Cetuximab in combination with chemoradiotherapy prior to surgery in patients with resectable, locally advanced esophageal carcinoma : a prospective, multicenter phase lb-ll trial of the Swiss Group for Clinical Cancer Research (SAKK 75/06) : 4570

Background: Cetuximab significantly enhances efficacy of radiotherapy and chemotherapy in head and neck cancer. We investigated the safety and feasibility of adding cetuximab to neoadjuvant chemoradiation of locally advanced esophageal cancer. Methods: Pts with resectable, locally advanced squamous cell carcinoma (SCC) or adenocarcinoma (AC) of the thoracic esophagus or gastroesophageal junction (staged by EUS, CT and PET scan) were treated with 2 cycles of induction chemotherapy (docetaxel 75mg/m2, cisplatin 75mg/m2 q3w and weekly cetuximab 250mg/m2), followed by concomitant chemo- immuno-radiation therapy (CIRT: docetaxel 20mg/m2, cisplatin 25mg/m2 and cetuximab 250mg/m2 weekly five times concomitant with 45 Gy radiotherapy in 25 fractions); followed by surgery 4-8 weeks later. The phase I part consisted of 2 cohorts of 7 patients each, without and with docetaxel during CIRT, respectively. Interpatient dose-escalation (adding docetaxel during CIRT) was possible if < 2 out of 7 pts of the 1st cohort experienced limiting toxicity. Having finished the phase 1 part, 13 additional patients were treated with docetaxel-containing CIRT in a phase II part. Pathological response was evaluated according to the Mandard classification. Results: 27 pts from 12 institutions were included. As of today, results from 20 pts are available (cohort 1: 7, cohort 2: 7, phase ll : 6). Median age was 64yrs (range 47-71). 11 AC; 9 SCC. 19 pts (95%) completed CIRT (1 pt stopped treatment during induction therapy due to sepsis). 17 pts underwent resection (no surgery: 1pt for PD, 1pt for cardiac reasons). Grade 3 toxicities during CIRT included anorexia 15%, dysphagia/esophagitis 15%, fatigue 10%, nausea 10%, pruritus 5%, dehydration 5%, nail changes 5% and rash 5% .1 pt suffered from pulmonary embolism. 13 pts (65%, intention-to-treat) showed a complete or near complete pathological remission (cohort 1: 5, cohort 2: 4, phase II: 4). Conclusions: Adding cetuximab to preoperative chemoradiation for esophageal cancer is safe and feasible in a community-based multicenter setting. Antineoplastic activity is encouraging with 65% pathological responders.

Feasibility of radiotherapy or chemoradiotherapy after taxane-based induction chemotherapy for nonoperated locally advanced head and neck squamous cell carcinomas.

To assess the use of radiotherapy (RT) or concurrent chemoradiotherapy (CRT) following taxane-based induction chemotherapy (T-ICT) in locally advanced head and neck squamous cell carcinoma (LAHNSCC) and to evaluate the tolerability of CRT after T-ICT. From 01/2006 to 08/2012, 173 LAHNSCC patients treated as a curative intent by T-ICT, followed by definitive RT/CRT were included in this analysis. There was an 86% objective response (OR) after ICT among 154 evaluable patients. Forty-four patients received less than three cycles (25%) and 20 received only one cycle of T-ICT. The 3-year actuarial overall survival (OS) was 49% and there was no OS difference according to the type of ICT (regimen or number of cycle) or the addition of concurrent CT (cisplatin, carboplatin, or cetuximab) to RT. In multivariate analysis (MVA), clinically involved lymph node (cN+), age more than 60 years, the absence of OR after ICT, and performance status of at least 1 predicted for a decreased OS, with hazard ratios (HR) of 2.8, 2.2, 2.1, and 2, respectively. The 3-year actuarial locoregional control (LRC) and distant control (DC) rates were 52 and 73%, respectively. In MVA, the absence of OR after ICT (HR: 3.2), cN+ (HR: 3), and age more than 60 years (HR: 1.7) were prognostic for a lower LRC whereas cN+ (HR: 4.2) and carboplatin-based T-ICT (HR: 2.9) were prognostic for a lower DC. The number of cycles (≤ 2) received during ICT was borderline significant for DC in the MVA (P=0.08). Among patients receiving less than or equal to three cycles of ICT, higher outcomes were observed in patients who received cisplatin-based T-ICT (vs. carboplatin-based T-ICT) or subsequent CRT (vs. RT). T-ICT in our experience, followed by RT or CRT, raises several questions on the role and type of induction, and the efficacy of CRT over RT. The role of RT or CRT following induction, although feasible in these advanced patients, awaits answers from randomized trials.

