Synergistic antitumor activity of epidermal growth factor receptor tyrosine kinase inhibitor gefitinib and IFN-alpha in head and neck cancer cells in vitro and in vivo

Targeted therapy for head and neck cancer: signaling pathways and clinical studies

Head and neck cancer (HNC) is malignant, genetically complex and difficult to treat and is the sixth most frequent cancer, with tobacco, alcohol and human papillomavirus being major risk factors. Based on epigenetic data, HNC is remarkably heterogeneous, and treatment remains challenging. There is a lack of significant improvement in survival and quality of life in patients with HNC. Over half of HNC patients experience locoregional recurrence or distal metastasis despite the current multiple traditional therapeutic strategies and immunotherapy. In addition, resistance to chemotherapy, radiotherapy and some targeted therapies is common. Therefore, it is urgent to explore more effective and tolerable targeted therapies to improve the clinical outcomes of HNC patients. Recent targeted therapy studies have focused on identifying promising biomarkers and developing more effective targeted therapies. A well understanding of the pathogenesis of HNC contributes to learning more about its inner association, which provides novel insight into the development of small molecule inhibitors. In this review, we summarized the vital signaling pathways and discussed the current potential therapeutic targets against critical molecules in HNC, as well as presenting preclinical animal models and ongoing or completed clinical studies about targeted therapy, which may contribute to a more favorable prognosis of HNC. Targeted therapy in combination with other therapies and its limitations were also discussed.

HDAC class I inhibitor domatinostat sensitizes pancreatic cancer to chemotherapy by targeting cancer stem cell compartment via FOXM1 modulation

BACKGROUND

Pancreatic ductal adenocarcinoma (PDAC) represents an unmet clinical need due to the very poor prognosis and the lack of effective therapy. Here we investigated the potential of domatinostat (4SC-202), a new class I histone deacetylase (HDAC) inhibitor, currently in clinical development, to sensitize PDAC to first line standard gemcitabine (G)/taxol (T) doublet chemotherapy treatment.

METHODS

Synergistic anti-tumor effect of the combined treatment was assessed in PANC1, ASPC1 and PANC28 PDAC cell lines in vitro as well as on tumor spheroids and microtissues, by evaluating combination index (CI), apoptosis, clonogenic capability. The data were confirmed in vivo xenograft models of PANC28 and PANC1 cells in athymic mice. Cancer stem cells (CSC) targeting was studied by mRNA and protein expression of CSC markers, by limiting dilution assay, and by flow cytometric and immunofluorescent evaluation of CSC mitochondrial and cellular oxidative stress. Mechanistic role of forkhead box M1 (FOXM1) and downstream targets was evaluated in FOXM1-overexpressing PDAC cells.

RESULTS

We showed that domatinostat sensitized in vitro and in vivo models of PDAC to chemotherapeutics commonly used in PDAC patients management and particularly to GT doublet, by targeting CSC compartment through the induction of mitochondrial and cellular oxidative stress. Mechanistically, we showed that domatinostat hampers the expression and function of FOXM1, a transcription factor playing a crucial role in stemness, oxidative stress modulation and DNA repair. Domatinostat reduced FOXM1 protein levels by downregulating mRNA expression and inducing proteasome-mediated protein degradation thus preventing nuclear translocation correlated with a reduction of FOXM1 target genes. Furthermore, by overexpressing FOXM1 in PDAC cells we significantly reduced domatinostat-inducing oxidative mitochondrial and cellular stress and abolished GT sensitization, both in adherent and spheroid cells, confirming FOXM1 crucial role in the mechanisms described. Finally, we found a correlation of FOXM1 expression with poor progression free survival in PDAC chemotherapy-treated patients.

CONCLUSIONS

Overall, we suggest a novel therapeutic strategy based on domatinostat to improve efficacy and to overcome resistance of commonly used chemotherapeutics in PDAC that warrant further clinical evaluation.

Gallic acid suppresses colon cancer proliferation by inhibiting SRC and EGFR phosphorylation

The aim of the present study was to investigate the effects of gallic acid (GA) on the proliferation and apoptosis of colon cancer cells and to further clarify the mechanism of GA function associated with SRC and EGFR phosphorylation. HCT116 and HT29 cells were treated with different concentrations of GA for 24 h. Cell proliferation and apoptosis were analyzed using plate clone formation and flow cytometry assays, respectively. In addition, the expression of apoptosis-related proteins was examined by western blotting. Furthermore, the level of STAT3, AKT, SRC and EGFR phosphorylation was analyzed by western blotting and immunofluorescence. Subsequently, the SRC inhibitor PP2 and the EGFR inhibitor gefitinib were used to analyze the GA-associated mechanisms. In addition, a xenograft tumor model was established to confirm the effects of GA in vivo. The results indicated that GA inhibited cell proliferation and promoted cell apoptosis by upregulating the ratio of cleaved caspase-3/pro-caspase-3 and cleaved caspase-9/pro-caspase-9. Concurrently, GA decreased the level of phosphorylated (p)-SRC, p-EGFR, p-AKT and p-STAT3. Following treatment with PP2 and gefitinib in both cancer cell lines and animal model, GA was demonstrated to inhibit EGFR and SRC phosphorylation to downregulate STAT3 and AKT phosphorylation. In vivo, GA prevented tumor growth, promoted tumor apoptosis and decreased the level of p-SRC, p-EGFR, p-STAT3 and p-AKT. In conclusion, GA was indicated to suppress colon cancer proliferation by inhibiting SRC and EGFR phosphorylation.

Valproic Acid Synergizes With Cisplatin and Cetuximab in vitro and in vivo in Head and Neck Cancer by Targeting the Mechanisms of Resistance

Recurrent/metastatic head and neck squamous cell carcinoma (R/M HNSCC) is a devastating malignancy with a poor prognosis. The combination of cisplatin (CDDP) plus cetuximab (CX) is one of the standard first-line treatments in this disease. However, this therapeutic regimen is often associated with high toxicity and resistance, suggesting that new combinatorial strategies are needed to improve its therapeutic index. In our study, we evaluated the antitumor effects of valproic acid (VPA), a well-known antiepileptic agent with histone deacetylase inhibitory activity, in combination with CDDP/CX doublet in head and neck squamous cell carcinoma (HNSCC) models. We demonstrated, in HNSCC cell lines, but not in normal human fibroblasts, that simultaneous exposure to equitoxic doses of VPA plus CDDP/CX resulted in a clear synergistic antiproliferative and pro-apoptotic effects. The synergistic antitumor effect was confirmed in four different 3D-self-assembled spheroid models, suggesting the ability of the combined approach to affect also the cancer stem cells compartment. Mechanistically, VPA enhanced DNA damage in combination treatment by reducing the mRNA expression of ERCC Excision Repair 1, a critical player in DNA repair, and by increasing CDDP intracellular concentration via upregulation at transcriptional level of CDDP influx channel copper transporter 1 and downregulation of the ATPAse ATP7B involved in CDDP-export. Valproic acid also induced a dose-dependent downregulation of epidermal growth factor receptor (EGFR) expression and of MAPK and AKT downstream signaling pathways and prevent CDDP- and/or CX-induced EGFR nuclear translocation, a well-known mechanism of resistance to chemotherapy. Indeed, VPA impaired the transcription of genes induced by non-canonical activity of nuclear EGFR, such as cyclin D1 and thymidylate synthase. Finally, we confirmed the synergistic antitumor effect also in vivo in both heterotopic and orthotopic models, demonstrating that the combined treatment completely blocked HNSCC xenograft tumors growth in nude mice. Overall, the introduction of a safe and generic drug such as VPA into the conventional treatment for R/M HNSCC represents an innovative and feasible antitumor strategy that warrants further clinical evaluation. A phase II clinical trial exploring the combination of VPA and CDDP/CX in R/M HNSCC patients is currently ongoing in our institute.

