MULTITARGETED POLYPHARMACOTHERAPY for CANCER TREATMENT. THEORETICAL CONCEPTS and PROPOSALS.

INTRODUCTION: . The pharmacological treatment of cancer has evolved from cytotoxic to molecular targeted therapy. The median survival gains of 124 drugs approved by the FDA from 2003 to 2021 is 2.8 months. Targeted therapy is based on the somatic mutation theory, which has some paradoxes and limitations. While efforts of targeted therapy must continue, we must study newer approaches that could advance therapy and affordability for patients. AREAS COVERED: This work briefly overviews how cancer therapy has evolved from cytotoxic chemotherapy to current molecular-targeted therapy. The limitations of the one-target, one-drug approach considering cancer as a robust system and the basis for multitargeting approach with polypharmacotherapy using repurposing drugs. EXPERT OPINION: Multitargeted polypharmacotherapy for cancer with repurposed drugs should be systematically investigated in preclinical and clinical studies. Remarkably, most of these proposed drugs already have a long history in the clinical setting, and their safety is known. In principle, the risk of their simultaneous administration should not be greater than that of a first-in-human phase I study as long as the protocol is developed with strict vigilance to detect early possible side effects from their potential interactions. Research on cancer therapy should go beyond the prevailing paradigm targeted therapy.

Selection of clinically relevant drug concentrations for in vitro studies of candidates drugs for cancer repurposing: a proposal.

Drug repurposing of widely prescribed patent-off and cheap drugs may provide affordable drugs for cancer treatment. Nevertheless, many preclinical studies of cancer drug repurposing candidates use in vitro drug concentrations too high to have clinical relevance. Hence, preclinical studies must use clinically achievable drug concentrations. In this work, several FDA-approved cancer drugs are analyzed regarding the correlation between the drug inhibitory concentrations 50% (IC50) tested in cancer cell lines and their corresponding peak serum concentration (Cmax) and area under the curve (AUC) reported in clinical studies of these drugs. We found that for most targeted cancer drugs, the AUC and not the Cmax is closest to the IC50; therefore, we suggest that the initial testing of candidate drugs for repurposing could select the AUC pharmacokinetic parameter and not the Cmax as the translated drug concentration for in vitro testing. Nevertheless, this is a suggestion only as experimental evidence does not exist to prove this concept. Studies on this issue are required to advance in cancer drug repurposing.

PaSTe. Blockade of the Lipid Phenotype of Prostate Cancer as Metabolic Therapy: A Theoretical Proposal.

BACKGROUND: Prostate cancer is the most frequently diagnosed malignancy in 112 countries and is the leading cause of death in eighteen. In addition to continuing research on prevention and early diagnosis, improving treatments and making them more affordable is imperative. In this sense, the therapeutic repurposing of low-cost and widely available drugs could reduce global mortality from this disease. The malignant metabolic phenotype is becoming increasingly important due to its therapeutic implications. Cancer generally is characterized by hyperactivation of glycolysis, glutaminolysis, and fatty acid synthesis. However, prostate cancer is particularly lipidic; it exhibits increased activity in the pathways for synthesizing fatty acids, cholesterol, and fatty acid oxidation (FAO). OBJECTIVE: Based on a literature review, we propose the PaSTe regimen (Pantoprazole, Simvastatin, Trimetazidine) as a metabolic therapy for prostate cancer. Pantoprazole and simvastatin inhibit the enzymes fatty acid synthase (FASN) and 3-hydroxy-3-methylglutaryl-coenzyme A reductase (HMGCR), therefore, blocking the synthesis of fatty acids and cholesterol, respectively. In contrast, trimetazidine inhibits the enzyme 3-b-Ketoacyl-CoA thiolase (3-KAT), an enzyme that catalyzes the oxidation of fatty acids (FAO). It is known that the pharmacological or genetic depletion of any of these enzymes has antitumor effects in prostatic cancer. RESULTS: Based on this information, we hypothesize that the PaSTe regimen will have increased antitumor effects and may impede the metabolic reprogramming shift. Existing knowledge shows that enzyme inhibition occurs at molar concentrations achieved in plasma at standard doses of these drugs. CONCLUSION: We conclude that this regimen deserves to be preclinically evaluated because of its clinical potential for the treatment of prostate cancer.

