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.

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.

The inhibitory and transcriptional effects of the epigenetic repurposed drugs hydralazine and valproate in lymphoma cells.

Lymphoma is a disease that affects countless lives each year. In order to combat this disease, researchers have been exploring the potential of DNMTi and HDACi drugs. These drugs target the cellular processes that contribute to lymphomagenesis and treatment resistance. Our research evaluated the effectiveness of a combination of two such drugs, hydralazine (DNMTi) and valproate (HDACi), in B-cell and T-cell lymphoma cell lines. Here we show that the combination of hydralazine and valproate decreased the viability of cells over time, leading to the arrest of cell-cycle and apoptosis in both B and T-cells. This combination of drugs proved to be synergistic, with each drug showing significant growth inhibition individually. Microarray analyses of HuT 78 and Raji cells showed that the combination of hydralazine and valproate resulted in the up-regulation of 562 and 850 genes, respectively, while down-regulating 152 and 650 genes. Several proapoptotic and cell cycle-related genes were found to be up-regulated. Notably, three and five of the ten most up-regulated genes in HuT 78 and Raji cells, respectively, were related to immune function. In summary, our study suggests that the combination of hydralazine and valproate is an effective treatment option for both B- and T-lymphomas. These findings are highly encouraging, and we urge further clinical evaluation to validate our research and potentially improve lymphoma treatment.

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.

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.

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.

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.

Acetylator status and N-acetyltransferase 2 gene polymorphisms; phenotype-genotype correlation with the sulfamethazine test.

N-acetyltransferase 2 (NAT2) catalyzes the bioactivation and/or detoxification of drugs and carcinogens. The aim of this study was to establish the correlation between the NAT2 genotype and the acetylating phenotype in a Mexican population using sulfamethazine as a probe. From a total of 122 individuals, 73 (59.8%) were slow and 49 (40.2%) were fast acetylators. Eleven individuals (9%) had the wild-type genotype (NAT2*4/NAT2*4). The most frequent genotype was NAT2*4/NAT2*5B observed in 20.66% of individuals. In conclusion, our results show that an accurate prediction of the acetylation phenotype by genotyping can be achieved in around half of the population. Further studies with a larger number of individuals are required to establish correlations between phenotype and genotype in half of that patients having a genotype combined with slow/rapid alleles.

Hydralazine and magnesium valproate as epigenetic treatment for myelodysplastic syndrome. Preliminary results of a phase-II trial.

Decitabine and azacitidine, two DNA methyltransferase (DNMT) inhibitors, are the current standard of treatment for myelodysplastic syndrome (MDS). Histone deacetylase (HDAC) inhibitors are also being tested against MDS. Both drug classes synergize in their gene reactivating and anticancer activities. The combination of hydralazine and valproate (Transkrip®), a DNMT and HDAC inhibitor, respectively), has been developed as epigenetic therapy under the drug repositioning concept. To evaluate the clinical efficacy and safety of hydralazine and valproate against MDS, an open phase-II study for previously treated patients with MDS was conducted. The hydralazine dose was given according with the acetylator phenotype, and valproate was dosed at 30 mg/kg/day. Response was graded with International Working Group criteria. Toxicity was evaluated by the Common Toxemia Criteria-National Cancer Institute version 3 scale. From November 2007 to January 2010, 12 patients were included. Median age±SD was 53±19.78 years (range, 23-79 years); median time from diagnosis to inclusion in the study was 7.9 months (range 2.6-36.1 months). Median of previous treatment was 2 (range, 1-6). Refractory cytopenia with multilineage dysplasia was diagnosed in ten cases, and refractory anemia with excess of blasts in two. Overall response was documented in six (50%) of 12 cases, including one CR, one PR, and four hematological improvements of the erythroid series. Two patients (16.6%) progressed to acute myeloid leukemia. Hemoglobin increased from 7.4 to 10.3 g/dL (in 13 weeks), neutrophils, from 1.1 to 2.0 (in 3 weeks), and platelets, from 66×10(9) to 72×10(9)/L (in 2 weeks). Transfusional requirements decreased from 2.3 to 0 U bi-monthly for red blood cells and from 0.5 to 0 U bi-monthly for platelets in responding patients. Main toxicities were mild, including somnolence and nausea. Preliminary results of this phase-II study suggest that the combination of hydralazine and valproate is a promising non-toxic and effective therapy for MDS.

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.

Weekly topotecan as second- or third-line treatment in patients with recurrent or metastatic cervical cancer.