A co-formulation of interferons type I and II enhances temozolomide response in glioblastoma with unmethylated MGMT promoter status

Temozolomide (TMZ) is a chemotherapeutic used for the treatment of glioblastoma. The MGMT repair enzyme (O'-(6)-methyl guanine-DNA-methyltransferase) promoter methylation is a predictive biomarker to TMZ response; interferons (IFNs) type I can downregulate MGMT expression improving survival in patients with unmethylated MGMT promoter. HeberFERON is a co-formulation of IFNs type I and II with higher antiproliferative effect over glioblastoma cell lines than individual IFNs. We investigated the proliferative response of patient-derived glioblastoma cultures to HeberFERON and its combination with TMZ in relation to MGMT promoter methylation and the regulation of MGMT transcript after HeberFERON treatment. Eleven glioblastoma-derived cultures, molecularly classified according to TCGA and MGMT promoter methylation, were assayed for proliferation inhibition with HeberFERON at low doses (1-25 IU/mL) [alone or combined with TMZ] or at higher doses (50-200 IU/mL) using CellTiter-Glo Luminescent Cell Viability Assay (Promega). Eight cultures were further treated with 100 IU/mL of HeberFERON for 72 h, total RNA purified (Qiagen) and converted to cDNA (Superscript III kit, Invitrogen) as quantitative PCR templates. Changes of MGMT&P53 transcripts level were monitored. Response of cultures to HeberFERON is variable, dose-dependent and apparently independent from TCGA classification and MGMT methylation status, based on the eight Classical cultures data. When combining HeberFERON with TMZ there was an increase in cell death for cultures, 2/4 with methylated and 5/5 with unmethylated MGMT promoter. In two out five cultures with unmethylated MGMT status, we observed a decrease of MGMT gene levels and an increase in P53 encoding gene levels. HeberFERON and TMZ combination should be further assayed in glioblastoma, mainly for those with unmethylated MGMT promoter.

Emerging Functions of Human IFIT Proteins in Cancer

Interferon-induced protein with tetratricopeptide repeats (IFIT) genes are prominent interferon-stimulated genes (ISGs). The human IFIT gene family consists of four genes named IFIT1, IFIT2, IFIT3, and IFIT5. The expression of IFIT genes is very low in most cell types, whereas their expression is greatly enhanced by interferon treatment, viral infection, and pathogen-associated molecular patterns (PAMPs). The proteins encoded by IFIT genes have multiple tetratricopeptide repeat (TPR) motifs. IFIT proteins do not have any known enzymatic roles. However, they execute a variety of cellular functions by mediating protein-protein interactions and forming multiprotein complexes with cellular and viral proteins through their multiple TPR motifs. The versatile tertiary structure of TPR motifs in IFIT proteins enables them to be involved in distinct biological functions, including host innate immunity, antiviral immune response, virus-induced translation initiation, replication, double-stranded RNA signaling, and PAMP recognition. The current understanding of the IFIT proteins and their role in cellular signaling mechanisms is limited to the antiviral immune response and innate immunity. However, recent studies on IFIT protein functions and their involvement in various molecular signaling mechanisms have implicated them in cancer progression and metastasis. In this article, we focused on critical molecular, biological and oncogenic functions of human IFIT proteins by reviewing their prognostic significance in health and cancer. Research suggests that IFIT proteins could be novel therapeutic targets for cancer therapy.

Semi-Synthetic Ingenol Derivative from Euphorbia tirucalli Inhibits Protein Kinase C Isotypes and Promotes Autophagy and S-phase Arrest on Glioma Cell Lines

The identification of signaling pathways that are involved in gliomagenesis is crucial for targeted therapy design. In this study we assessed the biological and therapeutic effect of ingenol-3-dodecanoate (IngC) on glioma. IngC exhibited dose-time-dependent cytotoxic effects on large panel of glioma cell lines (adult, pediatric cancer cells, and primary cultures), as well as, effectively reduced colonies formation. Nevertheless, it was not been able to attenuate cell migration, invasion, and promote apoptotic effects when administered alone. IngC exposure promoted S-phase arrest associated with p21CIP/WAF1 overexpression and regulated a broad range of signaling effectors related to survival and cell cycle regulation. Moreover, IngC led glioma cells to autophagy by LC3B-II accumulation and exhibited increased cytotoxic sensitivity when combined to a specific autophagic inhibitor, bafilomycin A1. In comparison with temozolomide, IngC showed a mean increase of 106-fold in efficacy, with no synergistic effect when they were both combined. When compared with a known compound of the same class, namely ingenol-3-angelate (I3A, Picato^®), IngC showed a mean 9.46-fold higher efficacy. Furthermore, IngC acted as a potent inhibitor of protein kinase C (PKC) activity, an emerging therapeutic target in glioma cells, showing differential actions against various PKC isotypes. These findings identify IngC as a promising lead compound for the development of new cancer therapy and they may guide the search for additional PKC inhibitors.

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.

IFIT1 and IFIT3 promote oral squamous cell carcinoma metastasis and contribute to the anti-tumor effect of gefitinib via enhancing p-EGFR recycling

IFIT1 and IFIT3 are abundant products of interferon-stimulating genes. While the importance of IFIT1 and IFIT3 in the prognosis of cancer has been reported, the molecular basis of IFIT1 and IFIT3 in cancer progression remains unexplored. In the present study, we investigated the modes of action and the clinical significance of IFIT1 and IFIT3 in oral squamous cell carcinoma (OSCC). Ectopic expression of IFIT1 or IFIT3 induced OSCC cell invasion by promoting the epithelial-mesenchymal transition, whereas IFIT1 or IFIT3 knockdown exhibited opposite effects. Overexpression of IFIT1 or IFIT3 promoted tumor growth, regional and distant metastasis in xenograft and orthotopic nude mice models. Most importantly, IFIT1 or IFIT3 overexpression increased the levels of p-EGFR^Y1068 and p-AKT^S473 in OSCC cells and also enhanced tumor inhibitory effect of gefitinib. By immunoprecipitation and LC-MS/MS analysis, we found that IFIT1 and IFIT3 interacted with ANXA2 that enhanced p-EGFR^Y1068 endosomal recycling. Depletion of ANXA2 using siRNA therefore abolished p-EGFR^Y1068 and p-AKT^S473 expression in IFIT1- or IFIT3-overexpressed cells. Furthermore, a significant positive association of increased IFIT1 and IFIT3 expression with advanced T-stage, lymph node metastasis, perineural invasion, lymphovascular invasion, extranodal extension, and poor overall survival rate was confirmed in OSCC patients. We also found a statistically positive correlation of p-EGFR^Y1068 expression with IFIT1 and IFIT3 in OSCC tumors and poor clinical outcome in patients. Collectively, we demonstrated a novel role of IFIT1 and IFIT3 in driving OSCC progression and metastasis by interacting with ANXA2 and hence enhancing p-EGFR recycling and its downstream signaling.

