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Supplementary Figure S3 shows a heatmap of gene expression in the scale of log2 fold ratio between pre- and on-treatment tumor samples. The gene expression was obtained using the formula for a gene g: 2^[20-CT_g+HK]/1000 where CT is the cycle threshold used to detect the gene g. HK is the average over the cycle thresholds used to detect the three housekeeping genes: GUSB, PPIB, and PGK1. The columns of the heatmap represent the 11 target genes. The rows are the five patients labeled with their mutation status. The label is missing if a gene test was not done or not available. Abbreviation: RT-PCR, reverse transcriptase polymerase chain reaction.

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Background We report a Phase 1 study of LY3076226, an antibody–drug conjugate composed of human IgG1 monoclonal antibody against the human FGFR3 attached with a cleavable linker to the maytansine derivative DM4 in patients with advanced or metastatic cancer. Methods This study was comprised of two parts: (A) dose escalation in patients with advanced or metastatic cancer and (B) dose expansion in patients with urothelial carcinoma with locally determined FGFR3 alterations. The dose range of LY3076226 tested was 0.2–5.0 mg/kg as an intravenous infusion on Day 1 of each 21-day cycle. The primary objective was to determine a recommended phase 2 dose (RP2D). Results Twenty-five patients were enrolled (Part A: 22, Part B: 3) and received ≥ 1 dose of LY3076226. No dose-limiting toxicities were reported. LY3076226 was generally well tolerated; most of the toxicities were Grade 1 or 2. Two patients experienced treatment-related Grade 3 toxicity (embolism and decreased platelet count). Four patients experienced serious adverse events (not treatment-related), all in Part A. Dose-proportional exposure was observed, with an estimated half-life of 2–7 days. No responses were seen with LY3076226 treatment. Stable disease persisting for > 6 months was observed in 1 patient receiving 3.2 mg/kg of LY3076226. Conclusion The study demonstrates acceptable safety and tolerability of LY3076226 up to the 5.0 mg/kg dose. Recruitment was stopped due to pipeline prioritization. Dose escalation of LY3076226 beyond 5.0 mg/kg in patients with advanced tumors may be possible. The trial was registered on August 19, 2015 under identifier NCT02529553 with ClinicalTrials.gov.

SummaryBACKGROUND LY3023414 is a selective, ATP competitive inhibitor of class I PI3K isoforms, mTORC1/2 and DNA-PK. A Phase 1 dose escalation, 200 mg twice daily (BID) of LY3023414 was the determined recommended phase 2 dose (RP2D). We report the antitumor activity and safety of LY3023414 monotherapy in patients with advanced mesothelioma.METHODS Patients enrolled had advanced malignant pleural or peritoneal mesothelioma with measurable disease, ECOG PS 0–1, were refractory or ineligible to receive standard therapies. Patients received LY3023414 200 mg BID. This dose expansion cohort is intended to evaluate preliminary antitumor activity of LY3023414 by overall response rate. Safety, tolerability and pharmacokinetics were assessed. Biomarkers associated with treatment response was an exploratory endpoint. RESULTS Forty-two patients received LY3023414 for a median duration of 11.2 weeks (range: 1.1–53.0). One patient had a confirmed partial response (PR) (ORR 2.4%). Three patients had an unconfirmed PR. Seventeen patients had stable disease (SD) (DCR 43%). Most common adverse events (AEs) included fatigue (43%), nausea (43%), decreased appetite (38%), vomiting (33%), and diarrhea (29%). AEs were mostly mild or moderate. Grade ≥ 3 AEs were reported for 21% of patients with fatigue as the most frequent event (10%). Alterations of BAP1 were identified in 11/19 patients as the most common molecular aberration, followed by SETD2 and NF2 alterations. No obvious pattern of genetic changes/mutations in single genes or pathways was associated with anti-tumor activity. CONCLUSION LY3023414 monotherapy (200 mg BID) demonstrated an acceptable and manageable safety profile with limited single-agent activity in patients with advanced mesothelioma. ClinicalTrials.gov identifier: NCT01655225; Date of registration: 19 July 2012.

Background: KRAS G12C mutations are recurrent oncogenic events in patients (pts) with NSCLC, CRC, and other tumors, and are found in ~14% of NSCLC and 5% of CRC. While KRAS G12C inhibitors have demonstrated activity in pts, overall efficacy may be limited by incomplete target occupancy. LY3537982 is a novel, orally bioavailable, highly selective, and potent inhibitor of the KRAS G12C protein with the potential to deliver >90% target occupancy in pts. In preclinical studies, LY3537982 demonstrated dose-dependent tumor growth inhibition in vivo as a single agent in a KRAS G12C NSCLC PDX model, and robust tumor regression in combination with other agents in vivo in a KRAS G12C sensitive NSCLC model.1 Methods: LOXO-RAS-20001 is an open-label, multi-center, first-in-human Phase 1 study of oral LY3537982 in pts with KRAS G12C-mutant advanced solid tumors. This study consists of 2 parts: Phase 1a dose escalation to evaluate LY3537982 monotherapy and Phase 1b dose expansion to evaluate both LY3537982 monotherapy and in combination. Dose escalation will follow a modified toxicity probability interval-2 (mTPI-2) method, allowing for backfill to previously cleared dose levels that demonstrate therapeutically relevant exposures or direct evidence of clinical activity. DLT evaluation period will be 21 days. The primary objective of Phase 1a is to determine the LY3537982 recommended phase 2 dose (RP2D). Part 1b will enroll pts into dose expansion cohorts based on tumor type (NSCLC, CRC, other solid tumors) and prior treatment including KRAS G12C inhibitor refractory NSCLC. Key objectives of Phase 1b are to determine the safety and tolerability of LY3537982 monotherapy, and in combination with various agents: abemaciclib, erlotinib, cetuximab, an investigational ERK inhibitor (LY3214996), an investigational Aurora A kinase inhibitor (LY3295668), and an anti-PD1 antibody. Key secondary objectives include determining the pharmacokinetic properties, and antitumor activity of LY3537982 based on overall response rate (ORR), progression-free survival (PFS), time to response (TTR), and duration of response (DOR) per RECIST v1.1. Eligible pts must have measurable disease per RECIST v1.1, have a KRAS G12C mutation in tumor tissue or ctDNA, have locally advanced, unresectable and/or metastatic cancer per disease specific criteria, and be appropriate candidates for experimental therapy or refused available therapy. Additionally, pts must be ≥18 years old, have ECOG PS of 0-1, and have adequate organ function. Key exclusion criteria include presence of serious cardiac conditions, interstitial lung disease, symptomatic CNS malignancy, symptomatic CNS metastasis, or carcinomatous meningitis. The trial is currently enrolling patients (NCT04956640). References: 1. Peng S-B, et al. 2021 Cancer Res 81(13 Suppl):1259. Citation Format: Natraj Reddy Ammakkanavar, Justin Call, Toshio Shimizu, Yasutoshi Kuboki, Shiyao Liu, Melinda D. Willard, Michael Axelson, Rebecca S. Heist, Amita Patnaik. A first-in-human phase 1 study of LY3537982, a novel, highly selective and potent KRAS G12C inhibitor in patients with KRAS G12C mutant advanced solid tumors (trial in progress) [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr CT202.

