Young-Soon Na

Capillarisin inhibits constitutive and inducible STAT3 activation through induction of SHP-1 and SHP-2 tyrosine phosphatases.

Signal transducers and activators of transcription (STAT)-3 is a latent cytosolic transcription factor that has been closely associated with survival, proliferation, chemoresistance, and metastasis of tumor cells. Whether the anti-proliferative, pro-apoptotic, and anti-metastatic effects of capillarisin (CPS), derived from Artemisia capillaris (Compositae), are linked to its capability to inhibit STAT3 activation was investigated. We found that CPS specifically inhibited both constitutive and inducible STAT3 activation at tyrosine residue 705 but not at serine residue 727 in human multiple myeloma cells. Besides the inhibition of STAT3 phosphorylation, CPS also abrogated STAT3 constitutive activity and nuclear translocation. The suppression of STAT3 was mediated through the inhibition of activation of upstream JAK1, JAK2, and c-Src kinases. Treatment with the protein tyrosine phosphatase (PTP) inhibitor pervanadate treatment reversed the CPS-induced down-regulation of JAK1/2 and STAT3, thereby suggesting the involvement of a PTP. Indeed, knockdown of the SHP-1 and SHP-2 genes by small interfering RNA suppressed the ability of CPS to inhibit JAK1 and STAT3 activation, suggesting the critical role of both SHP-1 and SHP-2 in its possible mechanism of action. CPS downregulated the expression of STAT3-regulated antiapoptotic and proliferative gene products; and this correlated with suppression of cell viability, the accumulation of cells in sub-G1 phase of cell cycle and induction of apoptosis. Moreover, CPS potentiated bortezomib-induced apoptotic effects in MM cells, and this correlated with down-regulation of various gene products that mediate cell proliferation (Cyclin D1 and COX-2), cell survival (Bcl-2, Bcl-xl, IAP1, IAP2, and Survivin), invasion (MMP-9), and angiogenesis (VEGF). Thus, overall, our results suggest that CPS is a novel blocker of STAT3 activation and thus may have a potential in negative regulation of growth, metastasis, and chemoresistance of tumor cells.

The Role of KRAS Mutations in Predicting the Efficacy of Cetuximab-Plus-Irinotecan Therapy in Irinotecan-Refractory Korean Metastatic Colorectal Cancer Patients

Objective: This study evaluated the clinical relevance of KRAS and BRAF mutational status in 66 irinotecan-refrac- tory Korean metastatic colorectal cancer (mCRC) patients treated with cetuximab-plus-irinotecan-based chemotherapy. Methods: A total of 66 irinotecan-refractory mCRC patients treated with cetuximab-plus-irinotecan-based chemotherapy were included. Tumors were screened for KRAS mutations (codons 12 and 13) and a BRAF mutation (V600E) using direct sequencing and the Snapshot assay. Results: The objective response rate (RR) for treatment was 21.2% (14/66) and skin rashes were observed in 43 (65.2%) of the 66 patients. A KRAS mutation was detected in 27 (40.9%) tumors, and was associated with lower RR (wild-type vs. mutated KRAS: 33.3 vs. 3.7%, p = 0.005) and shorter progression-free survival (PFS) and overall survival (OS; PFS: 6.4 vs. 2.0 months, p = 0.005; OS: 17.8 vs. 7.1 months, p = 0.001). Severe skin toxicity was associated with better RR and longer PFS and OS. BRAF mutations were not detected. Multivariate analysis revealed that KRAS status and skin toxicity were independent predictive factors of PFS and OS. Conclusions: This study indicates the clinical relevance of KRAS mutations in predicting the efficacy of cetuximab-plus-irinotecan-based chemotherapy in irinotecan-refractory Korean mCRC patients.

The histone deacetylase inhibitor PXD101 increases the efficacy of irinotecan in in vitro and in vivo colon cancer models.

