Antitumor Effects Of Combined Treatment Research Articles

Tubeimoside-I, an inhibitor of HSPD1, enhances cytotoxicity of oxaliplatin by activating ER stress and MAPK signaling pathways in colorectal cancer

Ethnopharmacological relevanceTubeimoside-I (TBM) promotes various cancer cell death by increasing the reactive oxygen species (ROS) production. However, the specific molecular mechanisms of TBM and its impact on oxaliplatin-mediated anti-CRC activity are not yet fully understood. Aim of the studyTo elucidate the therapeutic effect and underlying molecular mechanism of TBM on oxaliplatin-mediated anti-CRC activity. Materials and methods3-(4,5-Dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT), colony formation, wound healing assays and flow cytometry were conducted to investigate the changes in cell phenotypes and ROS generation. Real-time quantitative PCR (qRT-PCR) and western blotting were performed to detect the expressions of related mRNA and proteins. Finally, mouse xenograft models demonstrated that synergistic anti-tumor effects of combined treatment with TBM and oxaliplatin. ResultsThe synergistic enhancement of the anti-tumor effects of oxaliplatin in colon cancer cells by TBM involved in the regulation of ROS-mediated endoplasmic reticulum (ER) stress, C-jun-amino-terminal kinase (JNK), and p38 MAPK signaling pathways. Mechanistically, TBM increased ROS generation in colon cancer cells by inhibiting heat shock protein 60 (HSPD1) expression. Knocking down HSPD1 increased TBM-induced antitumor activity and ROS generation in colon cancer cells. The mouse xenograft tumor models further validated that the combination therapy exhibited stronger anti-tumor effects than monotherapy alone. ConclusionsCombined therapy with TBM and oxaliplatin might be an effective therapeutic strategy for some CRC patients.

Regorafenib activates oxidative stress by inhibiting SELENOS and potentiates oxaliplatin-induced cell death in colon cancer cells

Colorectal cancer (CRC) is the third most common cancer, and is one of the leading causes of cancer-related death worldwide. At the time of diagnosis, about 20% of patients with CRC present metastatic disease. Regorafenib, an oral multi-kinase inhibitor, has been demonstrated the efficacy and tolerability in patients with metastatic CRC. Oxaliplatin is a frontline treatment regimen for CRC, and combination treatments with oxaliplatin and other chemotherapeutic agents exert superior therapeutic effects. However, side effects and drug resistance limited their further clinical application. Here, we found that combined treatment with regorafenib and oxaliplatin synergistically enhanced anti-tumor activities in CRC by activating reactive oxygen species (ROS) mediated endoplasmic reticulum (ER) stress, C-Jun-amino-terminal kinase (JNK) and p38 signaling pathways. Regorafenib promoted ROS production by suppressing the expression of selenoprotein S (SELENOS). Knocking down SELENOS sensitized ROS-mediated anti-tumor effects of regorafenib in CRC cells. Furthermore, mouse xenograft models demonstrated that synergistic anti-tumor effects of combined treatment with regorafenib and oxaliplatin. This study provided solid experimental evidences for the combined treatment with regorafenib and oxaliplatin in CRC.

Regorafenib induces NOX5-mediated endoplasmic reticulum stress and potentiates the anti-tumor activity of cisplatin in non-small cell lung cancer cells

Lung cancer is one of the most commonly diagnosed cancers worldwide. Although cisplatin-based chemotherapy regimens serve a pivotal role in non-small cell lung cancer (NSCLC) treatment, drug resistance and serious side effects limited its further clinical application. Regorafenib, a small-molecule multi-kinase inhibitor, was demonstrated to have promising anti-tumor activity in various solid tumors. In the present study, we found that regorafenib markedly enhanced cisplatin-induced cytotoxicity in lung cancer cells by activating reactive oxygen species (ROS)-mediated endoplasmic reticulum stress (ER Stress), c-Jun N-terminal kinase (JNK) and p38 mitogen-activated protein kinase (MAPK) signaling pathways. Regorafenib increased ROS generation by promoting NADPH oxidase 5 (NOX5) expression, and knocking down NOX5 attenuated ROS-mediated cytotoxicity of regorafenib in lung cancer cells. Additionally, mice xenograft model validated that synergistic anti-tumor effects of combined treatment with regorafenib and cisplatin. Our results suggested that combination therapy with regorafenib and cisplatin may serve as a potential therapeutic strategy for some NSCLC patients.