Background We report a Phase 1 study of LY3076226, an antibody-drug conjugate composed of human IgG1 monoclonal antibody against the human FGFR3 attached with a cleavable linker to the maytansine derivative DM4 in patients with advanced or metastatic cancer. Methods This study was comprised of two parts: (A) dose escalation in patients with advanced or metastatic cancer and (B) dose expansion in patients with urothelial carcinoma with locally determined FGFR3 alterations. The dose range of LY3076226 tested was 0.2-5.0 mg/kg as an intravenous infusion on Day 1 of each 21-day cycle. The primary objective was to determine a recommended phase 2 dose (RP2D). Results Twenty-five patients were enrolled (Part A: 22, Part B: 3) and received ≥ 1 dose of LY3076226. No dose-limiting toxicities were reported. LY3076226 was generally well tolerated; most of the toxicities were Grade 1 or 2. Two patients experienced treatment-related Grade 3 toxicity (embolism and decreased platelet count). Four patients experienced serious adverse events (not treatment-related), all in Part A. Dose-proportional exposure was observed, with an estimated half-life of 2-7 days. No responses were seen with LY3076226 treatment. Stable disease persisting for 6 months was observed in 1 patient receiving 3.2 mg/kg of LY3076226. Conclusion The study demonstrates acceptable safety and tolerability of LY3076226 up to the 5.0 mg/kg dose. Recruitment was stopped due to pipeline prioritization. Dose escalation of LY3076226 beyond 5.0 mg/kg in patients with advanced tumors may be possible. The trial was registered on August 19, 2015 under identifier NCT02529553 with ClinicalTrials.gov.

The phase I study characterized the safety, pharmacokinetics, anti-tumor activity, and recommended phase II dose/schedule of LY3164530 in patients with advanced or metastatic cancer. Patients received LY3164530 on days 1 and 15 (Schedule 1: 300, 600, 1000, and 1250 mg) or Days 1, 8, 15, and 22 (Schedule 2: 500 and 600 mg) of each 28 days cycle. Dose escalation used a modified toxicity probability interval model. Dose escalation defined a maximum tolerated dose (MTD) of 1000 mg on Schedule 1 and 500 mg on Schedule 2. Treatment-emergent adverse events related to study treatment were consistent with epidermal growth factor receptor (EGFR) inhibition and included maculopapular rash/dermatitis acneiform (83%, Grade 3/4 17%), hypomagnesemia (55%, Grade 3/4 7%), paronychia (35%), fatigue (28%, Grade 3/4 3%), skin fissures (24%), and hypokalemia (21%, Grade 3/4 7%). Partial response was achieved in three patients on Schedule 2 with colorectal cancer (n = 2) or squamous cell cancer. Overall response rate (ORR) was 10.3%, disease control rate (ORR + stable disease [SD]) was 51.7 and 17.2% of patients had SD ≥ 4 months. The in vivo stability of the bispecific antibody was confirmed. Schedule 2 provided greater and more consistent inhibition of mesenchymal-epithelial transition (MET)/EGFR throughout the dosing interval than Schedule 1. Although this study defined the LY3164530 MTD and pharmacokinetics on both schedules, significant toxicities associated with EGFR inhibition and lack of a potential predictive biomarker limit future development. Nonetheless, the results provide insight into the development of bispecific antibody therapy.

Merestinib is an oral multi-kinase inhibitor targeting a limited number of oncokinases including MET, AXL, RON and MKNK1/2. Here, we report that merestinib inhibits neurotrophic receptor tyrosine kinases NTRK1/2/3 which are oncogenic drivers in tumors bearing NTRK fusion resulting from chromosomal rearrangements. Merestinib is shown to be a type II NTRK1 kinase inhibitor as determined by x-ray crystallography. In KM-12 cells harboring TPM3-NTRK1 fusion, merestinib exhibits potent p-NTRK1 inhibition in vitro by western blot and elicits an anti-proliferative response in two- and three-dimensional growth. Merestinib treatment demonstrated profound tumor growth inhibition in in vivo cancer models harboring either a TPM3-NTRK1 or an ETV6-NTRK3 gene fusion. To recapitulate resistance observed from type I NTRK kinase inhibitors entrectinib and larotrectinib, we generated NIH-3T3 cells exogenously expressing TPM3-NTRK1 wild-type, or acquired mutations G595R and G667C in vitro and in vivo. Merestinib blocks tumor growth of both wild-type and mutant G667C TPM3-NTRK1 expressing NIH-3T3 cell-derived tumors. These preclinical data support the clinical evaluation of merestinib, a type II NTRK kinase inhibitor (NCT02920996), both in treatment naïve patients and in patients progressed on type I NTRK kinase inhibitors with acquired secondary G667C mutation in NTRK fusion bearing tumors.