PurposeHistone deacetylase inhibitors (HDACIs), such as PXD101 and suberoylanilide hydroxamic acid, inhibit proliferation and stimulate apoptosis of tumor cells. The enhanced effectiveness of chemotherapy or radiotherapy when combined with HDACIs has been observed in several cancers. In this study, we investigated the antitumor effect of PXD101 combined with irinotecan in colon cancer.MethodsHCT116 and HT29 colon cancer cells for cell viability assay were treated with PXD101 and/or SN-38, the active form of irinotecan. Antitumor effects of HCT116 and HT29 xenografts treated with these combinations were evaluated. [18F]FLT-PET was used to detect early responses to PXD101 and irinotecan in colon cancer.ResultsPXD101 and SN38 possessed dose-dependent antiproliferative activity against HCT116 and HT29 cells and exerted a synergistic effect when used in combination. In xenografted mice, PXD101 in combination with irinotecan dramatically inhibited tumor growth without causing additive toxicity. Apoptotic effects on xenograft tumors were greater with combined treatment than with irinotecan alone. [18F]FLT-PET imaging revealed a 64% decrease in [18F]FLT uptake in tumors of HCT116 xenograft-bearing mice treated with a combination of PXD101 and irinotecan, indicating a decrease in thymidine kinase 1 (TK1) activity. These results were supported by Western blot analyses showing a decrease in tumor thymidine kinase 1 protein levels, suggesting that [18F]FLT-PET can be used to non-invasively detect early responses to these agents.ConclusionsThese data show that PXD101 increases the cytotoxic activity of irinotecan in in vitro and in vivo colon cancer models and suggest these agent combinations should be explored in the treatment of colon cancer.

Upregulation of SPRR3 promotes colorectal tumorigenesis.

Hereditary colorectal cancer develops through a series of well-defined genetic and histological changes. However, elucidation of the canonical pathway based on hereditary colorectal cancer has not provided a clear explanation of the molecular mechanisms of sporadic colorectal cancer. To identify the alterative pathways involved in sporadic colorectal tumorigenesis, we performed gene expression analysis in patients with sporadic colorectal tumors. A comparison analysis of gene expression profiles revealed a pattern of upregulation of small proline rich repeat protein 3 (SPRR3) in tumor samples. SPRR3 has previously been reported to be downregulated in esophageal cancer. However, in the present study, we observed that SPRR3 was strongly upregulated in 31 of 35 samples of sporadic colorectal tumors (88%). We also determined that overexpression of SPRR3 not only accelerates colorectal cancer cell proliferation but also is associated with lymphovascular invasion in colorectal cancer. Moreover, AKT was activated and p53 levels were decreased in cells that overexpressed SPRR3. In contrast to the pattern seen in esophageal cancer, these results suggest that increased expression of SPRR3 is involved in colorectal tumorigenesis.

Decursin chemosensitizes human multiple myeloma cells through inhibition of STAT3 signaling pathway.

Recent reports have indicated that decursin can induce apoptosis, suppress tumor growth, and inhibit angiogenesis. In this experiment, we investigated how decursin could potentiate the cytotoxic effects of bortezomib in human multiple myeloma cells. We found that decursin inhibited cell viability in U266, MM.1S and ARH77 cells, but not in peripheral blood mononuclear cells (PBMC). Decursin-induced apoptosis through the activation of caspase-8, -9, and -3 in U266 cells. This correlated with the down-regulating of cyclin D1, bcl-2, bcl-xL, survivin, and the vascular endothelial growth factor (VEGF), which are all regulated by the activation of signal transducers and the activator of transcription 3 (STAT3). Indeed, decursin inhibited constitutive STAT3 activation through inhibition of the activation of Janus-activated kinase 2 (JAK2) in U266 cells. In addition, decursin inhibited interleukin-6-inducible STAT3 activation in a time-dependent manner in MM.1S cells. Interestingly, decursin significantly potentiated the apoptotic effects of bortezomib in U266 cells. These effects of decursin were correlated with the suppression of constitutive STAT3 activation in U266 cells. Overall, these results suggest that decursin is a novel blocker of STAT3 activation and it may be a potential candidate for overcoming chemo-resistance through suppression of this signaling.

