Mutant PIK3CA as a negative predictive biomarker for treatment with a highly selective PIM1 inhibitor in human colon cancer.

Significant improvement in targeted therapy for colorectal cancer (CRC) has occurred over the past few decades since the approval of the EGFR inhibitor cetuximab. However, cetuximab is used only for patients possessing the wild-type oncogene KRAS, NRAS, and BRAF, and even most of these eventually acquire therapeutic resistance, via activation of parallel oncogenic pathways such as RAS-MAPK or PI3K/Akt/mTOR. The two aforementioned pathways also contribute to the development of therapeutic resistance in CRC patients, due to compensatory and feedback mechanisms. Therefore, combination drug therapies (versus monotherapy) targeting these multiple pathways may be necessary for further efficacy against CRC. In this study, we identified PIK3CA mutant (PIK3CA MT) as a determinant of resistance to SMI-4a, a highly selective PIM1 kinase inhibitor, in CRC cell lines. In CRC cell lines, SMI-4a showed its effect only in PIK3CA wild type (PIK3CA WT) cell lines, while PIK3CA MT cells did not respond to SMI-4a in cell death assays. In vivo xenograft and PDX experiments confirmed that PIK3CA MT is responsible for the resistance to SMI-4a. Inhibition of PIK3CA MT by PI3K inhibitors restored SMI-4a sensitivity in PIK3CA MT CRC cell lines. Taken together, these results demonstrate that sensitivity to SMI-4a is determined by the PIK3CA genotype and that co-targeting of PI3K and PIM1 in PIK3CA MT CRC patients could be a promising and novel therapeutic approach for refractory CRC patients.

DGG-300273, a novel WNT/ß-catenin inhibitor, induces apoptotic cell death by activating ROS-BIM signaling in a Wnt-dependent manner in colon cancer cells.

Dysregulated Wnt signaling is associated with malignant oncogenic transformation, especially in colon cancer. Recently, numerous drugs have been developed based on tumorigenesis biomarkers, thus having high potential as drug targets. Likewise, WNT/ß-catenin pathway members are attractive therapeutic targets for colon cancer and are currently in various stages of development. However, although inhibitors of proteins regulating the WNT/ß-catenin signaling pathway have been extensively studied, they have yet to be clinically approved, and the underlying molecular mechanism(s) of their anticancer effects remain poorly understood. Herein, we show that a novel WNT/ß-catenin inhibitor, DGG-300273, inhibits colon cancer cell growth in a Wnt-dependent manner due to upregulation of the BCL2-family protein Bim and caspase-dependent apoptotic cell death. Additionally, DGG-300273-mediated cell death occurs by increased reactive oxygen species (ROS), as shown by abrogation of apoptotic cell death and ROS production following pretreatment with the antioxidant N-acetylcysteine. These results suggest that DGG-300273 represents a promising investigational drug for the treatment of Wnt-associated cancer, thus warranting further characterization and study.

CJ14939, a Novel JAK Inhibitor, Increases Oxaliplatin-induced Cell Death Through JAK/STAT Pathway in Colorectal Cancer.