Mutations in ERK signaling drive a significant percentage of malignancies. LY3009120, a pan-RAF and dimer inhibitor, has preclinical activity in RAS- and BRAF-mutated cell lines including BRAF-mutant melanoma resistant to BRAF inhibitors. This multicenter, open-label, phase I clinical trial (NCT02014116) consisted of part A (dose escalation) and part B (dose confirmation) in patients with advanced/metastatic cancer. In part A, oral LY3009120 was dose escalated from 50 to 700 mg twice a day on a 28-day cycle. In part B, 300 mg LY3009120 was given twice a day. The primary objective was to identify a recommended phase II dose (RP2D). Secondary objectives were to evaluate safety, pharmacokinetics, and preliminary efficacy. Identification of pharmacodynamic biomarkers was exploratory. In parts A and B, 35 and 16 patients were treated, respectively (N = 51). In part A, 6 patients experienced eight dose-limiting toxicities. The RP2D was 300 mg twice a day. Common (>10%) any-grade drug-related treatment-emergent adverse events were fatigue (n = 15), nausea (n = 12), dermatitis acneiform (n = 10), decreased appetite (n = 7), and maculopapular rash (n = 7). The median duration of treatment was 4 weeks; 84% of patients completed one or two cycles of treatment. Exposures observed at 300 mg twice a day were above the preclinical concentration associated with tumor regression. Eight patients had a best overall response of stable disease; there were no complete or partial clinical responses. Despite adequate plasma exposure levels, predicted pharmacodynamic effects were not observed.

Anti-EGFR antibodies are effective in therapies for late-stage colorectal cancer (CRC); however, many tumours are unresponsive or develop resistance. We performed genomic analysis of intrinsic and acquired resistance to anti-EGFR therapy in prospectively collected tumour samples from 25 CRC patients receiving cetuximab (an EGFR inhibitor). Of 25 CRC patients, 13 displayed intrinsic resistance to cetuximab; 12 were intrinsically sensitive. We obtained six re-biopsy samples at acquired resistance from the intrinsically sensitive patients. NCOA4–RET and LMNA–NTRK1 fusions and NRG1 and GNAS amplifications were found in intrinsic-resistant patients. In cetuximab-sensitive patients, we found KRAS K117N and A146T mutations in addition to BRAF V600E, AKT1 E17K, PIK3CA E542K, and FGFR1 or ERBB2 amplifications. The comparison between baseline and acquired-resistant tumours revealed an extreme shift in variant allele frequency of somatic variants, suggesting that cetuximab exposure dramatically selected for rare resistant subclones that were initially undetectable. There was also an increase in epithelial-to-mesenchymal transition at acquired resistance, with a reduction in the immune infiltrate. Furthermore, characterization of an acquired-resistant, patient-derived cell line showed that PI3K/mTOR inhibition could rescue cetuximab resistance. Thus, we uncovered novel genomic alterations that elucidate the mechanisms of sensitivity and resistance to anti-EGFR therapy in metastatic CRC patients.

Regulators of G Protein Signaling (RGS proteins) inhibit G protein-coupled receptor (GPCR) signaling by accelerating the GTP hydrolysis rate of activated Gα subunits. Some RGS proteins exert additional signal modulatory functions, and RGS12 is one such protein, with five additional, functional domains: a PDZ domain, a phosphotyrosine-binding domain, two Ras-binding domains, and a Gα·GDP-binding GoLoco motif. RGS12 expression is temporospatially regulated in developing mouse embryos, with notable expression in somites and developing skeletal muscle. We therefore examined whether RGS12 is involved in the skeletal muscle myogenic program. In the adult mouse, RGS12 is expressed in the tibialis anterior (TA) muscle, and its expression is increased early after cardiotoxin-induced injury, suggesting a role in muscle regeneration. Consistent with a potential role in coordinating myogenic signals, RGS12 is also expressed in primary myoblasts; as these cells undergo differentiation and fusion into myotubes, RGS12 protein abundance is reduced. Myoblasts isolated from mice lacking Rgs12 expression have an impaired ability to differentiate into myotubes ex vivo, suggesting that RGS12 may play a role as a modulator/switch for differentiation. We also assessed the muscle regenerative capacity of mice conditionally deficient in skeletal muscle Rgs12 expression (via Pax7-driven Cre recombinase expression), following cardiotoxin-induced damage to the TA muscle. Eight days post-damage, mice lacking RGS12 in skeletal muscle had attenuated repair of muscle fibers. However, when mice lacking skeletal muscle expression of Rgs12 were cross-bred with mdx mice (a model of human Duchenne muscular dystrophy), no increase in muscle degeneration was observed over time. These data support the hypothesis that RGS12 plays a role in coordinating signals during the myogenic program in select circumstances, but loss of the protein may be compensated for within model syndromes of prolonged bouts of muscle damage and repair.

Objectives Metastatic non–small cell lung cancer (mNSCLC) is characterized by complex genomic alterations. NF1 mutations may confer distinct clinical characteristics within NSCLC, and real-world evidence on concurrent mutations, treatment patterns, and health outcomes is lacking. Materials and Methods This retrospective study was performed in patients with mNSCLC treated in the Flatiron Health network who underwent the FoundationOne tumor-sequencing. Anticancer therapies, concurrent mutations, real-world progression-free survival (rwPFS), and overall survival (OS) were assessed. Results Of the 1663 patients, 103 patients were identified with NF1 mutation. Concurrent mutations with Ki-ras2 Kirsten rat sarcoma viral oncogene homolog (16.5%) and epidermal growth factor receptor fusion (6.8%) were the most frequent. In patients with NF1 mutation only (n = 57), 42% were women, 86% patients had smoking history, and 70% had non-squamous cell carcinoma type. Most (51%) of the patients with NF1 mutations received a single line of therapy versus other mutations and the overall treated population (44%). Platinum-based chemotherapy was the predominant first-line therapy, with programmed cell death-1/programmed cell death-ligand-1 inhibitors as subsequent lines of therapy. The NF1 mutation only group had numerically the shortest median rwPFS (82 days) than other mutation groups. Median OS for the NF1 mutation group in first, second, and third lines of therapy was 321, 498, and 210 days, respectively. Conclusions NF1 mutations confer distinct clinical characteristics in patients with mNSCLC. These patients may have different trajectories for progression and survival than seen for other mutations, experience less systemic therapy after first-line therapy, and may have shorter survival.