Genetic Polymorphisms of FcγRIIa and FcγRIIIa Are Not Predictive of Clinical Outcomes after Cetuximab plus Irinotecan Chemotherapy in Patients with Metastatic Colorectal Cancer

Objective: The anti-epidermal growth factor receptor monoclonal antibody cetuximab has been shown to be effective in patients with wild-type KRAS metastatic colorectal cancer (mCRC). Fragment C γ receptor (FcγR) polymorphisms may predict the effectiveness of cetuximab, but this has not been established. This study investigated the clinical relevance of FcγR gene polymorphisms and KRAS status in iri-notecan-refractory mCRC patients treated with cetuximab. Methods: The total number of irinotecan-refractory mCRC patients studied was 118. Among them, 117 and 107 patients were screened for KRAS mutations and genetic polymorphisms of FcγRIIa-131H/R and FcγRIIIa-158V/F, respectively. The association of FcγR polymorphisms and KRAS mutations with clinical outcome was analyzed. Results:KRAS mutations were found in 33 patients (27.1%). Wild-type KRAS was associated with a better response rate (p < 0.001), longer progression-free survival (p < 0.001) and longer overall survival (p < 0.001). FcγRIIa H/H, H/R and R/R polymorphisms were observed in 54, 49 and 4 patients, respectively, and FcγRIIIa V/V, V/F and F/F polymorphisms were observed in 6, 65, and 36 patients, respectively. Clinical outcomes were not significantly associated with either FcγRIIa or FcγRIIIa polymorphisms or with combinations of KRAS status and FcγR polymorphisms. Conclusion: The FcγRIIa and FcγRIIIa polymorphisms may not be useful molecular biomarkers for the activity of cetuximab in patients with mCRC.

Ring Finger Protein 149 Is an E3 Ubiquitin Ligase Active on Wild-type v-Raf Murine Sarcoma Viral Oncogene Homolog B1 (BRAF)

Background: BRAF is a downstream effector kinase of Ras. Results: RNF149, a RING finger domain-containing E3 ubiquitin ligase, is one of the several proteins shown to interact with wild-type BRAF by tandem affinity purification. Conclusion: RNF149 induces ubiquitination and subsequent proteasomal degradation of wild-type but not mutant BRAF. Significance: This is the first ubiquitin ligase shown to degrade wild-type BRAF in a proteasome-dependent manner. Members of the RAF family (ARAF, BRAF, and CRAF/RAF-1) are involved in a variety of cellular activities, including growth, survival, differentiation, and transformation. An oncogene encodes BRAF, the function of which is linked to MEK activation. BRAF is the most effective RAF kinase in terms of induction of MEK/ERK activity. However, the mechanisms involved in BRAF regulation remain unclear. In the present work, we used a tandem affinity purification approach to show that RNF149 (RING finger protein 149) interacts with wild-type BRAF. The latter protein is a RING domain-containing E3 ubiquitin ligase involved in control of gene transcription, translation, cytoskeletal organization, cell adhesion, and epithelial development. We showed that RNF149 bound directly to the C-terminal kinase-containing domain of wild-type BRAF and induced ubiquitination, followed by proteasome-dependent degradation, of the latter protein. Functionally, RNF149 attenuated the increase in cell growth induced by wild-type BRAF. However, RNF149 did not bind to mutant BRAF or induce ubiquitination thereof. Thus, we show that RNF149 is an E3 ubiquitin ligase active on wild-type BRAF.

Vorinostat in combination with capecitabine plus cisplatin as a first-line chemotherapy for patients with metastatic or unresectable gastric cancer: phase II study and biomarker analysis

Background:Vorinostat, a histone deacetylase (HDAC) inhibitor, was investigated in combination with capecitabine plus cisplatin (XP) as a first-line chemotherapy for patients with unresectable or metastatic gastric cancer (GC).Methods:Eligible patients received 400 mg vorinostat once daily on days 1–14, 1000 mg m−2 capecitabine twice daily on days 1–14, and 60 mg m−2 cisplatin on day 1 every 3 weeks. Plasma levels of acetyl-H3, HDAC2, and p21 were measured for correlative analysis. The primary end point was the 6-month progression-free survival (PFS) rate. Secondary end points included the response rate, PFS, overall survival (OS), and safety profile.Results:A total of 45 patients with HER2-negative GC were included in this study. The objective response rate was 42%. The median PFS was 5.9 months, and the 6-month PFS rate was 44.4%. The median OS was 12.7 months. Most common grade 3–4 toxicities were neutropenia (41%), fatigue (34%), anorexia (32%), thromboembolism (27%), stomatitis (14%), and thrombocytopenia (11%). High plasma acetyl-H3 and p21 levels were significantly associated with a poor OS (P=0.02 and P=0.03, respectively).Conclusions:Vorinostat-XP is a feasible first-line chemotherapy for patients with advanced GC. However, this trial did not meet its primary end point, and more adverse events were observed in comparison with the historical data of flouropyrimidine–platinium doublet regimens.