In vitro screening of cytotoxic activity of euphol from Euphorbia tirucalli on a large panel of human cancer-derived cell lines

A large number of classic antineoplastic agents are derived from plants. Euphorbia tirucalli L. (Euphorbiaceae) is a subtropical and tropical plant, used in Brazilian folk medicine against many diseases, including cancer, yet little is known about its true anticancer properties. The present study evaluated the antitumor effect of the tetracyclic triterpene alcohol, euphol, the main constituent of E. tirucalli in a panel of 73 human cancer lines from 15 tumor types. The biological effect of euphol in pancreatic cells was also assessed. The combination index was further used to explore euphol interactions with standard drugs. Euphol showed a cytotoxicity effect against several cancer cell lines (IC₅₀ range, 1.41–38.89 µM), particularly in esophageal squamous cell (11.08 µM) and pancreatic carcinoma cells (6.84 µM), followed by prostate, melanoma, and colon cancer. Cytotoxicity effects were seen in all cancer cell lines, with more than half deemed highly sensitive. Euphol inhibited proliferation, motility and colony formation in pancreatic cancer cells. Importantly, euphol exhibited synergistic interactions with gemcitabine and paclitaxel in pancreatic and esophageal cell lines, respectively. To the best of our knowledge, this study constitutes the largest in vitro screening of euphol efficacy on cancer cell lines and revealed its in vitro anti-cancer properties, particularly in pancreatic and esophageal cell lines, suggesting that euphol, either as a single agent or in combination with conventional chemotherapy, is a potential anti-cancer drug.

UniPR1331, a small molecule targeting Eph/ephrin interaction, prolongs survival in glioblastoma and potentiates the effect of antiangiogenic therapy in mice

Glioblastoma multiforme (GBM) is the most malignant brain tumor, showing high resistance to standard therapeutic approaches that combine surgery, radiotherapy, and chemotherapy. As opposed to healthy tissues, EphA2 has been found highly expressed in specimens of glioblastoma, and increased expression of EphA2 has been shown to correlate with poor survival rates. Accordingly, agents blocking Eph receptor activity could represent a new therapeutic approach. Herein, we demonstrate that UniPR1331, a pan Eph receptor antagonist, possesses significant in vivo anti-angiogenic and anti-vasculogenic properties which lead to a significant anti-tumor activity in xenograft and orthotopic models of GBM. UniPR1331 halved the final volume of tumors when tested in xenografts (p<0.01) and enhanced the disease-free survival of treated animals in the orthotopic models of GBM both by using U87MG cells (40 vs 24 days of control, p<0.05) or TPC8 cells (52 vs 16 days, p<0.01). Further, the association of UniPR1331 with the anti-VEGF antibody Bevacizumab significantly increased the efficacy of both monotherapies in all tested models. Overall, our data promote UniPR1331 as a novel tool for tackling GBM.

Cell division cycle 7 is a potential therapeutic target in oral squamous cell carcinoma and is regulated by E2F1

Cell division cycle 7 (Cdc7) plays important roles in the regulation of the initiation of DNA replication throughout S phase. Whether inhibition of Cdc7 has a direct antitumour effect in oral squamous cell carcinoma (OSCC) remains unclear. In this study, XL413, a novel Cdc7 inhibitor, markedly inhibited the viability of OSCC cells but not that of non-tumour primary cells. There was a synergistic effect between XL413 and DNA-damaging agents (e.g. cisplatin and 5-fluorouracil) on OSCC in vitro and in vivo. Moreover, XL413 exhibited a notable antitumour effect on OSCC patients with high Cdc7 expression in mini patient-derived xenografts model. The proliferation was significantly inhibited in OSCC cells after Cdc7 silencing. Cdc7 knockdown significantly induced apoptosis in OSCC cell lines. Furthermore, we demonstrated that Cdc7 was overexpressed and transcriptionally regulated by E2F1 in OSCC by using chromatin immunoprecipitation and luciferase assays. Our results reveal that XL413 has an excellent antitumour effect in OSCC. Importantly, it does not inhibit the proliferation of non-tumour cells. These findings suggest that the overexpression of Cdc7 promotes progression in OSCC and that inhibition of Cdc7 is a very promising therapy for OSCC patients.

Enhancement of radiosensitivity by the novel anticancer quinolone derivative vosaroxin in preclinical glioblastoma models

Purpose

Glioblastoma multiforme (GBM) is the most aggressive brain tumor. The activity of vosaroxin, a first-in-class anticancer quinolone derivative that intercalates DNA and inhibits topoisomerase II, was investigated in GBM preclinical models as a single agent and combined with radiotherapy (RT).

Results

Vosaroxin showed antitumor activity in clonogenic survival assays, with IC₅₀ of 10−100 nM, and demonstrated radiosensitization. Combined treatments exhibited significantly higher γH2Ax levels compared with controls. In xenograft models, vosaroxin reduced tumor growth and showed enhanced activity with RT; vosaroxin/RT combined was more effective than temozolomide/RT. Vosaroxin/RT triggered rapid and massive cell death with characteristics of necrosis. A minor proportion of treated cells underwent caspase-dependent apoptosis, in agreement with in vitro results. Vosaroxin/RT inhibited RT-induced autophagy, increasing necrosis. This was associated with increased recruitment of granulocytes, monocytes, and undifferentiated bone marrow–derived lymphoid cells. Pharmacokinetic analyses revealed adequate blood-brain penetration of vosaroxin. Vosaroxin/RT increased disease-free survival (DFS) and overall survival (OS) significantly compared with RT, vosaroxin alone, temozolomide, and temozolomide/RT in the U251-luciferase orthotopic model.

Materials and Methods

Cellular, molecular, and antiproliferative effects of vosaroxin alone or combined with RT were evaluated in 13 GBM cell lines. Tumor growth delay was determined in U87MG, U251, and T98G xenograft mouse models. (DFS) and (OS) were assessed in orthotopic intrabrain models using luciferase-transfected U251 cells by bioluminescence and magnetic resonance imaging.

Conclusions

Vosaroxin demonstrated significant activity in vitro and in vivo in GBM models, and showed additive/synergistic activity when combined with RT in O6-methylguanine methyltransferase-negative and -positive cell lines.

Interferon-alpha enhances the antitumour activity of EGFR-targeted therapies by upregulating RIG-I in head and neck squamous cell carcinoma

Background:

The epidermal growth factor receptor (EGFR)-targeted therapies have been tested in the clinic as treatments for head and neck squamous cell carcinoma (HNSCC). Owing to intrinsic or acquired resistance, EGFR-targeted therapies often lead to a low response rate and treatment failure. Interferon-alpha (IFNα) is a chemosensitising agent and multi-functional cytokine with a tumour inhibitory effect. However, the synergic effect of IFNα and EGFR-targeted therapies (erlotinib and nimotuzumab) and their mechanisms in HNSCC remain unclear.

Methods:

The interactions between IFNα, erlotinib, and nimotuzumab were evaluated in vitro in HNSCC cells. The synergistic effect of IFNα (20 000 IU per day, s.c.), erlotinib (50 mg kg⁻¹ per day, i.g.) and nimotuzumab (10 mg kg⁻¹ per day, i.p.) was further confirmed in vivo using HNSCC xenografts in nude mice. The upregulation of retinoic-acid inducible gene I (RIG-I) induced by IFNα and EGFR-targeted therapies and its mechanism were detected in vitro and in vivo.

Results:

IFNα enhances the antitumour effects of erlotinib and nimotuzumab on HNSCC cells both in vitro and in vivo. Importantly, both IFNα and EGFR-targeted therapies promote the expression of RIG-I by activating signal transducers and activators of transcription 1 (STAT1) in HNSCC cells. RIG-I knockdown reduced the sensitivity of HN4 and HN30 cells to IFNα, erlotinib, and nimotuzumab. Moreover, IFNα transcriptionally induced RIG-I expression in HNSCC cells through STAT1.

Conclusions:

IFNα enhances the effect of EGFR-targeted therapies by upregulating RIG-I, and its expression may represent a predictor of the effectiveness of a combination treatment including IFNα in HNSCC.

