Vorinostat synergises with capecitabine through upregulation of thymidine phosphorylase

Stochasticity of anticancer mechanisms underlying clinical effectiveness of vorinostat

The Food and Drug Administration (FDA) has approved vorinostat, also called Zolinza®, for its effectiveness in fighting cancer. This drug is a suberoyl-anilide hydroxamic acid belonging to the class of histone deacetylase inhibitors (HDACis). Its HDAC inhibitory potential allows it to accumulate acetylated histones. This, in turn, can restore normal gene expression in cancer cells and activate multiple signaling pathways. Experiments have proven that vorinostat induces histone acetylation and cytotoxicity in many cancer cell lines, increases the level of p21 cell cycle proteins, and enhances pro-apoptotic factors while decreasing anti-apoptotic factors. Additionally, it regulates the immune response by up-regulating programmed death-ligand 1 (PD-L1) and interferon gamma receptor 1 (IFN-γR1) expression, and can impact proteasome and/or aggresome degradation, endoplasmic reticulum function, cell cycle arrest, apoptosis, tumor microenvironment remodeling, and angiogenesis inhibition. In this study, we sought to elucidate the precise molecular mechanism by which Vorinostat inhibits HDACs. A deeper understanding of these mechanisms could improve our understanding of cancer cell abnormalities and provide new therapeutic possibilities for cancer treatment.

A Pilot Study of the Combination of Entinostat with Capecitabine in Advanced Breast Cancer

Background

Breast cancer has an unacceptably high recurrence rate when any residual disease is found following neoadjuvant treatment of high-risk disease. Based on clinical data suggesting an adjuvant role for epigenetic modifying agents in breast cancer and preclinical data suggesting synergistic activity of entinostat combined with capecitabine, we conducted a phase I, open-label study of these agents in metastatic breast cancer (MBC). Both agents have published doses for use in combination therapy, but the agents had not previously been combined with each other in a human trial.

Methods

A multisite phase I dose escalation study was performed at two academic centers. Patients with pretreated, HER2-negative MBC, and measurable disease were enrolled. Dual dose escalation was performed via a Bayesian partial order continual assessment method. Dose levels ranged from entinostat 3 mg to 5 mg and capecitabine 800 mg/m2 to 1000 mg/m2.

Results

Thirteen patients with MBC and a median of 4 lines of prior therapy were enrolled across four dose level combinations. The most common toxicities were neutropenia, thrombocytopenia, and palmar-plantar dysesthesia, which were expected toxicities. No new safety signals were observed. One dose-limiting toxicity was observed, which did not exceed a prespecified toxicity rate of 25%. The median treatment duration was 2.37 months. No partial nor complete responses were observed. The study was halted early prior to entering an expansion phase, due to drug supply limitations.

Conclusion

The tested dosing combinations of entinostat and capecitabine are likely safe in heavily pretreated metastatic breast cancer. This study's clinical investigation of entinostat in breast cancer was halted, but drug development of this agent continues outside the US. There remains a need for postoperative adjuvant drug therapy for the subpopulation of breast cancer patients with high-risk residual cancer after curative therapy. This trial is registered with NCT03473639.

Capecitabine-A "Permanent Mission" in Head and Neck Cancers "War Council"?

Capecitabine, an oral pro-drug that is metabolized to 5-FU, has been used in clinical practice for more than 20 years, being part of the therapeutic standard for digestive and breast cancers. The use of capecitabine has been evaluated in many trials including cases diagnosed in recurrent or metastatic settings. Induction regimens or a combination with radiation therapy were evaluated in head and neck cancers, but 5-FU still remained the fluoropyrimidine used as a part of the current therapeutic standard. Quantifications of levels or ratios for enzymes are involved in the capecitabine metabolism to 5-FU but are also involved in its conversion and elimination that may lead to discontinuation, dose reduction or escalation of treatment in order to obtain the best therapeutic ratio. These strategies based on biomarkers may be relevant in the context of the implementation of precision oncology. In particular for head and neck cancers, the identification of biomarkers to select possible cases of severe toxicity requiring discontinuation of treatment, including "multi-omics" approaches, evaluate not only serological biomarkers, but also miRNAs, imaging and radiomics which will ensure capecitabine a role in both induction and concomitant or even adjuvant and palliative settings. An approach including routine testing of dihydropyrimidine dehydrogenase (DPD) or even the thymidine phosphorylase (TP)/DPD ratio and the inclusion of miRNAs, imaging and radiomics parameters in multi-omics models will help implement "precision chemotherapy" in HNC, a concept supported by the importance of avoiding interruptions or treatment delays in this type of cancer. The chemosensitivity and prognostic features of HPV-OPC cancers open new horizons for the use of capecitabine in heavily pretreated metastatic cases. Vorinostat and lapatinib are agents that can be associated with capecitabine in future clinical trials to increase the therapeutic ratio.

Epigenetic Approaches to Overcome Fluoropyrimidines Resistance in Solid Tumors

Simple Summary

Fluoropyrimidines represent the backbone of many combination chemotherapy regimens for the treatment of solid cancers but are still associated with toxicity and mechanisms of resistance. In this review, we focused on the epigenetic modifiers histone deacetylase inhibitors (HDACis) and on their ability to regulate specific genes and proteins involved in the fluoropyrimidine metabolism and resistance mechanisms. We presented emerging preclinical and clinical studies, highlighting the mechanisms by which HDACis can prevent/overcome the resistance and/or enhance the therapeutic efficacy of fluoropyrimidines, potentially reducing their toxicity, and ultimately improving the overall survival of cancer patients.

Abstract

Although fluoropyrimidines were introduced as anticancer agents over 60 years ago, they are still the backbone of many combination chemotherapy regimens for the treatment of solid cancers. Like other chemotherapeutic agents, the therapeutic efficacy of fluoropyrimidines can be affected by drug resistance and severe toxicities; thus, novel therapeutic approaches are required to potentiate their efficacy and overcome drug resistance. In the last 20 years, the deregulation of epigenetic mechanisms has been shown to contribute to cancer hallmarks. Histone modifications play an important role in directing the transcriptional machinery and therefore represent interesting druggable targets. In this review, we focused on histone deacetylase inhibitors (HDACis) that can increase antitumor efficacy and overcome resistance to fluoropyrimidines by targeting specific genes or proteins. Our preclinical data showed a strong synergistic interaction between HDACi and fluoropyrimidines in different cancer models, but the clinical studies did not seem to confirm these observations. Most likely, the introduction of increasingly complex preclinical models, both in vitro and in vivo, cannot recapitulate human complexity; however, our analysis of clinical studies revealed that most of them were designed without a mechanistic approach and, importantly, without careful patient selection.

Histone deacetylases: A novel class of therapeutic targets for pancreatic cancer

Pancreatic cancer is the seventh leading cause of cancer death worldwide, with a low 5-year survival rate. Novel agents are urgently necessary to treat the main pathological type, known as pancreatic ductal carcinoma (PDAC). The dysregulation of histone deacetylases (HDACs) has been identified in association with PDAC, which can be more easily targeted by small molecular inhibitors than gene mutations and may represent a therapeutic breakthrough for PDAC. However, the contributions of HDACs to PDAC remain controversial, and pharmacokinetic challenges have limited the application of HDAC inhibitors (HDACis) in PDAC. This review summarizes the mechanisms associated with success and failure of HDACis in PDAC and discusses the recent progress made in HDACi development and application, such as combination therapies designed to enhance efficacy. More precise strategies involving HDACis might eventually improve the outcomes of PDAC treatment.