Antitumor effect of combination treatment of Astragalus polysaccharide and PD-L1 antibody on mice with Lewis lung carcinoma

Antitumor effect of combination treatment of Astragalus polysaccharide and PD-L1 antibody on mice with Lewis lung carcinoma

Abstract B19: Robust antitumor effect of doxorubicin prodrug combined with anti-PD-1 in murine squamous cell cancer model

Abstract Background: Combination therapy of anti-PD-1 agents with other class of chemotherapeutic agents to improve treatment outcome is being attempted. Anthracycline-derived chemotherapeutic agents are known to activate immunogenic cell-death mechanism. Previously, we developed caspase-3 specific prodrug, MPD-1 containing doxorubicin. It is linked to peptide moiety cleavable by caspase-3 produced during apoptosis induced by radiation therapy (RT). We hypothesized that anti-PD-1 alone may activate MPD-1 by producing caspase-3 and reinforce antitumor efficacy of MPD-1 and anti-PD-1 effect. This study was designed to evaluate the antitumor effects of combined treatment of anti-PD-1 and MPD-1 in murine squamous cell carcinoma models. Methods: Murine SCC VII (squamous cell carcinoma) cells were inoculated to flank of mice, female C3H/J. We divided 6 treatment groups; control, RT, anti-PD-1, anti-PD-1 with MPD-1, RT with MPD-1, and triple therapy (anti-PD-1 + RT + MPD-1) (n = 5/each group). After tumor grew up to 100-200 mm3, treatment was initiated. Tumor size and mice weight were measured. Expression of caspase-3 was evaluated in cell lines and tumor tissues after each treatment. Distribution of CD8+, CD4+, and FoxP3+ cells was analyzed. Results: RT with MPD-1, anti-PD-1 with MPD-1, and triple treatment enhanced the synergistic antitumor activity compared to single treatment in SCC VII bearing mice. Anti-PD-1 with MPD-1 presented slightly better antitumor effect than RT with MPD-1. Caspase-3 was produced in tumor tissue of anti-PD-1 treatment group, which enhanced antitumor effect of activated MPD-1, while cell after anti-PD-1 did not enhance caspase-3 expression. Triple treatment suppressed tumor growth mostly, which was sustained more than 2 weeks even after cessation of treatment. Proportion of CD45+CD8+ T-cells in triple treatment group was increased mostly among tumor-infiltrating lymphocytes. Body weight of each treatment group was not significantly different. Conclusion: Systemic anti-PD-1 initiates apoptosis and produces caspase-3. This process activates MPD-1 and induces sequential mediated by tumor-infiltrating lymphocytes. Combined anti-PD-1 and MPD-1 treatment will be effective for the distant metastatic lesions. Citation Format: Yoon Se Lee, Minsu Kwon, In Kyung Son, Youngro Byun, Sang Yoon Kim. Robust antitumor effect of doxorubicin prodrug combined with anti-PD-1 in murine squamous cell cancer model [abstract]. In: Proceedings of the AACR Special Conference on Tumor Immunology and Immunotherapy; 2018 Nov 27-30; Miami Beach, FL. Philadelphia (PA): AACR; Cancer Immunol Res 2020;8(4 Suppl):Abstract nr B19.

Oxaliplatin resistance is enhanced by saracatinib via upregulation Wnt-ABCG1 signaling in hepatocellular carcinoma