Does Therapeutic Repurposing in Cancer Meet the Expectations of Having Drugs at a Lower Price?

Therapeutic repurposing emerged as an alternative to the traditional drug discovery and development model (DDD) of new molecular entities (NMEs). It was anticipated that by being faster, safer, and cheaper, the development would result in lower-cost drugs. As defined in this work, a repurposed cancer drug is one approved by a health regulatory authority against a non-cancer indication that then gains new approval for cancer. With this definition, only three drugs are repurposed for cancer: Bacillus Calmette-Guerin (BCG) vaccine (superficial bladder cancer, thalidomide [multiple myeloma], and propranolol [infantile hemangioma]). Each of these has a different history regarding price and affordability, and it is not yet possible to generalize the impact of drug repurposing on the final price to the patient. However, the development, including the price, does not differ significantly from an NME. For the end consumer, the product's price is unrelated to whether it followed the classical development or repurposing. Economic constraints for clinical development, and drug prescription biases for repurposing drugs, are barriers yet to be overcome. The affordability of cancer drugs is a complex issue that varies from country to country. Many alternatives for having affordable drugs have been put forward, however these measures have thus far failed and are, at best, palliative. There are no immediate solutions to the problem of access to cancer drugs. It is necessary to critically analyze the impact of the current drug development model and be creative in implementing new models that genuinely benefit society.

Progress in Metabolic Studies of Gastric Cancer and Therapeutic Implications.

BACKGROUND: Worldwide, gastric cancer is ranked the fifth malignancy in incidence and the third malignancy in mortality. Gastric cancer causes an altered metabolism that can be therapeutically exploited. OBJECTIVE: The objective of this study is to provide an overview of the significant metabolic alterations caused by gastric cancer and propose a blockade. METHODS: A comprehensive and up-to-date review of descriptive and experimental publications on the metabolic alterations caused by gastric cancer and their blockade. This is not a systematic review. RESULTS: Gastric cancer causes high rates of glycolysis and glutaminolysis. There are increased rates of de novo fatty acid synthesis and cholesterol synthesis. Moreover, gastric cancer causes high rates of lipid turnover via fatty acid ß-oxidation. Preclinical data indicate that the individual blockade of these pathways via enzyme targeting leads to antitumor effects in vitro and in vivo. Nevertheless, there is no data on the simultaneous blockade of these five pathways, which is critical as tumors show metabolic flexibility in response to the availability of nutrients. This means tumors may activate alternate routes when one or more are inhibited. We hypothesize there is a need to simultaneously block them to avoid or decrease the metabolic flexibility that may lead to treatment resistance. CONCLUSION: There is a need to explore the preclinical efficacy and feasibility of combined metabolic therapy targeting the pathways of glucose, glutamine, fatty acid synthesis, cholesterol synthesis, and fatty acid oxidation. This may have therapeutical implications because we have clinically available drugs that target these pathways in gastric cancer.

BAPST. A Combo of Common Use Drugs as Metabolic Therapy for Cancer: A Theoretical Proposal.

Cancer therapy advances have yet to impact global cancer mortality. One of the factors limiting mortality burden reduction is the high cost of cancer drugs. Cancer drug repurposing has already failed to meet expectations in terms of drug affordability. The three FDA-approved cancer drugs developed under repurposing: all-trans-retinoic acid, arsenic trioxide, and thalidomide do not differ in price from other drugs developed under the classical model. Though additional factors affect the whole process from inception to commercialization, the repurposing of widely used, commercially available, and cheap drugs may help. This work reviews the concept of the malignant metabolic phenotype and its exploitation by simultaneously blocking key metabolic processes altered in cancer. We elaborate on a combination called BAPST, which stands for the following drugs and pathways they inhibit: Benserazide (glycolysis), Apomorphine (glutaminolysis), Pantoprazole (Fatty-acid synthesis), Simvastatin (mevalonate pathway), and Trimetazidine (Fatty-acid oxidation). Their respective primary indications are: • Parkinson's disease (benserazide and apomorphine). • Peptic ulcer disease (pantoprazole). • Hypercholesterolemia (simvastatin). • Ischemic heart disease (trimetazidine). When used for their primary indication, the literature review on each of these drugs shows that they have a good safety profile and lack predicted pharmacokinetic interaction among them. Based on that, we propose that the BAPST regimen merits preclinical testing.