RES-529: a PI3K/AKT/mTOR pathway inhibitor that dissociates the mTORC1 and mTORC2 complexes

RES-529 (previously named Palomid 529, P529) is a phosphoinositide 3-kinase (PI3K)/AKT/mechanistic target of rapamycin (mTOR) pathway inhibitor that interferes with the pathway through both mTOR complex 1 (mTORC1) and mTOR complex 2 (mTORC2) dissociation. This compound is currently being developed in oncology and ophthalmology. The oncology focus is for the treatment of glioblastoma, where it has received orphan designation by the US Food and Drug Administration, and prostate cancer. We present a review of the PI3K/AKT/mTOR pathway, its role in tumorigenesis, and the potential of RES-529 in cancer treatment. RES-529 inhibits mTORC1/mTORC2 activity in various cancer cell lines, as noted by decreased phosphorylation of substrates including ribosomal protein S6, 4E-BP1, and AKT, leading to cell growth inhibition and death, with activity generally in the range of 5–15 μmol/l. In animal tumor models where the PI3K/AKT/mTOR pathway is abnormally activated (i.e. glioblastoma, prostate cancer, and breast cancer), RES-529 reduces tumor growth by as much as 78%. RES-529 treatment is synergistic with radiation therapy, chemotherapy, and hormonal therapy in reducing tumor growth, potentially by preventing PI3K/AKT/mTOR pathway activation associated with these treatments. Furthermore, this compound has shown antiangiogenic activity in several animal models. mTORC1 and mTORC2 have redundant and distinct activities that contribute toward oncogenesis. Current inhibitors of this pathway have primarily targeted mTORC1, but have shown limited clinical efficacy. Inhibitors of mTORC1 and mTORC2 such as RES-529 may therefore have the potential to overcome the deficiencies found in targeting only mTORC1.

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.

Pharmacological treatment with inhibitors of nuclear export enhances the antitumor activity of docetaxel in human prostate cancer

Background and aims

Docetaxel (DTX) modestly increases patient survival of metastatic castration-resistant prostate cancer (mCRPC) due to insurgence of pharmacological resistance. Deregulation of Chromosome Region Maintenance (CRM-1)/ exportin-1 (XPO-1)-mediated nuclear export may play a crucial role in this phenomenon.

Material and methods

Here, we evaluated the effects of two Selective Inhibitor of Nuclear Export (SINE) compounds, selinexor (KPT-330) and KPT-251, in association with DTX by using 22rv1, PC3 and DU145 cell lines with their. DTX resistant derivatives.

Results and conclusions

We show that DTX resistance may involve overexpression of β-III tubulin (TUBB3) and P-glycoprotein as well as increased cytoplasmic accumulation of Foxo3a. Increased levels of XPO-1 were also observed in DTX resistant cells suggesting that SINE compounds may modulate DTX effectiveness in sensitive cells as well as restore the sensitivity to DTX in resistant ones. Pretreatment with SINE compounds, indeed, sensitized to DTX through increased tumor shrinkage and apoptosis by preventing DTX-induced cell cycle arrest. Basally SINE compounds induce FOXO3a activation and nuclear accumulation increasing the expression of FOXO-responsive genes including p21, p27 and Bim causing cell cycle arrest. SINE compounds-catenin and survivin supporting apoptosis. βdown-regulated Cyclin D1, c-myc, Nuclear sequestration of p-Foxo3a was able to reduce ABCB1 and TUBB3 H2AX levels, prolonged γ expression. Selinexor treatment increased DTX-mediated double strand breaks (DSB), and reduced the levels of DNA repairing proteins including DNA PKc and Topo2A. Our results provide supportive evidence for the therapeutic use of SINE compounds in combination with DTX suggesting their clinical use in mCRPC patients.

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.

Role of Type I and II Interferons in Colorectal Cancer and Melanoma

Cancer can be considered an aberrant organ with a hierarchical composition of different cell populations. The tumor microenvironment, including the immune cells and related cytokines, is crucial during all the steps of tumor development. In particular, type I and II interferons (IFNs) are involved in a plethora of mechanisms that regulate immune responses in cancer, thus balancing immune escape versus immune surveillance. IFNs are involved in both the direct and indirect regulation of cancer cell proliferation and metastatic potential. The mutational background of genes involved in IFNs signaling could serve as a prognostic biomarker and a powerful tool to screen cancer patients eligible for checkpoint blocking therapies. We herewith describe the latest findings regarding the contribution of IFNs in colorectal cancer and melanoma by researching their dual role as either tumor promoter or suppressor, in diverse tumor types, and microenvironmental context. We are reporting the most innovative and promising approaches of IFN-based therapies that have achieved considerable outcomes in clinical oncology practice and explain the possible mechanisms responsible for their failure.

The brain-penetrating CXCR4 antagonist, PRX177561, increases the antitumor effects of bevacizumab and sunitinib in preclinical models of human glioblastoma

Background

Glioblastoma recurrence after treatment with the anti-vascular endothelial growth factor (VEGF) antibody bevacizumab is characterized by a highly infiltrative and malignant behavior that renders surgical excision and chemotherapy ineffective. It has been demonstrated that anti-VEGF/VEGFR therapies control the invasive phenotype and that relapse occurs through the increased activity of CXCR4. We therefore hypothesized that combining bevacizumab or sunitinib with the novel CXCR4 antagonist, PRX177561, would have superior antitumor activity.

Methods

The effects of bevacizumab, sunitinib, and PRX177561 were tested alone or in combination in subcutaneous xenografts of U87MG, U251, and T98G cells as well as on intracranial xenografts of luciferase tagged U87MG cells injected in CD1-nu/nu mice. Animals were randomized to receive vehicle, bevacizumab (4 mg/kg iv every 4 days), sunitinib (40 mg/kg po qd), or PRX177561 (50 mg/kg po qd).

Results

The in vivo experiments demonstrated that bevacizumab and sunitinib increase the in vivo expression of CXCR4, SDF-1α, and TGFβ1. In addition, we demonstrate that the co-administration of the novel brain-penetrating CXCR4 antagonist, PRX177561, with bevacizumab or sunitinib inhibited tumor growth and reduced the inflammation. The combination of PRX177561 with bevacizumab resulted in a synergistic reduction of tumor growth with an increase of disease-free survival (DSF) and overall survival (OS), whereas the combination of PRX177561 with sunitinib showed a mild additive effect.

Conclusions

The CXC4 antagonist PRX177561 may be a valid therapeutic complement to anti-angiogenic therapy, particularly when used in combination with VEGF/VEGFR inhibitors. Therefore, this compound deserves to be considered for future clinical evaluation.

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.

Novel antimicrobial peptide-modified azithromycin-loaded liposomes against methicillin-resistant Staphylococcus aureus

Infections caused by multidrug-resistant bacteria, such as methicillin-resistant Staphylococcus aureus (MRSA), have become a public threat; therefore, development of new antimicrobial drugs or strategies is urgently required. In this study, a new antibacterial peptide DP7-C (Chol-suc-VQWRIRVAVIRK-NH2) and DP7-C-modified azithromycin (AZT)-loaded liposomes (LPs) are developed for the treatment of MRSA infection, and it was found that DP7-C inserted into the LP lipid bilayer not only functioned as a carrier to encapsulate the antibiotic AZT but also synergized the antibacterial effect of the encapsulated AZT. In vitro assays showed that DP7-C-modified LPs possessed sustained drug release profile and immune regulatory effect and did not show obvious cytotoxicity in mammal cells, but they did not possess direct antibacterial activity in vitro. In vivo studies revealed that DP7-C-modified LPs did not exhibit obvious side effects or toxicity in mice but were able to significantly reduce the bacterial counts in an MRSA-infectious mouse model and possessed high antibacterial activity. In particular, DP7-C-modified AZT-loaded LPs showed more positive therapeutic effects than either DP7-C-modified blank LPs or nonmodified AZT-loaded LPs treatment alone. Molecular mechanism studies demonstrated that DP7-C formulations effectively upregulated the production of anti-inflammatory cytokines and chemokines without inducing harmful immune response, suggesting that DP7-C was synergistic with AZT against the bacterial infection by activating the innate immune response. Most importantly, although DP7-C activated the innate immune response, it did not possess direct antibacterial activity in vitro, indicating that DP7-C did not possess the potential to induce bacteria resistance. The findings indicate that DP7-C-modified AZT-loaded LPs developed in this study have a great potential required for the clinical treatment of MRSA infections.