Topotecan is active in advanced or metastatic cervical cancer even in patients who have received prior cisplatin-based chemotherapy, although hematologic toxicity has limited its use. Studies in cervical cancer have utilized topotecan administered on days 1-5 of each 21- or 28-day cycle. Alternative schedules, such as weekly schemes, have proven to ameliorate hematological toxicity. The objective of this study was to analyze the results of weekly topotecan as second- or third-line therapy in advanced or metastatic cervical cancer. Eligible patients had histologically confirmed cervical carcinoma, measurable disease, and at least one prior chemotherapy regimen. Topotecan was administered at a dose of 3 mg/m(2) (maximum, 5 mg per dose) diluted in 250 ml of normal saline in a 30-min infusion weekly for every 28 days. We assessed response and toxicity. Twenty-two patients entered this study. Eighteen patients were evaluable for toxicity and response. Patients received a mean 3.5 courses (range, 1-6 courses). No complete or partial responses were observed; five (27.7%) patients exhibited disease stabilization as maximum response (two in irradiated sites, and three in lung/mediastinum). Median progression-free interval was 3.5 months (95% confidence interval [CI]: 3.75-4 months) and median overall survival was 7 months (95% CI: 6-8.7 months). Weekly topotecan administration achieved disease stabilization in 27.7% of heavily pre-treated patients. The achievement could be of worth in this setting in which disease prolongation is desirable.

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.

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.

The prince and the pauper. A tale of anticancer targeted agents.

Cancer rates are set to increase at an alarming rate, from 10 million new cases globally in 2000 to 15 million in 2020. Regarding the pharmacological treatment of cancer, we currently are in the interphase of two treatment eras. The so-called pregenomic therapy which names the traditional cancer drugs, mainly cytotoxic drug types, and post-genomic era-type drugs referring to rationally-based designed. Although there are successful examples of this newer drug discovery approach, most target-specific agents only provide small gains in symptom control and/or survival, whereas others have consistently failed in the clinical testing. There is however, a characteristic shared by these agents: -their high cost-. This is expected as drug discovery and development is generally carried out within the commercial rather than the academic realm. Given the extraordinarily high therapeutic drug discovery-associated costs and risks, it is highly unlikely that any single public-sector research group will see a novel chemical "probe" become a "drug". An alternative drug development strategy is the exploitation of established drugs that have already been approved for treatment of non-cancerous diseases and whose cancer target has already been discovered. This strategy is also denominated drug repositioning, drug repurposing, or indication switch. Although traditionally development of these drugs was unlikely to be pursued by Big Pharma due to their limited commercial value, biopharmaceutical companies attempting to increase productivity at present are pursuing drug repositioning. More and more companies are scanning the existing pharmacopoeia for repositioning candidates, and the number of repositioning success stories is increasing. Here we provide noteworthy examples of known drugs whose potential anticancer activities have been highlighted, to encourage further research on these known drugs as a means to foster their translation into clinical trials utilizing the more limited public-sector resources. If these drug types eventually result in being effective, it follows that they could be much more affordable for patients with cancer; therefore, their contribution in terms of reducing cancer mortality at the global level would be greater.

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.

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.

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.

Expression of platelet derived growth factor family members and the potential role of imatinib mesylate for cervical cancer.

BACKGROUND: Despite significant achievements in the treatment of cervical cancer, it is still a deadly disease; hence newer therapeutical modalities are needed. Preliminary investigations suggest that platelet-derived growth factor (PDGF) might have a role in the development of cervical cancer, therefore it is important to determine whether this growth factor pathway is functional and its targeting with imatinib mesylate leads to growth inhibition of cervical cancer cells. RESULTS: PDGF receptors (PDGFR) and their ligands are frequently expressed in cervical cancer and the majority exhibited a combination of family members co-expression. A number of intronic and exonic variations but no known mutations in the coding sequence of the PDGFRalpha gene were found in cancer cell lines and primary tumors. Growth assays demonstrated that PDGFBB induces growth stimulation that can be blocked by imatinib and that this tyrosine kinase inhibitor on its own inhibits cell growth. These effects were associated with the phosphorylation status of the receptor. CONCLUSION: The PDGFR system may have a role in the pathogenesis of cervical cancer as their members are frequently expressed in this tumor and cervical cancer lines are growth inhibited by the PDGFR antagonist imatinib.

Antineoplastic effects of the DNA methylation inhibitor hydralazine and the histone deacetylase inhibitor valproic acid in cancer cell lines.

BACKGROUND: Among the epigenetic alterations occurring in cancer, DNA hypermethylation and histone hypoacetylation are the focus of intense research because their pharmacological inhibition has shown to produce antineoplastic activity in a variety of experimental models. The objective of this study was to evaluate the combined antineoplastic effect of the DNA methylation inhibitor hydralazine and the histone deacetylase inhibitor valproic acid in a panel of cancer cell lines. RESULTS: Hydralazine showed no growth inhibitory effect on cervical, colon, breast, sarcoma, glioma, and head & neck cancer cell lines when used alone. On the contrary, valproic acid showed a strong growth inhibitory effect that is potentiated by hydralazine in some cell lines. Individually, hydralazine and valproic acid displayed distinctive effects upon global gene over-expression but the number of genes over-expressed increased when cells were treated with the combination. Treatment of HeLa cells with hydralazine and valproic acid lead to an increase in the cytotoxicity of gemcitabine, cisplatin and adriamycin. A higher antitumor effect of adriamycin was observed in mice xenografted with human fibrosarcoma cells when the animals were co-treated with hydralazine and valproic acid. CONCLUSION: Hydralazine and valproic acid, two widely used drugs for cardiovascular and neurological conditions respectively have promising antineoplastic effects when used concurrently and may increase the antitumor efficacy of current cytotoxic agents.