Drug repurposing for cancer therapy, easier said than done.

Drug repurposing for cancer therapy is currently a hot topic of research. Theoretically, in contrast to the known hurdles of developing new molecular entities, the approach of repurposing has several advantages. Mostly, it is said that it is faster, safer, easier, and cheaper. In the real world, however, there are only three repurposed drugs so far, that are listed in widely recognized cancer guidelines, but a large number of them are being studied. Among the many barriers to repurposing cancer drugs, economical-driven are the most important that difficult the clinical development of them. In this review, we provide an overview of the current status of drug repurposing for cancer therapy and the barriers that need to be overcome to realize the benefit of this approach. It means to have repositioned drugs for cancer therapy accepted as standard therapy for cancer indications at low cost.

Barriers for Pharmaceutical Innovation With Focus in Cancer Drugs, the Case of Mexico.

Drug innovation does not only generate economic growth but also portrays a country's efforts toward innovation. The article reviews the current status on the innovation of the Mexican pharmaceutical industry with a focus on cancer drugs. The authors examined the scientific and nonscientific literature in search of the origin of innovative cancer drugs, as well as the regulatory frames by which these drugs are approved in Mexico. The article presents a narrative analysis of the author's experiences on the barriers that impede pharmaceutical innovation in Mexico. To the best of the authors' knowledge, there was only 1 domestic approval by COFEPRIS, the Mexican health regulatory agency, of an anticancer product developed under a repositioning approach. Among the barriers impeding drug innovation in Mexico are, but not be limited to, insufficient funds for the discovery phase; unaffordable or limited capacity for performing preclinical studies under good laboratory practices (GLP); lengthy clinical trial approval; unfavorable conditions for clinical trials for both academic and domestic pharmaceutical industry-sponsored studies; unclear policies for drug approvals and marketing. The authors state specific proposals for overcoming these barriers to generate a climate for increasing participation of academic and existing domestic pharmaceutical industry as well as to increase venture capital and favor start-up and early-stage companies. In conclusion, Mexico has the human resources and material infrastructure to innovate. The implementation of these and any other constructive proposals are just a matter of political will.

Growth inhibition and transcriptional effects of ribavirin in lymphoma.

Ribavirin exhibits inhibitory effects on the epigenetic enzyme enhancer of zeste homolog 2 (EZH2), which participates in lymphomagenesis. Additionally, preclinical and clinical studies have demonstrated the anti­lymphoma activity of this drug. To further investigate the potential of ribavirin as an anticancer treatment for lymphoma, the tumor­suppressive effects of ribavirin were analyzed in lymphoma cell lines. The effects of ribavirin on the viability and clonogenicity of the B­cell lymphoma cell line Pfeiffer (EZH2­mutant), Toledo (EZH2 wild­type) and cutaneous T­cell lymphoma Hut78 cell line were assessed. Expression of EZH2 and trimethylation status of histone 3, lysine 27 trimethylated (H3K27m3) was also determined in response to ribavirin. The transcriptional effects of ribavirin on Hut78 cells were analyzed by microarray expression and the results were validated by reverse transcription­quantitative polymerase chain reaction, western blotting and knockout of signal transducer and activator of transcription 1 (STAT1). The results of the present study demonstrated that ribavirin suppressed the growth and clonogenicity of cells in a dose­dependent manner. Ribavirin did not affect the expression of EZH2 nor altered its activity as evaluated by H3K27 trimethylation status. Furthermore, the results of transcriptome analysis indicated that the majority of the canonical pathways affected by ribavirin were associated with the immune system, including 'antigen presentation', 'communication between innate and adaptive immune cells' and 'cross­talk between dendritic and natural killer cells'. The results of gene expression analysis were confirmed, by demonstrating at the RNA and protein levels, downregulation of stearoyl­CoA desaturase and upregulation of STAT1. Depletion of STAT1, which was proposed as a key regulator of the aforementioned pathways, exerted growth inhibitory effects almost to the same extent as ribavirin. In conclusion, ribavirin was proposed to exert growth inhibitory effects on lymphoma cell lines, particularly Hut78 cells, a cutaneous T­cell lymphoma cell line. Of note, these effects may depend on, at least in part, the activation of canonical immune pathways regulated by the key factors STAT1 and interferon­Î³. Our results provide insight into the anti­lymphoma potential of ribavirin; however, further investigations in preclinical and clinical studies are required to determine the effectiveness of ribavirin as a therapeutic agent for treating lymphoma.