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.

Interferon-α reduces the gefitinib sensitivity of human non-small cell lung cancer

AIM OF THE STUDY

Many studies have shown that interferon-α (IFN-α) enhances the antiproliferative effect of gefitinib in some solid tumours. We aimed to determine the effect of combining IFN-α with gefitinib in human non-small cell lung cancer (NSCLC) cell lines (A549, H1299, HCC827) with different EGFR and K-Ras gene statuses.

MATERIAL AND METHODS

An MTT assay was used to assess cell proliferation. Apoptosis was detected by an Annexin V/propidium iodide assay using flow cytometry, and western blotting was used to determine the expression of epidermal growth factor receptor/phosphorylated epidermal growth factor receptor (EGFR/p-EGFR) and signal transducers and activators of transcription 3/phosphorylated signal transducers and activators of transcription 3 (STAT3/p-STAT3).

RESULTS

There was an additive interaction when gefitinib was combined with IFN-α in all cell lines; however, there was antagonism when gefitinib followed IFN-α pretreatment in three cell lines. Notably, IFN-α pretreatment significantly reduced the gefitinib sensitivity of HCC827 cells. Surprisingly, while IFN-α inhibited STAT3 phosphorylation in cell lines, gefitinib could do so.

CONCLUSIONS

The results might confirm the hypothesis that IFN-α induces gefitinib sensitivity of NSCLC, and IFN-α inhibits phosphorylation of STAT3, which may be dependent on EGFR signal activation playing a role in the reduction of gefitinib sensitivity after IFN-α treatment in NSCLC cell lines.

Antitumor Activity of BRAF Inhibitor and IFNα Combination in BRAF-Mutant Melanoma

BACKGROUND

BRAF(V600E)-mediated MAPK pathway activation is associated in melanoma cells with IFNAR1 downregulation. IFNAR1 regulates melanoma cell sensitivity to IFNα, a cytokine used for the adjuvant treatment of melanoma. These findings and the limited therapeutic efficacy of BRAF-I prompted us to examine whether the efficacy of IFNα therapy of BRAF(V600E) melanoma can be increased by its combination with BRAF-I.

METHODS

BRAF/NRAS genotype, ERK activation, IFNAR1, and HLA class I expression were tested in 60 primary melanoma tumors from treatment-naive patients. The effect of BRAF-I on IFNAR1 expression was assessed in three melanoma cell lines and in four biopsies of BRAF(V600E) metastases. The antiproliferative, pro-apoptotic and immunomodulatory activity of BRAF-I and IFNα combination was tested in vitro and in vivo utilizing three melanoma cell lines, HLA class I-MA peptide complex-specific T-cells and immunodeficient mice (5 per group for survival and 10 per group for tumor growth inhibition). All statistical tests were two-sided. Differences were considered statistically significant when the P value was less than .05.

RESULTS

The IFNAR1 level was statistically significantly (P < .001) lower in BRAF(V600E) primary melanoma tumors than in BRAF wild-type tumors. IFNAR1 downregulation was reversed by BRAF-I treatment in the three melanoma cell lines (P ≤ .02) and in three out of four metastases. The IFNAR1 level in the melanoma tumors analyzed was increased as early as 10 to 14 days following the beginning of the treatment. These changes were associated with: 1) an increased susceptibility in vitro of melanoma cells to the antiproliferative (P ≤ .04), pro-apoptotic (P ≤ .009) and immunomodulatory activity, including upregulation of HLA class I antigen APM component (P ≤ .04) and MA expression as well as recognition by cognate T-cells (P < .001), of BRAF-I and IFNα combination and 2) an increased survival (P < .001) and inhibition of tumor growth of melanoma cells (P < .001) in vivo by BRAF-I and IFNα combination.

CONCLUSIONS

The described results provide a strong rationale for the clinical trials implemented in BRAF(V600E) melanoma patients with BRAF-I and IFNα combination.

Erastin Disrupts Mitochondrial Permeability Transition Pore (mPTP) and Induces Apoptotic Death of Colorectal Cancer Cells

We here evaluated the potential anti-colorectal cancer activity by erastin, a voltage-dependent anion channel (VDAC)-binding compound. Our in vitro studies showed that erastin exerted potent cytotoxic effects against multiple human colorectal cancer cell lines, possibly via inducing oxidative stress and caspase-9 dependent cell apoptosis. Further, mitochondrial permeability transition pore (mPTP) opening was observed in erastin-treated cancer cells, which was evidenced by VDAC-1 and cyclophilin-D (Cyp-D) association, mitochondrial depolarization, and cytochrome C release. Caspase inhibitors, the ROS scavenger MnTBAP, and mPTP blockers (sanglifehrin A, cyclosporin A and bongkrekic acid), as well as shRNA-mediated knockdown of VDAC-1, all significantly attenuated erastin-induced cytotoxicity and apoptosis in colorectal cancer cells. On the other hand, over-expression of VDAC-1 augmented erastin-induced ROS production, mPTP opening, and colorectal cancer cell apoptosis. In vivo studies showed that intraperitoneal injection of erastin at well-tolerated doses dramatically inhibited HT-29 xenograft growth in severe combined immunodeficient (SCID) mice. Together, these results demonstrate that erastin is cytotoxic and pro-apoptotic to colorectal cancer cells. Erastin may be further investigated as a novel anti-colorectal cancer agent.

Multiple receptor tyrosine kinase activation attenuates therapeutic efficacy of the fibroblast growth factor receptor 2 inhibitor AZD4547 in FGFR2 amplified gastric cancer

Fibroblast growth factor receptor 2 (FGFR2)-targeted therapy has attracted considerable attention as novel anticancer agents in gastric cancer (GC). However, intrinsic or acquired drug resistance has emerged as a major challenge to their clinical use. In this study, we demonstrated that several receptor tyrosine kinase (RTK), including EGFR, HER3 and MET, activations contributed to AZD4547 (a selective FGFR2 inhibitor) hyposensitivity in FGFR2 amplified GC cells. The rescue effect was abrogated by inhibiting these RTKs with their targeted tyrosine kinase inhibitors (TKIs). In addition, synergy in growth inhibition was observed when the GC cells were treated with a combination of AZD4547 and cetuximab (an EGFR monoclonal antibody) both in vitro and in vivo. More importantly, tissue microarray analysis revealed that these resistance-conferring RTKs were highly expressed in FGFR2 positive GC patients. Taken together, these observations demonstrated RTKs including EGFR, HER3 and MET activations as novel mechanisms of hyposensitivity to AZD4547. It will be clinically valuable to investigate the involvement of RTK-mediated signaling in intrinsicor acquired resistance to FGFR2 TKIs in GC. A combination targeted therapeutic strategy may be recommended for treating FGFR2 amplified GC patients with these RTK activations.

