth inhibition when XL413 is combined with the EZH2 inhibitor GSK343 or BRPF1/2/3 inhibitor OF1. Mechanistically, XL413 with GSK343 or OF1 synergistically altered the expression of tumor-suppressive genes, leading to higher apoptosis than the single agent alone. Collectively, these results identify CDC7 as a driver of melanoma tumor growth and metastasis that can be targeted alone or in combination with EZH2 or BRPF1/2/3 inhibitors.

N-acylsphingosine amidohydrolase 1 promotes melanoma growth and metastasis by suppressing peroxisome biogenesis-induced ROS production.

OBJECTIVE: Metabolic deregulation is a key hallmark of cancer cells and has been shown to drive cancer growth and metastasis. However, not all metabolic drivers of melanoma are known. Based on our finding that N-acylsphingosine amidohydrolase 1 (ASAH1) is overexpressed in melanoma, the objective of these studies was to establish its role in melanoma tumor growth and metastasis, understand its mechanism of action, and evaluate ASAH1 targeting for melanoma therapy. METHODS: We used publicly available melanoma datasets and patient-derived samples of melanoma and normal skin tissue and analyzed them for ASAH1 mRNA expression and ASAH1 protein expression using immunohistochemistry. ASAH1 was knocked down using short-hairpin RNAs in multiple melanoma cell lines that were tested in a series of cell culture-based assays and mouse-based melanoma xenograft assays to monitor the effect of ASAH1 knockdown on melanoma tumor growth and metastasis. An unbiased metabolomics analysis was performed to identify the mechanism of ASAH1 action. Based on the metabolomics findings, the role of peroxisome-mediated reactive oxygen species (ROS) production was explored in regard to mediating the effect of ASAH1. The ASAH1 inhibitor was used alone or in combination with a BRAFV600E inhibitor to evaluate the therapeutic value of ASAH1 targeting for melanoma therapy. RESULTS: We determined that ASAH1 was overexpressed in a large percentage of melanoma cells and regulated by transcription factor E2F1 in a mitogen-activated protein (MAP) kinase pathway-dependent manner. ASAH1 expression was necessary to maintain melanoma tumor growth and metastatic attributes in cell cultures and mouse models of melanoma tumor growth and metastasis. To identify the mechanism by which ASAH1 facilitates melanoma tumor growth and metastasis, we performed a large-scale and unbiased metabolomics analysis of melanoma cells expressing ASAH1 short-hairpin RNAs (shRNAs). We found that ASAH1 inhibition increased peroxisome biogenesis through ceramide-mediated PPARγ activation. ASAH1 loss increased ceramide and peroxisome-derived ROS, which in turn inhibited melanoma growth. Pharmacological inhibition of ASAH1 also attenuated melanoma growth and enhanced the effectiveness of BRAF kinase inhibitor in the cell cultures and mice. CONCLUSIONS: Collectively, these results demonstrate that ASAH1 is a druggable driver of melanoma tumor growth and metastasis that functions by suppressing peroxisome biogenesis, thereby inhibiting peroxisome-derived ROS production. These studies also highlight the therapeutic utility of ASAH1 inhibitors for melanoma therapy.

PSPH promotes melanoma growth and metastasis by metabolic deregulation-mediated transcriptional activation of NR4A1.

Metabolic deregulation, a hallmark of cancer, fuels cancer cell growth and metastasis. Here, we show that phosphoserine phosphatase (PSPH), an enzyme of the serine metabolism pathway, is upregulated in patient-derived melanoma samples. PSPH knockdown using short hairpin RNAs (shRNAs) blocks melanoma tumor growth and metastasis in both cell culture and mice. To elucidate the mechanism underlying PSPH action, we evaluated PSPH shRNA-expressing melanoma cells using global metabolomics and targeted mRNA expression profiling. Metabolomics analysis showed an increase in 2-hydroxyglutarate (2-HG) levels in PSPH knockdown cells. 2-HG inhibits the TET family of DNA demethylases and the Jumonji family of histone demethylases (KDM and JMJD), which is known to impact gene expression. Consistent with these data, PSPH knockdown in melanoma cells showed reduced DNA 5-hydroxymethylcytosine (5hmC) and increased histone H3K4me3 modifications. 2-HG treatment also inhibited melanoma growth. The nCounter PanCancer Pathways Panel-based mRNA expression profiling revealed attenuation of a number of cancer-promoting pathways upon PSPH knockdown. In particular, PSPH was necessary for nuclear receptor NR4A1 expression. Ectopic NR4A1 expression partly rescued the growth of melanoma cells expressing PSPH shRNA. Collectively, these results link PSPH to the facilitation of melanoma growth and metastasis through suppression of 2-HG and thus activation of pro-oncogenic gene expression.