Pharmacodynamics of current and emerging treatments for cervical cancer.

Introduction: Beyond early stages of cervical cancer (1A1, IA2, IB1, IIA1,), locally advanced disease (IB2, IIA2, IIA2, IIB, IIIA, IIIB, IIIC, IVA) and advanced (metastatic, recurrent or persistent disease) patients require drug therapy either as radiosensitizer, adjuvant or as palliative systemic chemotherapy. Areas covered: This review briefly discusses the achievements in treating cervical cancer. Expert opinion: Two studies are ongoing to optimize treatment after radical hysterectomy. These studies compare chemoradiation versus radiation in intermediate-risk patients or increasing treatment intensity (chemoradiation plus adjuvant chemotherapy versus chemoradiation) for high-risk and locally advanced cervical cancer. Concerning advanced disease, bevacizumab increased median survival for only 3.5 months when added to a cisplatin-doublet. Although this increase is slightly superior to the 2.9 months gained with cisplatin topotecan versus cisplatin, (0.6 months of difference), the doublet plus bevacizumab is considered the standard of care. Recently, pembrolizumab became an alternative for advanced disease that progresses to first-line treatment. Beyond that, the number of phase II and phase III trials in advanced disease is limited but on the increase. HPV E6/E7 oncoproteins are the Achilles Heel of cervical cancer, and there is cautious optimism that antagonists of these oncoproteins will be further developed.

Orlistat as a FASN inhibitor and multitargeted agent for cancer therapy.

INTRODUCTION: Cancer cells have increased glycolysis and glutaminolysis. Their third feature is increased de novo lipogenesis. As such, fatty acid (FA) synthesis enzymes are over-expressed in cancer and their depletion causes antitumor effects. As fatty acid synthase (FASN) plays a pivotal role in this process, it is an attractive target for cancer therapy. AREAS COVERED: This is a review of the lipogenic phenotype of cancer and how this phenomenon can be exploited for cancer therapy using inhibitors of FASN, with particular emphasis on orlistat as a repurposing drug. EXPERT OPINION: Disease stabilization only has been observed with a highly selective FASN inhibitor used as a single agent in clinical trials. It is too early to say whether the absence of tumor responses other than stabilization results because even full inhibition of FASN is not enough to elicit antitumor responses. The FASN inhibitor orlistat is a 'dirty' drug with target-off actions upon at least seven targets with a proven role in tumor biology. The development of orlistat formulations suited for its intravenous administration is a step ahead to shed light on the concept that drug promiscuity can or not be a virtue.

Ivermectin as an inhibitor of cancer stem­like cells.

The aim of the present study was to demonstrate that ivermectin preferentially inhibited cancer stem­like cells (CSC) in breast cancer cells and downregulated the expression of 'stemness' genes. Computational searching of DrugBank, a database of approved drugs, was performed using the principles of two­dimensional similarity searching; the chemical structure of salinomycin was used as a query. Growth inhibition of the breast cancer cell lin e MDA­MB­231 by ivermectin was investigated in the total cell population, in cell spheroids and in sorted cells that expressed cluster of differentiation (CD)44+/CD24­. The effects of ivermectin treatment on the expression of pluripotency and self­renewal transcription factors, such as homeobox protein nanog (nanog), octamer­binding protein 4 (oct­4) and SRY­box 2 (sox­2), were evaluated by reverse transcription­quantitative polymerase chain reaction and western blotting. Ivermectin exhibited a similarity value of 0.78 in reference to salinomycin. Ivermectin demonstrated an inhibitory effect upon the growth of MDA­MB­231 cells in the range of 0.2­8 µM. Ivermectin preferentially inhibits the viability of CSC­enriched populations (CD44+/CD24­ and cells growing in spheroids) compared with the total cell population. The opposite pattern was observed with paclitaxel treatment. Ivermectin exposure reduced the expression of nanog, oct­4 and sox­2 at the mRNA and protein levels. Ivermectin preferentially inhibited the CSC subpopulation in the MDA­MB­231 cells and downregulated the expression of genes involved in the maintenance of pluripotency and self­renewal.