BackgroundChemo-resistance in hepatocellular carcinoma (HCC) is a major problem, and acquired drug resistance prevents cancer therapies from achieving complete responses. Molecular targeting therapy presents an opportunity to impede tumor through combination or sequential therapy, while the accurate effect is vague.MethodsThe efficacy of combinations between oxaliplatin and anti-cancer molecular targeting drugs was screened. Strangely, the combined chemotherapy with oxaliplatin and saracatinib induced significantly antagonistic effects. Then the antitumor effects of combined treatment with saracatinib and oxaliplatin were confirmed in wide type HCC as well as in saracatinib- and oxaliplatin-resistant HCC. RNA sequencing was used to explore the resistance mechanism, and the roles of ATP-binding cassette transporter G1 (ABCG1) and Wnt signaling in oxaliplatin resistance were confirmed.ResultsChemotherapy with oxaliplatin and saracatinib individually induced strong anti-HCC effects, while combined or sequential treatment of HCC cells with these two drugs exhibited reduced efficacy compared to treatment with the single drugs. And it was saracatinib treatment caused oxaliplatin resistance. RNA sequencing revealed 458 genes that were altered by treatment with saracatinib and oxaliplatin. Of these, the gene encoding ABCG1 and Wnt-associated genes were significantly upregulated. Upregulation of ABCG1 and oxaliplatin resistance were associated with activation of Wnt signaling. Interference with ABCG1 expression or inhibition of Wnt signaling resulted in reversal of the saracatinib-induced oxaliplatin resistance in HCC.ConclusionsThese studies demonstrated that combined or sequential chemotherapy with oxaliplatin and saracatinib reduced antitumor efficacy, and this antagonism was attributed to the activation of Wnt signaling and upregulation of ABCG1 by saracatinib.

Synergistic Antitumor Effects of Combined Treatment with HSP90 Inhibitor and PI3K/mTOR Dual Inhibitor in Cisplatin-Resistant Human Bladder Cancer Cells.

PurposeThe current study aimed to investigate the synergistic antitumor effect of combined treatment with 17-DMAG (HSP90 inhibitor) and NVP-BEZ235 (PI3K/mTOR dual inhibitor) on cisplatin-resistant human bladder cancer cells.Materials and MethodsHuman bladder cancer cells exhibiting cisplatin resistance (T24R2) were exposed to escalating doses of 17-DMAG (2.5–20 nM) with or without NVP-BEZ236 (0.5–4 µM) in combination with cisplatin. Antitumor effects were assessed by CCK-8 analysis. Based on the dose-response study, synergistic interactions between the two regimens were evaluated using clonogenic assay and combination index values. Flow cytometry and Western blot were conducted to analyze mechanisms of synergism.ResultsDose- and time-dependent antitumor effects for 17-DMAG were observed in both cisplatin-sensitive (T24) and cisplatin-resistant cells (T24R2). The antitumor effect of NVP-BEZ235, however, was found to be self-limiting. The combination of 17-DMAG and NVP-BEZ235 in a 1:200 fixed ratio showed a significant antitumor effect in cisplatin-resistant bladder cancer cells over a wide dose range, and clonogenic assay showed compatible results with synergy tests. Three-dimensional analysis revealed strong synergy between the two drugs with a synergy volume of 201.84 µM/mL2%. The combination therapy resulted in G1-phase cell cycle arrest and caspase-dependent apoptosis confirmed by the Western blot.ConclusionHSP90 inhibitor monotherapy and in combination with the PI3K/mTOR survival pathway inhibitor NVP-BEZ235 shows a synergistic antitumor effect in cisplatin-resistant bladder cancers, eliciting cell cycle arrest at the G1 phase and induction of caspase-dependent apoptotic pathway.

Depletion of tumor-associated macrophages enhances the anti-tumor effect of docetaxel in a murine epithelial ovarian cancer

Docetaxel (DTXL), a new member of the taxoid family, has been used for cancer treatment. However, increasing cases of DTXL resistance have been reported. Tumor-associated macrophages (TAMs) have been implicated in tumor invasion and chemo-resistance. Eliminating TAMs by inhibiting colony stimulating factor-1 receptor (CSF-1R) has emerged as a promising strategy for cancer treatment. BLZ945 is a CSF-1R inhibitor and has anti-tumor function. In present study, anti-tumor effects of combination treatment of BLZ945 and DTXL were investigated. We established a mouse ovarian cancer model and investigated the effect of BLZ945, DTXL single treatment or combination treatment on TAMs infiltration, tumor growth, CD8+ T cell infiltration and cancer metastasis. DTXL treatment increased the infiltration while BLZ945 induced cell apoptosis in macrophages. DTXL/BLZ945 combination treatment significantly inhibited tumor growth, reduced the abundance of TAMs, increased CD8+ T cell infiltration and prevented lung metastasis. Depletion of Tumor-Associated Macrophages (TAMs) by BLZ945 enhanced the anti-tumor effect of DTXL in a murine epithelial ovarian cancer.