PON2 subverts metabolic gatekeeper functions in B cells to promote leukemogenesis.

Unlike other cell types, developing B cells undergo multiple rounds of somatic recombination and hypermutation to evolve high-affinity antibodies. Reflecting the high frequency of DNA double-strand breaks, adaptive immune protection by B cells comes with an increased risk of malignant transformation. B lymphoid transcription factors (e.g., IKZF1 and PAX5) serve as metabolic gatekeepers by limiting glucose to levels insufficient to fuel transformation. We here identified aberrant expression of the lactonase PON2 in B cell acute lymphoblastic leukemia (B-ALL) as a mechanism to bypass metabolic gatekeeper functions. Compared to normal pre-B cells, PON2 expression was elevated in patient-derived B-ALL samples and correlated with poor clinical outcomes in pediatric and adult cohorts. Genetic deletion of Pon2 had no measurable impact on normal B cell development. However, in mouse models for BCR-ABL1 and NRASG12D-driven B-ALL, deletion of Pon2 compromised proliferation, colony formation, and leukemia initiation in transplant recipient mice. Compromised leukemogenesis resulted from defective glucose uptake and adenosine triphosphate (ATP) production in PON2-deficient murine and human B-ALL cells. Mechanistically, PON2 enabled glucose uptake by releasing the glucose-transporter GLUT1 from its inhibitor stomatin (STOM) and genetic deletion of STOM largely rescued PON2 deficiency. While not required for glucose transport, the PON2 lactonase moiety hydrolyzes the lactone-prodrug 3OC12 to form a cytotoxic intermediate. Mirroring PON2 expression levels in B-ALL, 3OC12 selectively killed patient-derived B-ALL cells but was well tolerated in transplant recipient mice. Hence, while B-ALL cells critically depend on aberrant PON2 expression to evade metabolic gatekeeper functions, PON2 lactonase activity can be leveraged as synthetic lethality to overcome drug resistance in refractory B-ALL.

Metformin induced lactic acidosis impaired response of cancer cells towards paclitaxel and doxorubicin: Role of monocarboxylate transporter.

Abnormal glucose metabolism in cancer cells causes generation and secretion of excess lactate, which results in acidification of the extracellular microenvironment. This altered metabolism aids not only in survival and proliferation but also in suppressing immune-mediated destruction of cancer cells. However, how it influences the response of cancer cells to chemotherapeutic drugs is not clearly understood. We employed appropriate in vitro approaches to explore the role of mono-carboxylate transporter 4 (MCT4) mediated altered intra and extracellular pH on the outcome of the therapeutic efficacy of chemotherapeutic drugs in breast and lung cancer models. We demonstrate by in vitro experiments that inhibition of complex I enhances glycolysis and increases expression as well as membrane translocation of MCT4. It causes a decrease in extracellular pH (pHe) and impairs doxorubicin and paclitaxel's therapeutic efficacy. Acidic pHe inhibits doxorubicin's uptake, while acidic intracellular pH (pH i) impairs the efficacy of paclitaxel. Under in vivo experimental settings, the modulation of pHe with phloretin or alkalizer (NaHCO3) enhances cytotoxicity of drugs and inhibits the growth of MCF-7 xenografts in mice. In a nutshell, this study indicates that MCT4 mediated extracellular acidosis is involved in impairing chemotherapeutic drugs' efficacy on cancer cells. Therefore, the use of pH neutralizing agents or MCT inhibitors may be beneficial towards circumventing impairment in the efficacy of certain drugs that are sensitive to pH changes.

LIMK2 promotes the metastatic progression of triple-negative breast cancer by activating SRPK1.