The combination of BRAF and MEK inhibitors have been clinically studied, and three different combinations (dabrafenib plus trametinib, vemurafenib plus cobimetinib and encorafenib plus binimetinib) are approved by the FDA for treatment of melanoma patients with BRAF V600E mutation. Published reports indicate that each combination has a different efficacy and toxicity profile. It is believed that the toxicity profile of some of these drugs is linked to their pharmacokinetic (PK) profile leading to prolonged pharmacodynamics (PD) or target inhibition. ERK inhibitors have been discovered recently to overcome the acquired resistance to BRAF plus MEK inhibitors in BRAF-mutant melanoma and for combination therapies in RAS/MAPK altered cancers including KRAS-mutant cancers. Several ERK inhibitors have entered clinical development as monotherapy or in combination. However, it is not clear what the minimum time on target is required for efficacy without causing significant toxicity, and whether that would differentiate the therapeutic index of one inhibitor from another. Therefore, we have conducted PK-PD-efficacy relationship studies of different MEK and ERK inhibitors with different PK profiles in mice in BRAF-mutant or KRAS-mutant xenograft models to determine the minimum time on target required for efficacy. We have tested the PK-PD-efficacy of MEK inhibitors trametinib and cobimetinib, as well as ERK inhibitors BVD-523, GDC-0994 and LY3214996 in BRAF V600E or KRAS mutant xenograft models including A375 BRAF V600E melanoma, Colo205 BRAF V600E colorectal carcinoma and HCT116 KRAS G13D colorectal carcinoma. Additionally, an infusion study with LY3214996 was conducted in rats implanted with HCT116 colorectal carcinoma tumors, where drug exposure was controlled for a specified time to get ≥50% pRSK1 inhibition. Our data suggests that ≥50% inhibition of pRSK1 for 8h is required for significant efficacy of ERK inhibitor LY3214996, which is similar to the data presented for GDC-0994 (Robarge K et al, Abstract number DDT02-03, AACR Annual Meeting 2014). Overall assessment of the data in different models suggested that ≥50% target inhibition for 8-16h is enough for significant tumor growth inhibition and regressions by an ERK inhibitor in BRAF-mutant or KRAS-mutant tumors without any obvious toxicity as measured by body weight loss or mortality. LY3214996 is in Phase 1 clinical development and the preliminary PK profile in patients looks as predicted from preclinical data. Therefore, we believe that the PK profile of LY3214996 offers flexibility with dose and schedule to balance efficacy and safety, and to achieve a better therapeutic index in combination therapy for RAS/MAPK pathway altered cancers. Citation Format: Shripad V. Bhagwat, Weihua Shen, Baohui Zhao, Shufen Cai, Lisa Kindler, William T. McMillen, Eunice Yuen, Denis McCann, Jason Manro, Andrew J. Dropsey, Melinda D. Willard, Sajan Joseph, Sheng-Bin Peng. Temporal inhibition of ERK is sufficient for tumor growth inhibition in KRAS-mutant or BRAF-mutant tumors [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 5225.

Background: Anti-EGFR antibodies are effective therapies for many late-stage colorectal cancer (CRC) patients; however, many tumors are unresponsive or develop resistance. Methods: We performed whole exome sequencing and RNA sequencing of 25 CRC patients who received cetuximab treatment. We obtained tissue specimens at acquired resistance and performed genomic analysis. Findings: Of 25 patients, 13 were categorized as intrinsic resistant and 12 were intrinsic sensitive tumor to cetuximab regardless of lines of therapy. Of 12 cetuximab sensitive tumors, we obtained 6 samples at acquired resistance to cetuximab. In the resistance group, we identified iNCOA4-RET and LMNA-NTRK1 fusions and NRG1 and GNAS amplifications without any aberrations in RAS/RAF pathway genes. For cetuximab-sensitive tumors, there were no major aberrations in the RAS pathway in all 12 tumors. Two PR patients showed KRAS K117N and A146T mutations, which are in KRAS exon 4 rather than in the more dominant exon 2. Other genomic aberrations found in the 12 PR patient cohort were BRAF V600E, AKT1 E17K, PIK3CA E542K, FGFR1, and ERBB2 CN amplifications. The comparison between baseline and at progression samples revealed an extreme loss and simultaneous gain of somatic variants in acquired resistance tumors suggesting that cetuximab exposure dramatically selected for rare resistant subclones of the baseline tumor that were initially undetectable. There was an increase in epithelial to mesenchymal transition (EMT) at acquired resistance with a reduction in the immune infiltrate. Interpretation: Each patient demonstrated varying genomic alterations which may facilitate in understanding the underlying culprit mechanism for cetuximab resistance at baseline. Funding Statement: This work was supported by a grant from the Korean Health Technology R&D Project, Ministry of Health & Welfare, Republic of Korea (HI14C2750 to YSP, HI14C3418 to JL), the SMC Biobank (to HCK and JL). Declaration of Interests: Lilly employees: SB, PJE, JNC, IHW, TG, SSW, HQ, JCT, JL, MW, RDN, AA, CR No conflicts of interest declared (JL, STK, SYK, JYH, YSP, JOP, HL, WKK, HCK) Ethics Approval Statement: All study participants provided written informed consent and the study was approved by the institutional review board.