KPT-330, a potent and selective exportin-1 (XPO-1) inhibitor, shows antitumor effects modulating the expression of cyclin D1 and survivin [corrected] in prostate cancer models

BACKGROUND AND AIMS

Increased expression of Chromosome Region Maintenance (CRM-1)/exportin-1 (XPO-1) has been correlated with poor prognosis in several aggressive tumors, making it an interesting therapeutic target. Selective Inhibitor of Nuclear Export (SINE) compounds bind to XPO-1 and block its ability to export cargo proteins. Here, we investigated the effects of a new class of SINE compounds in models of prostate cancer.

MATERIAL AND METHODS

We evaluated the expression of XPO-1 in human prostate cancer tissues and cell lines. Next, six SINE (KPT-127, KPT-185, KPT-205, KPT-225, KPT-251 and KPT-330) compounds having different potency with broad-spectrum, tumor-selective cytotoxicity, tolerability and pharmacokinetic profiles were tested in a panel of prostate cancer cells representing distinct differentiation/progression states of disease and genotypes. Two SINE candidates for clinical trials (KPT-251 and KPT-330) were also tested in vivo in three cell models of aggressive prostate cancer engrafted in male nude mice.

RESULTS AND CONCLUSIONS

XPO-1 is overexpressed in prostate cancer compared to normal or hyperplastic tissues. Increased XPO-1 expression, mainly in the nuclear compartment, was associated with increased Gleason score and bone metastatic potential supporting the use of SINEs in advanced prostate cancer. SINE compounds inhibited proliferation and promoted apoptosis of tumor cells, but did not affect immortalized non-transformed prostate epithelial cells. Nuclei from SINE treated cells showed increased protein localization of XPO-1, survivin and cyclin D1 followed by degradation of these proteins leading to cell cycle arrest and apoptosis. Oral administration of KPT-251 and KPT-330 in PC3, DU145 and 22rv1 tumor-bearing nude mice reduced tumor cell proliferation, angiogenesis and induced apoptosis. Our results provide supportive evidence for the therapeutic use of SINE compounds in advanced/castration resistant prostate cancers and warrants further clinical investigation.

CXCR4 pharmacogical inhibition reduces bone and soft tissue metastatic burden by affecting tumor growth and tumorigenic potential in prostate cancer preclinical models

BACKGROUND

The majority of prostate cancer (Pca) patient morbidity can be attributed to bone metastatic events, which poses a significant clinical obstacle. Therefore, a better understanding of this phenomenon is imperative and might help to develop novel therapeutic strategies. Stromal cell-derived factor 1α (SDF-1α) and its receptor CXCR4 have been implicated as regulators of bone resorption and bone metastatic development, suggesting that agents able to suppress this signaling pathway may be used as pharmacological treatments. In this study we studied if two CXCR4 receptor antagonists, Plerixafor and CTE9908, may affect bone metastatic disease induced by Pca in preclinical experimental models

METHODS

To verify the hypothesis that CXCR4 inhibition affects Pca metastatic disease, selective CXCR4 compounds, Plerixafor, and CTE9908, were tested in preclinical models known to generate bone lesions. Additionally, the expression levels of CXCR4 and SDF-1α were analyzed in a number of human tissues derived from primary tumors, lymph-nodes and osseous metastases of Pca as well as in a wide panel of human Pca cell lines to non-tumorigenic and tumorigenic phenotype.

RESULTS

Bone-derived Pca cells express higher CXCR4 levels than other Pca cell lines. This differential expression was also observed in human Pca samples. In vitro evidence supports the hypothesis that factors produced by bone microenvironment differentially sustain CXCR4 and SDF1-α expression with respect to prostate microenvironment determining increased efficacy toward Plerixafor. The use of SDF1-α neutralizing antibodies greatly reduced the increase of CXCR4 expression in cells co-cultured with bone stromal cells (BMSc) and to a lesser extent in cells co-cultured with prostate stromal cells (HPSc) and partially reduced SDF1-α Plerixafor efficacy. SDF-1α induced tumor cell migration and invasion, as well as MMP-9, MMP-2, and uPA expression, which were reduced by Plerixafor. The incidence of X-ray detectable bone lesions was significantly reduced following Plerixafor and CTE9908 treatment Kaplan-Meier probability plots showed a significant improvement in the overall survival of mice treated with Plerixafor and CTE9908. The reduced intra-osseous growth of PC3 and PCb2 tumor cells after intratibial injection, as a result of Plerixafor and CTE9908 treatment, correlated with decreased osteolysis and serum levels of both mTRAP and type I collagen fragments (CTX), which were significantly lower with respect to controls.

CONCLUSIONS

Our report provides novel information on the potential activity of CXCR4 inhibitors on the formation and progression of Pca bone and soft tissue metastases and supports a biological rationale for the use of these inhibitors in men at high risk to develop clinically evident bone lesions.

Potentials of interferon therapy in the treatment of pancreatic cancer

Pancreatic cancer is a highly aggressive malignancy with limited treatment options. To improve survival for patients with pancreatic cancer, research has focused on other treatment modalities like adding biological modulators such as type-I interferons (IFNs). Type I IFNs (ie, IFN-α/IFN-β) have antiproliferative, antiviral, and immunoregulatory activities. Furthermore, they are able to induce apoptosis, exert cell cycle blocking, and sensitize tumor cells for chemo- and radiotherapy. A few years ago in vitro, in vivo, and several clinical trials have been described regarding adjuvant IFN-α therapy in the treatment of pancreatic cancer. Some studies reported a remarkable increase in the 2- and 5-year survival. Unfortunately, the only randomized clinical trial did not show a significant increase in overall survival, although the increased median survival implicated that some patients in the experimental group benefited from the adjuvant IFN-α therapy. Furthermore, encouraging in vitro and in vivo data points to a possible role for adjuvant IFN therapy. However, up till now, the use of IFNs in the treatment of pancreatic cancer remains controversial. This review, therefore, aims to describe, based on the available data, whether there is a distinct role for IFN therapy in the treatment of pancreatic cancer.

Functional genetic approach identifies MET, HER3, IGF1R, INSR pathways as determinants of lapatinib unresponsiveness in HER2-positive gastric cancer

PURPOSE

Targeting human epidermal growth factor receptor 2 (HER2) therapy is currently considered as the standard treatment for HER2-positive (HER2+) advanced gastric cancer. However, as seen in recent clinical trials, most of HER2+ gastric cancer are actually unresponsive to HER2-targeted agents, including lapatinib. The aim of this study is to identify the responsible receptor tyrosine kinases (RTK) potentially conferring lapatinib unresponsiveness in HER2+ gastric cancer and elucidate the molecular mechanism underlying this RTKs-induced resistance.

EXPERIMENTAL DESIGN

A functional RNAi screen targeting human RTKs and related growth factors was used to identify candidate RTKs conferring lapatinib unresponsiveness in HER2+ gastric cancer cells. Independent siRNAs transfection and corresponding ligands supplement were performed to validate the effects of candidate RTKs on lapatinib sensitivity. Cross-talks of pathways involved were analyzed via Western blot analysis. Cell apoptosis and cell motility were detected using FACS system and Transwell assay. Immunohistochemistry was used to analyze protein expression in clinical samples.

RESULTS

MET, HER3, insulin-like growth factor (IGF)-1R, and INSR were identified to mediate lapatinib unresponsiveness in HER2+ gastric cancer cells. Activation of these bypass RTKs attenuated lapatinib-induced apoptosis and suppression of cell motility, mechanistically because of restimulating the shared downstream AKT or ERK signaling, as well as restimulating WNT signaling and epithelial-to-mesenchymal transition (EMT)-like process. Patients' specimens revealed that these unresponsiveness-conferring RTKs were particularly enriched in the majority of patients with HER2+ gastric cancer.