Triple-negative breast cancer (TNBC) is a highly metastatic breast cancer subtype and due to the lack of hormone receptors and HER2 expression, TNBC has limited therapeutic options with chemotherapy being the primary choice for systemic therapy. LIM Domain Kinase 2 (LIMK2) is a serine/threonine kinase that plays an important role in the regulation of actin filament dynamics. Here, we show that LIM domain kinase 2 (LIMK2) is overexpressed in TNBC, and short-hairpin RNA (shRNA)-mediated LIMK2 knockdown or its pharmacological inhibition blocks metastatic attributes of TNBC cells. To determine the mechanism by which LIMK2 promotes TNBC metastatic progression, we performed stable isotope labeling by amino acids in cell culture (SILAC) based unbiased large-scale phosphoproteomics analysis. This analysis identified 258 proteins whose phosphorylation was significantly reduced due to LIMK2 inhibition. Among these proteins, we identified SRSF protein kinase 1 (SRPK1), which encodes for a serine/arginine protein kinase specific for the SR (serine/arginine-rich domain) family of splicing factors. We show that LIMK2 inhibition blocked SRPK1 phosphorylation and consequentially its activity. Furthermore, similar to LIMK2, genetic inhibition of SRPK1 by shRNAs or its pharmacological inhibition blocked the metastatic attributes of TNBC cells. Moreover, the pharmacological inhibition of LIMK2 blocked metastatic progression in mice without affecting primary tumor growth. In sum, these results identified LIMK2 as a facilitator of distal TNBC metastasis and a potential target for preventing TNBC metastatic progression.

KLF7 promotes pancreatic cancer growth and metastasis by up-regulating ISG expression and maintaining Golgi complex integrity.

Pancreatic ductal adenocarcinoma (PDAC) is an aggressive cancer with a dismal prognosis. Currently, there is no effective therapy for PDAC, and a detailed molecular and functional evaluation of PDACs is needed to identify and develop better therapeutic strategies. Here we show that the transcription factor Krüppel-like factor 7 (KLF7) is overexpressed in PDACs, and that inhibition of KLF7 blocks PDAC tumor growth and metastasis in cell culture and in mice. KLF7 expression in PDACs can be up-regulated due to activation of a MAP kinase pathway or inactivation of the tumor suppressor p53, two alterations that occur in a large majority of PDACs. ShRNA-mediated knockdown of KLF7 inhibits the expression of IFN-stimulated genes (ISGs), which are necessary for KLF7-mediated PDAC tumor growth and metastasis. KLF7 knockdown also results in the down-regulation of Discs Large MAGUK Scaffold Protein 3 (DLG3), resulting in Golgi complex fragmentation, and reduced protein glycosylation, leading to reduced secretion of cancer-promoting growth factors, such as chemokines. Genetic or pharmacologic activation of Golgi complex fragmentation blocks PDAC growth and metastasis similar to KLF7 inhibition. Our results demonstrate a therapeutically amenable, KLF7-driven pathway that promotes PDAC growth and metastasis by activating ISGs and maintaining Golgi complex integrity.

Loss of thymidine kinase 1 inhibits lung cancer growth and metastatic attributes by reducing GDF15 expression.

Metabolic alterations that are critical for cancer cell growth and metastasis are one of the key hallmarks of cancer. Here, we show that thymidine kinase 1 (TK1) is significantly overexpressed in tumor samples from lung adenocarcinoma (LUAD) patients relative to normal controls, and this TK1 overexpression is associated with significantly reduced overall survival and cancer recurrence. Genetic knockdown of TK1 with short hairpin RNAs (shRNAs) inhibits both the growth and metastatic attributes of LUAD cells in culture and in mice. We further show that transcriptional overexpression of TK1 in LUAD cells is driven, in part, by MAP kinase pathway in a transcription factor MAZ dependent manner. Using targeted and gene expression profiling-based approaches, we then show that loss of TK1 in LUAD cells results in reduced Rho GTPase activity and reduced expression of growth and differentiation factor 15 (GDF15). Furthermore, ectopic expression of GDF15 can partially rescue TK1 knockdown-induced LUAD growth and metastasis inhibition, confirming its important role as a downstream mediator of TK1 function in LUAD. Collectively, our findings demonstrate that TK1 facilitates LUAD tumor and metastatic growth and represents a target for LUAD therapy.

Anaplastic Lymphoma Kinase Confers Resistance to BRAF Kinase Inhibitors in Melanoma.