Purpose The phase I study characterized the safety, pharmacokinetics, anti-tumor activity, and recommended phase II dose/schedule of LY3164530 in patients with advanced or metastatic cancer. Methods Patients received LY3164530 on days 1 and 15 (Schedule 1: 300, 600, 1000, and 1250 mg) or Days 1, 8, 15, and 22 (Schedule 2: 500 and 600 mg) of each 28 days cycle. Dose escalation used a modified toxicity probability interval model. Results Dose escalation defined a maximum tolerated dose (MTD) of 1000 mg on Schedule 1 and 500 mg on Schedule 2. Treatment-emergent adverse events related to study treatment were consistent with epidermal growth factor receptor (EGFR) inhibition and included maculopapular rash/dermatitis acneiform (83%, Grade 3/4 17%), hypomagnesemia (55%, Grade 3/4 7%), paronychia (35%), fatigue (28%, Grade 3/4 3%), skin fissures (24%), and hypokalemia (21%, Grade 3/4 7%). Partial response was achieved in three patients on Schedule 2 with colorectal cancer (n = 2) or squamous cell cancer. Overall response rate (ORR) was 10.3%, disease control rate (ORR + stable disease [SD]) was 51.7 and 17.2% of patients had SD ≥ 4 months. The in vivo stability of the bispecific antibody was confirmed. Schedule 2 provided greater and more consistent inhibition of mesenchymal-epithelial transition (MET)/EGFR throughout the dosing interval than Schedule 1. Conclusions Although this study defined the LY3164530 MTD and pharmacokinetics on both schedules, significant toxicities associated with EGFR inhibition and lack of a potential predictive biomarker limit future development. Nonetheless, the results provide insight into the development of bispecific antibody therapy. Electronic supplementary material The online version of this article (10.1007/s00280-018-3623-7) contains supplementary material, which is available to authorized users.

2035 Background: BM in NSCLC pts are associated with significant morbidity and mortality. This analysis describes the frequency and timing of BM development, pt characteristics, systemic txs, and OS in NSCLC pts with and without BM. Methods: This retrospective observational study identified pts from the Flatiron-Foundation Medicine NSCLC Clinico-Genomic Database diagnosed from 1 Jan 2011 to 31 Oct 2017 with adv NSCLC and a tumor sample analyzed via FoundationOne. Tx pattern data were summarized by period (1 Jan 2011-1 Mar 2015; 2 Mar 2015-31 Dec 2017), therapy class (eg, anti-VEGF and EGFR, platinum-based), and BM occurrence. Descriptive statistics were used to summarize data; Chi-square and t-tests assessed statistically significant differences. OS was measured by site of met (BM only vs no-BM only vs BM and no-BM) via K-M methods from adv diagnosis until death or last activity date (censored). Results: Of 3257 pts, 1018/3257 (31.3%) had BM during follow-up; 726/1018 (71.3%) presented with BM within 30 days of adv diagnosis. The median age at adv diagnosis was 66.2 yrs. Relative to pts without BM, BM pts were younger, more likely to be female, of Asian descent, have stage IV disease, ≥2 met sites (including BM) at initial presentation, ≥3 met sites (including BM) during follow-up, and non-squamous histology (all p < 0.01). Approximately 78% (n = 2534) were treated with ≥1 systemic tx; platinum-based chemo-combinations were the most common 1st line tx, regardless of BM status. Increased use of PD-1/L1 tx was seen in 1st, 2nd, and 3rdline during the latter vs earlier period. No statistically significant difference in OS was observed in pts with BM only (17.1 mos; 95% CI 12.5-29.9), no-BM only (21 mos; 95% CI 19.4-22.8), or BM and no-BM (20.4 mos; 95% CI 18.9-23.3) (log rank p = 0.3027). Conclusions: In met NSCLC pts with a tumor sample that was molecularly profiled, OS was comparable, regardless of site(s) of disease; additional multivariate analyses including molecular profiles are needed. BM screening at initial diagnosis is important given the frequency in NSCLC. Future studies should assess whether the shift in systemic tx patterns impact the development and clinical outcomes.

3001 Background: LY3214996 is a selective and potent ERK1/2 inhibitor that has demonstrated tumor growth inhibition in several pre-clinical tumor models with BRAF, RAS, or MAP2K1 mutations. This is the first-in-human Phase 1 Study of LY3214996 in adv CA pts. Methods: The goals of this DE study were to determine a recommended Phase 2 dose (RP2D), safety, pharmacokinetic (PK), and preliminary efficacy of LY3214996 (NCT02857270; I8S-MC-JUAB; Eli Lilly & Co.). Pts with adv CA, ≥18 yrs of age, ECOG ≤1, and with adequate organ function were eligible. Pharmacodynamic (PD) biomarkers including pRSK were evaluated in blood and paired tumor tissue. The DE phase evaluated PO doses using the Bayesian model-based toxicity band method. Results: A total of 51 pts with median age of 62 yrs (range: 21-81) received at least 1 dose of LY3214996 with a median of 3 cycles (range: 1-12). Most pts had a mutation in RAS (N = 33) or BRAF (N = 16) and had a median of 4 prior lines of treatment. The DLTs observed in the study include grade (G) 3 cough and fatigue, G3 dehydration, increased creatinine (Cr), G3 increased CPK, G3 rash > 7 days, and 1 pt with renal failure. TRAEs to LY3214996 occurring in ≥10% of pts included nausea, vomiting, diarrhea, dermatitis acneiform, fatigue, pruritus, and blurred vision. LY3214996 exposures increased with dose. Tumor regression was observed in 7 pts with BRAF/non -BRAF mutant CA including 5 pts who failed prior IO/MAPK inhibitors. Four pts achieved stable disease (2 BRAF, 1 RAS and 1 CRAF mutation) that lasted > 4 mos. Up to 100% pRSK decrease from baseline in tumor was observed. Conclusions: LY3214996 had an acceptable safety profile, favorable PK, and potent tumor PD inhibition at RP2D. This supports further exploration of LY3214996 as monotherapy and in combination in CA pts with activating MAPK pathway alterations. Clinical trial information: NCT02857270.