Using predictive machine learning models for drug response simulation by calibrating patient-specific pathway signatures

The utility of pathway signatures lies in their capability to determine whether a specific pathway or biological process is dysregulated in a given patient. These signatures have been widely used in machine learning (ML) methods for a variety of applications including precision medicine, drug repurposing, and drug discovery. In this work, we leverage highly predictive ML models for drug response simulation in individual patients by calibrating the pathway activity scores of disease samples. Using these ML models and an intuitive scoring algorithm to modify the signatures of patients, we evaluate whether a given sample that was formerly classified as diseased, could be predicted as normal following drug treatment simulation. We then use this technique as a proxy for the identification of potential drug candidates. Furthermore, we demonstrate the ability of our methodology to successfully identify approved and clinically investigated drugs for four different cancers, outperforming six comparable state-of-the-art methods. We also show how this approach can deconvolute a drugs' mechanism of action and propose combination therapies. Taken together, our methodology could be promising to support clinical decision-making in personalized medicine by simulating a drugs' effect on a given patient.

In Vivo Evaluation of the Combined Anticancer Effects of Cisplatin and SAHA in Nonsmall Cell Lung Carcinoma Using [18F]FAHA and [18F]FDG PET/CT Imaging

Combining standard drugs with low doses of histone deacetylase inhibitors (HDACIs) is a promising strategy to increase the efficacy of chemotherapy. The ability of well-tolerated doses of HDACIs that act as chemosensitizers for platinum-based chemotherapeutics has recently been proven in many types and stages of cancer in vitro and in vivo. Detection of changes in HDAC activity/expression may provide important prognostic and predictive information and influence treatment decision-making. Use of [¹⁸F] FAHA, a HDAC IIa-specific radionuclide, for molecular imaging may enable longitudinal, noninvasive assessment of HDAC activity/expression in metastatic cancer. We evaluated the synergistic anticancer effects of cisplatin and the histone deacetylase inhibitor suberoylanilide hydroxamic acid (SAHA) in xenograft models of nonsmall cell lung cancer (NSCLC) using [¹⁸F] FAHA and [¹⁸F] FDG PET/CT imaging. Cisplatin alone significantly increased [¹⁸F] FAHA accumulation and reduced [¹⁸F] FDG accumulation in H441 and PC14 xenografts; coadministration of cisplatin and SAHA resulted in the opposite effects. Immunochemical staining for acetyl-histone H3 confirmed the PET/CT imaging findings. Moreover, SAHA had a more significant effect on the acetylome in PC14 (EGFR exon 19 deletion mutation) xenografts than H441 (wild-type EGFR and KRAS codon 12 mutant) xenografts. In conclusion, [¹⁸F] FAHA enables quantitative visualization of HDAC activity/expression in vivo, thus, may represent a clinically useful, noninvasive tool for the management of patients who may benefit from synergistic anticancer therapy.

SAHA Overcomes 5-FU Resistance in IFIT2-Depleted Oral Squamous Cell Carcinoma Cells

Simple Summary

IFIT2 depletion is associated with increased epithelial-mesenchymal transition and metastasis. The main aim of our study was to understand the link between drug resistance and IFIT2 depletion. In this study, we confirmed resistance to multiple common therapeutic drugs, particularly 5-FU, which showed especially high resistance in IFIT2-depleted cells. Interestingly, combination of SAHA and 5-FU overcame 5-FU resistance in IFIT2-depleted cells. Hence, our findings suggest that IFIT2 expression may be used as a biomarker to decide whether to undergo 5-FU treatment, but also the SAHA and 5-FU combination may be a potential new treatment regimen to augment 5-FU therapy in patients with thymidylate synthase-mediated drug-resistant oral squamous cell carcinoma.

Abstract

Interferon-induced protein with tetratricopeptide repeats 2 (IFIT2) is a member of the interferon-stimulated gene family that contains tetratricopeptide repeats (TPRs), which mediate protein–protein interactions in various biological systems. We previously showed the depletion of IFIT2 enhanced cell migration and metastatic activity in oral squamous cell carcinoma (OSCC) cells via the activation of atypical PKC signaling. In this study, we found that IFIT2-knockdown cells displayed higher resistance to 5-fluorouracil (5-FU) than control cells. The comet assay and annexin V analysis showed decreased DNA damage and cell death in IFIT2-knockdown cells compared to control cells treated with 5-FU. Cell cycle progression was also perturbed by 5-FU treatment, with the accumulation of IFIT2-depleted cells in S phase in a time-dependent manner. We further observed the overexpression of thymidylate synthase (TS) and thymidine kinase (TK) in IFIT2-knockdown cells. Inhibition of TS alone or double inhibition of TS and TK1 using the siRNA technique increased susceptibility to 5-FU in IFIT2-knockdown cells. We further identified that suberanilohydroxamic acid (SAHA) treatment decreased the expression of TS in IFIT2-knockdown cells and demonstrated that pretreatment with SAHA sensitized IFIT2-knockdown cells to 5-FU in vitro and in vivo. In conclusion, IFIT2 knockdown enhances TS expression, which mediates 5-FU resistance, and SAHA pretreatment suppresses TS expression and hence sensitizes cells to 5-FU. SAHA will be an effective strategy for the treatment of OSCC patients with 5-FU resistance.

Synergistic antitumor interaction of valproic acid and simvastatin sensitizes prostate cancer to docetaxel by targeting CSCs compartment via YAP inhibition

BACKGROUND

Despite the introduction of several novel therapeutic approaches that improved survival, metastatic castration-resistant prostate cancer (mCRPC) remains an incurable disease. Herein we report the synergistic antitumor interaction between two well-known drugs used for years in clinical practice, the antiepileptic agent with histone deacetylase inhibitory activity valproic acid and the cholesterol lowering agent simvastatin, in mCRPC models.

METHODS

Synergistic anti-tumor effect was assessed on PC3, 22Rv1, DU145, DU145R80, LNCaP prostate cancer cell lines and EPN normal prostate epithelial cells, by calculating combination index (CI), caspase 3/7 activation and colony formation assays as well as on tumor spheroids and microtissues scored with luminescence 3D-cell viability assay. Cancer stem cells (CSC) compartment was studied evaluating specific markers by RT-PCR, western blotting and flow cytometry as well as by limiting dilution assay. Cholesterol content was evaluated by ¹H-NMR. Overexpression of wild-type YAP and constitutively active YAP5SA were obtained by lipofectamine-based transfection and evaluated by immunofluorescence, western blotting and RT-PCR. 22Rv1 R_39 docetaxel resistant cells were selected by stepwise exposure to increasing drug concentrations. In vivo experiments were performed on xenograft models of DU145R80, 22Rv1 parental and docetaxel resistant cells, in athymic mice.

RESULTS

We demonstrated the capacity of the combined approach to target CSC compartment by a novel molecular mechanism based on the inhibition of YAP oncogene via concurrent modulation of mevalonate pathway and AMPK. Because both CSCs and YAP activation have been associated with chemo-resistance, we tested if the combined approach can potentiate docetaxel, a standard of care in mCRCP treatment. Indeed, we demonstrated, both in vitro and in vivo models, the ability of valproic acid/simvastatin combination to sensitize mCRPC cells to docetaxel and to revert docetaxel-resistance, by mevalonate pathway/YAP axis modulation.

CONCLUSION

Overall, mCRPC progression and therapeutic resistance driven by CSCs via YAP, can be tackled by the combined repurposing of two generic and safe drugs, an approach that warrants further clinical development in this disease.

A possible link to uracil DNA glycosylase in the synergistic action of HDAC inhibitors and thymidylate synthase inhibitors

It is well established that thymidylate synthase inhibitors can cause cellular toxicity through uracil DNA glycosylase (UNG2)-dependent pathways. Additionally, thymidylate synthase inhibitors and HDAC inhibitors are known to act synergistically in a variety of cancer types. A recent article from J. Transl. Med. links these together by demonstrating widespread depletion of UNG2 levels across a variety of cell lines treated with HDAC inhibitors. Recent findings suggest that UNG2 depletion by HDAC inhibitors would likely be an effective method to sensitize cells to thymidylate synthase inhibitors. This is particularly important for cancer types that are typically resistant to thymidylate synthase inhibitors, such as cells that are deficient in p53 activity.