BACKGROUND/AIM: Colorectal cancer is reported to have the highest mortality rate among human malignancies. Although many research results for the treatment of colorectal cancer have been reported, there is no suitable treatment when resistance has developed. Therefore, it is necessary to develop new therapeutic agents. Janus kinase (JAK)/signal transducer and activator of transcription (STAT) signaling plays an essential role in cell differentiation, proliferation, and survival. Abnormal activation of the JAK/STAT signaling pathway, by gene mutation or amplification, may induce cancer development, and sustained JAK/STAT activation is involved in chemoresistance. While many therapeutic agents have been developed to treat colon cancer, there remains no drug to overcome resistance to chemotherapies. The purpose of this study was to determine the potential of CJ14939 as a novel JAK inhibitor for the treatment of colorectal cancer. MATERIALS AND METHODS: In this study, cell culture, cell death assay, 3- (4,5-dimethylthiazol-2-yl)-5-(3-carboxymethoxyphenyl)-2-(4-sulfophenyl)-2H-tetrazolium assay, colony formation assay, immunoblot analysis and tumor xenograft were applied. RESULTS: CJ14939 induced cell death, and inhibited phosphorylation of JAK1 and STAT3 in colorectal cancer cells. Furthermore, CJ14939 also promoted oxaliplatin-induced cell death, up-regulated expression of cleaved caspase-3, and down-regulated expression of phospho-JAK1 and phospho-STAT3. In vivo, co-treatment with CJ14939 and oxaliplatin notably reduced tumor growth when compared with CJ14939 or oxaliplatin treatment alone. CONCLUSION: This study identifies the important potential of CJ14939 in colorectal cancer treatment and suggests that combining CJ14939 with oxaliplatin might be a novel therapeutic strategy for patients with colorectal cancer.

Inhibition of JAK1/2 can overcome EGFR-TKI resistance in human NSCLC.

Non-small lung cancer (NSCLC) is the most common cancer in the world. The epidermal growth factor receptor (EGFR) gene is mutated in approximately 10% of lung cancer cases in the US and 50% of lung cancer in Asia. The representative target therapeutic agent, erlotinib (EGFR tyrosine kinase inhibitor; EGFR TKI), is effective in inactivating EGFR in lung cancer patients. However, approximately 50-60% of patients are resistant to EGFR TKI. These populations are associated with the EGFR mutation. To overcome resistance to EGFR TKI, we discovered a JAK1 inhibitor, CJ14939. We investigated the efficacy of CJ14939 in human NSCLC cell lines in vitro and in vivo. Our results showed that CJ14939 induced the inhibition of cell growth. Moreover, we demonstrated that combination treatment with erlotinib and CJ14939 induced cell death in vitro and inhibited tumor growth in vivo. In addition, we confirmed the suppression of phosphorylated EGFR, JAK1, and Stat3 expression in erlotinib and CJ14939-treated human NSCLC cell lines. Our results provide evidence that JAK inhibition overcomes resistance to EGFR TKI in human NSCLCs.

Chemosensitivity to HM90822, a novel synthetic IAP antagonist, is determined by p-AKT-inducible XIAP phosphorylation in human pancreatic cancer cells.

Inhibitor of apoptosis proteins (IAPs) are overexpressed in the majority of cancers and prevent apoptosis by inhibiting caspases. IAPs have therefore attracted considerable attention as potential targets for anticancer therapy. Here, we demonstrated that HM90822 (abbreviated HM822; a new synthetic IAP antagonist) induced apoptotic cell death via proteasome-dependent degradation of BIR2/3 domain-containing IAPs in human pancreatic cancer cells. HM822 inhibited the expression of XIAP and cIAP1/2 proteins in Panc-1 and BxPC-3 cells, which are sensitive to HM822. HM822 also induced IAP ubiquitination and promoted proteasome-dependent IAP degradation. However, cells expressing phospho-XIAP (Ser87) and AKT exhibited resistance to HM822. In other words, the overexpression of AKT-CA (constitutive active form for AKT) or AKT-WT induced resistance to HM822. In addition, in Panc-1 xenograft and orthotopic mouse models, we revealed that tumor growth was suppressed by the administration of HM822. Taken together, these results suggest that HM822 induces apoptosis through ubiquitin/proteasome-dependent degradation of BIR3 domain-containing IAPs. These findings suggest that phospho-XIAP and phospho-AKT may be used as biomarkers for predicting the efficacy of HM822 in pancreatic cancer patients.

A phase I/II study of poziotinib combined with paclitaxel and trastuzumab in patients with HER2-positive advanced gastric cancer.