Multicenter phase II trial of gefitinib first-line therapy followed by chemotherapy in advanced non-small-cell lung cancer (NSCLC): SAKK protocol 19/03.

BACKGROUND: Gefitinib is active in patients with pretreated non-small-cell lung cancer (NSCLC). We evaluated the activity and toxicity of gefitinib first-line treatment in advanced NSCLC followed by chemotherapy at disease progression. PATIENTS AND METHODS: In all, 63 patients with chemotherapy-naive stage IIIB/IV NSCLC received gefitinib 250 mg/day. At disease progression, gefitinib was replaced by cisplatin 80 mg/m(2) on day 1 and gemcitabine 1250 mg/m(2) on days 1, 8 for up to six 3-week cycles. Primary end point was the disease stabilization rate (DSR) after 12 weeks of gefitinib. RESULTS: After 12 weeks of gefitinib, the DSR was 24% and the response rate (RR) was 8%. Median time to progression (TtP) was 2.5 months and median overall survival (OS) 11.5 months. Never smokers (n = 9) had a DSR of 56% and a median OS of 20.2 months; patients with epidermal growth factor receptor (EGFR) mutation (n = 4) had a DSR of 75% and the median OS was not reached after the follow-up of 21.6 months. In all, 41 patients received chemotherapy with an overall RR of 34%, DSR of 71% and median TtP of 6.7 months. CONCLUSIONS: First-line gefitinib monotherapy led to a DSR of 24% at 12 weeks in an unselected patients population. Never smokers and patients with EGFR mutations tend to have a better outcome; hence, further trials in selected patients are warranted.

Solid-phase synthesis and DNA binding studies of dichloroplatinum(II) conjugates of dicarba analogues of octreotide as a new anticancer drugs

The first dichloroplatinum(II) conjugates of dicarba analogues of octreotide , which is expected to act as a"tumour-targeting device", have been efficiently synthesized following a stepwise solid-phase approach; these compounds emulate the mechanism of cisplatin since they form a 1,2-intrastrand cross-link with two consecutive guanines of an oligonucleotide.

Effect of low-dose chest irradiation before chemotherapy on the rate of local failure in small-cell lung cancer.

PURPOSE: To evaluate the rate of tumor recurrence within the irradiated volume after initial low-dose irradiation of limited-stage small-cell lung cancer (SCLC), to assess the tolerance of a sequential combination of low-dose chest irradiation followed by chemotherapy, and to confirm the responsiveness of limited-stage SCLC to low-dose irradiation. METHODS AND MATERIALS: In this pilot study, 26 patients with limited-stage SCLC were treated by first-line 20-Gy thoracic irradiation followed 3 weeks later by chemotherapy (cisplatin, doxorubicin, and etoposide for six cycles). RESULTS: We present our final results with a median follow-up of surviving patients of 7 years. The response rate to this low-dose irradiation was 83%, with an overall response rate to radiochemotherapy of 96% and a median survival of 21 months. No unexpected early or late toxicity was observed. The rate of initial isolated local failure was 8%, which compares favorably with other published series using higher doses of radiochemotherapy. CONCLUSION: An initial chest irradiation of 20 Gy before chemotherapy could be sufficient to reduce the risk of local failure during the time of survival of patients with limited-stage SCLC. Potential advantages of this treatment may be the prevention of resistance mechanisms to radiotherapy induced by preliminary chemotherapy and a reduced radiation-induced toxicity.