Melanoma frequently harbors oncogenic mutations in the BRAF gene, which drives melanoma growth. Therefore, BRAF kinase inhibitors (BRAFi) are developed and approved for treating BRAF-mutant melanoma. However, the efficacy of BRAFi is limited due to acquired resistance, and in over 40% of melanoma, the causes of BRAFi resistance remain unknown. Here, using a human phospho-receptor tyrosine kinase array we identified Anaplastic Lymphoma Kinase (ALK) as a driver of acquired BRAFi resistance in melanoma. We found that ALK ligand FAM150A was necessary for ALK activation and ALK via the PI3K/AKT pathway was sufficient to confer resistance to BRAFi. ALK inhibitor (ALKi) ceritinib inhibited BRAFi-resistant melanoma in cell culture and mice. Residual BRAFi and ALKi dual resistant melanoma cells from ceritinib-treated mice were sensitive to a broad-spectrum anti-apoptotic protein inhibitor, AT101. Collectively, our results provide a framework for treating BRAF-mutant melanoma that sequentially uses different targeted therapies based on post-treatment tumor evolution.

Dissecting the role of RNA modification regulatory proteins in melanoma.

Melanoma is the deadliest form of skin cancer. Despite recent advances in medicine and the development of new treatments for melanoma, cures remain elusive as acquired resistance to both targeted and immunotherapies are becoming common. Therefore, more studies are conducted to dissect underlying molecular mechanisms that drive melanoma growth in order to provide better therapeutic option. Here, employing a comprehensive and unbiased analysis of different RNA modification regulatory proteins using various publicly available databases we identify the most relevant RNA modifying proteins that plays crucial role in melanoma development. Our study started with the analysis of various genetic alterations (amplifications, mutations/deletion) as well as RNA overexpression of these RNA modification regulatory proteins in The Cancer Genome Atlas melanoma database. We then analyzed their expression in The Human Protein Atlas data. The result of analysis revealed that only a subset of RNA modification regulatory proteins are overexpressed in >75% of melanoma patient cases as compared to normal skin. However, when examined in Oncomine dataset we found only two genes (METTL4 and DNMT3A) were significantly overexpressed in melanoma samples versus normal skin samples and matched with the results of The Human Protein Atlas data. Therefore, we functionally validated METTL4 and DNMT3A using shRNA-mediated knockdown and found that their knockdown in melanoma cells led to melanoma cells growth inhibition. Collectively, in this study, we investigated the epitranscriptomic landscape of melanoma using various publicly available database and identified DNMT3A and METTL4 as the most relevant potential regulators of melanoma growth.

Heparan Sulfate and Heparan Sulfate Proteoglycans in Cancer Initiation and Progression.

Heparan sulfate (HS) are complex unbranched carbohydrate chains that are heavily modified by sulfate and exist either conjugated to proteins or as free, unconjugated chains. Proteins with covalently bound Heparan sulfate chains are termed Heparan Sulfate Proteoglycans (HSPGs). Both HS and HSPGs bind to various growth factors and act as co-receptors for different cell surface receptors. They also modulate the dynamics and kinetics of various ligand-receptor interactions, which in turn can influence the duration and potency of the signaling. HS and HSPGs have also been shown to exert a structural role as a component of the extracellular matrix, thereby altering processes such as cell adhesion, immune cell infiltration and angiogenesis. Previous studies have shown that HS are deregulated in a variety of solid tumors and hematological malignancies and regulate key aspects of cancer initiation and progression. HS deregulation in cancer can occur as a result of changes in the level of HSPGs or due to changes in the levels of HS biosynthesis and remodeling enzymes. Here, we describe the major cell-autonomous (proliferation, apoptosis/senescence and differentiation) and cell-non-autonomous (angiogenesis, immune evasion, and matrix remodeling) roles of HS and HSPGs in cancer. Finally, we discuss therapeutic opportunities for targeting deregulated HS biosynthesis and HSPGs as a strategy for cancer treatment.

Elevated circulatory levels of leptin and resistin impair therapeutic efficacy of dacarbazine in melanoma under obese state.