BACKGROUND: Poziotinib (HM781-36B) is an irreversible pan-HER tyrosine kinase inhibitor which targets EGFR, HER2, and HER4. This prospective, multicenter, open-label, phase I/II study determined the maximum tolerated dose (MTD) and evaluated the safety and efficacy of poziotinib combined with paclitaxel and trastuzumab in patients with HER2-positive advanced gastric cancer (GC). METHODS: Patients with HER2-positive GC previously treated with one line of chemotherapy received oral poziotinib (8 mg or 12 mg) once daily for 14 days, followed by 7 days off. Paclitaxel (175 mg/m2 infusion) and trastuzumab (8 mg/kg loading dose, then 6 mg/kg infusion) were administered concomitantly with poziotinib on day 1 every 3 weeks. RESULTS: In the phase I part, 12 patients were enrolled (7 at dose level 1, 5 at dose level 2). One patient receiving poziotinib 8 mg and 2 receiving poziotinib 12 mg had dose-limiting toxicities (DLTs); all DLTs were grade 4 neutropenia, one with fever. The most common poziotinib-related adverse events were diarrhea, rash, stomatitis, pruritus and loss of appetite. The MTD of poziotinib was determined to be 8 mg/day and this was used in the phase II part which enrolled 32 patients. Two patients (6.3%) had complete responses and 5 (15.6%) had partial responses (objective response rate 21.9%). Median progression-free survival and overall survival were 13.0 weeks (95% CI 9.8-21.9) and 29.5 weeks (95% CI 17.9-59.2), respectively. CONCLUSIONS: The MTD of poziotinib combined with paclitaxel and trastuzumab was 8 mg/day. This combination yielded promising anti-tumor efficacy with manageable toxicity in previously treated patients with HER2-positive GC.

Targeting ß-catenin overcomes MEK inhibition resistance in colon cancer with KRAS and PIK3CA mutations.

BACKGROUND: Mitogen-activated protein kinases (MEK 1/2) are central components of the RAS signalling pathway and are attractive targets for cancer therapy. These agents continue to be investigated in KRAS mutant colon cancer but are met with significant resistance. Clinical investigations have demonstrated that these strategies are not well tolerated by patients. METHODS: We investigated a biomarker of response for MEK inhibition in KRAS mutant colon cancers by LC-MS/MS analysis. We tested the MEK inhibitor in PIK3CA wild(wt) and mutant(mt) colon cancer cells. In addition, we tested the combinational effects of MEK and TNKS inhibitor in vitro and in vivo. RESULTS: We identified ß-catenin, a key mediator of the WNT pathway, in response to MEK inhibitor. MEK inhibition led to a decrease in ß-catenin in PIK3CA wt colon cancer cells but not in mt. Tumour regression was promoted by combination of MEK inhibition and NVP-TNS656, which targets the WNT pathway. Furthermore, inhibition of MEK promoted tumour regression in colon cancer patient-derived xenograft models expressing PIK3CA wt. CONCLUSIONS: We propose that inhibition of the WNT pathway, particularly ß-catenin, may bypass resistance to MEK inhibition in human PIK3CA mt colon cancer. Therefore, we suggest that ß-catenin is a potential predictive marker of MEK inhibitor resistance.

SH003 selectively induces p73­dependent apoptosis in triple­negative breast cancer cells.