Novel Chemotherapy Combinations in Advanced Gastric Cancer: an Updated Meta-Analysis

Combination chemotherapy is widely accepted for patients with advanced gastric cancer, but uncertainty remains regarding the choice of the regimen. Objectives: To assess the effect of: Comparison 1) irinotecan versus non-irinotecancontaining regimens, comparison 2) docetaxel versus non-docetaxel-containing regimens, comparison 3) regimens including oral 5-FU prodrugs versus intravenous fluoropyrimidines, comparison 4) oxaliplatin versus cisplatin-containing regimens on overall survival. Search Strategy: We searched: Cochrane Central Register of Controlled Trials, MEDLINE, EMBASE, proceedings from ECCO, ESMO, ASCO until December 2009. Selection Criteria: Randomised controlled trials on the above mentioned chemotherapy regimens in advanced or metastatic denocarcinoma of the stomach or GE-junction. Results: The meta-analysis of overall survival for comparison 1) included 4 trials, 640 patients, and results in a HR of 0.86 (95% CI 0.73-1.02) in favour of the irinotecancontaining regimens. For comparison 2) 4 trials with a total of 924 patients have been included in the analysis of overall survival. The resulting HR is 0.93 (95% CI 0.79-1.09) in favour of the docetaxel-containing regimens, with moderate heterogeneity (I2 =7%). For comparison 3 and 4, one major relevant study (Cunningham 2008) could not be included in this meta-analysis after discussion because it included patients with squamous cell cancer of the esophagus as well. Thus, for comparison 3) one relevant study (Kang 2009; 316 patients) comparing capecitabine versus 5-FU in combination with cisplatin is eligible. The resulting HR is 0.85 (95%CI 0.65-1.11) in favour of the oral regimen. For comparison 4) two eligible trials were identified (Al Batran 2008, Popov 2008; 292 patients) with a resulting HR of 0.82 (95% CI 0.47-1.45) in favour of the oxaliplatin-based regimens. For three further trials data is incomplete at present. Conclusions: Chemotherapy combinations including irinotecan, oxaliplatin, docetaxel or oral 5-FU prodrugs are alternative treatment options to cisplatin/5-FU or cisplatin/ 5-FU/anthracycline-combinations, but do not provide significant advantages in overall survival. Supported by: KKS Halle, grant number [BMBF/FKZ 01GH01GH0105]. Disclosure: All authors have declared no conflicts of interest.

The DNA repair protein ALKBH2 mediates temozolomide resistance in human glioblastoma cells.

INTRODUCTION: Glioblastoma multiforme (GBM; World Health Organization astrocytoma grade IV) is the most frequent and most malignant primary brain tumor in adults. Despite multimodal therapy, all such tumors practically recur during the course of therapy, causing a median survival of only 14.6 months in patients with newly diagnosed GBM. The present study was aimed at examining the expression of the DNA repair protein AlkB homolog 2 (ALKBH2) in human GBM and determining whether it could promote resistance to temozolomide chemotherapy. METHODS: ALKBH2 expression in GBM cell lines and in human GBM was determined by quantitative real-time PCR (qRT-PCR) and gene expression analysis, respectively. Drug sensitivity was assessed in GBM cells overexpressing ALKBH2 and in cells in which ALKBH2 expression was silenced by small-interfering (si)RNA. ALKBH2 expression following activation of the p53 pathway was examined by western blotting and qRT-PCR. RESULTS: ALKBH2 was abundantly expressed in established GBM cell lines and human GBM, and temozolomide exposure increased cellular ALKBH2 expression levels. Overexpression of ALKBH2 in the U87 and U251 GBM cell lines enhanced resistance to the methylating agents temozolomide and methyl methanesulfonate but not to the nonmethylating agent doxorubicin. Conversely, siRNA-mediated knockdown of ALKBH2 increased sensitivity of GBM cells to temozolomide and methyl methanesulfonate but not to doxorubicin or cisplatin. Nongenotoxic activation of the p53 pathway by the selective murine double minute 2 antagonist nutlin-3 caused a significant decrease in cellular ALKBH2 transcription levels. CONCLUSION: Our findings identify ALKBH2 as a novel mediator of temozolomide resistance in human GBM cells. Furthermore, we place ALKBH2 into a new cellular context by showing its regulation by the p53 pathway.