Randomized phase II study of valproic acid in combination with bevacizumab and oxaliplatin/fluoropyrimidine regimens in patients with RAS-mutated metastatic colorectal cancer: the REVOLUTION study protocol

Background

Despite effective treatments, metastatic colorectal cancer (mCRC) prognosis is still poor, mostly in RAS-mutated tumors, thus suggesting the need for novel combinatorial therapies. Epigenetic alterations play an important role in initiation and progression of cancers, including CRC. Histone-deacetylase inhibitors (HDACi) have shown activity in combination with chemotherapy in the treatment of solid tumors. Owing to its HDACi activity and its safe use for epileptic disorders, valproic acid (VPA) is a good candidate for anticancer therapy that we have largely explored preclinically translating our findings in currently ongoing clinical studies. We have shown in CRC models that HDACi, including VPA, induces synergistic antitumor effects in combination with fluoropyrimidines. Furthermore, unpublished results from our group demonstrated that VPA induces differentiation and sensitization of CRC stem cells to oxaliplatin. Moreover, preclinical and clinical data suggest that HDACi may prevent/reverse anti-angiogenic resistance.

Methods/Design

A randomized, open-label, two-arm, multicenter phase-II study will be performed to explore whether the addition of VPA to first line bevacizumab/oxaliplatin/fluoropyrimidine regimens (mFOLFOX-6/mOXXEL) might improve progression-free survival (PFS) in RAS-mutated mCRC patients. A sample size of 200 patients was calculated under the hypothesis that the addition of VPA to chemotherapy/bevacizumab can improve PFS from 9 to 12 months, with one-sided alpha of 0.20 and a power of 0.80. Secondary endpoints are overall survival, objective response rate, metastases resection rate, toxicity, and quality of life. Moreover, the study will explore several prognostic and predictive biomarkers on blood samples, primary tumors, and on resected metastases.

Discussion

The "Revolution" study aims to improve the treatment efficacy of RAS-mutated mCRC through an attractive strategy evaluating the combination of VPA with standard cancer treatment. Correlative studies could identify novel biomarkers and could add new insight in the mechanism of interaction between VPA, fluoropyrimidine, oxaliplatin, and bevacizumab.

Trial Registration

EudraCT: 2018-001414-15; ClinicalTrials.gov identifier: NCT04310176.

Implication for Cancer Stem Cells in Solid Cancer Chemo-Resistance: Promising Therapeutic Strategies Based on the Use of HDAC Inhibitors

Resistance to therapy in patients with solid cancers represents a daunting challenge that must be addressed. Indeed, current strategies are still not effective in the majority of patients; which has resulted in the need for novel therapeutic approaches. Cancer stem cells (CSCs), a subset of tumor cells that possess self-renewal and multilineage differentiation potential, are known to be intrinsically resistant to anticancer treatments. In this review, we analyzed the implications for CSCs in drug resistance and described that multiple alterations in morphogenetic pathways (i.e., Hippo, Wnt, JAK/STAT, TGF-β, Notch, Hedgehog pathways) were suggested to be critical for CSC plasticity. By interrogating The Cancer Genome Atlas (TCGA) datasets, we first analyzed the prevalence of morphogenetic pathways alterations in solid tumors with associated outcomes. Then, by highlighting epigenetic relevance in CSC development and maintenance, we selected histone deacetylase inhibitors (HDACi) as potential agents of interest to target this subpopulation based on the pleiotropic effects exerted specifically on altered morphogenetic pathways. In detail, we highlighted the role of HDACi in solid cancers and, specifically, in the CSC subpopulation and we pointed out some mechanisms by which HDACi are able to overcome drug resistance and to modulate stemness. Although, further clinical and preclinical investigations should be conducted to disclose the unclear mechanisms by which HDACi modulate several signaling pathways in different tumors. To date, several lines of evidence support the testing of novel combinatorial therapeutic strategies based on the combination of drugs commonly used in clinical practice and HDACi to improve therapeutic efficacy in solid cancer patients.

Vorinostat Potentiates 5-Fluorouracil/Cisplatin Combination by Inhibiting Chemotherapy-Induced EGFR Nuclear Translocation and Increasing Cisplatin Uptake

The 5-fluorouracil/cisplatin (5FU/CDDP) combination is one of the most widely used treatment options for several solid tumors. However, despite good anticancer responses, this regimen is often associated with high toxicity and treatment resistance. In our study, we evaluated whether the histone deacetylase inhibitor (HDACi), vorinostat, may induce synergistic antitumor and proapoptotic effects in combination with 5FU/CDDP in squamous cancer cell models. We demonstrated in cancer cell lines, including the intrinsic CDDP-resistant Cal27 cells, that simultaneous exposure to equitoxic doses of vorinostat plus 5FU/CDDP results in strong synergistic antiproliferative and proapoptotic effects related to cell-cycle perturbation and DNA damage induction. These effects were confirmed in vivo in both orthotopic and heterotopic xenograft mouse models of Cal27 cells. Mechanistically, vorinostat reverted 5FU/CDDP-induced EGFR phosphorylation and nuclear translocation, leading to the impairment of nuclear EGFR noncanonical induction of genes such as thymidylate synthase and cyclin D1. These effects were exerted by vorinostat, at least in part, by increasing lysosomal-mediated EGFR protein degradation. Moreover, vorinostat increased platinum uptake and platinated DNA levels by transcriptionally upregulating the CDDP influx channel copper transporter 1 (CTR1). Overall, to our knowledge, this study is the first to demonstrate the ability of vorinostat to inhibit two well-known mechanisms of CDDP resistance, EGFR nuclear translocation and CTR1 overexpression, adding new insight into the mechanism of the synergistic interaction between HDACi- and CDDP-based chemotherapy and providing the rationale to clinically explore this combination to overcome dose-limiting toxicity and chemotherapy resistance.

Valproic acid exhibits anti-tumor activity selectively against EGFR/ErbB2/ErbB3-coexpressing pancreatic cancer via induction of ErbB family members-targeting microRNAs

Background

Deregulated ErbB signaling plays an important role in tumorigenesis of pancreatic cancer. However, patients with pancreatic cancer benefit little from current existed therapies targeting the ErbB signaling. Here, we explore the potential anti-tumor activity of Valproic acid against pancreatic cancer via targeting ErbB family members.

Methods

Cell viability assay and apoptosis evaluation were carried out to determine the efficacy of VPA on pancreatic cancer cells. Western blot analyses were performed to determine the expression and activation of proteins. Apoptosis enzyme-linked immunosorbent assay was used to quantify cytoplasmic histone associated DNA fragments. Lentiviral expression system was used to introduce overexpression of exogeneous genes or gene-targeting short hairpin RNAs (shRNAs). qRT-PCR was carried out to analyze the mRNAs and miRNAs expression levels. Tumor xenograft model was established to evaluate the in vivo anti-pancreatic cancer activity of VPA.

Results

VPA preferentially inhibited cell proliferation/survival of, and induced apoptosis in EGFR/ErbB2/ErbB3-coexpressing pancreatic cancer cells within its clinically achievable range [40~100 mg/L (0.24~0.6 mmol/L)]. Mechanistic investigations revealed that VPA treatment resulted in simultaneous significant down-regulation of EGFR, ErbB2, and ErbB3 in pancreatic cancer cells likely via induction of ErbB family members-targeting microRNAs. Moreover, the anti-pancreatic cancer activity of VPA was further validated in tumor xenograft model.

Conclusions

Our data strongly suggest that VPA may be added to the treatment regimens for pancreatic cancer patients with co-overexpression of the ErbB family members.

Electronic supplementary material

The online version of this article (10.1186/s13046-019-1160-9) contains supplementary material, which is available to authorized users.