Therapeutic effects of lenvatinib in combination with rAd-p53 for the treatment of non-small cell lung cancer.

The aim of the present study was to analyze the effects of the combined treatment of lenvatinib and adenoviral delivered p53 gene (rAd-p53) on non-small cell lung cancer (NSCLC) cells and a total of 120 patients with NSCLC. The therapeutic effects of gene therapy of rAd-p53 and target therapy of Lenvatinib were investigated in NSCLC patients. The anti-tumor effects of combined treatment of llenvatinib and rAd-p53 was administered orally once-daily in NSCLC patients. Patients with NSCLC were divided into three groups and received lenvatinib (n=40), rAd-p53 (n=40) or combined treatment of lenvatinib and rAd-p53 (n=40) for a total of 30 days. Results showed that p53 was down-regulated and VEGFR, FGFR and PDGFR-β were up-regulated in NSCLC tissues compared to adjacent normal tissues. Combined treatment of Lenvatinib and rAd-p53 markedly inhibited NSCLC cell growth, migration and invasion, and promoted apoptosis compared to either lenvatinib or rAd-p53 alone. The most common treatment-related adverse events included hypertension, diarrhea, nausea, proteinuria and body weight loss. Outcomes indicated that combined treatment of lenvatinib and rAd-p53 markedly inhibited tumor growth compared to lenvatinib and rAd-p53 alone for NSCLC patients. Combined treatment of lenvatinib and rAd-p53 did not exhibit drug accumulation after 30-day treatment. In conclusion, these outcomes indicate that combined treatment of lenvatinib and rAd-p53 may be an efficient therapeutic schedule for the treatment of NSCLC patients.

Anticancer effects of combinational treatment with BRAFV600E siRNA and PI3K pathway inhibitors in melanoma cell lines harboring BRAFV600E.

In the present study, the anti-tumor effects of combination treatment with an siRNA targeting B-Raf proto-oncogene serine/threonine kinase (BRAF)V600E and phosphoinositide 3-kinase (PI3K) signaling pathway inhibitors was investigated in melanoma cell lines harboring BRAFV600E. Human melanoma A375 and WM115 cells were treated with siRNA targeting to BRAF or BRAFV600E, combined with treatment with PI3K signaling pathway inhibitors. CCK-8 and EdU proliferation assays were performed to assess cell viability and proliferation, respectively, following treatment. In addition, flow cytometry analysis was performed to determine cell cycle distribution, and western blot analysis was performed to analyze the activity of the extracellular signal-regulated kinase (ERK) and PI3Ksignaling pathways following treatment. Targeting BRAFV600E using small interfering (si)RNA significantly decreased cell viability and DNA replication in tumor cell lines that harbor oncogenic BRAFV600E. Inhibition of BRAFV600E by siRNA combined with treatment with PI3K or mammalian target of rapamycin signaling pathway inhibitors significantly decreased cell viability and proliferation compared with siRNA or inhibitor treatment alone. Concomitant BRAFV600E and PI3K inhibition led to G1/S phase arrest in melanoma cells. However, melanoma cells in which oncogenic BRAFV600E is not highly expressed (WM115 cells) were not sensitive to BRAFV600E targeted therapy. The PI3K signaling pathway inhibitors were more effective in this cell line. The results from the present study provide an insight into the potential effectiveness of combination therapy and personalized cancer treatments.