CONCLUSIONS

MET, HER3, IGF1R, and INSR pathways activation represent novel mechanism underlying lapatinib unresponsiveness in HER2+ gastric cancer. Combination strategy may be recommended in treating patients with HER2+ gastric cancer with these pathways activation.

Antitumor effects of saffron-derived carotenoids in prostate cancer cell models

Crocus sativus L. extracts (saffron) are rich in carotenoids. Preclinical studies have shown that dietary intake of carotenoids has antitumor effects suggesting their potential preventive and/or therapeutic roles. We have recently reported that saffron (SE) and crocin (CR) exhibit anticancer activity by promoting cell cycle arrest in prostate cancer (PCa) cells. It has also been demonstrated that crocetin esters are produced after SE gastrointestinal digestion by CR hydrolysis. The aim of the present report was to investigate if SE, crocetin (CCT), and CR affected in vivo tumor growth of two aggressive PCa cell lines (PC3 and 22rv1) which were xenografted in male nude mice treated by oral gavage with SE, CR, and CCT. We demonstrated that the antitumor effects of CCT were higher when compared to CR and SE and treatments reverted the epithelial-mesenchymal transdifferentiation (EMT) as attested by the significant reduction of N-cadherin and beta-catenin expression and the increased expression of E-cadherin. Additionally, SE, CR, and CCT inhibited PCa cell invasion and migration through the downmodulation of metalloproteinase and urokinase expression/activity suggesting that these agents may affect metastatic processes. Our findings suggest that CR and CCT may be dietary phytochemicals with potential antitumor effects in biologically aggressive PCa cells.

Head and neck cancer: past, present and future

Head and neck cancer consists of a diverse group of cancers that ranges from cutaneous, lip, salivary glands, sinuses, oral cavity, pharynx and larynx. Each group dictates different management. In this review, the primary focus is on head and neck squamous cell carcinoma (HNSCC) arising from the mucosal lining of the oral cavity and pharynx, excluding nasopharyngeal cancer. Presently, HNSCC is the sixth most prevalent neoplasm in the world, with approximately 900,000 cases diagnosed worldwide. Prognosis has improved little in the past 30 years. In those who have survived, pain, disfigurement and physical disability from treatment have had an enormous psychosocial impact on their lives. Management of these patients remains a challenge, especially in developing countries where this disease is most common. Of all human cancers, HNSCC is the most distressing since the head and neck is the site of the most complex functional anatomy in the human body. Its areas of responsibility include breathing, the CNS, vision, hearing, balance, olfaction, taste, swallowing, voice, endocrine and cosmesis. Cancers that occur in this area impact on these important human functions. Consequently, in treating cancers of the head and neck, the effects of the treatment on the functional outcome of the patient need the most serious consideration. In assessing the success of HNSCC treatment, consideration of both the survival and functional deficits that the patient may suffer as a consequence of their treatment are of paramount importance. For this reason, the modern-day management of head and neck patients should be carried out in a multidisciplinary head and neck clinic.

The dual mTORC1 and mTORC2 inhibitor AZD8055 inhibits head and neck squamous cell carcinoma cell growth in vivo and in vitro

The serine/threonine kinase mammalian target of rapamycin (mTOR) promotes cell survival and proliferation, and is constitutively activated in head and neck squamous cell carcinoma (HNSCC). Thus mTOR is an important target for drug development in this disease. Here we tested the anti-tumor ability of AZD8055, the novel mTOR inhibitor, in HNSCC cells. AZD8055 induced dramatic cell death of HNSCC lines (Hep-2 and SCC-9) through autophagy. AZD8055 blocked both mTOR complex (mTORC) 1 and mTORC2 activation without affecting Erk in cultured HNSCC cells. Meanwhile, AZD8055 induced significant c-Jun N-terminal kinase (JNK) activation, which was also required for cancer cell death. JNK inhibition by its inhibitors (SP 600125 and JNK-IN-8), or by RNA interference (RNAi) alleviated AZD8055-induced cell death. Finally, AZD8055 markedly increased the survival of Hep-2 transplanted mice through a significant reduction of tumor growth, without apparent toxicity, and its anti-tumor ability was more potent than rapamycin. Meanwhile, AZD8055 administration activated JNK while blocking mTORC1/2 in Hep-2 tumor engrafts. Our current results strongly suggest that AZD8055 may be further investigated for HNSCC treatment in clinical trials.

Deguelin induces both apoptosis and autophagy in cultured head and neck squamous cell carcinoma cells

Head and neck squamous cell carcinoma (HNSCC) represents more than 5% of all cancers diagnosed annually in United States and around the world. Despite advances in the management of patients with this disease, the survival has not been significantly improved, and the search for potential alternative therapies is encouraging. Here we demonstrate that deguelin administration causes a significant HNSCC cell death. Deguelin induces both cell apoptosis and autophagy by modulating multiple signaling pathways in cultured HNSCC cells. Deguelin inhibits Akt signaling, and down-regulates survivin and cyclin-dependent kinase 4 (Cdk4) expressions, by disrupting their association with heat shock protein-90 (Hsp-90). Deguelin induces ceramide production through de novo synthase pathway to promote HNSCC cell death. Importantly, increased ceramide level activates AMP-activated protein kinase (AMPK), which then directly phosphorylates Ulk1 and eventually leads to cell autophagy. We found that a low dose of deguelin sensitized HNSCC cells to 5-FU. Finally, using a nude mice Hep-2 xenograft model, we also showed a significant anti-tumor ability of deguelin in vivo. Together, we suggest that deguelin may represent a novel and effective chemo-agent against HNSCC.

Current treatment of cutaneous squamous cancer and molecular strategies for its sensitization to new target-based drugs

INTRODUCTION

Cutaneous squamous cell carcinoma (cSCC) is considered one of the most common skin malignancy with a relatively high risk of metastasis occurrence.

AREAS COVERED

We discuss the pathogenetic mechanisms of cSCC and the main therapeutic strategies available for the treatment of cSCC.

EXPERT OPINION

Chemotherapy and biological therapy with Interferon α (IFN-α) and cis retinoic acid are active but give limited results. Recently, strategies based on the use of molecularly target-based agents (MTA) have been used with promising results. Based on the available findings, we hypothesize that SCC cells can develop survival and resistance mechanisms to MTAs. The detection of these mechanisms could be useful in designing strategies able to overcome the latter and to potentiate the anticancer activity of MTAs. We describe the example of the EGF-dependent survival pathway elicited by IFN-α and the different strategies to abrogate this survival pathway. Other strategies to potentiate the antitumor activity of cytotoxic agents such as docetaxel or cisplatin are also discussed. Illuminating examples are the inhibition of multichaperone activity or the inactivation of the proteasome. In conclusion, a new dawn based upon the rationale use of MTAs is rising up in the treatment of advanced cSCC.

Role of mitochondrial uncoupling protein 2 in cancer cell resistance to gemcitabine

Cancer cells exhibit an endogenous constitutive oxidative stress higher than that of normal cells, which renders tumours vulnerable to further reactive oxygen species (ROS) production. Mitochondrial uncoupling protein 2 (UCP2) can mitigate oxidative stress by increasing the influx of protons into the mitochondrial matrix and reducing electron leakage and mitochondrial superoxide generation. Here, we demonstrate that chemical uncouplers or UCP2 over-expression strongly decrease mitochondrial superoxide induction by the anticancer drug gemcitabine (GEM) and protect cancer cells from GEM-induced apoptosis. Moreover, we show that GEM IC(50) values well correlate with the endogenous level of UCP2 mRNA, suggesting a critical role for mitochondrial uncoupling in GEM resistance. Interestingly, GEM treatment stimulates UCP2 mRNA expression suggesting that mitochondrial uncoupling could have a role also in the acquired resistance to GEM. Conversely, UCP2 inhibition by genipin or UCP2 mRNA silencing strongly enhances GEM-induced mitochondrial superoxide generation and apoptosis, synergistically inhibiting cancer cell proliferation. These events are significantly reduced by the addition of the radical scavenger N-acetyl-l-cysteine or MnSOD over-expression, demonstrating a critical role of the oxidative stress. Normal primary fibroblasts are much less sensitive to GEM/genipin combination. Our results demonstrate for the first time that UCP2 has a role in cancer cell resistance to GEM supporting the development of an anti-cancer therapy based on UCP2 inhibition associated to GEM treatment.