Development and validation of a quantitative method for thymidine phosphorylase activity in peripheral blood mononuclear cells

The enzyme thymidine phosphorylase (TP) is important for activation of capecitabine and 5-fluorouracil. Assessment of TP phenotype might be suitable for identification of patients at risk of fluoropyrimidine-induced toxicity. In this paper, we describe the development and validation an assay for TP activity in peripheral blood mononuclear cells (PBMCs). The assay was based on ex vivo conversion of the TP substrate thymidine to thymine. The amount of thymine formed was determined by high-performance liquid chromatography - ultraviolet detection (HPLC-UV) with 5-bromouracil as internal standard. Lymphocytes and monocytes were purified from isolated PBMCs to examine cell-specific TP activity. TP activity in PBMCs demonstrated Michaelis-Menten kinetics. The lower limit of quantification was 2.3 µg PBMC protein and assay linearity was demonstrated up to 22.7 µg PBMC protein. Within-day and between-day precisions were ≤9.2% and ≤6.0%, respectively. Adequate stability TP activity was demonstrated after long-term storage of PBMC dry pellets and lysates at -80 °C. In monocytes, TP activity was approximately 3 times higher than in lymphocytes. Clinical applicability was demonstrated in samples that were collected from five cancer patients. A simple, precise and sensitive HPLC-UV assay for quantification of TP activity in PBMCs was developed that can be applied for clinical research.

A452, an HDAC6-selective inhibitor, synergistically enhances the anticancer activity of chemotherapeutic agents in colorectal cancer cells

Although histone deacetylase inhibitors (HDACi) alone could be clinically useful, these are most recently used in combination with other anticancer agents in clinical trials for cancer treatment. Recently, we reported the anticancer activity of an HDAC6-selective inhibitor A452 toward various cancer cell types. This study aims to present a potent synergistic antiproliferative effect of A452/anticancer agent treatment in colorectal cancer cells (CRC) cells, independently of the p53 status. A452 in combination with irinotecan, or SAHA is more potent than either drug alone in the apoptotic pathway as evidenced by activated caspase-3 and PARP, increased Bak and pp38, decreased Bcl-xL, pERK, and pAKT, and induced apoptotic cells. Furthermore, A452 enhances DNA damage induced by anticancer agents as indicated by the increased accumulation of γH2AX and the activation of the checkpoint kinase Chk2. The silencing of HDAC6 enhances the cell growth inhibition and cell death caused by anticancer agents. In addition, A452 induces the synergistic suppression of cell migration and invasion. This study suggests a mechanism by which HDAC6-selective inhibition can enhance the efficacy of specific anticancer agents in CRC cells.

Wnt Signalling-Targeted Therapy in the CMS2 Tumour Subtype: A New Paradigm in CRC Treatment?

Colorectal cancers (CRC) belonging to the consensus molecular subtype 2 (CMS2) have the highest incidence rate, affect mainly the distal colon and rectum, and are characterized by marked Wnt/β-catenin/Transcription Factor 7-Like 2 (TCF7L2) pathway activation and also by activation of epidermal growth factor receptor (EGFR) signalling. Despite having the highest overall survival, CMS2 tumours are often diagnosed at stage III when an adjuvant chemotherapy-based regimen is recommended. Nevertheless, colorectal cancer stem cells (CSCs) and circulating tumour cells may still evade the current therapeutic options and metastasize, stressing the need to develop more tailored therapeutic strategies. For example, activation of EGFR signalling is being used as a target for tailored therapy, however, therapy resistance is frequently observed. Therefore, targeting the Wnt signalling axis represents an additional therapeutic strategy, considering that CMS2 tumours are "Wnt-addicted". Several efforts have been made to identify Wnt antagonists, either of synthetic or natural origin. However, an inverse gradient of Wnt/β-catenin/TCF7L2 signalling activity during CRC progression has been suggested, with early stage and metastatic tumours displaying high and low Wnt signalling activities, respectively, which lead us to revisit the "just-right" signalling model. This may pinpoint the use of Wnt signalling agonists instead of antagonists for treatment of metastatic stages, in a context-dependent fashion. Moreover, the poor immunogenicity of these tumours challenges the use of recently emerged immunotherapies. This chapter makes a journey about CMS2 tumour characterization, their conventional treatment, and how modulation of Wnt signalling or immune response may be applied to CRC therapy. It describes the newest findings in this field and indicates where more research is required.

Synergistic antitumor interaction between valproic acid, capecitabine and radiotherapy in colorectal cancer: critical role of p53

Background

Recurrence with distant metastases has become the predominant pattern of failure in locally advanced rectal cancer (LARC), thus the integration of new antineoplastic agents into preoperative fluoropyrimidine-based chemo-radiotherapy represents a clinical challenge to implement an intensified therapeutic strategy.

The present study examined the combination of the histone deacetylase inhibitor (HDACi) valproic acid (VPA) with fluoropyrimidine-based chemo-radiotherapy on colorectal cancer (CRC) cells.

Methods

HCT-116 (p53-wild type), HCT-116 p53^−/− (p53-null), SW620 and HT29 (p53-mutant) CRC cell lines were used to assess the antitumor interaction between VPA and capecitabine metabolite 5′-deoxy-5-fluorouridine (5′-DFUR) in combination with radiotherapy and to evaluate the role of p53 in the combination treatment. Effects on proliferation, clonogenicity and apoptosis were evaluated, along with γH2AX foci formation as an indicator for DNA damage.

Results

Combined treatment with equipotent doses of VPA and 5′-DFUR resulted in synergistic effects in CRC lines expressing p53 (wild-type or mutant). In HCT-116 p53^−/− cells we observed antagonist effects. Radiotherapy further potentiated the antiproliferative, pro-apoptotic and DNA damage effects induced by 5′-DFUR/VPA combination in p53 expressing cells.

Conclusions

These results highlighted the role of VPA as valuable candidate to be added to preoperative chemo-radiotherapy in LARC. On these bases we launched the ongoing phase I/II study of VPA and short-course radiotherapy plus capecitabine as preoperative treatment in low-moderate risk rectal cancer (V-shoRT-R3).

Electronic supplementary material

The online version of this article (10.1186/s13046-017-0647-5) contains supplementary material, which is available to authorized users.

Synergistic antitumor activity of histone deacetylase inhibitors and anti-ErbB3 antibody in NSCLC primary cultures via modulation of ErbB receptors expression

ErbB3, a member of the ErbB family receptors, has a key role in the development and progression of several cancers, including non-small cell lung cancer (NSCLC), and in the establishment of resistance to therapies, leading to the development of anti-ErbB3 therapies.

In this study we demonstrated, in a set of malignant pleural effusion-derived cultures of NSCLC, the synergistic antitumor effect of a histone deacetylase inhibitor (HDACi), such as vorinostat or valproic acid (VPA), in combination with the anti-ErbB3 monoclonal antibody (MoAb) A3. Synergistic interaction was observed in 2D and in 3D cultures conditions, both in fully epithelial cells expressing all ErbB receptors, and in cells that had undergone epithelial to mesenchymal transition and expressed low levels of ErbB3. We provided evidences suggesting that differential modulation of ErbB receptors by vorinostat or VPA, also at low doses corresponding to plasma levels easily reached in treated patients, is responsible for the observed synergism. In details, we showed in epithelial cells that both vorinostat and VPA induced time- and dose-dependent down-regulation of all three ErbB receptors and of downstream signaling. On the contrary, in A3-resistant mesenchymal cells, we observed time- and dose-dependent increase of mRNA and protein levels as well as surface expression of ErbB3, paralleled by down-regulation of EGFR and ErbB2. Our results suggest that the combination of a HDACi plus an anti-ErbB3 MoAb represents a viable strategy that warrants further evaluation for the treatment of NSCLC patients.