Synergistic antitumor effects of combination treatment with metronomic doxorubicin and VEGF-targeting RNAi nanoparticles

Conventional cancer treatment strategies have been aimed at eradicating all cancer cells. To this end, standard chemotherapeutic approaches have relied on the maximum tolerated dose (MTD) of cytotoxic drugs with a long off-therapy interval, leading to heavy toxic side effects accompanied by drug resistance. To avoid the problems associated with the traditional MTD chemotherapy, metronomic chemotherapy with relatively low dose continuous treatments of cytotoxic drugs has been proposed as an alternative to the predominant paradigm of directly killing all cancer cells. Low-dose metronomic (LDM) chemotherapy is expected to have not only antitumor effects without toxicity and drug resistance, but also beneficial anti-angiogenic effects by causing selective apoptosis of tumor endothelial cells. In an attempt to keep the drug resistance under control and halt exponential tumor growth, herein, we combined LDM chemotherapy with a second anti-angiogenic strategy. The selective blockade of vascular endothelial growth factor (VEGF) in combination with metronomic doxorubicin (Dox) induced synergistic antitumor effects mainly through an antiangiogenic mechanism. For specific VEGF suppression, VEGF-targeting siRNA was delivered to tumor tissue using polymerized siRNA/thiolated glycol chitosan (poly-siVEGF/tGC) nanoparticles, leading to efficient VEGF gene knockdown in tumor tissue with a sequence-specific manner. Although the single treatment with metronomic Dox and poly-siVEGF/tGC nanoparticles alone showed some antitumor activity, notably, the combination of the two therapies resulted in superb tumor regression without causing systemic toxicity or drug resistance. Thus, these results suggest that the VEGF-targeted RNAi using poly-siRNA/tGC nanoparticles in combination with LDM chemotherapy could be a promising synergistic strategy for controlling tumor growth by enhancing the efficacy of anti-angiogenesis while minimizing toxicity and drug resistance.

Phenoxodiol enhances the antitumor activity of gemcitabine in gallbladder cancer through suppressing Akt/mTOR pathway.

Gallbladder cancer is the most common and aggressive type of biliary tract cancer with poor prognosis due to both its inability to be detected at an early stage and its poor sensitivity to conventional therapies. Gemcitabine has been more and more widely used for the treatment of gallbladder cancer; however, the response rate is not satisfactory. Phenoxodiol is an isoflavone analog with antitumor activity against a variety of cancers. In our current work, we examined the effect of phenoxodiol on gallbladder cancer cells and to determine whether phenoxodiol can enhance the antitumor activity of gemcitabine in gallbladder cancer. The combined treatment of phenoxodiol and gemcitabine was more effective at inhibiting cell proliferation than either chemotherapeutic agent treatment alone. Meanwhile, phenoxodiol arrests cell cycle progression in the G0-G1 phase. In addition, phenoxodiol and gemcitabine inhibit the phosphorylation of PI3K/Akt-signaling pathway as well as modulate the expression of apoptosis-relevant molecules. Furthermore, the antitumor effect of combination treatment with phenoxodiol and gemcitabine on gallbladder cancer was evaluated using a murine gallbladder cancer xenograft model and the results suggested that phenoxodiol enhanced the in vivo antitumor activity of gemcitabine. Taken together, our study suggested that the combination treatment with phenoxodiol and gemcitabine might offer optimal therapeutic benefits for patients with gallbladder cancer.

Inhibition of Nuclear Factor Kappa-B Enhances the Antitumor Effect of Combination Treatment with Tumor Necrosis Factor-Alpha Gene Therapy and Gemcitabine for Pancreatic Cancer in Mice

Combination therapy with tumor necrosis factor-alpha (TNF-α) gene delivery and gemcitabine is a new therapeutic approach for pancreatic cancer. However, the efficacy of both TNF-α and gemcitabine is suppressed due to activation of nuclear factor-kappa B (NF-κB). We hypothesized that nafamostat mesilate (FUT175), an NF-κB inhibitor, enhances the antitumor effect of combination treatment with an adenoviral vector-expressing TNF-α (AxCAhTNF-α) and gemcitabine for pancreatic cancer in mice. In vitro, we assessed that FUT175 inhibited both TNF-α- and gemcitabine-induced NF-κB activation and enhanced apoptosis in human pancreatic cancer cell lines (MIAPaCa-2 and AsPC-1). In vivo, we established a xenograft pancreatic cancer model in mice by subcutaneous injection of MIAPaCa-2 and AsPC-1. The animals were treated with AxCAhTNF-α intratumorally and gemcitabine intraperitoneally once a week (combination group) or AxCAhTNF-α intratumorally and gemcitabine intraperitoneally once a week as well as FUT175 intraperitoneally 3 times a week (triple combination group). In vitro, FUT175 inhibited both TNF-α- and gemcitabine-induced NF-κB activation and enhanced induction of apoptosis. In the triple combination group, tumor growth in vivo was significantly slower and there were more apoptotic cells than in the combination group (p < 0.05). Inhibition of NF-κB by FUT175 enhances the antitumor effect of combined TNF-α gene therapy and gemcitabine for pancreatic cancer.