2014 Background: Molecular alterations (MA) found in brain (Br) mets of NSCLC pts can differ from primary and/or other met sites, which may explain why therapies targeting primary tumors are less effective at preventing and treating intracranial disease. We analyzed the frequency of known driver genes in adv NSCLC pts and the association with overall survival (OS). Methods: This retrospective observational study identified pts from the Flatiron- Foundation Medicine NSCLC Clinico-Genomic Database who were diagnosed with adv NSCLC from 1 Jan 2011 to 31 Oct 2017 and had tumor tissue analyzed at any time following initial diagnosis via targeted DNA sequencing by FoundationOne. Descriptive statistics summarized MA from lung and met sites (Br and non-brain [NB]). OS was measured from adv diagnosis to death or last activity date (censored). Multivariable Cox proportional hazard regression model was used for time-to-event analysis. Results: Of 3257 pts, data were available from lung (n = 1621), Br (n = 180), and NB sites (n = 377): liver (n = 167), bone (n = 124), adrenal (n = 63), and spine (n = 23). Median age at adv diagnosis was 66.2 yrs. TP53(63.3%), KRAS(28.8%), EGFR(15.6%), STK11 (13.5%), and CDKN2A(8.5%) were frequently mutated genes in lung samples. Genes for Br vs NB sites included TP53(70.6%; 64.7%), KRAS(36.1%; 26.5%), EGFR (9.4%; 18.8%), STK11 (18.9%; 12.7%), and CDKN2A(6.1%; 10.1). KEAP1alterations were also present in 10% (Br), 7.4% (NB), and 6% of lung samples. In treated pts, lack of alterations in select genes ( STK11, TP53, KEAP1) was associated with longer OS, whereas lack of other alterations ( ARID1A, EGFR, ALK, ROS1) was associated with a shorter OS (p < 0.05). Patients with select mutations co-occurring with KRAS had higher risk of death compared to those with KRAS only (p < 0.05). Conclusions: Based on pts with NSCLC whose tumor tissue underwent DNA sequencing, the most frequently altered genes in lung and Br samples included TP53, KRAS, EGFR, STK11, and CDKN2A, with some being significantly associated with OS. Prognosis of NSCLC pts depends on clinical, demographic, and genomic factors and should be carefully considered to optimize clinical outcome.

1042 Background: Few real-world studies have characterized the frequency of genomic alterations of MBC tumors. Data characterizing alterations before and after treatment containing a CDK4 & 6 inhibitor (CDK4 & 6i) are similarly limited. We explore the genomic landscape of HR+/HER2- MBC tumors from patients (pts) treated with a CDK4 & 6i in order to characterize potential mechanisms underlying sensitivity and resistance. Methods: NGS results of tumor and liquid biopsies obtained from 130 pts with estrogen receptor (ER+)/progesterone receptor (PR+)/HER2- MBC between Jan 2008 to Sept 2016 were analyzed. All pts received therapy containing a CDK4 & 6i for MBC at a community cancer network and had NGS results available before and/or after exposure to CDK4 & 6i. Samples were classified as sensitive (n = 69; duration of therapy ≥6 mo) or resistant (n = 61; duration of therapy < 6 mo). The frequency of genomic alterations with likely or known significance including short variants, indels, copy number variants, and fusions were characterized. Results: Alterations in 215 unique genes were identified from the NGS results; PIK3CA, TP53, ESR1, CCND1, and FGFR1 were the most frequently altered genes. Select alterations in ESR1 (n = 21 vs 9) and RAD21 (n = 5 vs 0) were more frequent after exposure to CDK4 & 6i. In NGS obtained before exposure to CDK4 & 6i, alterations in select genes including RB1, MDM2, AURKA, and MYC were more frequent in the resistant samples, whereas ARID1A alterations were more frequent in sensitive samples. Of the 6 pts with paired NGS samples pre- and post-CDK4 & 6i treatment, alterations in MYC, CDKN2A, PIK3CA, BRCA1, or RB1 were acquired in 3 pts. Conclusions: Based on real-world data, this study describes the genomic landscape of ER+/PR+/HER2- MBC tumors from pts treated with CDK4 & 6i and identifies potential mechanisms underlying sensitivity and resistance to this new class of drugs. Further evaluation in larger datasets is warranted. Data inclusive of other ER/PR subtypes will be presented.

Heterotrimeric G-protein Gα subunits and GoLoco motif proteins are key members of a conserved set of regulatory proteins that influence invertebrate asymmetric cell division and vertebrate neuroepithelium and epithelial progenitor differentiation. GoLoco motif proteins bind selectively to the inhibitory subclass (Gαi) of Gα subunits, and thus it is assumed that a Gαi·GoLoco motif protein complex plays a direct functional role in microtubule dynamics underlying spindle orientation and metaphase chromosomal segregation during cell division. To address this hypothesis directly, we rationally identified a point mutation to Gαi subunits that renders a selective loss-of-function for GoLoco motif binding, namely an asparagine-to-isoleucine substitution in the αD-αE loop of the Gα helical domain. This GoLoco-insensitivity (“GLi”) mutation prevented Gαi1 association with all human GoLoco motif proteins and abrogated interaction between the Caenorhabditis elegans Gα subunit GOA-1 and the GPR-1 GoLoco motif. In contrast, the GLi mutation did not perturb any other biochemical or signaling properties of Gαi subunits, including nucleotide binding, intrinsic and RGS protein-accelerated GTP hydrolysis, and interactions with Gβγ dimers, adenylyl cyclase, and seven transmembrane-domain receptors. GoLoco insensitivity rendered Gαi subunits unable to recruit GoLoco motif proteins such as GPSM2/LGN and GPSM3 to the plasma membrane, and abrogated the exaggerated mitotic spindle rocking normally seen upon ectopic expression of wild type Gαi subunits in kidney epithelial cells. This GLi mutation should prove valuable in establishing the physiological roles of Gαi·GoLoco motif protein complexes in microtubule dynamics and spindle function during cell division as well as to delineate potential roles for GoLoco motifs in receptor-mediated signal transduction.

