Targeting HIF-1α is a prerequisite for cell sensitivity to dichloroacetate (DCA) and metformin

Novel cancer treatment paradigm targeting hypoxia-induced factor in conjunction with current therapies to overcome resistance

Chemotherapy, radiotherapy, targeted therapy, and immunotherapy are established cancer treatment modalities that are widely used due to their demonstrated efficacy against tumors and favorable safety profiles or tolerability. Nevertheless, treatment resistance continues to be one of the most pressing unsolved conundrums in cancer treatment. Hypoxia-inducible factors (HIFs) are a family of transcription factors that regulate cellular responses to hypoxia by activating genes involved in various adaptations, including erythropoiesis, glucose metabolism, angiogenesis, cell proliferation, and apoptosis. Despite this critical function, overexpression of HIFs has been observed in numerous cancers, leading to resistance to therapy and disease progression. In recent years, much effort has been poured into developing innovative cancer treatments that target the HIF pathway. Combining HIF inhibitors with current cancer therapies to increase anti-tumor activity and diminish treatment resistance is one strategy for combating therapeutic resistance. This review focuses on how HIF inhibitors could be applied in conjunction with current cancer treatments, including those now being evaluated in clinical trials, to usher in a new era of cancer therapy.

CCDC65 as a new potential tumor suppressor induced by metformin inhibits activation of AKT1 via ubiquitination of ENO1 in gastric cancer

The coiled-coil domain containing protein members have been well documented for their roles in many diseases including cancers. However, the function of the coiled-coil domain containing 65 (CCDC65) remains unknown in tumorigenesis including gastric cancer. Methods: CCDC65 expression and its correlation with clinical features and prognosis of gastric cancer were analyzed in tissue. The biological role and molecular basis of CCDC65 were performed via in vitro and in vivo assays and a various of experimental methods including co-immunoprecipitation (Co-IP), GST-pull down and ubiquitination analysis et al. Finally, whether metformin affects the pathogenesis of gastric cancer by regulating CCDC65 and its-mediated signaling was investigated. Results: Here, we found that downregulated CCDC65 level was showed as an unfavourable factor in gastric cancer patients. Subsequently, CCDC65 or its domain (a.a. 130-484) was identified as a significant suppressor in GC growth and metastasis in vitro and in vivo. Molecular basis showed that CCDC65 bound to ENO1, an oncogenic factor has been widely reported to promote the tumor pathogenesis, by its domain (a.a. 130-484) and further promoted ubiquitylation and degradation of ENO1 by recruiting E3 ubiquitin ligase FBXW7. The downregulated ENO1 decreased the binding with AKT1 and further inactivated AKT1, which led to the loss of cell proliferation and EMT signal. Finally, we observed that metformin, a new anti-cancer drug, can significantly induce CCDC65 to suppress ENO1-AKT1 complex-mediated cell proliferation and EMT signals and finally suppresses the malignant phenotypes of gastric cancer cells. Conclusion: These results firstly highlight a critical role of CCDC65 in suppressing ENO1-AKT1 pathway to reduce the progression of gastric cancer and reveals a new molecular mechanism for metformin in suppressing gastric cancer. Our present study provides a new insight into the mechanism and therapy for gastric cancer.

Targeting Glucose Metabolism of Cancer Cells with Dichloroacetate to Radiosensitize High-Grade Gliomas

As the cornerstone of high-grade glioma (HGG) treatment, radiotherapy temporarily controls tumor cells via inducing oxidative stress and subsequent DNA breaks. However, almost all HGGs recur within months. Therefore, it is important to understand the underlying mechanisms of radioresistance, so that novel strategies can be developed to improve the effectiveness of radiotherapy. While currently poorly understood, radioresistance appears to be predominantly driven by altered metabolism and hypoxia. Glucose is a central macronutrient, and its metabolism is rewired in HGG cells, increasing glycolytic flux to produce energy and essential metabolic intermediates, known as the Warburg effect. This altered metabolism in HGG cells not only supports cell proliferation and invasiveness, but it also contributes significantly to radioresistance. Several metabolic drugs have been used as a novel approach to improve the radiosensitivity of HGGs, including dichloroacetate (DCA), a small molecule used to treat children with congenital mitochondrial disorders. DCA reverses the Warburg effect by inhibiting pyruvate dehydrogenase kinases, which subsequently activates mitochondrial oxidative phosphorylation at the expense of glycolysis. This effect is thought to block the growth advantage of HGGs and improve the radiosensitivity of HGG cells. This review highlights the main features of altered glucose metabolism in HGG cells as a contributor to radioresistance and describes the mechanism of action of DCA. Furthermore, we will summarize recent advances in DCA's pre-clinical and clinical studies as a radiosensitizer and address how these scientific findings can be translated into clinical practice to improve the management of HGG patients.