Replacement treatment with microRNA-143 and -145 induces synergistic inhibition of the growth of human bladder cancer cells by regulating PI3K/Akt and MAPK signaling pathways

We recently reported that both microRNA (miR)-143 and -145 are downregulated in human bladder cancer T24 cells and that miR-143 targets ERK5. In this study, we assessed the anti-tumor effects of combination treatment with miR-143 and -145 on bladder cancer cell lines T24, SNK57, and NKB1, in which the expression levels of miR-143 and -145 are downregulated. The ectopic expression of both miR-143 and -145 led to a significantly synergistic growth inhibition of T24 and NKB1 cells, but not that of SNK57 cells with the levels of miR-143 and -145 higher than those in T24 and NKB1 cells. The MAPK signaling pathway in NKB1 cells and both PI3K/Akt and MAPK signaling pathways in T24 cells were synergistically repressed by the co-treatment with miR-143 and -145. We newly elucidated that miR-143 targeted akt and that miR-145 targeted integrin-linked kinase (ilk) in T24 cells based on the results of a luciferase activity assay. Silencing of ilk significantly inhibited the growth of all the bladder cancer cells tested. Also, the level of phosphorylated ERK1/2 in T24 cells and that of phosphorylated Akt in SNK57 and NKB1 cells were decreased by ilk silencing. This study has provided novel important evidence with regard to the functions of anti-oncogenic miR-143 and -145 and also suggests the possible use of miR-143 and -145 for combination replacement therapy in cancers in which both miRNAs are downregulated.

Inhibition of NF-kappaB enhances the anti-tumor effect of combination treatment with tumor necrosis factor-alpha (TNF-alpha) gene therapy and gemcitabine for pancreatic cancer in mice

Inhibition of NF-kappaB enhances the anti-tumor effect of combination treatment with tumor necrosis factor-alpha (TNF-alpha) gene therapy and gemcitabine for pancreatic cancer in mice

Abstract IA18: Molecular mechanisms regulating synergistic effect of immunotherapy and chemotherapy of cancer

Abstract Despite recent advances in the development of new chemotherapeutic drugs and improvements in radiation therapy, conventional cancer therapy often falls short of the goal of controlling tumor progression. Therapeutic cancer vaccines and adoptive T-cell transfer are long considered as very attractive therapeutic options in the treatment of cancer. However, clinical trials of different cancer vaccines performed in recent years demonstrated rather weak clinical efficacy. It has become apparent that therapeutic cancer vaccines given as a single agent may not produce substantial clinical benefits and combination with conventional methods of treatment will be necessary. The use of conventional cancer chemotherapy in combination with cancer vaccines was previously not considered as very attractive due to the potent immunosuppressive effect usually associated with chemotherapy. This paradigm was challenged in recent years by serendipitous observations made in a number of phase I/II clinical trials that reported high rates of objective clinical responses when cancer vaccines were combined with chemotherapy. The paradox is that the types of chemotherapy that are used in lung cancer are known to suppress the immune system. We have recently demonstrated that chemotherapy and cytotoxic T cells (CTL) have a synergistic cytotoxic effect that may be mediated by mannose-6-phosphate receptor (MPR). We have shown that when cancer vaccines or adoptive T-cell transfer are used as a single modality, only limited numbers of T cells are able to penetrate the tumor parenchyma. CTLs exert their cytotoxic effect only against tumor cells that express specific antigen, since it requires a direct cell-cell contact, and release of perforin and granzymes (GrzB). If chemotherapy is administered immediately after immunotherapy, it causes disruption of tumor stroma that allows for better penetration of antigen-specific T cells. Chemotherapy via autophagy causes substantial increase in MPR expression on tumor cells. Small number of activated CTLs interacting with tumor cells expressing tumor antigen can release GrzB that can penetrate into neighboring tumor cells without requirement for cell-cell contact. Therefore large number of tumor cells including those that do not express specific antigen would be susceptible to the effect of CTLs. This may explain substantial enhancement of antitumor effect of combined treatment. It is likely that this effect would not be long-lasting since CTL activity will be eliminated by chemotherapy and the immune suppressive tumor microenvironment. However, it may provide a sufficient window to achieve a significant antitumor effect. Since memory T cells are more resistant to chemotherapy than effector T cells, it is possible that subsequent immunization would be able to boost antitumor immunity and thus provide a longer lasting effect of combined therapy.