Randomized Trial of prophylactic granulocyte colony-stimulating factor during rapid COJEC induction in pediatric patients with high-risk neuroblastoma: the European HR-NBL1/SIOPEN study.

Purpose To reduce the incidence of febrile neutropenia during rapid COJEC (cisplatin, vincristine, carboplatin, etoposide, and cyclophosphamide given in a rapid delivery schedule) induction. In the High-Risk Neuroblastoma-1 (HR-NBL1) trial, the International Society of Paediatric Oncology European Neuroblastoma Group (SIOPEN) randomly assigned patients to primary prophylactic (PP) versus symptom-triggered granulocyte colony-stimulating factor (GCSF; filgrastim). Patients and Methods From May 2002 to November 2005, 239 patients in 16 countries were randomly assigned to receive or not receive PPGCSF. There were 144 boys with a median age of 3.1 years (range, 1 to 17 years) of whom 217 had International Neuroblastoma Staging System (INSS) stage 4 and 22 had stage 2 or 3 MYCN-amplified disease. The prophylactic arm received a single daily dose of 5 μg/kg GCSF, starting after each of the eight COJEC chemotherapy cycles and stopping 24 hours before the next cycle. Chemotherapy was administered every 10 days regardless of hematologic recovery, provided that infection was controlled. Results The PPGCSF arm had significantly fewer febrile neutropenic episodes (P = .002), days with fever (P = .004), hospital days (P = .017), and antibiotic days (P = .001). Reported Common Toxicity Criteria (CTC) graded toxicity was also significantly reduced: infections per cycle (P = .002), fever (P < .001), severe leucopenia (P < .001), neutropenia (P < .001), mucositis (P = .002), nausea/vomiting (P = .045), and constipation (P = .008). Severe weight loss was reduced significantly by 50% (P = .013). Protocol compliance with the rapid induction schedule was also significantly better in the PPGCSF arm shown by shorter time to completion (P = .005). PPGCSF did not adversely affect response rates or success of peripheral-blood stem-cell harvest. Following these results, PPG-GSF was advised for all patients on rapid COJEC induction.

Carcinomes épidermoïdes de l'hypopharynx et du larynx : prise en charge fondée sur les preuves Squamous cell carcinoma of the hypopharynx and larynx: evidence-based care.

Les carcinomes épidermoïdes de l'hypopharynx et du larynx peuvent être traités par chirurgie et/ou radiothérapie en fonction de la taille tumorale. Pour les petites tumeurs, les résultats sont équivalents. Pour les tumeurs localement avancées, l'approche chirurgicale est mutilante et nécessite une (pharyngo)laryngectomie totale. La chimioradiothérapie exclusive a montré tout son intérêt mais au prix de séquelles tardives. Dans le but de diminuer ces séquelles et les mutilations, la chimiothérapie d'induction par cisplatine, docétaxel et 5FU à visée de préservation d'organe devient le standard de traitement mais il manque des études solides de comparaison de cette approche avec la chimioradiothérapie exclusive. Il n'est pas possible de conclure quant à la supériorité d'un schéma en survie globale. Quand la chimiothérapie d'induction est choisie, les modalités de potentialisation éventuelle de la radiothérapie ne sont pas établies. Squamous cell carcinomas of larynx and hypopharynx can be treated by surgery and/or radiotherapy according to tumor size. For small tumors, the results are similar. For locally advanced tumors, the surgical approach is mutilating and requires a total (pharyngo)laryngectomy. Exclusive chemoradiotherapy has shown its interest at the cost of late sequelae. In order to reduce these effects and mutilation, induction chemotherapy with cisplatin, docetaxel and 5FU for organ preservation becomes the standard treatment but there are no solid studies comparing this approach with the exclusive chemoradiotherapy. And it is not possible to conclude as to the superiority of a scheme in terms of overall survival. When chemotherapy is chosen, the modalities of any potentiation of radiation have not been yet established.