In vivo invasion of head and neck squamous cell carcinoma cells does not require macrophages

Invasion of tumor cells into the local stroma is an important component in cancer progression. Here we report studies of the in vivo invasion of head and neck squamous cell carcinoma (HNSCC) cells in response to applied gradients of a growth factor [epidermal growth factor (EGF)] and a chemokine (CXCL12), using orthotopic floor-of-mouth models. Analysis of the invading cells indicated that >75% of them were tumor cells, about 15% macrophages, and <10% were unidentified. Surprisingly, although macrophages invaded together with tumor cells, macrophage contributions were not required for HNSCC invasion. CXCL12-induced in vivo invasion of HNSCC cells was also observed and found to occur via a unidirectional transactivation of epidermal growth factor receptor (EGFR) through CXCR4. Inhibition of tumor necrosis factor-α-converting enzyme using TNF-α protease inhibitor-2 selectively inhibited CXCL12-induced invasion but not EGF-induced invasion, consistent with CXCL12 activation of EGFR via release of EGFR ligands.

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.

Effects of lipoic acid, caffeic acid and a synthesized lipoyl-caffeic conjugate on human hepatoma cell lines

Hepatocellular carcinoma (HCC) is among the most aggressive and fatal cancers. Its treatment with conventional chemotherapeutic agents is inefficient, due to several side effects linked to impaired organ function typical of liver diseases. Consequently, there exists a decisive requirement to explore possible alternative chemopreventive and therapeutic strategies. The use of dietary antioxidants and micronutrients has been proposed for HCC successful management. The aim of this work was to test in vitro the effects of lipoic acid, caffeic acid and a new synthesized lipoyl-caffeic conjugate on human hepatoma cell lines in order to assess their effect on tumor cell growth. The results of cytotoxicity assays at different times showed that the cell viability was directly proportional to the molecule concentrations and incubation times. Moreover, to evaluate the pro- or anti-inflammatory effects of these molecules, the cytokine concentrations were evaluated in treated and untreated cellular supernatants. The obtained cytokine pattern showed that, at the increasing of three molecules concentrations, three pro-inflammatory cytokines such as IL-1β, IL-8 and TNF-α decreased whereas the anti-inflammatory cytokine such as IL-10 increased.

Gemcitabine response in pancreatic adenocarcinoma cells is synergistically enhanced by dithiocarbamate derivatives

Pancreatic adenocarcinoma is a common malignancy that remains refractory to all available therapies, including the gold standard drug gemcitabine (GEM). We investigated the effect of the combination of GEM and each of the ionophore compounds pyrrolidine dithiocarbamate (PDTC) and disulfiram [DSF; 1-(diethylthiocarbamoyldisulfanyl)-N,N-diethylmethanethioamide] on p53(-/-) pancreatic adenocarcinoma cell growth. PDTC or DSF synergistically inhibited cell proliferation when used in combination with GEM by inducing apoptotic cell death. This effect was associated with an increased mitochondrial O(2)(•-) production and was further enhanced by zinc ions. Basal levels of mitochondrial O(2)(•-) or manganese superoxide dismutase (MnSOD) strictly correlated with the IC(50) for GEM or the percentage of synergism. Thus, the most relevant values of the antiproliferative synergism were obtained in GEM-resistant pancreatic adenocarcinoma cell lines. Interestingly, the GEM-sensitive T3M4 cells transfected with MnSOD expression vector showed mitochondrial O(2)(•-) and IC(50) for GEM similar to those of resistant cell lines. In vivo experiments performed on nude mice xenotransplanted with the GEM-resistant PaCa44 cell line showed that only the combined treatment with GEM and DSF/Zn completely inhibited the growth of the tumoral masses. These results and the consideration that DSF is already used in clinics strongly support the GEM and DSF/Zn combination as a new approach to overcoming pancreatic cancer resistance to standard chemotherapy.

Vorinostat synergises with capecitabine through upregulation of thymidine phosphorylase

Background:

Potentiation of anticancer activity of capecitabine is required to improve its therapeutic index. In colorectal cancer (CRC) cells, we evaluated whether the histone deacetylase-inhibitor vorinostat may induce synergistic antitumour effects in combination with capecitabine by modulating the expression of thymidine phosphorylase (TP), a key enzyme in the conversion of capecitabine to 5-florouracil (5-FU), and thymidylate synthase (TS), the target of 5-FU.

Methods:

Expression of TP and TS was measured by real-time PCR, western blotting and immunohistochemistry. Knockdown of TP was performed by specific small interfering RNA. Antitumour activity of vorinostat was assessed in vitro in combination with the capecitabine active metabolite deoxy-5-fluorouridine (5′-DFUR) according to the Chou and Talay method and by evaluating apoptosis as well as in xenografts-bearing nude mice in combination with capecitabine.

Results:

Vorinostat induced both in vitro and in vivo upregulation of TP as well as downregulation of TS in cancer cells, but not in ex vivo treated peripheral blood lymphocytes. Combined treatment with vorinostat and 5′-DFUR resulted in a synergistic antiproliferative effect and increased apoptotic cell death in vitro. This latter effect was impaired in cells where TP was knocked. In vivo, vorinostat plus capecitabine potently inhibited tumour growth, increased apoptosis and prolonged survival compared with control or single-agent treatments.

Conclusions:

Overall, this study suggests that the combination of vorinostat and capecitabine is an innovative antitumour strategy and warrants further clinical evaluation for the treatment of CRC.

Investigational EGFR-targeted therapy in head and neck squamous cell carcinoma

IMPORTANCE OF THE FIELD

EGFR is an established therapeutic target in head and neck squamous cell carcinoma (HNSCC). The EGFR-targeting monoclonal antibody cetuximab (Erbitux, Imclone Systems, Inc., Branchburg, USA) was FDA-approved for use in HNSCC in 2006. The molecular basis for the efficacy of an antibody approach compared with inhibition of EGFR tyrosine kinase function using small-molecule inhibitors, or downregulation of protein expression via antisense strategies, remains incompletely understood.

AREAS COVERED IN THIS REVIEW

A literature search was performed to identify studies elucidating mechanisms of action of several approaches to targeting EGFR in HNSCC (monoclonal antibodies, tyrosine kinase inhibitors, antisense approaches, and ligand-toxin conjugates).

WHAT THE READER WILL GAIN

Monoclonal antibodies decrease tumor growth via receptor endocytosis and recruitment of host immune defenses. Tyrosine kinase inhibitors bind to the ATP binding pocket of the tyrosine kinase domain, inhibiting signaling. Antisense approaches decrease EGFR expression with high specificity, though drug delivery remains problematic. Ligand-toxin conjugates facilitate the entry of toxin and the ADP-ribosylation of the ribosome, thereby inhibiting translation.

TAKE HOME MESSAGE

Elucidation mechanisms by which these different strategies inhibit EGFR function may enhance the development of more effective treatments for HNSCC and enable prospective identification of individuals who will benefit from EGFR inhibition.