Gimeracil, a component of S-1, may enhance the antitumor activity of X-ray irradiation in human cancer xenograft models in vivo

Chemoradiotherapy is a useful treatment strategy in patients with locally advanced cancers. In particular, combination of 5-fluorouracil (5-FU) with X-ray irradiation is effective for the treatment of some types of gastrointestinal cancers. We investigated the antitumor effects of combination treatment with X-ray and S-1, a unique formulation of 5-FU, on human cancer xenografts in nude mice and compared the efficacy of this treatment to that of radiotherapy combined with cisplatin, UFT, another oral 5-FU prodrug, and intravenous 5-FU. Tumors implanted into the left hind legs of mice were treated with a dose of 2 or 5 Gy X-ray irradiation on days 1 and 8, and S-1, UFT and 5-FU were administered for 14 days. The efficacy of combined treatment with 8.3 mg/kg S-1 and 2 Gy X-ray irradiation in treating non-small cell lung cancer xenografts (Lu-99 and LC-11) was significantly higher than that of treatment with S-1 alone or 2 Gy X-ray irradiation alone, and the antitumor activity of combined treatment was similar to that of 5 Gy X-ray irradiation alone. Although 8.3 mg/kg S-1 and 17.5 mg/kg UFT had equivalent antitumor activity; the antitumor efficacy of combination treatment with S-1 and 2 Gy X-ray irradiation on LC-11 tumors was significantly higher than that of combination treatment with UFT and 2 Gy X-ray irradiation. Combination treatment with S-1 and X-ray irradiation was also more effective against pancreatic tumors than combination treatment with intravenous 5-FU and X-ray irradiation. To elucidate the reason for the increased antitumor efficacy of combination treatment with S-1 and X-ray irradiation, the antitumor effect of gimeracil, one of the components of S-1, was tested in combination with 2 Gy X-ray irradiation. These experiments demonstrated that gimeracil enhanced the efficacy of X-ray irradiation against lung as well as head and neck cancer xenografts in a dose-dependent manner. Furthermore, we observed decreased expression of γ-H2AX protein, a marker of DNA repair, in LC-11 tumors treated with X-ray irradiation and gimeracil compared to that observed in tumors treated with X-ray irradiation alone, suggesting that gimeracil may inhibit rapid repair of X-ray-induced DNA damage in tumors. The present study suggests that chemoradiotherapy using S-1 acts through a novel mechanism and may prove useful in treating patients with locally advanced cancers whose disease progression is difficult to control using chemotherapy alone.

Synergistic Antitumor Effect of S-1 and HER2-Targeting Agents in Gastric Cancer with HER2 Amplification

Amplification of human epidermal growth factor receptor 2 (HER2) has been detected in 20% to 30% of gastric cancers and is associated with a poor outcome. Combination therapies with HER2-targeting agents and cytotoxic agents are considered a potential therapeutic option for gastric cancer with HER2 amplification. We have now investigated the effects of combination treatment with the oral fluoropyrimidine S-1 and the HER2-targeting agents lapatinib or trastuzumab in gastric cancer cells with or without HER2 amplification. We used 5-fluorouracil (5FU) instead of S-1 for in vitro experiments, given that tegafur, a component of S-1, is metabolized to 5FU in the liver. The combination of 5FU and HER2-targeting agents synergistically inhibited cell proliferation and exhibited an enhanced proapoptotic effect in gastric cancer cells with HER2 amplification, but not in those without it. Lapatinib or trastuzumab also induced downregulation of thymidylate synthase (TS) expression and activity only in cells with HER2 amplification. The combination of 5FU and TS depletion by RNA interference also exhibited an enhanced proapoptotic effect in cells with HER2 amplification. These observations thus suggest that lapatinib-induced or trastuzumab-induced downregulation of TS is responsible, at least in part, for the synergistic antitumor effect of combined treatment with 5FU and HER2-targeting agents. The antitumor effect of the combination of S-1 and HER2-targeting agents in vivo was also greater than that of either drug alone. Our preclinical findings thus indicate that the combination of S-1 and HER2-targeting agents is a promising treatment option for gastric cancer with HER2 amplification.