Neoadjuvant chemotherapy and radiotherapy followed by surgery in selected patients with stage IIIB non-small-cell lung cancer: a multicentre phase II trial.

BACKGROUND: Stage IIIB non-small-cell lung cancer (NSCLC) is usually thought to be unresectable, and is managed with chemotherapy with or without radiotherapy. However, selected patients might benefit from surgical resection after neoadjuvant chemotherapy and radiotherapy. The aim of this multicentre, phase II trial was to assess the efficacy and toxicity of a neoadjuvant chemotherapy and radiotherapy followed by surgery in patients with technically operable stage IIIB NSCLC. METHODS: Between September, 2001, and May, 2006, patients with pathologically proven and technically resectable stage IIIB NSCLC were sequentially treated with three cycles of neoadjuvant chemotherapy (cisplatin with docetaxel), immediately followed by accelerated concomitant boost radiotherapy (44 Gy in 22 fractions) and definitive surgery. The primary endpoint was event-free survival at 12 months. Efficacy analyses were done by intention to treat. This trial is registered with ClinicalTrials.gov, number NCT00030810. FINDINGS: 46 patients were enrolled, with a median age of 60 years (range 28-70). 13 (28%) patients had N3 disease, 36 (78%) had T4 disease. All patients received chemotherapy; 35 (76%) patients received radiotherapy. The main toxicities during chemotherapy were neutropenia (25 patients [54%] at grade 3 or 4) and febrile neutropenia (nine [20%]); the main toxicity after radiotherapy was oesophagitis (ten patients [29%]; nine grade 2, one grade 3). 35 patients (76%) underwent surgery, with pneumonectomy in 17 patients. A complete (R0) resection was achieved in 27 patients. Peri-operative complications occurred in 14 patients, including two deaths (30-day mortality 5.7%). Seven patients required a second surgical intervention. Pathological mediastinal downstaging was seen in 11 of the 28 patients who had lymph-node involvement at enrolment, a complete pathological response was seen in six patients. Event-free survival at 12 months was 54% (95% CI 39-67). After a median follow-up of 58 months, the median overall survival was 29 months (95% CI 16.1-NA), with survival at 1, 3, and 5 years of 67% (95% CI 52-79), 47% (32-61), and 40% (24-55). INTERPRETATION: A treatment strategy of neoadjuvant chemotherapy and radiotherapy followed by surgery is feasible in selected patients. Toxicity is considerable, but manageable. Survival compares favourably with historical results of combined treatment for less advanced stage IIIA disease. FUNDING: Swiss Group for Clinical Cancer Research (SAKK) and an unrestricted educational grant by Sanofi-Aventis (Switzerland).

Benefit of anti-HER2-coated paclitaxel-loaded immuno-nanoparticles in the treatment of disseminated ovarian cancer: Therapeutic efficacy and biodistribution in mice.