Thymidine phosphorylase: A potential new target for treating cardiovascular disease

We recently found that thymidine phosphorylase (TYMP), also known as platelet-derived endothelial cell growth factor, plays an important role in platelet activation in vitro and thrombosis in vivo by participating in multiple signaling pathways. Platelets are a major source of TYMP. Since platelet-mediated clot formation is a key event in several fatal diseases, such as myocardial infarction, stroke and pulmonary embolism, understanding TYMP in depth may lead to uncovering novel mechanisms in the development of cardiovascular diseases. Targeting TYMP may become a novel therapeutic for cardiovascular disorders. In this review article, we summarize the discovery of TYMP and the potential molecular mechanisms of TYMP involved in the development of various diseases, especially cardiovascular diseases. We also offer insights regarding future studies exploring the role of TYMP in the development of cardiovascular disease as well as in therapy.

Epigenetic modifiers in immunotherapy: a focus on checkpoint inhibitors

Immune surveillance should be directed to suppress tumor development and progression, involving a balance of coinhibitory and costimulatory signals that amplify immune response without overwhelming the host. Immunotherapy confers durable clinical benefit in 'immunogenic tumors', whereas in other tumors the responses are modest. Thus, immune checkpoint inhibitors may need to be combined with strategies to boost immune response or increase the tumor immune profile. Epigenetic aberrations contribute significantly to carcinogenesis. Recent findings suggest that epigenetic drugs prime the immune response by increasing expression of tumor-associated antigens and immune-related genes, as well as modulating chemokines and cytokines involved in immune system activation. This review describes our current understanding regarding epigenetic and immunotherapy combination, focusing on immune response priming to checkpoint blockade.

Valproic acid potentiates the anticancer activity of capecitabine in vitro and in vivo in breast cancer models via induction of thymidine phosphorylase expression

The prognosis of patients with metastatic breast cancer remains poor, and thus novel therapeutic approaches are needed. Capecitabine, which is commonly used for metastatic breast cancer in different settings, is an inactive prodrug that takes advantage of elevated levels of thymidine phosphorylase (TP), a key enzyme that is required for its conversion to 5-fluororacil, in tumors. We demonstrated that histone deacetylase inhibitors (HDACi), including low anticonvulsant dosage of VPA, induced the dose- and time-dependent up-regulation of TP transcript and protein expression in breast cancer cells, but not in the non-tumorigenic breast MCF-10A cell line. Through the use of siRNA or isoform-specific HDACi, we demonstrated that HDAC3 is the main isoform whose inhibition is involved in the modulation of TP. The combined treatment with capecitabine and HDACi, including valproic acid (VPA), resulted in synergistic/additive antiproliferative and pro-apoptotic effects in breast cancer cells but not in TP-knockout cells, both in vitro and in vivo, highlighting the crucial role of TP in the synergism observed. Overall, this study suggests that the combination of HDACi (e.g., VPA) and capecitabine is an innovative antitumor strategy that warrants further clinical evaluation for the treatment of metastatic breast cancer.

Phase II clinical study of valproic acid plus cisplatin and cetuximab in recurrent and/or metastatic squamous cell carcinoma of Head and Neck-V-CHANCE trial

BACKGROUND

Recurrent/metastatic squamous cell carcinoma of the head and neck (SCCHN) has a poor prognosis and the combination of cisplatin and cetuximab, with or without 5-fluorouracil, is the gold standard treatment in this stage. Thus, the concomitant use of novel compounds represents a critical strategy to improve treatment results. Histone deacetylase inhibitors (HDACi) enhance the activity of several anticancer drugs including cisplatin and anti-Epidermal Growth Factor Receptor (anti-EGFR) compounds. Preclinical studies in models have shown that vorinostat is able to down regulate Epidermal Growth Factor Receptor (EGFR) expression and to revert epithelial to mesenchimal transition (EMT). Due to its histone deacetylase (HDAC) inhibiting activity and its safe use as a chronic therapy for epileptic disorders, valproic acid (VPA) has been considered a good candidate for anticancer therapy. A reasonable option may be to employ the combination of cisplatin, cetuximab and VPA in recurrent/metastatic SCCHN taking advantage of the possible positive interaction between histone deacetylase inhibitors, cisplatin and/or anti-EGFR.

METHOD/DESIGN

V-CHANCE is a phase 2 clinical trial evaluating, in patients with recurrent/metastatic squamous cell carcinoma of the head and neck never treated with first-line chemotherapy, the concomitant standard administration of cisplatin (on day 1, every 3 weeks) and cetuximab (on day 1, weekly), in combination with oral VPA given daily from day -14 with a titration strategy in each patient (target serum level of 50-100 μg/ml). Primary end point is the objective response rate measured according to Response Evaluation Criteria in Solid Tumors (RECIST). Sample size, calculated according to Simon 2 stage minimax design will include 21 patients in the first stage with upper limit for rejection being 8 responses, and 39 patients in the second stage, with upper limit for rejection being 18 responses. Secondary endpoints are time to progression, duration of response, overall survival, safety. Objectives of the translational study are the evaluation on tumor samples of markers of treatment efficacy/resistance (i.e. γH2AX, p21/WAF, RAD51, XRCC1, EGFR, p-EGFR, Ki-67) and specific markers of VPA HDAC inhibitory activity (histones and proteins acetylation, Histone deacetylase isoforms) as well as valproate test, histones and proteins acetylation of peripheral blood mononuclear cell, tested on blood samples at baseline and at different time points during treatment.

DISCUSSION

Overall, this study could provide a less toxic and more effective first-line chemotherapy regimen in patients with recurrent/metastatic squamous cell carcinoma of the head and neck by demonstrating the feasibility and efficacy of cisplatin/cetuximab plus valproic acid. Moreover, correlative studies could help to identify responder patients, and will add insights in the mechanism of the synergistic interaction between these agents.

EUDRACT NUMBER

2014-001523-69 TRIAL REGISTRATION: ClinicalTrials.gov number, NCT02624128.

Vorinostat enhances the cisplatin-mediated anticancer effects in small cell lung cancer cells

BACKGROUND

Vorinostat, a histone deacetylase (HDAC) inhibitor, is a promising agent for cancer therapy. Combining vorinostat with cisplatin may relax the chromatin structure and facilitate the accessibility of cisplatin, thus enhancing its cytotoxicity. Studies have not yet investigated the effects of the combination of vorinostat and cisplatin on small cell lung cancer (SCLC).

METHODS

We first assessed the efficacy of vorinostat with etoposide/cisplatin (EP; triple combination) and then investigated the effects of cotreatment with vorinostat and cisplatin on H209 and H146 SCLC cell lines. The anticancer effects of various combinations were determined in terms of cell viability, apoptosis, cell cycle distribution, and vorinostat-regulated proteins. We also evaluated the efficacy of vorinostat/cisplatin combination in H209 xenograft nude mice.

RESULTS

Our data revealed that the triple combination engendered a significant reduction of cell viability and high apoptotic cell death. In addition, vorinostat combined with cisplatin enhanced cell growth inhibition, induced apoptosis, and promoted cell cycle arrest. We observed that the acetylation levels of histone H3 and α-tubulin were higher in combination treatments than in vorinostat treatment alone. Moreover, vorinostat reduced the expression of thymidylate synthase (TS), and TS remained inhibited after cotreament with cisplatin. Furthermore, an in vivo study revealed that the combination of vorinostat and cisplatin significantly inhibited tumor growth in xenograft nude mice (tumor growth inhibition T/C% = 20.5 %).

CONCLUSIONS

Combined treatments with vorinostat promote the cytotoxicity of cisplatin and induce the expression of vorinostat-regulated acetyl proteins, eventually enhancing antitumor effects in SCLC cell lines. Triple combinations with a low dosage of cisplatin demonstrate similar therapeutic effects. Such triple combinations, if applied clinically, may reduce the undesired adverse effects of cisplatin. The effects of the combination of vorinostat and cisplatin should be evaluated further before conducting clinical trials for SCLC treatment.