Targeting Glucose Metabolism of Cancer Cells with Dichloroacetate to Radiosensitize High-Grade Gliomas

As the cornerstone of high-grade glioma (HGG) treatment, radiotherapy temporarily controls tumor cells via inducing oxidative stress and subsequent DNA breaks. However, almost all HGGs recur within months. Therefore, it is important to understand the underlying mechanisms of radioresistance, so that novel strategies can be developed to improve the effectiveness of radiotherapy. While currently poorly understood, radioresistance appears to be predominantly driven by altered metabolism and hypoxia. Glucose is a central macronutrient, and its metabolism is rewired in HGG cells, increasing glycolytic flux to produce energy and essential metabolic intermediates, known as the Warburg effect. This altered metabolism in HGG cells not only supports cell proliferation and invasiveness, but it also contributes significantly to radioresistance. Several metabolic drugs have been used as a novel approach to improve the radiosensitivity of HGGs, including dichloroacetate (DCA), a small molecule used to treat children with congenital mitochondrial disorders. DCA reverses the Warburg effect by inhibiting pyruvate dehydrogenase kinases, which subsequently activates mitochondrial oxidative phosphorylation at the expense of glycolysis. This effect is thought to block the growth advantage of HGGs and improve the radiosensitivity of HGG cells. This review highlights the main features of altered glucose metabolism in HGG cells as a contributor to radioresistance and describes the mechanism of action of DCA. Furthermore, we will summarize recent advances in DCA’s pre-clinical and clinical studies as a radiosensitizer and address how these scientific findings can be translated into clinical practice to improve the management of HGG patients.

HIF1α-dependent upregulation of ATAD2 promotes proliferation and migration of stomach cancer cells in response to hypoxia

Stomach cancer is a difficult-to-treat disease. Lack of detection markers and limited understanding of the disease mechanisms contribute to the aggressive nature of stomach cancer cells (SCCs). Recently, an ATPase, ATAD2 has been found to be highly expressed in stomach cancer contributing to increased malignancy. However, nothing is known about the mechanism of ATAD2 upregulation and its involvement in stomach carcinogenesis. Since hypoxic microenvironment plays a crucial role in the progression of solid tumors like stomach cancer; we have examined the regulation and function of ATAD2 expression in hypoxic SCCs. ATAD2 is induced in hypoxia-treated SCCs. Stomach adenocarcinoma and metastatic tissues with high HIF1α level also show enhanced ATAD2 expression. In the absence of hypoxia-inducible factor HIF1α, ATAD2 protein level is found to be less indicating towards a potential correlation between them. We identify the presence of HIF1α-binding site (HBS) and HIF1α ancillary site (HAS) in the ATAD2 promoter. Using both in vitro and in vivo binding studies, we confirm that HIF1α binds with the ATAD2 promoter in hypoxic condition. ATAD2 upregulation promotes proliferation and migration of SCCs exposed to hypoxia. Thus, we identify ATAD2 as a hypoxia-responsive and HIF1α-regulated gene and elucidate that upregulated expression of ATAD2 enhances tumor-promoting functions in hypoxic SCCs. Therefore, we propose ATAD2 as a promising therapeutic target for stomach cancer.

Hypoxia and hyperglycaemia determine why some endometrial tumours fail to respond to metformin

BACKGROUND

High expression of Ki67, a proliferation marker, is associated with reduced endometrial cancer-specific survival. Pre-surgical metformin reduces tumour Ki-67 expression in some women with endometrial cancer. Metformin's anti-cancer activity may relate to effects on cellular energy metabolism. Since tumour hypoxia and glucose availability are major cellular redox determinants, we evaluated their role in endometrial cancer response to metformin.