8-Hydrocalamenene, Derived from Reynoutria elliptica, Suppresses Constitutive STAT3 Activation, Inhibiting Proliferation and Enhancing Chemosensitization of Human Multiple Myeloma Cells

The identification of the active compounds of herbal medicines and the molecular targets of those compounds is an attractive therapeutic objective. Reynoutria elliptica has been used for the treatment of various inflammatory diseases as a Korean folk remedy. Based on the evidence that anti-inflammatory agents frequently exert antiproliferative activity, we tested two sesquiterpene derivatives, 8-hydrocalamenene (HC) and 8,14-dihydrocalamenene (DHC), for their ability to induce apoptosis and suppress signal transducer and activator of transcription 3 (STAT3) activation in multiple myeloma (MM) U266 cells. We found that HC inhibited cell viability in U266, but not in peripheral blood mononuclear cells. HC exerted significant cytotoxicity and induced substantial subG1-phase arrest and apoptosis as compared with DHC. HC inhibited the expression of gene products involved in antiapoptosis (Bcl-2 and Bcl-xL), proliferation (cyclin D1), and invasion (MMP-9), all of which are known to be regulated by STAT3. Furthermore, HC up-regulated cyclin-dependent kinase inhibitor p21 and induced apoptosis through the activation of caspase-8, -9, and -3 in U266 cells. Interestingly, HC blocked constitutive STAT3 activation through the inhibition of activation of upstream kinases Janus-like kinase 1 (JAK1), JAK2, and c-Src and up-regulated PIAS3. Deletion of STAT3 reversed cytotoxic effects and the down-regulation of cyclin D1 and c-myc by HC in MM cells. Finally, this sesquiterpene significantly synergized the cytotoxic and apoptotic effects of bortezomib in U266 cells. Taken together, these results suggest that HC is a novel blocker of STAT3 activation which may have a potential in the prevention and treatment of MM.

Prognostic impact of fibroblast growth factor receptor 2 gene amplification in patients receiving fluoropyrimidine and platinum chemotherapy for metastatic and locally advanced unresectable gastric cancers

Although Fibroblast growth factor receptor (FGFR) 2 gene amplification and its prognostic significance have been reported in resectable gastric cancers, information on these features remains limited in the metastatic setting. The presence of FGFR2 amplification was assessed in formalin-fixed, paraffin-embedded tissues using a quantitative PCR-based gene copy number assay with advanced gastric cancer cohorts. A total of 327 patients with tumor portion of ≥70% were analyzed for clinical features. Among these patients, 260 who received first-line fluoropyrimidine and platinum chemotherapy were analyzed for survival. Sixteen of 327 patients (4.9%) exhibited FGFR2 amplification. The amplification group showed associations with age <65 years, Borrmann type 4 disease, poor performance status, poorly differentiated histology, extra-abdominal lymph node metastases, and bone metastases. The median overall survival (OS) and progression-free survival (PFS) were found to be 12.7 and 5.8 months, respectively. In univariate analysis, PFS did not differ between amplification and no amplification groups (hazard ratio [HR]=1.34, 95% confidence interval [CI]: 0.78-2.31, p=0.290), although the OS was significantly shorter in the amplification group (HR=1.92, 95% CI: 1.13-3.26, p=0.015). However, multivariate analysis indicated that FGFR2 amplification was not an independent prognostic factor for OS (HR=1.42, 95% CI: 0.77-2.61, p=0.261). Although FGFR2 amplification is associated with poorer OS, it does not appear to be an independent prognostic predictor in patients with advanced gastric cancer treated with palliative fluoropyrimidine and platinum chemotherapy.