Tissue transglutaminase (TG2) is involved in the resistance of cancer cells to the histone deacetylase (HDAC) inhibitor vorinostat

Vorinostat demonstrated preclinical and clinical efficacy in human cancers and is the first histone deacetylase inhibitor (HDACi) approved for cancer treatment. Tissue transglutaminase (TG2) is a multifunctional enzyme that catalyzes a Ca²⁺ dependent transamidating reaction resulting in covalent cross-links between proteins. TG2 acts also as G-protein in trans-membrane signaling and as a cell surface adhesion mediator. TG2 up-regulation has been demonstrated in several cancers and its expression levels correlate with resistance to chemotherapy and metastatic potential. We demonstrated that the anti-proliferative effect of the HDACi vorinostat is paralleled by the induction of TG2 mRNA and protein expression in cancer cells but not in ex vivo treated peripheral blood lymphocytes. This effect was also shared by other pan-HDACi and resulted in increased TG2 transamidating activity. Notably, high TG2 basal levels in a panel of cancer cell lines correlated with lower vorinostat antiproliferative activity. Notably, in TG2-knockdown cancer cells vorinostat anti-proliferative and pro-apoptotic effects were enhanced, whereas in TG2-full-length transfected cells were impaired, suggesting that TG2 could represent a mechanism of intrinsic or acquired resistance to vorinostat. In fact, co-treatment of tumor cells with inhibitors of TG2 transamidating activity potentiated the antitumor effect of vorinostat. Moreover, vorinostat-resistant MCF7 cells selected by stepwise increasing concentrations of the drug, significantly overexpressed TG2 protein compared to parental cells, and co-treatment of these cells with TG2 inhibitors reversed vorinostat-resistance. Taken together, our data demonstrated that TG2 is involved in the resistance of cancer cells to vorinostat, as well as to other HDACi.

Phase I trial of vorinostat added to chemoradiation with capecitabine in pancreatic cancer

BACKGROUND AND PURPOSE

This single institution phase I trial determined the maximum tolerated dose (MTD) of concurrent vorinostat and capecitabine with radiation in non-metastatic pancreatic cancer.

MATERIAL AND METHODS

Twenty-one patients received escalating doses of vorinostat (100-400mg daily) during radiation. Capecitabine was given 1000mg q12 on the days of radiation. Radiation consisted of 30Gy in 10 fractions. Vorinostat dose escalation followed the standard 3+3 design. No dose escalation beyond 400mg vorinostat was planned. Diffusion-weighted (DW)-MRI pre- and post-treatment was used to evaluate in vivo tumor cellularity.

RESULTS

The MTD of vorinostat was 400mg. Dose limiting toxicities occurred in one patient each at dose levels 100mg, 300mg, and 400mg: 2 gastrointestinal toxicities and one thrombocytopenia. The most common adverse events were lymphopenia (76%) and nausea (14%). The apparent diffusion coefficient (ADC) increased in most tumors. Nineteen (90%) patients had stable disease, and two (10%) had progressive disease at time of surgery. Eleven patients underwent surgical exploration with four R0 resections and one R1 resection. Median overall survival was 1.1years (95% confidence interval 0.78-1.35).

CONCLUSIONS

The combination of vorinostat 400mg daily M-F and capecitabine 1000mg q12 M-F with radiation (30Gy in 10 fractions) was well tolerated with encouraging median overall survival.

Vorinostat synergizes with EGFR inhibitors in NSCLC cells by increasing ROS via up-regulation of the major mitochondrial porin VDAC1 and modulation of the c-Myc-NRF2-KEAP1 pathway

In non-small-cell lung cancer (NSCLC) patients, the activation of alternative pathways contributes to the limited efficacy of the epidermal growth factor receptor (EGFR) tyrosine kinase inhibitors (TKIs) gefitinib and erlotinib. The present study examines a panel of EGFR wild-type, K-Ras mutated, NSCLC lines, which were all intrinsically resistant to EGFR-TKIs, and demonstrates that the histone deacetylase inhibitor vorinostat can improve the therapeutic efficacy of gefitinib or erlotinib, inducing strong synergistic antiproliferative and pro-apoptotic effects that are paralleled by reactive oxygen species accumulation and by increased DNA damage. By knockdown experiments, we suggested that the up-regulation of voltage-dependent anion-selective channel protein 1 (VDAC1), the major mitochondrial porin of the outer mitochondrial membrane, which was induced by vorinostat and further increased by the combination, could be functionally involved in oxidative stress-dependent apoptosis. Significantly, we also observed the attenuation of the expression of both the enzyme hexokinase1, a negative VDAC1 regulator, and the anti-apoptotic porin VDAC2, only in the combination setting, suggesting convergent mechanisms that enhanced mitochondria-dependent apoptosis by targeting VDAC protein functions. Furthermore, the prosurvival capacities of the cells were also inhibited by the combination treatments, as shown by complete pAKT deactivation, increased GSK3β expression, and c-Myc down-regulation. Finally, we observed that the combination treatment of vorinostat and either of the EGFR-TKIs induced the down-regulation of the c-Myc-regulated nuclear factor erythroid 2-related factor 2 (NRF2) transcription factor and the up-regulation of the NRF2 repressor Kelch-like ECH-associated protein 1 regulator (KEAP1). These two genes are crucial for the redox stress response, often dysfunctional in NSCLC, and involved in EGFR-TKI resistance. Taken together, these results are the first to demonstrate that altering redox homeostasis is a new mechanism underlying the observed synergism between vorinostat and EGFR TKIs in NSCLC.

Antitumor activity of vorinostat-incorporated nanoparticles against human cholangiocarcinoma cells

Background

The aim of this study is to evaluate the anticancer activity of vorinostat-incorporated nanoparticles (vorinostat-NPs) against HuCC-T1 human cholangiocarcinoma cells. Vorinostat-NPs were fabricated by a nanoprecipitation method using poly(dl-lactide-co-glycolide)/poly(ethylene glycol) copolymer.

Results

Vorinostat-NPs exhibited spherical shapes with sizes <100 nm. Vorinostat-NPs have anticancer activity similar to that of vorinostat in vitro. Vorinostat-NPs as well as vorinostat itself increased acetylation of histone-H3. Furthermore, vorinostat-NPs have similar effectiveness in the suppression or expression of histone deacetylase, mutant type p53, p21, and PARP/cleaved caspase-3. However, vorinostat-NPs showed improved antitumor activity against HuCC-T1 cancer cell-bearing mice compared to vorinostat, whereas empty nanoparticles had no effect on tumor growth. Furthermore, vorinostat-NPs increased the expression of acetylated histone H3 in tumor tissue and suppressed histone deacetylase (HDAC) expression in vivo. The improved antitumor activity of vorinostat-NPs can be explained by molecular imaging studies using near-infrared (NIR) dye-incorporated nanoparticles, i.e. NIR-dye-incorporated nanoparticles were intensively accumulated in the tumor region rather than normal one.

Conclusions

Our results demonstrate that vorinostat and vorinostat-NPs exert anticancer activity against HuCC-T1 cholangiocarcinoma cells by specific inhibition of HDAC expression. Thus, we suggest that vorinostat-NPs are a promising candidate for anticancer chemotherapy in cholangiocarcinoma.Graphical abstract

Elucidating the molecular aspects of colorectal cancer and their clinical importance

Over the last 10 years, crucial improvements have been made in the pursuit of more effective therapies for colorectal cancer (CRC). In understanding the basis of CRC biology we have evolved from the classical ‘adenoma to carcinoma transition’ hypothesis, to the identification of two CRC clusters (microsatellite instability and chromosomal instability) and further classifications based on epigenetic events. Thanks to these advances in molecular analyses, key pathways, notably that of the EGFR, are now integrated into standard practice for therapeutic management and other pathways are being explored for blocking driving mutations and overcoming drug resistance. Genetic profiling is being developed to better predict prognosis and treatment response. The CRC subtyping consortium has combined and reanalyzed genetic signature data sets from several international groups. A definitive genetic CRC classification is currently being established and will be critical for clinical development of therapeutic strategies.