METHODS

Endometrial cancer biopsies from women treated with pre-surgical metformin were tested for the hypoxia markers, HIF-1α and CA-9. Endometrial cancer cell lines were treated with metformin in variable glucose concentrations in normoxia or hypoxia and cell viability, mitochondrial biogenesis, function and energy metabolism were assessed.

RESULTS

In women treated with metformin (n = 28), Ki-67 response was lower in hypoxic tumours. Metformin showed minimal cytostatic effects towards Ishikawa and HEC1A cells in conventional medium (25 mM glucose). In low glucose (5.5 mM), a dose-dependent cytostatic effect was observed in normoxia but attenuated in hypoxia. Tumours treated with metformin showed increased mitochondrial mass (n = 25), while in cultured cells metformin decreased mitochondrial function. Metformin targets mitochondrial respiration, however, in hypoxic, high glucose conditions, there was a switch to glycolytic metabolism and decreased metformin response.

CONCLUSIONS

Understanding the metabolic adaptations of endometrial tumours may identify patients likely to derive clinical benefit from metformin.

Metformin: The Answer to Cancer in a Flower? Current Knowledge and Future Prospects of Metformin as an Anti-Cancer Agent in Breast Cancer

Interest has grown in studying the possible use of well-known anti-diabetic drugs as anti-cancer agents individually or in combination with, frequently used, chemotherapeutic agents and/or radiation, owing to the fact that diabetes heightens the risk, incidence, and rapid progression of cancers, including breast cancer, in an individual. In this regard, metformin (1, 1-dimethylbiguanide), well known as ‘Glucophage’ among diabetics, was reported to be cancer preventive while also being a potent anti-proliferative and anti-cancer agent. While meta-analysis studies reported a lower risk and incidence of breast cancer among diabetic individuals on a metformin treatment regimen, several in vitro, pre-clinical, and clinical studies reported the efficacy of using metformin individually as an anti-cancer/anti-tumor agent or in combination with chemotherapeutic drugs or radiation in the treatment of different forms of breast cancer. However, unanswered questions remain with regards to areas such as cancer treatment specific therapeutic dosing of metformin, specificity to cancer cells at high concentrations, resistance to metformin therapy, efficacy of combinatory therapeutic approaches, post-therapeutic relapse of the disease, and efficacy in cancer prevention in non-diabetic individuals. In the current article, we discuss the biology of metformin and its molecular mechanism of action, the existing cellular, pre-clinical, and clinical studies that have tested the anti-tumor potential of metformin as a potential anti-cancer/anti-tumor agent in breast cancer therapy, and outline the future prospects and directions for a better understanding and re-purposing of metformin as an anti-cancer drug in the treatment of breast cancer.

Metformin in breast cancer: preclinical and clinical evidence

Metformin, a well-acknowledged biguanide, safety profile and multiaction drug with low cost for management of type 2 diabetes, makes a first-class candidate for repurposing. The off-patent drug draws huge attention for repositioned for anticancer drug delivery recently. Still few unanswered questions are challenging, among them one leading question; can metformin use as a generic therapy for all breast cancer subtypes? And is metformin able to get over the problem of drug resistance? The review focused on the mechanisms of metformin action specifically for breast cancer therapy and overcoming the resistance; also discusses preclinical and ongoing and completed clinical trials. The existing limitation such as therapeutic dose specifically for cancer treatment, resistance of metformin in breast cancer and organic cation transporters heterogeneity of the drug opens up a new pathway for improved understanding and successful application as repurposed effective chemotherapeutics for breast cancer. However, much more additional research is needed to confirm the accurate efficacy of metformin treatment for prevention of cancer and its recurrence.

