Kyu-pyo Kim

The MEK1/2 inhibitor AS703026 circumvents resistance to the BRAF inhibitor PLX4032 in human malignant melanoma cells.

Background:Although inhibitors of the proto-oncogene BRAF have shown excellent antitumor activity against malignant melanoma, their efficacy is limited by the development of acquired drug resistance, a process in which reactivation of MAP kinase (MEK) is known to play an important role. In this study, we evaluated the efficacy of AS703026, a new MEK inhibitor, in BRAF inhibitor–resistant melanoma cell lines. Methods:Two melanoma cells lines, RPMI-7951 and SK-MEL5, harboring an activating mutation of BRAF (V600E) were treated with the BRAF inhibitor PLX4032 to select a BRAF inhibitor–resistant cell line for further study. Cell viability assay was determined with MTS [3-(4,5-dimethylthiazol-2-yl)-5-(3-carboxymethoxyphenyl)-2-(4-sulfophenyl)-2H-tetrazolium] assay and trypan blue exclusion method; apoptosis assay was performed by annexin-V staining. Knockdown of BRAF was investigated by small interfering RNA. Results:RPMI-7951 cells exhibited an increased sensitivity to combined treatment with PLX4032 and AS703026 compared to either drug alone. Consistent with this, the combination of PLX4032 and AS703026 significantly induced apoptosis, whereas each drug used alone did not, as demonstrated by a flow cytometric analysis of annexin-V/propidium iodide–stained cells and Western blot analysis of cleaved caspase-3. Notably, immunoblot analyses also showed a depletion of phosphorylated-ERK with combined drug treatment. In addition, AS703026 synergized with small interfering RNA–mediated downregulation of BRAF to produce results similar to those of combined treatment with PLX4032 and AS703026. Conclusions:Our results suggest that combined treatment with AS703026 and a BRAF inhibitor overcomes the resistance to BRAF inhibitors in malignant melanoma cells harboring a mutant form of BRAF.

Second-line cetuximab⁄irinotecan versus oxaliplatin⁄ fluoropyrimidines for metastatic colorectal cancer with wild-type KRAS

The goal of the present study was to compare the efficacy of the combination of cetuximab and irinotecan to the combination of oxaliplatin and fluoropyrimidines as second‐line chemotherapy in patients with irinotecan‐refractory and oxaliplatin‐naïve metastatic colorectal cancer (mCRC) harboring wild‐type KRAS. The study included 120 patients with mCRC who had progressed after irinotecan‐containing first‐line chemotherapy and were never treated with oxaliplatin; 40 patients with wild‐type KRAS were accrued prospectively in the experimental arm (arm A), and 80 patients accrued retrospectively were divided into control arms B (n = 46) and C (n = 34) according to KRAS genotype. Second‐line treatments consisted of cetuximab plus irinotecan for arm A, and oxaliplatin plus either 5‐fluorouracil (FOLFOX) or capecitabine (CapeOX) for the control arms. The median progression‐free survival (PFS) was 8.3, 5.8 and 3.9 months, for arms A, B and C, respectively, with statistical significance favoring arm A (P = 0.007). Differences in overall survival did not reach statistical significance (18.3 vs 12.6 vs 12.9, P = 0.138), although there was a trend toward longer overall survival in arm A. In terms of benefit from oxaliplatin‐containing regimens either as second‐line or third‐line therapy, the median PFS was 5.0 months in arms B and C as second‐line therapy, and 4.0 months in arm A as third‐line therapy, with no statistical significance (P = 0.385). Second‐line cetuximab plus irinotecan is a valid treatment strategy for mCRC patients with irinotecan‐refractory and oxaliplatin‐naïve tumors harboring wild‐type KRAS. Oxaliplatin‐containing chemotherapy resulted in equivalent PFS both as a second‐line and a third‐line therapy, enabling delay of the administration of FOLFOX and CapeOX until subsequent treatment cycles.

SAHA, an HDAC inhibitor, overcomes erlotinib resistance in human pancreatic cancer cells by modulating E-cadherin