Phase 1/2 study of valproic acid and short-course radiotherapy plus capecitabine as preoperative treatment in low-moderate risk rectal cancer-V-shoRT-R3 (Valproic acid--short Radiotherapy--rectum 3rd trial)

BACKGROUND

Locally advanced rectal cancer (LARC) is a heterogeneous group of tumors where a risk-adapted therapeutic strategy is needed. Short-course radiotherapy (SCRT) is a more convenient option for LARC patients than preoperative long-course RT plus capecitabine. Histone-deacetylase inhibitors (HDACi) have shown activity in combination with RT and chemotherapy in the treatment of solid tumors. Valproic acid (VPA) is an anti-epileptic drug with HDACi and anticancer activity. In preclinical studies, our group showed that the addition of HDACi, including VPA, to capecitabine produces synergistic antitumour effects by up-regulating thymidine phosphorylase (TP), the key enzyme converting capecitabine to 5-FU, and by downregulating thymidylate synthase (TS), the 5-FU target.

METHODS/DESIGN

Two parallel phase-1 studies will assess the safety of preoperative SCRT (5 fractions each of 5 Gy, on days 1 to 5) combined with (a) capecitabine alone (increasing dose levels: 500-825 mg/m2/bid), on days 1-21, or (b) capecitabine as above plus VPA (oral daily day -14 to 21, with an intra-patient titration for a target serum level of 50-100 microg/ml) followed by surgery 8 weeks after the end of SCRT, in low-moderate risk RC patients. Also, a randomized phase-2 study will be performed to explore whether the addition of VPA and/or capecitabine to preoperative SCRT might increase pathologic complete tumor regression (TRG1) rate. A sample size of 86 patients (21-22/arm) was calculated under the hypothesis that the addition of capecitabine or VPA to SCRT can improve the TRG1 rate from 5% to 20%, with one-sided alpha = 0.10 and 80% power.Several biomarkers will be evaluated comparing normal mucosa with tumor (TP, TS, VEGF, RAD51, XRCC1, Histones/proteins acetylation, HDAC isoforms) and on blood samples (polymorphisms of DPD, TS, XRCC1, GSTP1, RAD51 and XRCC3, circulating endothelial and progenitors cells; PBMCs-Histones/proteins acetylation). Tumor metabolism will be measured by 18FDG-PET at baseline and 15 days after the beginning of SCRT.

DISCUSSION

This project aims to improve the efficacy of preoperative treatment of LARC and to decrease the inconvenience and the cost of standard long-course RT. Correlative studies could identify both prognostic and predictive biomarkers and could add new insight in the mechanism of interaction between VPA, capecitabine and RT.EudraCT Number: 2012-002831-28.

TRIAL REGISTRATION

ClinicalTrials.gov number, NCT01898104.

Panobinostat synergizes with zoledronic acid in prostate cancer and multiple myeloma models by increasing ROS and modulating mevalonate and p38-MAPK pathways

Patients with advanced prostate cancer (PCa) and multiple myeloma (MM) have limited long-term responses to available therapies. The histone deacetylase inhibitor panobinostat has shown significant preclinical and clinical anticancer activity in both hematological and solid malignancies and is currently in phase III trials for relapsed MM. Bisphosphonates (BPs), such as zoledronic acid (ZOL), inhibit osteoclast-mediated bone resorption and are indicated for the treatment of bone metastasis. BPs, including ZOL, have also shown anticancer activity in several preclinical and clinical studies. In the present report, we found a potent synergistic antiproliferative effect of panobinostat/ZOL treatment in three PCa and three MM cell lines as well as in a PCa ZOL-resistant subline, independently of p53/KRAS status, androgen dependency, or the schedule of administration. The synergistic effect was also observed in an anchorage-independent agar assay in both ZOL-sensitive and ZOL-resistant cells and was confirmed in vivo in a PCa xenograft model. The co-administration of the antioxidant N-acetyl-L-cysteine blocked the increased reactive oxygen species generation and apoptosis observed in the combination setting compared with control or single-agent treatments, suggesting that oxidative injury plays a functional role in the synergism. Proapoptotic synergy was also partially antagonized by the addition of geranyl-geraniol, which bypasses the inhibition of farnesylpyrophosphate synthase by ZOL in the mevalonate pathway, supporting the involvement of this pathway in the synergy. Finally, at the molecular level, the inhibition of basal and ZOL-induced activation of p38-MAPK by panobinostat in sensitive and ZOL-resistant cells and in tumor xenografts could explain, at least in part, the observed synergism.

Interferon-α enhances 5'-deoxy-5-fluorouridine-induced apoptosis by ERK-dependant upregulation of thymidine phosphorylase

5-Florouracil (5-FU) is the basic agent used in the treatment of gastric cancer. Capecitabine, a prodrug of 5-FU, displays increased antitumor efficacy compared with 5-FU in the clinic. 5′-Deoxy-5-fluorouracil (5′-DFUR), the metabolite of capecitabine, is converted to 5-FU by the enzyme thymidine phosphorylase (TP), which is present at high concentrations in human tumors. In this study, we investigated the effect of interferon-α (IFN-α) on the sensitivity of gastric cancer cells to treatment with 5′-DFUR and its relationship with TP expression. Preincubation of gastric cancer cells with IFN-α enhanced 5′-DFUR-induced apoptosis via IFN-α-mediated upregulation of TP. The depletion of TP with small interfering RNA (siRNA) obviously inhibited IFN-α-induced upregulation of TP expression and thus prevented apoptosis induced by IFN-α and 5′-DFUR. Treatment with IFN-α and combined IFN-α and 5′-DFUR treatment were also associated with concomitant activation of ERK signaling. Treatment with the ERK inhibitor PD98059 or depletion of ERK with siRNA partially reversed IFN-α-induced upregulation of TP expression, thus partially preventing apoptosis induced by IFN-α and 5′-DFUR. Taken together, our study shows that IFN-α enhanced 5′-DFUR-induced apoptosis in gastric cancer cells by upregulation of TP expression, which is partially regulated by activation of ERK signaling.

Research development of the relationship between thymidine phosphorylase expression and colorectal carcinoma

Thymidine phosphorylase (TP) is a key enzyme that contributes to the composition and decomposition of pyrimidine nucleotides. TP seems homologous to platelet-derived endothelial cell growth factor, and its effects on inducing vascularization and anti-apoptosis are closely related to growth and metastasis of colorectal carcinoma. In addition, TP is a key enzyme that catalyzes the transformation from 5-fluorouracil (FU) prodrugs of 5′-deoxy-5-fluorouridine (5′-DFUR) to 5-FU. The activity of TP is closely related to the sensitivity of colorectal carcinoma cells to fluorouracil drugs and targeted therapy. Given the important functions of TP in growth, metastasis, tumor treatment, and prognosis, determining its expression mechanism is significant. This article summarizes the research development of TP expression in colorectal carcinoma, tumor neovascularization, cytotoxicity activation of 5′-DFUR, and colorectal carcinoma therapy.

Pharmacokinetic evaluation of capecitabine in breast cancer

INTRODUCTION

Capecitabine , an oral prodrug of 5-fluorouracil (5-FU), is adsorbed in its intact form through the intestine and metabolized to 5-FU in tumour cells. In metastatic breast cancer (MBC), capecitabine is an effective and well-tolerated therapeutic option both in monotherapy and in combination with chemotherapeutic or molecular-targeted agents.

AREAS COVERED

We summarized data on pharmacokinetics and pharmacodynamics of capecitabine. We also produced a general review of the most relevant clinical studies of capecitabine in MBC. A literature search was performed using PubMed database including selected articles published in English language up to October 2012.

EXPERT OPINION

The unique pharmacodynamic/pharmacokinetic features represent the bases of the reduced toxicity and the activity of capecitabine in several tumours. Although during the past 10 years there has been an increasing use of this drug in MBC both as single agent and in combination, encouraging results of well tolerated and active combinations with novel agents will lead to a more extensive and protracted use of capecitabine. In view of this, some aspects should be further clarified such as the optimal starting dose and the introduction of alternative schedules of treatment.