Triple-negative breast cancer (TNBC) is a breast cancer subtype that has an aggressive phenotype, is highly metastatic, has limited treatment options and is associated with a poor prognosis. In addition, metastatic TNBC has no preferred standard chemotherapy due to resistance to anthracyclines and taxanes. The present study demonstrated that a herbal extract, SH003, reduced cell viability and induced apoptosis in TNBC without cell cytotoxicity. Cell viability was examined using trypan blue exclusion and colony formation assays, which revealed a decrease in the cell viability. Additionally, apoptosis was determined using flow cytometry and a sub­G1 assay, which revealed an increase in the proportion of cells in the sub­G1 phase. The present study investigated the anticancer effect of SH003 in the Hs578T, MDA­MB­231 and ZR­751 TNBC cell lines, and in the MCF7 and T47D non­TNBC cell lines. Western blot analysis revealed that the expression levels of poly­ADP­ribose polymerase (PARP) cleavage protein in cells treated with SH003 were increased dose­dependent manner, indicating that SH003 induced apoptosis via a caspase­dependent pathway. Pre­treatment with the caspase inhibitor Z­VAD reduced SH003­induced apoptosis was examined using trypan blue exclusion. Moreover, SH003 treatment enhanced the p73 levels in MDA­MB­231 cells but not in MCF7 cells. Transfection of p73 small interfering RNA (siRNA) in MDA­MB0231 cells revealed that the apoptotic cell death induced by SH003 was significantly impaired in comparison with scramble siRNA transfected MDA­MB­231 cells. This was examined using trypan blue exclusion and flow cytometry analysis (sub­G1). In addition, SH003 and paclitaxel exhibited synergistic anticancer effects on TNBC cells. The results indicate that SH003 exerts its anticancer effect via p73 protein induction and exhibits synergistic anticancer effects when combined with paclitaxel.

L-Ascorbic acid can abrogate SVCT-2-dependent cetuximab resistance mediated by mutant KRAS in human colon cancer cells.

Colon cancer patients with mutant KRAS are resistant to cetuximab, an antibody directed against the epidermal growth factor receptor, which is an effective clinical therapy for patients with wild-type KRAS. Numerous combinatorial therapies have been tested to overcome the resistance to cetuximab. However, no combinations have been found that can be used as effective therapeutic strategies. In this study, we demonstrate that L-ascorbic acid partners with cetuximab to induce killing effects, which are influenced by sodium-dependent vitamin C transporter 2 (SVCT-2) in human colon cancer cells with a mutant KRAS. L-Ascorbic acid treatment of human colon cancer cells that express a mutant KRAS differentially and synergistically induced cell death with cetuximab in a SVCT-2-dependent manner. The ectopic expression of SVCT-2 induced sensitivity to L-ascorbic acid treatment in human colon cancer cells that do not express SVCT-2, whereas the knockdown of endogenous SVCT-2 induced resistance to L-ascorbic acid treatment in SVCT-2-positive cells. Moreover, tumor regression via the administration of L-ascorbic acid and cetuximab in mice bearing tumor cell xenografts corresponded to SVCT-2 protein levels. Interestingly, cell death induced by the combination of L-ascorbic acid and cetuximab resulted in both apoptotic and necrotic cell death. These cell death mechanisms were related to a disruption of the ERK pathway and were represented by the impaired activation of RAFs and the activation of the ASK-1-p38 pathway. Taken together, these results suggest that resistance to cetuximab in human colon cancer patients with a mutant KRAS can be bypassed by L-ascorbic acid in an SVCT-2-dependent manner. Furthermore, SVCT-2 in mutant KRAS colon cancer may act as a potent marker for potentiating L-ascorbic acid co-treatment with cetuximab.

Targeting FGFR Pathway in Human Hepatocellular Carcinoma: Expressing pFGFR and pMET for Antitumor Activity.