Pancreatic cancer is one of the most lethal cancers and remains a major unsolved health problem. Less than 20xa0% of patients are surgical candidates, and the median survival for non-resected patients is approximately 3 to 4xa0months. Despite the existence of many conventional cancer therapies, few targeted therapies have been developed for pancreatic cancer. Combination therapy using erlotinib and gemcitabine is an approved standard chemotherapy for advanced pancreatic cancer, but it has marginal therapeutic benefit. To try to improve the therapeutic outlook, we studied the efficacy of another combination treatment and the relevance to E-cadherin in human pancreatic cancer cells. We treated two human pancreatic cancer cell lines with the histone deacetylase inhibitor (HDACi) SAHA. Interestingly, in these Panc-1 and Capan1 cells, we observed that the expression levels of E-cadherin and phosphorylated EGFR were gradually upregulated after treatment with SAHA. Furthermore, these cells underwent induced cell death after exposure to the combination treatment of SAHA and erlotinib. In Panc-1 cells, overexpression of E-cadherin activated the phosphorylation of EGFR and increased the cell sensitivity to erlotinib. In Capan1 cells, knocking down E-cadherin decreased the expression of phosphorylated EGFR, and these cells did not respond to erlotinib. Therefore, we demonstrated the efficacy of the combined treatment with SAHA and erlotinib in human pancreatic cancer cells, and we determined that the increased efficacy was due, at least in part, to the effects of SAHA on the expression of E-cadherin. Our studies suggest that E-cadherin may be a potent biomarker for pancreatic cancer.

A Trial Activation Initiative to Accelerate Trial Opening in an Academic Medical Center

Delays in trial opening should be considered critical for the sake of not only the sponsor but the patients, as they may result in inequities of care. The Asan Medical Center, in Seoul, Korea, implemented a trial activation initiative in July 2012, in an aim to expedite the trial initiation timeline. Time intervals between trial initiation steps and the rate of institutional review board (IRB) and clinical trial agreement (CTA) parallel submission were assessed. A higher rate of parallel IRB and CTA submissions was observed after initiative implementation (25.5% vs 52.3%; P < .001). Initiative applications were shown to significantly accelerate the median trial opening time, from 114 to 81 days (P < .001). Strategic processing of parallel submissions greatly shortened the median time required for trial initiation from 117 to 61 days compared with sequential submissions (P < .001). A trial activation initiative including parallel IRB and CTA submissions is an effective tool for accelerating trial commencements.

Increased incidence of chemoport-related thrombosis in patients with colorectal cancer receiving bevacizumab: A single-institutional experience

Objective Chemoport-related thrombosis (CRT) is a serious complication that causes morbidities and interrupts administration of intravenous cancer therapy. We investigated the incidence and risk of CRT in colorectal cancer (CRC) patients treated with bevacizumab (BEV). Methods We retrospectively reviewed 1,534 CRC patients who received chemotherapy with or without BEV using a chemoport between 2014 and 2016. Results The participants had a median age of 58 (18−85) years, and 60.3% were male. All participants were stratified into three groups: adjuvant chemotherapy (AC) (n=670), palliative chemotherapy (PC) without BEV (n=356), and PC with BEV (n=508). The median follow-up was 20.19 (interquartile range, 14.07−27.19) months. CRT occurred in 3.8% of all patients; incidence of symptomatic and asymptomatic CRT was 2.9% and 0.9%, respectively. CRT occurred more in patients with BEV (5.7%) than in patients without BEV (2.9%, P=0.008). The cumulative incidence of CRT in patients administered PC with BEV was significantly higher than that in those administered AC (P=0.011) and there was a trend toward increased CRT in patients administered PC with BEV compared with those administered PC without BEV (P=0.044). Multivariate analysis found that BEV treatment was the only variable that was significantly associated with CRT (hazard ratio, 2.06; 95% confidence interval, 1.24−3.43; P=0.006). Conclusions BEV treatment was significantly associated with increased incidence of CRT in CRC patients.

Process Innovation Improves Trial Operation Efficiency

Background: Despite the fact that unaddressed delays in clinical trial operation could severely compromise the overall effort invested, there seems to be a lack of concerted effort in reforming such delays. This study evaluated the composite effect of initiatives in reforming trial operation efficiency. Methods: A high-volume academic medical center in Korea has implemented various initiatives to improve the trial operation efficiency by expediting times from institutional review board (IRB) submission to approval, from IRB submission to trial open for subject enrollment, and from trial open to first patient-in. The initiatives include implementation of the protocol preliminary review, parallel processing of the clinical trial agreement review in line with the protocol submission to the IRB, and involvement of project manager for operational risk management. Times from IRB submission to approval, from IRB submission to trial open, and from trial open to first patient-in before and after implementation of initiatives were compared. Results: The median time required in IRB approval was meaningfully shorter in the postinitiative group (19 vs 14 days; P < .001). The median times from IRB submission to trial open for subject enrollment and from trial open to first patient-in were reduced significantly in the postinitiative group (trial open: 25 vs 18 days, P < .001; first patient-in: 111.5 vs 100 days, P = .014). Conclusions: The initiatives were effective in reforming trial operational efficiency. Additional studies to address the cause of operational delay and modifiable factors influencing subject enrollment are needed to further improve operational efficiency.