Feasibility and antitumor efficacy in vivo, of simultaneously targeting glycolysis, glutaminolysis and fatty acid synthesis using lonidamine, 6-diazo-5-oxo-L-norleucine and orlistat in colon cancer.

The aim of the present study was to investigate in vivo the feasibility and efficacy of the combination of lonidamine (LND), 6-diazo-5-oxo-L-norleucine (DON) and orlistat to simultaneously target glycolysis, glutaminolysis and de novo synthesis of fatty acids, respectively. The doses of LND and DON used in humans were translated to mouse doses (77.7 mg/kg and 145.5 mg/kg, respectively) and orlistat was used at 240 mg/kg. Three schedules of LND, DON and orlistat at different doses were administered by intraperitoneal injection to BALB/c mice in a 21-day cycle (schedule 1: LND, 0.5 mg/day; DON, 0.25 mg/day 1, 5 and 9; orlistat, 240 mg/kg/day; schedule 2: LND, 0.1 mg/day; DON, 0.5 mg/day 1, 5 and 9; orlistat, 240 mg/kg/day; schedule 3: LND, 0.5 mg/day; DON, 0.08 mg/day 1, 5 and 9; orlistat, 360 mg/kg/day) to assess tolerability. To determine the antitumor efficacy, a syngeneic tumor model in BALB/c mice was created using colon cancer CT26.WT cells, and a xenogeneic tumor model was created in nude mice using the human colon cancer SW480 cell line. Mice were treated with schedule 1. Animals were weighed, clinically inspected during the experiment and the tumor volume was measured at day 21. The 3 schedules assessed in the tolerability experiments were well tolerated, as mice maintained their weight and no evident clinical signs of toxicity were observed. Combination treatment with schedule 1 significantly decreased tumor growth in each mouse model. No evident signs of toxicity were observed and mice maintained their weight during treatment. The triple metabolic blockade of the malignant phenotype appears feasible and promising for cancer therapy.

Viral inhibitors of NKG2D ligands for tumor surveillance.

INTRODUCTION: Natural Killer cells (NK) are key for the innate immune response against tumors and viral infections. Several viral proteins evade host immune response and target the NK cell receptor NKG2D and its ligands. Areas covered: This review aimed to describe the viruses and their proteins that interfere with the NKG2D receptor and their ligands, and how these interactions lead to immune evasion, host protection, and tissue damage from acute and chronic viral infections. Expert opinion: The study of viral proteins has already impacted the field of oncology. A prime example is the HBV vaccine and the development of antiviral drugs for HIV, Hepatitis C, and the family of Herpesviridae viruses. The NKG2D system seems to be a rational therapeutic target. Nevertheless, an effective cytotoxic response by NK cells is mediated by a network of activating and inhibitory receptors, the integration of which determines if the NK cell becomes cytotoxic or permissive. Immunotherapeutic agents that increase the antitumor lytic activity of NK cells through modulating activation and inhibitory signaling of NK cells are being developed. Nevertheless, more research is needed to dissect the integrative mechanism of NK cells function to fully exploit their antitumor and antiviral effector mechanisms.

The safety of drug treatments for cervical cancer.