The benefit of polymeric immuno-nanoparticles (NPs-Tx-HER), consisting of paclitaxel (Tx)-loaded nanoparticles coated with anti-HER2 monoclonal antibodies (Herceptin, trastuzumab), in cancer treatment was assessed in a disseminated xenograft ovarian cancer model induced by intraperitoneal inoculation of SKOV-3 cells overexpressing HER2 antigens. The study was focused on the evaluation of therapeutic efficacy and biodistribution of NPs-Tx-HER compared to other Tx formulations. The therapeutic efficacy was determined by two methods: bioluminescence imaging and survival rate. The treatment regimen consisted in an initial dose of 20mg/kg Tx administered as 10mg/kg intravenously (IV) and 10mg/kg intraperitonealy (IP), followed by five alternative IP and IV injections of 10mg/kg Tx every 3 days. The bioluminescence study has clearly shown the superior anti-tumor activity of NPs-Tx-HER compared to free Tx. As a confirmation of these results, a significantly longer survival of mice was observed for NPs-Tx-HER treatment compared to free Tx, Tx-loaded nanoparticles coated with an irrelevant mAb (Mabthera, rituximab) or Herceptin alone, indicating the potential of immuno-nanoparticles in cancer treatment. The biodistribution pattern of Tx was assessed on healthy and tumor bearing mice after IV or IP administration. An equivalent biodistribution profile was observed in healthy mice for Tx encapsulated either in uncoated nanoparticles (NPs-Tx) or in NPs-Tx-HER. No significant difference in Tx biodistribution was observed after IV or IP injection, except for a lower accumulation in the lungs when NPs were administered by IP. Encapsulated Tx accumulated in the organs of the reticulo-endothelial system (RES) such as the liver and spleen, whereas free Tx had a non-specific distribution in all tested organs. Compared to free Tx, the single dose injection (IV or IP) of encapsulated Tx in mice bearing tumors induced a higher tumor accumulation. However, no difference in overall tumor accumulation between NPs-Tx-HER and NPs-Tx was observed. In conclusion, the encapsulation of Tx into NPs-Tx-HER immuno-nanoparticles resulted in an improved efficacy of drug in the treatment of disseminated ovarian cancer overexpressing HER2 receptors.

Feasibility and efficacy of accelerated weekly concomitant boost postoperative radiation therapy combined with concomitant chemotherapy in patients with locally advanced head and neck cancer.

BACKGROUND: The aim of this study was to assess feasibility and efficacy of weekly concomitant boost accelerated postoperative radiation therapy (PORT) with concomitant chemotherapy (CT) in patients with locally advanced head and neck cancer (LAHNC). METHODS AND MATERIALS: Conformal or intensity-modulated 66-Gy RT was performed in 5.5 weeks in 40 patients. Cisplatin was given at days 1, 22, and 43. Median follow-up was 36 months. RESULTS AND DISCUSSION: Grade 3 mucositis, dysphagia, and erythema was observed in ten (25%), nine (23%), and six (13%) patients, respectively. Grade 3 or more anemia was observed in two (6%) patients, and leukopenia in five (13%) patients. No grade 3 or 4 thrombocytopenia was observed. Grade 3 nephrotoxicity was observed in one patient (3%). No treatment-related mortality was observed. Grade 2 or more xerostomia and edema were observed in ten (25%) and one (3%) patient, respectively. Locoregional relapse occurred in eight patients, and seven patients developed distant metastases. Median time to locoregional relapse was 6 months. Three-year overall, disease-free survival, and locoregional control rates were 63%, 62%, and 81%, respectively. Multivariate analysis revealed that the only prognostic factor was nodal status. CONCLUSION: Reducing overall treatment time using accelerated PORT/CT by weekly concomitant boost (six fractions per week) combined with concomitant cisplatin CT is easily feasible with acceptable morbidity.

The role of endogenous and exogenous RasGAP-derived fragment N in protecting cardiomyocytes from peroxynitrite-induced apoptosis.