Abstract C276: Ruxolitinib induces apoptotic cell death through the suppression of pJAK1 in human colon cancer cells.

Janus kinase (JAK) is one of the main upstream activators of signal transducers and activators of transcription (STAT) that are constitutively activated in various malignancies and are associated with cell growth, survival, and carcinogenesis. Here, we investigated to role of JAKs in colorectal cancer in order to develop effective therapeutic targets for ruxolitinib, which is the first JAK1/2 inhibitor to be approved by FDA. After examining the basal expression levels of phospho-JAK1 and phospho-JAK2, we measured the effects of ruxolitinib on the phosphorylation of JAK1/2 using western blot analysis. Cell viability was determined using the trypan blue exclusion assay. The cell death mechanism was identified by the activation of caspase 3 using western blot and annexin V staining. The basal levels of phospho-JAK1 and phospho-JAK2 were cancer cell type dependent. Colorectal cancer cell lines that phosphorylate both JAK1 and JAK2 include DLD-1 and RKO. Ruxolitinib inactivates both JAK1 and JAK2 in DLD-1 cells but inactivates only JAK1 in RKO cells. Cell death was proportional to the inactivation of JAK1 but not JAK2. Ruxolitinib causes caspase-dependent cell death, which is prevented by treatment with z-VAD. The inhibition of JAK1 phosphorylation seemed sufficient to allow ruxolitinib-mediated apoptosis. JAK1 is a key molecule that is involved in colon cancer cell survival and the inhibition of JAK1 by ruxolitinib results in caspase-dependent apoptosis in colorectal cancer cells. The use of selective JAK1 inhibitors could be an attractive therapy against colorectal cancer, but further clinical investigations are needed to test this possibility. Citation Information: Mol Cancer Ther 2013;12(11 Suppl):C276. Citation Format: Ho Jung An, Eun Kyoung Choi, Jin-Sun Kim, Seung-Woo Hong, Jai-Hee Moon, Jae-Sik Shin, Seung-Hee Ha, Kyu-Pyo Kim, Yong Sang Hong, Jae-Lyun Lee, Eun Kyung Choi, Jung Shin Lee, Dong-Hoon Jin, Tae Won Kim. Ruxolitinib induces apoptotic cell death through the suppression of pJAK1 in human colon cancer cells. [abstract]. In: Proceedings of the AACR-NCI-EORTC International Conference: Molecular Targets and Cancer Therapeutics; 2013 Oct 19-23; Boston, MA. Philadelphia (PA): AACR; Mol Cancer Ther 2013;12(11 Suppl):Abstract nr C276.

Abstract B30: Identification of new regulator in p53-mediated cellular senescence

The downstream events and target genes of p53 in senescence responses are not fully understood. Here, we identify a novel regulator, A-core gene, in p53-mediated cellular senescence. Overexpression of A-core in p53-deficient mouse embryonic fibroblasts (MEFs) accelerates senescence, whereas A-core gene knockdown by small interfering RNA (siRNA) leads to escape from p53-mediated senescence in p53-expressing MEFs. A-core overexpression also increased intracellular levels of reactive oxygen species (ROS). The ROS inhibitor N-acetyl-L-cysteine rescued A-core overexpression-induced senescence. Surprisingly, the elevated levels of ROS that accompanied A-core overexpression were paralleled by an increase in p21 expression. siRNA-mediated knockdown of p21 in A-core overexpressing MEFs abrogated the A-core-dependent increase in ROS levels, indicating that A-core acts through p21 induction and subsequent ROS elevation to trigger senescence. In addition, expression of the cell proliferation-related proteins cyclin E and B was decreased after A-core expression. Collectively, these results suggest that A-core is a downstream target of p53 that is sufficient to induce p21 expression and ROS production, and is necessary for p53-mediated senescence.nnCitation Format: Jae-Sik Shin, Seung-Woo Hong, Dae-Hee Lee, Jai-Hee Moon, Jeong Eun Kim, Yong Sang Hong, Kyu-pyo Kim, Jae-Lyun Lee, Eun Kyung Choi, Jung Shin Lee, Dong-Hoon Jin, Tae Won Kim. Identification of new regulator in p53-mediated cellular senescence. [abstract]. In: Proceedings of the Third AACR International Conference on Frontiers in Basic Cancer Research; Sep 18-22, 2013; National Harbor, MD. Philadelphia (PA): AACR; Cancer Res 2013;73(19 Suppl):Abstract nr B30.