Sema4A Responds to Hypoxia and Is Involved in Breast Cancer Progression

Semaphorin4A (Sema4A) is a family member of semaphorins expressed in immune cells and is also related with disease progression of tumor disease. In this study, we investigate the expression and pathological role of Sema4A in breast cancer (BCa). Our data showed that the expression of Sema4A increased in the tissues and serum of BCa patients when compared with normal controls. The expression of Sema4A in BCa cells could be induced by hypoxic treatment, whereas silencing hypoxia-inducible factor (HIF)-1α could attenuate the above induced. Furthermore, chromatin immunoprecipitation (ChIP) analysis demonstrated that HIF-1α could regulate the expression of Sema4A through directly binding to the promoter of Sema4A gene, whose enrichment could be further enhanced by hypoxic stimulation. In addition, silencing Sema4A could inhibit the proliferation, vascular endothelial growth factor (VEGF) production and the phosphorylation of Akt, extracellular signal-regulated kinase (ERK)1/2 mitogen-activated protein kinase (MAPK) and signal transduction and activator of transcription (STAT)3, but induce apoptosis of BCa cells in the presence of hypoxia. In contrast, recombinant human Sema4A treatment showed the opposite effects. Taken together, these results suggest that Sema4A could promote progression of BCa in the presence of hypoxia and it may hold potential for treatment target for BCa.

Effects of dichloroacetate as single agent or in combination with GW6471 and metformin in paraganglioma cells

Paragangliomas (PGLs) are infiltrating autonomic nervous system tumors that cause important morbidity. At present, surgery is the only effective therapeutic option for this rare tumor. Thus, new agents for PGL treatment should be identified. Using unique PGL cell models established in our laboratory, we evaluated the effect of dichloroacetate (DCA) as single agent or in a novel combination with other metabolic drugs, including GW6471 and metformin. DCA and metformin had not been tested before in PGL. DCA reduced PGL cell viability and growth through mechanisms involving reactivation of PDH complex leading to promotion of oxidative metabolism, with lowering of lactate and enhanced ROS production. This resulted in cell cycle inhibition and induction of apoptosis in PGL cells, as shown by flow cytometry and immunoblot analyses. Moreover, DCA drastically impaired clonogenic activity and migration of PGL cells. Also metformin reduced PGL cell viability as single agent and the combinations of DCA, GW6471 and metformin had strong effects on cell viability. Furthermore, combined treatments had drastic and synergistic effects on clonogenic ability. In conclusion, DCA, GW6471 and metformin as single agents and in combination appear to have promising antitumor effects in unique cell models of PGL.

Novel Quinoxaline-2-Carbonitrile-1,4-Dioxide Derivatives Suppress HIF1α Activity and Circumvent MDR in Cancer Cells

A series of 3-aryl/hetarylquinoxaline-2-carbonitrile-1,4-dioxides was synthesized and evaluated against breast cancer cell lines in normoxia and hypoxia. Selected compounds in this series demonstrated better cytotoxicity and comparable hypoxia selectivity than tirapazamine. In contrast to Dox, quinoxaline-1,4-dioxides showed potent cytotoxicity against different MDR cells. Compound 2g inhibits of cancer cell growth through p53-independent mechanisms. Our results showed that compound 2g sensitized MCF-7 cells to metformin in hypoxia. Treatment with 2g results in the increase of ROS accumulation in cancer cells. Compound 2g can be considered as the lead compound for further anticancer drug design, evaluation, and development of new potent antitumor agents.

Dichloroacetate Prevents Cisplatin-Induced Nephrotoxicity without Compromising Cisplatin Anticancer Properties

Cisplatin is an effective anticancer drug; however, cisplatin use often leads to nephrotoxicity, which limits its clinical effectiveness. In this study, we determined the effect of dichloroacetate, a novel anticancer agent, in a mouse model of cisplatin-induced AKI. Pretreatment with dichloroacetate significantly attenuated the cisplatin-induced increase in BUN and serum creatinine levels, renal tubular apoptosis, and oxidative stress. Additionally, pretreatment with dichloroacetate accelerated tubular regeneration after cisplatin-induced renal damage. Whole transcriptome sequencing revealed that dichloroacetate prevented mitochondrial dysfunction and preserved the energy-generating capacity of the kidneys by preventing the cisplatin-induced downregulation of fatty acid and glucose oxidation, and of genes involved in the Krebs cycle and oxidative phosphorylation. Notably, dichloroacetate did not interfere with the anticancer activity of cisplatin in vivo. These data provide strong evidence that dichloroacetate preserves renal function when used in conjunction with cisplatin.