INTRODUCTION: The treatment of some early-stage and most locally advanced disease cervical cancer patients consists of concurrent chemoradiation, while almost all with advanced disease require palliative chemotherapy. AREAS COVERED: This review is aimed to analyze the safety issues emerging from trials of chemoradiation for early-stage high-risk disease and locally advanced stages, as well as safety issues of trials of palliative chemotherapy for advanced disease. Safety issues on fertility preservation are also discussed. EXPERT OPINION: Cisplatin chemoradiation produces higher toxicity as compared to radiation alone, yet it is well-tolerated. Further advances would require (i) the development of more effective and tolerated combination chemoradiation regimens, (ii) demonstration of the efficacy and tolerability of adjuvant chemotherapy after cisplatin chemoradiation, and (iii) incorporation of targeted therapies into radiosensitizing regimens. A major problem continues to be the population of patients with advanced disease. The recent incorporation of bevacizumab into chemotherapy regimens represents a step forward; however, toxicity as well as economic issues may impede its wide acceptance worldwide. Preserving fertility in young women with cervical cancer is an issue that must be fully addressed. In this setting, neoadjuvant chemotherapy seems to increase fertlity rate without compromising oncological outcomes.

Ribavirin as a tri-targeted antitumor repositioned drug.

The aim of the present study was to demonstrate that ribavirin, a known inhibitor of eIF4E and inosine 5'-phosphate dehydrogenase (IMPDH), also inhibits histone methyltransferase zeste homolog 2 (EZH2). A computational searching revealed that ribavirin has a high structural similarity to 3-deazaneplanocin A (DZNep). The growth inhibitory effects of ribavirin as well as its effects upon epigenetic enzymes were evaluated in various cancer cell lines. siRNA assays were used to downregulate eIF4E, EZH2 and IMPDH to determine the contribution of these targets to the growth inhibitory effects of ribavirin. Ribavirin decreased EZH2 expression, inhibited histone methyltransferase activity and decreased H3K27 trimethylation. Ribavirin induced variable growth inhibition in a number of cell lines and downregulation of the targets, EZH2, eIF4E and IMPDH1 and 2 by siRNA led to comparable growth inhibition while no significant further reduction in viability was observed when siRNA transfected cells were treated with ribavirin. The results showed that ribavirin inhibits these cancer targets and should thus be studied for cancer therapy.

Hydralazine-valproate: a repositioned drug combination for the epigenetic therapy of cancer.

INTRODUCTION: DNA methylation (DNMTi) and histone deacetylase inhibitors (HDACi) are in development for cancer therapy. So far, four epigenetic drugs are approved for myelodysplastic syndrome (MDS) and cutaneous T-cell lymphoma (CTCL). The combination of hydralazine-valproate (TRANSKRIP(™)) is being repositioned as an oral DNMT and HDAC inhibitor. AREAS COVERED: Brief discussion on the current status of epigenetic drugs and studies published on the preclinical and clinical development of the hydralazine-valproate combination. EXPERT OPINION: Drug repositioning is a strategy for prompt and cost-efficient drug discovery. There is evidence that combining DNMTi with HDACi would be more efficacious than administering each agent on its own. Hydralazine-valproate is safe when used alone or in combination with chemotherapy or chemoradiation. The fact that both drugs are orally administered is another advantage over current epigenetic drugs. This combination is promising but larger studies are needed. Among these, the randomized Phase III trials in advanced and in locally advanced cervical cancer combined with chemotherapy and cisplatin-radiation respectively, would eventually confirm its efficacy. Studies on MDS and CTCL would also eventually prove the efficacy of hydralazine valproate so that in the coming years hydralazine-valproate could have a role in cancer epigenetic therapy.

The impact of DNA methylation technologies on drug toxicology.

INTRODUCTION: Drug toxicology is central to drug development. Despite improvements in our understanding of molecular and cell biology, high attrition rates in drug development continue, speaking to the difficulties of developing unequivocal methods to predict the efficacy and safety of drugs. AREAS COVERED: In this review, the authors provide a short overview of the 'omics' technologies that have been applied to drug toxicology, with an emphasis on a whole-genome DNA methylation analysis. Preliminary results from DNA methylation analysis technologies that may help in predicting response and efficacy of a drug are discussed. EXPERT OPINION: Currently, we cannot fully contextualize the application of epigenetics to the field of drug toxicology, as there are still many challenges to overcome before DNA methylation-based biomarkers can be effectively used in drug development. Comprehensive whole-genome DNA methylation methods for a unbiased analysis based on either microarray or next-generation sequencing need to be evaluated in drug toxicology in an intensive and systematic manner. Additionally, robust analysis systems need to be developed to decode the large amounts of data generated by whole-genome DNA methylation analyses as well as protocol standardization for reproducibility to develop meaningful databases that can be applied to drug toxicology.