BACKGROUND: Obesity is associated with increased risk, poor prognosis and outcome of therapy, in various cancers. Obesity-associated factors or adipokines, especially leptin and resistin, are purported to promote growth, survival, proliferation, and invasiveness of cancer cells. However, the mechanistic link between these adipokines and therapeutic response in malignancies is not clearly understood. METHODS: ob/ob and db/db mouse models were used in this study to evaluate the role of leptin and resistin towards the outcome of dacarbazine (DTIC) therapy in melanoma. Unique in vitro approaches were employed to complement in vivo findings by culturing melanoma cells in the serum collected from the experimental mice. RESULTS: Here, we have shown the role of important adipokines leptin and resistin in growth and the outcome of DTIC therapy in melanoma. Both leptin and resistin not only enhance proliferation of melanoma cells but also are involved in impairing the therapeutic efficacy of DTIC. Leptin and resistin treatment caused an increase in the protein levels of fatty acid synthase (FASN) and caveolin 1 (Cav-1) respectively, through their stabilization in A375 cells. Further, it was observed that leptin and resistin impaired the response of melanoma cells to DTIC via upregulation of heat shock protein 90 (Hsp90) and P-glycoprotein (P-gp) respectively. CONCLUSION: These findings unraveled the involvement of adipokines (leptin and resistin) in melanoma progression, and more importantly, in the outcome of DTIC therapy.

Weight control interventions improve therapeutic efficacy of dacarbazine in melanoma by reversing obesity-induced drug resistance.

BACKGROUND: Obesity-related cellular, metabolic, and molecular alterations have been shown to increase cancer risk and tumor progression and are associated with poorer therapeutic outcome in cancer patients. However, the impact of obesity and weight-control interventions on the therapeutic response in melanoma is poorly understood. METHODS: High fat diet (HFD)-induced obese mouse model was used in this study to evaluate the outcome of dacarbazine (DTIC) therapy in melanoma. We employed LC-MS/MS to determine the quantity of the drug in tumor, and in various tissues. Unique in vitro approach was used to complement in vivo findings by culturing melanoma cells in either conditioned medium (CM) obtained from differentiated adipocytes or in serum collected from experimental mice. RESULTS: We report that diet-induced obesity impairs the outcome of DTIC therapy and reduces overall survival in tumor-bearing mice. We provide evidence that obesity restricts the accessibility of DTIC to tumor tissue. Critically, upon curtailing adiposity, accumulation and efficacy of DTIC is significantly improved. Moreover, using appropriate in vitro approaches, we show that melanoma cells exhibit a drug-resistant phenotype when cultured in serum collected from diet-induced obese mice or in CM collected from 3T3-L1 adipocytes. The impaired therapeutic response to DTIC in obese state is mediated by fatty acid synthase (FASN), caveolin-1 (Cav-1), and P-glycoprotein (P-gp). The response to DTIC and overall survival were improved upon employing weight control interventions in the tumor-bearing HFD-fed (obese) mice. CONCLUSIONS: This study indicates that obesity not only supports rapid melanoma progression but also impairs the outcome of chemotherapy, which can be improved upon employing weight control interventions. From clinically relevant point of view, our study exemplifies the importance of lifestyle interventions in the treatment of obesity-promoted cancers.

Oncogene-directed alterations in cancer cell metabolism.

Oncogenes are key drivers of tumor growth. Although several cancer-driving mechanisms have been identified, the role of oncogenes in shaping metabolic patterns in cancer cells is only beginning to be appreciated. Recent studies show that oncogenes directly regulate critical metabolic enzymes and metabolic signaling pathways. Here, we present evidence for oncogene-directed cancer metabolic regulation and discuss the importance of identifying underlying mechanisms that can be targeted for developing precision cancer therapies.

Targeting metabolic flexibility by simultaneously inhibiting respiratory complex I and lactate generation retards melanoma progression.

Melanoma is a largely incurable skin malignancy owing to the underlying molecular and metabolic heterogeneity confounded by the development of resistance. Cancer cells have metabolic flexibility in choosing either oxidative phosphorylation (OXPHOS) or glycolysis for ATP generation depending upon the nutrient availability in tumor microenvironment. In this study, we investigated the involvement of respiratory complex I and lactate dehydrogenase (LDH) in melanoma progression. We show that inhibition of complex I by metformin promotes melanoma growth in mice via elevating lactate and VEGF levels. In contrast, it leads to the growth arrest in vitro because of enhanced extracellular acidification as a result of increased glycolysis. Inhibition of LDH or lactate generation causes decrease in glycolysis with concomitant growth arrest both in vitro and in vivo. Blocking lactate generation in metformin-treated melanoma cells results in diminished cell proliferation and tumor progression in mice. Interestingly, inhibition of either LDH or complex I alone does not induce apoptosis, whereas inhibiting both together causes depletion in cellular ATP pool resulting in metabolic catastrophe induced apoptosis. Overall, our study suggests that LDH and complex I play distinct roles in regulating glycolysis and cell proliferation. Inhibition of these two augments synthetic lethality in melanoma.