The MET receptor tyrosine kinase, the receptor for hepatocyte growth factor (HGF), has been implicated in cancer growth, invasion, migration, angiogenesis, and metastasis in a broad variety of human cancers, including human hepatocellular carcinoma (HCC). Recently, MET was suggested to be a potential target for the personalized treatment of HCC with an active HGF-MET signaling pathway. However, the mechanisms of resistance to MET inhibitors need to be elucidated to provide effective treatment. Here, we show that HCC cells exhibit different sensitivities to the MET inhibitor PHA665752, depending on the phosphorylation status of FGFR. Treatment of cells expressing both phospho-FGFR and phospho-MET with the inhibitor PHA665752 did not cause growth inhibition and cell death, whereas treatment with AZD4547, a pan-FGFR inhibitor, resulted in decreased colony formation and cleavage of caspase-3. Moreover, silencing of endogenous FGFR1 and FGFR2 by RNAi of HCC cells expressing phospho-FGFR, phospho-FGFR2, and phospho-MET overcame the resistance to PHA665752 treatment. Treatment of primary cancer cells from patients with HCC expressing both phospho-FGFR and phospho-MET with PHA665752 did not induce cell death, whereas AZD4547 treatment induced cell death through the cleavage of caspase-3. In addition, treatment of cells resistant to PHA665752 with AZD4547 abrogated the activation of downstream effectors of cell growth, proliferation, and survival. On the basis of these results, we conclude that the FGFR pathway is critical for HCC survival, and that targeting this pathway with AZD4547 may be beneficial for the treatment of patients with HCC-expressing phospho-FGFR and phospho-MET.

A novel small-molecule IAP antagonist, AZD5582, draws Mcl-1 down-regulation for induction of apoptosis through targeting of cIAP1 and XIAP in human pancreatic cancer.

Inhibitor of apoptosis proteins (IAPs) plays an important role in controlling cancer cell survival. IAPs have therefore attracted considerable attention as potential targets in anticancer therapy. In this study, we investigated the anti-tumor effect of AZD5582, a novel small-molecule IAP inhibitor, in human pancreatic cancer cells. Treating human pancreatic cancer cells with AZD5582 differentially induced apoptosis, dependent on the expression of p-Akt and p-XIAP. Moreover, the knockdown of endogenous Akt or XIAP via RNA interference in pancreatic cancer cells, which are resistant to AZD5582, resulted in increased sensitivity to AZD5582, whereas ectopically expressing Akt or XIAP led to resistance to AZD5582. Additionally, AZD5582 targeted cIAP1 to induce TNF-α-induced apoptosis. More importantly, AZD5582 induced a decrease of Mcl-1 protein, a member of the Bcl-2 family, but not that of Bcl-2 and Bcl-xL. Interestingly, ectopically expressing XIAP and cIAP1 inhibited the AZD5582-induced decrease of Mcl-1 protein, which suggests that AZD5582 elicits Mcl-1 decrease for apoptosis induction by targeting of XIAP and cIAP1. Taken together, these results indicate that sensitivity to AZD5582 is determined by p-Akt-inducible XIAP phosphorylation and by targeting cIAP1. Furthermore, Mcl-1 in pancreatic cancer may act as a potent marker to analyze the therapeutic effects of AZD5582.

Cellular inhibitor of apoptosis protein 1 (cIAP1) stability contributes to YM155 resistance in human gastric cancer cells.

YM155, which blocks the expression of survivin, a member of the inhibitor of apoptosis (IAP) family, induces cell death in a variety of cancer types, including prostate, bladder, breast, leukemia, and non-small lung cancer. However, the mechanism underlying gastric cancer susceptibility and resistance to YM155 is yet to be specified. Here, we demonstrate that cIAP1 stability dictates resistance to YM155 in human gastric cancer cells. Treatment of human gastric cancer cells with YM155 differentially induced cell death dependent on the stability of cIAP1 as well as survivin. Transfection with cIAP1 expression plasmids decreased cell sensitivity to YM155, whereas knockdown of endogenous cIAP1 using RNA interference enhanced sensitivity to YM155. In addition, double knockdown of survivin and cIAP1 significantly induced cell death in the YM155-resistant cell line, MKN45. We also showed that YM155 induced autoubiquitination and proteasome-dependent degradation of cIAP1. Surprisingly, survivin affected the stability of cIAP1 through binding, contributing to cell sensitivity to YM155. Thus, our findings reveal that YM155 sensitizes human gastric cancer cells to apoptotic cell death by degrading cIAP1, and furthermore, cIAP1 in gastric cancer cells may act as a PD marker for YM155 treatment.