Sustained inhibition of deacetylases is required for the antitumor activity of the histone deactylase inhibitors panobinostat and vorinostat in models of colorectal cancer

Despite compelling preclinical data in colorectal cancer (CRC), the efficacy of HDACIs has been disappointing in the clinic. The goal of this study was to evaluate the effectiveness of vorinostat and panobinostat in a dose- and exposure-dependent manner in order to better understand the dynamics of drug action and antitumor efficacy. In a standard 72 h drug exposure MTS assay, notable concentration-dependent antiproliferative effects were observed in the IC50 range of 1.2-2.8 μmol/L for vorinostat and 5.1-17.5 nmol/L for panobinostat. However, shorter clinically relevant exposures of 3 or 6 h failed to elicit any significant growth inhibition and in most cases a >24 h exposure to vorinostat or panobinostat was required to induce a sigmoidal dose-response. Similar results were observed in colony formation assays where ≥ 24 h of exposure was required to effectively reduce colony formation. Induction of acetyl-H3, acetyl-H4 and p21 by vorinostat were transient and rapidly reversed within 12 h of drug removal. In contrast, panobinostat-induced acetyl-H3, acetyl-H4, and p21 persisted for 48 h after an initial 3 h exposure. Treatment of HCT116 xenografts with panobinostat induced significant increases in acetyl-H3 and downregulation of thymidylate synthase after treatment. Although HDACIs exert both potent growth inhibition and cytotoxic effects when CRC cells were exposed to drug for ≥ 24 h, these cells demonstrate an inherent ability to survive HDACI concentrations and exposure times that exceed those clinically achievable. Continued efforts to develop novel HDACIs with improved pharmacokinetics/phamacodynamics, enhanced intratumoral delivery and class/isoform-specificity are needed to improve the therapeutic potential of HDACIs and HDACI-based combination regimens in solid tumors.

Radiosensitization by the histone deacetylase inhibitor vorinostat under hypoxia and with capecitabine in experimental colorectal carcinoma

Background

The histone deacetylase inhibitor vorinostat is a candidate radiosensitizer in locally advanced rectal cancer (LARC). Radiosensitivity is critically influenced by hypoxia; hence, it is important to evaluate the efficacy of potential radiosensitizers under variable tissue oxygenation. Since fluoropyrimidine-based chemoradiotherapy (CRT) is the only clinically validated regimen in LARC, efficacy in combination with this established regimen should be assessed in preclinical models before a candidate drug enters clinical trials.

Methods

Radiosensitization by vorinostat under hypoxia was studied in four colorectal carcinoma cell lines and in one colorectal carcinoma xenograft model by analysis of clonogenic survival and tumor growth delay, respectively. Radiosensitizing effects of vorinostat in combination with capecitabine were assessed by evaluation of tumor growth delay in two colorectal carcinoma xenografts models.

Results

Under hypoxia, radiosensitization by vorinostat was demonstrated in vitro in terms of decreased clonogenicity and in vivo as inhibition of tumor growth. Adding vorinostat to capecitabine-based CRT increased radiosensitivity of xenografts in terms of inhibited tumor growth.

Conclusions

Vorinostat sensitized colorectal carcinoma cells to radiation under hypoxia in vitro and in vivo and improved therapeutic efficacy in combination with capecitabine-based CRT in vivo. The results encourage implementation of vorinostat into CRT in LARC trials.

Chemotherapy and autophagy-mediated cell death in pancreatic cancer cells

Autophagy is an evolutionarily preserved degradation process of cytoplasmic cellular constituents and plays important physiological roles in human health and disease. It has been proposed that autophagy plays an important role both in tumor progression and in promotion of cancer cell death, although the molecular mechanisms responsible for this dual action of autophagy in cancer have not been elucidated. Pancreatic ductal adenocarcinoma is one of the most aggressive human malignancies with 2-3% five-year survival rate. Its poor prognosis has been attributed to the lack of specific symptoms and early detection tools, and its relatively refractory to traditional cytotoxic agents and radiotherapy. Experimental evidence pointed at autophagy as a pancreatic cancer cell mechanism to survive under adverse environmental conditions, or as a defective programmed cell death mechanism that favors pancreatic cancer cell resistance to treatment. Here, we consider several phenotypical alterations that have been related to increase or decrease the autophagic process in pancreatic tumor cells. We specially review autophagy as a cell death mechanism in response to chemotherapeutic drugs.

HDAC inhibitor vorinostat enhances the antitumor effect of gefitinib in squamous cell carcinoma of head and neck by modulating ErbB receptor expression and reverting EMT

Potentiation of epidermal growth factor receptor (EGFR) inhibitors is required in squamous cell carcinoma of head and neck (SCCHN) to improve their therapeutic index. We demonstrated that the histone deacetylase inhibitor vorinostat in combination with the EGFR tyrosine kinase inhibitor gefitinib induced synergistic inhibition of proliferation, migration, and invasion as well as induction of apoptosis in SCCHN cells, including cells resistant to gefitinib. We provided evidence suggesting that differential modulation of ErbB receptors together with reversion of epithelial-to-mesenchymal transition (EMT) by vorinostat represent mechanistic bases for the observed synergism. We demonstrated in epithelial CAL27 cells expressing EGFR, ErbB2, and ErbB3 that vorinostat downregulated the expression and signaling of all three receptors. In gefitinib-resistant KB and Hep-2 cells, both of which had undergone EMT and expressed very low levels of ErbB3, vorinostat reverted the mesenchymal phenotype by inducing both E-cadherin and ErbB3 and downregulating vimentin as well as EGFR and ErbB2. Both transcriptional and post-translational mechanisms were involved in the modulation of ErbB receptors by vorinostat. Attenuation of all ErbB transcripts in CAL27 cells as well as induction of ErbB3 transcript in Hep-2 and KB cells was seen upon vorinostat treatment. We showed that vorinostat induced ubiquitination of EGFR and ErbB2 and targeted them predominantly to lysosome-degradation in all cell lines, while the induction of ErbB3-ubiquitination in CAL27 cells led to proteasomes-degradation. Overall, this study suggests that the vorinostat/gefitinib combination represents a promising therapeutic strategy that warrants further clinical evaluation in SCCHN, including tumors intrinsically resistant to EGFR-inhibitors.

The TORC1/TORC2 inhibitor, Palomid 529, reduces tumor growth and sensitizes to docetaxel and cisplatin in aggressive and hormone-refractory prostate cancer cells

One of the major obstacles in the treatment of hormone-refractory prostate cancer (HRPC) is the development of chemo-resistant tumors. The aim of this study is to evaluate the role of Palomid 529 (P529), a novel TORC1/TORC2 inhibitor, in association with docetaxel (DTX) and cisplatin (CP). This work utilizes a wide panel of prostatic cancer cell lines with or without basal activation of Akt as well as two in vivo models of aggressive HRPC. The blockade of Akt/mTOR activity was associated to reduced cell proliferation and induction of apoptosis. Comparison of IC50 values calculated for PTEN-positive and PTEN-negative cell lines as well as the PTEN transfection in PC3 cells or PTEN silencing in DU145 cells revealed that absence of PTEN was indicative for a better activity of the drug. In addition, P529 synergized with DTX and CP. The strongest synergism was achieved when prostate cancer (PCa) cells were sequentially exposed to CP or DTX followed by treatment with P529. Treatment with P529 before the exposure to chemotherapeutic drugs resulted in a moderate synergism, whereas intermediated values of combination index were found when drugs were administered simultaneously. In vivo treatment of a combination of P529 with DTX or CP increased the percentage of complete responses and reduced the number of mice with tumor progression. Our results provide a rationale for combinatorial treatment using conventional chemotherapy and a Akt/mTOR inhibitor as promising therapeutic approach for the treatment of HRPC, a disease largely resistant to conventional therapies.