Antitumor effects of lapatinib (GW572016), a dual inhibitor of EGFR and HER-2, in combination with cisplatin or paclitaxel on head and neck squamous cell carcinoma

The epidermal growth factor receptor (EGFR) and a related family member, HER-2, are often overexpressed simultaneously in patients with a variety of malignant tumors, and the combination may cooperatively promote cancer cell growth and survival. Heterodimerization of EGFR and HER-2 has been known to create intense proliferative signals. Lapatinib (GW572016) is a small molecule that is administrated orally and functions as a reversible inhibitor of both EGFR and HER-2 tyrosine kinases. In the present study, we evaluated the antitumor effect of lapatinib on head and neck squamous cell carcinoma (HNSCC) cell lines in vitro and in vivo. In vivo we examined the antitumor effects of combined treatment with lapatinib and either cisplatin or paclitaxel. In vitro lapatinib displayed antiproliferative effects on HNSCC cells. The IC50 of lapatinib ranged between 13.6 and 60.2 microM after 24-h exposure to lapatinib. A correlation was not observed between results of in vitro proliferation assays for lapatinib and the expression of EGFR or HER-2. In vivo lapatinib displayed antitumor activity, and induced apoptosis in nude mice bearing an established xenograft of YCU-H891 cells. Lapatinib did not significantly inhibit angiogenesis. Combination treatment of lapatinib with cisplatin or paclitaxel enhanced antitumor activity mainly by inducing apoptosis. Inhibition of antiangiogenesis was observed only for combination treatment of lapatinib with paclitaxel (compared to vehicle control). These results suggest that: i) lapatinib has antitumor effects in vitro and in vivo; ii) lapatinib may be more effective in combination with cisplatin or paclitaxel; and iii) lapatinib might provide useful clinical benefits to HNSCC patients.

1-(3-C-Ethynyl-β-D-ribo-pentofuranosyl)cytosine (ECyd, TAS-106), a novel potent inhibitor of RNA polymerase, potentiates the cytotoxicity of CDDP in human cancer cells both in vitro and in vivo

1-(3-C-Ethynyl-beta-D-ribo-pentofuranosyl)cytosine (ECyd, TAS-106) is a novel antitumor ribonucleoside that inhibits RNA polymerase. In the present study, we investigated the cellular and molecular interactions between TAS-106 and cisplatin (CDDP) in vitro using A549 human lung cancer cells and the in vivo antitumor effect of combined treatment using OCC-1 and LX-1 human tumor xenografts. The treatment effects were determined by evaluating cytotoxicity, the cell cycle distribution, apoptosis induction and the expression of checkpoint-associated proteins. In vitro, the combination of TAS-106 and CDDP synergistically inhibited the growth of A549 cells, as determined using isobologram analysis. TAS-106 potently inhibited the expression of Chk1 protein and the phosphorylation of Chk1 and Chk2. Moreover, based on the inhibition of checkpoint-associated protein, TAS-106 abrogated the CDDP-induced S- and G2M-checkpoints and induced apoptosis in A549 cells. In vivo, TAS-106 alone showed antitumor activity; however, its combination with CDDP significantly enhanced the growth inhibition of OCC-1 and LX-1 tumors. Moreover, combination therapy with TAS-106 and CDDP in the OCC-1 xenograft model resulted in significant life-prolongation. These findings provide a rationale for combination chemotherapy using TAS-106 and CDDP in clinical settings.