Anti-EGFR antibodies, such as cetuximab, are effective therapies for many late-stage colorectal cancer (CRC) patients; unfortunately, many tumors are initially unresponsive while others show initial efficacy but eventually develop acquired resistance. Genomic studies of patient tumors, cell lines, and xenograft models have identified putative anti-EGFR resistance markers, including mutations in KRAS, NRAS, BRAF, PIK3CA, and the EGFR extracellular domain, as well as amplifications in ERBB2 and MET. In order to further confirm and identify new resistance mechanisms to anti-EGFR treatment in CRC, we performed retrospective genomic profiling of 25 CRC patients treated at Samsung Medical Center from 2006-2015. Patients received cetuximab containing chemo regimens with varying duration of responses, including acquired resistance cases. Our analysis identifies mutations in receptor tyrosine kinases, such as EGFR, NTRK1, and PDGFRA, as well as RAS/MAPK pathway genes that affect cetuximab response. We also uncover genomic alterations in ERBB2 and c-KIT as potential novel mechanisms regulating sensitivity to anti-EGFR antibodies. Additional genomic analyses of acquired resistance tumors and in vitro studies of a patient-derived cell line provide added insights into clonal selection and signaling pathways that bypass the EGFR blockade. Overall, our study elucidates important new facets in the landscape of anti-EGFR resistance mechanisms. Note: This abstract was not presented at the meeting. Citation Format: Steven M. Bray, Jeeyun Lee, Seung Tae Kim, Philip J. Ebert, John N. Calley, Isabella H. Wulur, Thejaswini Gopalappa, Swee Seong Wong, Hui-Rong Qian, Jason C. Ting, Jiangang Liu, Melinda D. Willard, Amit Aggarwal, Ruslan D. Novosiadly, Hee-Cheol Kim, Christoph Reinhard. Intrinsic and acquired resistance to cetuximab in colorectal cancer patients [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 4104. doi:10.1158/1538-7445.AM2017-4104

2507 Background: LY3009120, a pan-Raf and dimer inhibitor, demonstrates inhibition of phospho-Mek/Erk and tumor growth inhibition in several non-clinical cancer models with BRAF, NRAS, or KRAS mutations. This is the first-in-human phase 1 study of LY3009120 in patients (pts) with advanced cancer. Methods: The safety and tolerability of LY3009120 was evaluated in pts with cancer aged 18 years or older who had an ECOG performance status ≤1, at least 1 unidimensionally measurable lesion (RECIST 1.1), and adequate organ function (NCT02014116; I6X-MC-JBDA; Eli Lilly & Co.). The study sought to determine a recommended phase 2 dose using the toxicity band method and the safety, pharmacokinetic, and preliminary efficacy of LY3009120. Pharmacodynamic (PD) biomarkers, including pERK, p27 and Ki67, were evaluated in tumor tissue. The dose escalation phase evaluated dosages from 50 mg to 500 mg by mouth twice daily in pts with advanced cancers. Results: 34 pts (3 at 50 mg, 4 at 100 mg, 3 at 200 mg, 15 at 300 mg, 7 at 400 mg, and 2 at 500 mg) in dose escalation and 1 pt in dose expansion (1 at 300 mg) received at least one dose of LY3009120 by January 2, 2016 (median age = 47.4 yrs, range: 26-82 ). Most pts had a gene mutation (BRAF, n = 7; N/KRAS, n = 18); the most common cancer types included colon (n = 9), non–small cell lung cancer (n = 8), and pancreatic (n = 5). There were 6 dose-limiting toxicities in the dose escalation phase: 2 pts at 300 mg (G3 dermatitis acneiform [n = 1] and G2 blurred vision [n = 1]); 2 pts at 400 mg (G2 increased ALT with G3 hyperbilirubinemia [n = 1] and G3 increased ALT [n = 1]); 2 pts at 500 mg: (G3 arthralgia/myalgia [n = 1] and G3 stomatitis/pain [n = 1]). Based on these data, the maximum tolerated dose for LY3009120 was determined to be 300 mg twice daily. Treatment-emergent adverse events related to LY3009120 occurring in ≥10% of pts included fatigue (34%), nausea (31%), decreased appetite (20%), and dermatitis acneiform (20%) (Grade 1,2). A dose proportional increase in exposure was observed, but not at the 400 mg dose. The best response was stable disease in 5 pts. PD effect by rtPCR was not observed in tested paired tumor samples. Conclusions: LY3009120 is well tolerated at doses of 300 mg twice daily. Updated data from dose expansion will be presented in the meeting. Clinical trial information: NCT02014116.

Hepatocellular carcinoma (HCC) is one of the most deadly cancers worldwide and has no effective treatment, yet the molecular basis of hepatocarcinogenesis remains largely unknown. Here we report findings from a whole-genome sequencing (WGS) study of 88 matched HCC tumor/normal pairs, 81 of which are Hepatitis B virus (HBV) positive, seeking to identify genetically altered genes and pathways implicated in HBV-associated HCC. We find beta-catenin to be the most frequently mutated oncogene (15.9%) and TP53 the most frequently mutated tumor suppressor (35.2%). The Wnt/beta-catenin and JAK/STAT pathways, altered in 62.5% and 45.5% of cases, respectively, are likely to act as two major oncogenic drivers in HCC. This study also identifies several prevalent and potentially actionable mutations, including activating mutations of Janus kinase 1 (JAK1), in 9.1% of patients and provides a path toward therapeutic intervention of the disease.