Peroxynitrite (PN) is a potent nitrating and oxidizing agent generated during various pathological situations affecting the heart. The negative effects of PN result, at least in part, from its ability to activate caspases and apoptosis. RasGAP is a ubiquitously expressed protein that is cleaved sequentially by caspase-3. At low caspase-3 activity, RasGAP is cleaved into an N-terminal fragment, called fragment N, that protects cells by activating the Ras/PI3K/Akt pathway. At high caspase-3 activity, fragment N is further cleaved and this abrogates its capacity to stimulate the antiapoptotic Akt kinase. Fragment N formation is crucial for the survival of cells exposed to a variety of stresses. Here we investigate the pattern of RasGAP cleavage upon PN stimulation and the capacity of fragment N to protect cardiomyocytes. PN did not lead to sequential cleavage of RasGAP. Indeed, PN did not allow accumulation of fragment N because it induced its rapid cleavage into smaller fragments. No situations were found in cells treated with PN in which the presence of fragment N was associated with survival. However, expression of a caspase-resistant form of fragment N in cardiomyocytes protected them from PN-induced apoptosis. Our results indicate that the antiapoptotic pathway activated by fragment N is effective at inhibiting PN-induced apoptosis (as seen when cardiomyocytes express a capase-3-resistant form of fragment N) but because fragment N is too transiently generated in response to PN, no survival response is effectively produced. This may explain the marked deleterious consequences of PN generation in various organs, including the heart.

Revisiting G3BP1 as a RasGAP binding protein: sensitization of tumor cells to chemotherapy by the RasGAP 317-326 sequence does not involve G3BP1.

RasGAP is a multifunctional protein that controls Ras activity and that is found in chromosomal passenger complexes. It also negatively or positively regulates apoptosis depending on the extent of its cleavage by caspase-3. RasGAP has been reported to bind to G3BP1 (RasGAP SH3-domain-binding protein 1), a protein regulating mRNA stability and stress granule formation. The region of RasGAP (amino acids 317-326) thought to bind to G3BP1 corresponds exactly to the sequence within fragment N2, a caspase-3-generated fragment of RasGAP, that mediates sensitization of tumor cells to genotoxins. While assessing the contribution of G3BP1 in the anti-cancer function of a cell-permeable peptide containing the 317-326 sequence of RasGAP (TAT-RasGAP₃₁₇₋₃₂₆), we found that, in conditions where G3BP1 and RasGAP bind to known partners, no interaction between G3BP1 and RasGAP could be detected. TAT-RasGAP₃₁₇₋₃₂₆ did not modulate binding of G3BP1 to USP10, stress granule formation or c-myc mRNA levels. Finally, TAT-RasGAP₃₁₇₋₃₂₆ was able to sensitize G3BP1 knock-out cells to cisplatin-induced apoptosis. Collectively these results indicate that G3BP1 and its putative RasGAP binding region have no functional influence on each other. Importantly, our data provide arguments against G3BP1 being a genuine RasGAP-binding partner. Hence, G3BP1-mediated signaling may not involve RasGAP.

A WXW Motif Is Required for the Anticancer Activity of the TAT-RasGAP317-326 Peptide.

TAT-RasGAP317-326, a cell-permeable 10-amino acid-long peptide derived from the N2 fragment of p120 Ras GTPase-activating protein (RasGAP), sensitizes tumor cells to apoptosis induced by various anticancer therapies. This RasGAP-derived peptide, by targeting the deleted in liver cancer-1 (DLC1) tumor suppressor, also hampers cell migration and invasion by promoting cell adherence and by inhibiting cell movement. Here, we systematically investigated the role of each amino acid within the RasGAP317-326 sequence for the anticancer activities of TAT-RasGAP317-326. We report here that the first three amino acids of this sequence, tryptophan, methionine, and tryptophan (WMW), are necessary and sufficient to sensitize cancer cells to cisplatin-induced apoptosis and to reduce cell migration. The WMW motif was found to be critical for the binding of fragment N2 to DLC1. These results define the interaction mode between the active anticancer sequence of RasGAP and DLC1. This knowledge will facilitate the design of small molecules bearing the tumor-sensitizing and antimetastatic activities of TAT-RasGAP317-326.