Epigenetic therapy with hydralazine and magnesium valproate reverses imatinib resistance in patients with chronic myeloid leukemia.

UNLABELLED: The epigenetic drugs hydralazine and valproate were administered in a compassionate manner to 8 patients with chronic myeloid leukemia (CML) refractory to imatinib. Two patients had a complete hematologic response (25%),1 major cytogenetic response, 1 complete cytogenetic response (25% any cytogenetic response), and 3 (37.5%)stable disease. No grade 3 or 4 toxicity was observed. These results show the ability of epigenetic therapy to revert imatinib resistance. BACKGROUND: Epigenetic alterations participate in the development of acquired resistance to imatinib, hence, the DNA methylation, and histone deacetylase inhibitors hydralazine and valproate, respectively, has the potential to overcome it. PATIENT AND METHODS: A series of 8 patients with chronic myeloid leukemia (CML) refractory to imatinib mesylate with no access to second-generation tyrosine kinase inhibitors were treated with hydralazine and valproate in a compassionate manner. Clinical efficacy and safety of these drugs added to imatinib mesylate were evaluated. RESULTS: Two patients were in the blast phase, 5 were in the accelerated phase, and 1 was in the chronic phase. All the patients continued with the same dose of imatinib that they had been receiving at the time of development of resistance, with a median dose of 600 mg daily (range, 400-800 mg). The median time from diagnosis of CML to the start of hydralazine and valproate was 53.6 months (range, 19-84 months). Two (25%) patients had a complete hematologic response, one (12.5%) had an major cytogenetic response, and one (12.5%) had a complete cytogenetic response. Three (37.5%) patients had stable disease, and only one (12.5%) patient failed to respond. At a median follow-up time of 18 months (range, 3-18 months), the median survival had not been reached, and the projected overall survival was 63%. All the patients had mild neurologic toxicity, including distal tremor and somnolence. No grade 3 or 4 toxicity was observed. CONCLUSIONS: Our results suggest that the epigenetic drugs hydralazine and valproate revert the resistance to imatinib in patients with CML.

DNA methylation-independent reversion of gemcitabine resistance by hydralazine in cervical cancer cells.

BACKGROUND: Down regulation of genes coding for nucleoside transporters and drug metabolism responsible for uptake and metabolic activation of the nucleoside gemcitabine is related with acquired tumor resistance against this agent. Hydralazine has been shown to reverse doxorubicin resistance in a model of breast cancer. Here we wanted to investigate whether epigenetic mechanisms are responsible for acquiring resistance to gemcitabine and if hydralazine could restore gemcitabine sensitivity in cervical cancer cells. METHODOLOGY/PRINCIPAL FINDINGS: The cervical cancer cell line CaLo cell line was cultured in the presence of increasing concentrations of gemcitabine. Down-regulation of hENT1 & dCK genes was observed in the resistant cells (CaLoGR) which was not associated with promoter methylation. Treatment with hydralazine reversed gemcitabine resistance and led to hENT1 and dCK gene reactivation in a DNA promoter methylation-independent manner. No changes in HDAC total activity nor in H3 and H4 acetylation at these promoters were observed. ChIP analysis showed H3K9m2 at hENT1 and dCK gene promoters which correlated with hyper-expression of G9A histone methyltransferase at RNA and protein level in the resistant cells. Hydralazine inhibited G9A methyltransferase activity in vitro and depletion of the G9A gene by iRNA restored gemcitabine sensitivity. CONCLUSIONS/SIGNIFICANCE: Our results demonstrate that acquired gemcitabine resistance is associated with DNA promoter methylation-independent hENT1 and dCK gene down-regulation and hyper-expression of G9A methyltransferase. Hydralazine reverts gemcitabine resistance in cervical cancer cells via inhibition of G9A histone methyltransferase.