In cancer, the formation of chimeric gene fusions by genomic rearrangement causes aberrant receptor tyrosine kinase activation resulting in sustained oncogenic signaling driving tumorigenesis. Neurotrophic tyrosine receptor kinase 1 (NTRK1), the cognate receptor for nerve growth factor (NGF), has been reported in 7 tumor types as a NTRK1 kinase domain fused with several reported partners including the 5’ coiled-coil domain of the tropomysin TPM3 gene. The resultant NTRK1 fusion protein is present in about 1.5% of colorectal cancer (CRC), 3% of lung and 12% of papillary thyroid cancers. In addition, gene fusions involving NTRK2 and NTRK3 are present in about 19 different tumor types. Thus pharmacologically targeting NTRK kinase in cancers bearing NTRK fusions may provide treatment options to patients who otherwise might be resistant to standard oncolytic regimens. Merestinib (LY2801653) is an orally bioavailable small molecule inhibitor of several oncokinases, including MET, AXL, ROS1 and MKNK1/2. Merestinib and its two primary metabolites, M1 (LSN2800870) and M2 (LSN2887652) were shown in scanMaxSM kinase binding assays to inhibit all three NTRKs with an IC50 ranging from 15-320 nM, and in the cell-based PathHunter® NTRK1 assay with an IC50 ranging from 12-92 nM. Merestinib, M1 and M2 were evaluated in vitro in TPM3-NTRK1 fusion bearing CRC cells (KM-12). Merestinib, M1 and M2 reduced p-NTRK1 levels, cell proliferation (IC50 of 11 nM, 18 nM and 100 nM respectively) and anchorage independent growth (IC50 of 45 nM, 79 nM and 206 nM respectively). Crizotinib previously reported (Nat Med. 2013;19:1469-72) to have moderate activity against NTRK1, was used to treat a patient with NTRK1 fusion resulted with transient response. Crizotinib was shown here to also reduce p-NTRK1 levels, cell proliferation (IC50 = 88nM) and anchorage independent growth (IC50 = 276nM) in vitro in KM-12 cells. Merestinib treatment at 24 mg/kg once daily arrested tumor growth (T/C = 4%) in KM-12 xenograft tumor bearing mice. Crizotinib administered at 25 mg/kg twice daily in this same model did not result in tumor growth arrest (T/C = 39.5%). Merestinib treatment at 24 mg/kg once daily led to tumor regression in a CRC PDX xenograft model (EL1989) bearing the TPM3-NTRK1 fusion. Crizotinib treatment at 25 mg/kg twice daily in this model did not show tumor regression. Further pre-clinical studies of Merestinib inhibition of NTRK2 and NTRK3 gene fusion are ongoing. These data support the clinical evaluation of Merestinib in patients with tumors harboring NTRK fusion. Merestinib is currently being studied clinically in advanced cancers (NCT01285037). Citation Format: Bruce W. Konicek, Steve M. Bray, Andrew R. Capen, John N. Calley, Kelly M. Credille, Philip J. Ebert, Gary Heady, Bharvin K. Patel, Victoria L. Peek, Jennifer R. Stephens, Suzane L. Um, Melinda D. Willard, Isabella H. Wulur, Yi Zeng, Richard A. Walgren, Sau-Chi Betty Yan. Merestinib (LY2801653), targeting several oncokinases including NTRK1/2/3, shows potent anti-tumor effect in colorectal cell line- and patient-derived xenograft (PDX) model bearing TPM3-NTRK1 fusion. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 2647.

The roles of cholecystokinin 2 receptor (CCK2R) in numerous physiologic processes in the gastrointestinal tract and central nervous system are well documented. There has been some evidence that CCK2R alterations play a role in cancers, but the functional significance of these alterations for tumorigenesis is unknown. We have identified six mutations in CCK2R among a panel of 140 colorectal cancers and 44 gastric cancers. We show that these mutations increase receptor activity, activate multiple downstream signaling pathways, increase cell migration, and promote angiogenesis. Our findings suggest that somatic mutations in CCK2R may promote tumorigenesis through deregulated receptor activity and highlight the importance of evaluating CCK2R inhibitors to block both the normal and mutant forms of the receptor. Mol Cancer Res; 10(6); 739–49. ©2012 AACR.

Heterotrimeric G-proteins are molecular switches integral to a panoply of different physiological responses that many organisms make to environmental cues. The switch from inactive to active Gαβγ heterotrimer relies on nucleotide cycling by the Gα subunit: exchange of GTP for GDP activates Gα, whereas its intrinsic enzymatic activity catalyzes GTP hydrolysis to GDP and inorganic phosphate, thereby reverting Gα to its inactive state. In several genetic studies of filamentous fungi, such as the rice blast fungus Magnaporthe oryzae, a G42R mutation in the phosphate-binding loop of Gα subunits is assumed to be GTPase-deficient and thus constitutively active. Here, we demonstrate that Gα(G42R) mutants are not GTPase deficient, but rather incapable of achieving the activated conformation. Two crystal structure models suggest that Arg-42 prevents a typical switch region conformational change upon Gαi1(G42R) binding to GDP·AlF4 − or GTP, but rotameric flexibility at this locus allows for unperturbed GTP hydrolysis. Gα(G42R) mutants do not engage the active state-selective peptide KB-1753 nor RGS domains with high affinity, but instead favor interaction with Gβγ and GoLoco motifs in any nucleotide state. The corresponding Gαq(G48R) mutant is not constitutively active in cells and responds poorly to aluminum tetrafluoride activation. Comparative analyses of M. oryzae strains harboring either G42R or GTPase-deficient Q/L mutations in the Gα subunits MagA or MagB illustrate functional differences in environmental cue processing and intracellular signaling outcomes between these two Gα mutants, thus demonstrating the in vivo functional divergence of G42R and activating G-protein mutants., Author Summary Heterotrimeric G-proteins function as molecular switches to convey cellular signals. When a G-protein coupled receptor encounters its ligand at the cellular membrane, it catalyzes guanine nucleotide exchange on the Gα subunit, resulting in a shift from an inactive to an active conformation. G-protein signaling pathways are conserved from mammals to plants and fungi, including the rice blast fungus Magnaporthe oryzae. A mutation in the Gα subunit (G42R), previously thought to eliminate its GTPase activity, leading to constitutive activation, has been utilized to investigate roles of heterotrimeric G-protein signaling pathways in multiple species of filamentous fungi. Here, we demonstrate through structural, biochemical, and cellular approaches that G42R mutants are neither GTPase deficient nor constitutively active, but rather are unable to transition to the activated conformation. A direct comparison of M. oryzae fungal strains harboring either G42R or truly constitutively activating mutations in two Gα subunits, MagA and MagB, revealed markedly different phenotypes. Our results suggest that activation of MagB is critical for pathogenic development of M. oryzae in response to hydrophobic surfaces, such as plant leaves. Furthermore, the lack of constitutive activity by Gα(G42R) mutants prompts a re-evaluation of its use in previous genetic experiments in multiple fungal species.

Publisher Summary A large family of seven transmembrane-domain receptors for hormones, neurotransmitters, growth factors, chemoattractants, light, odorants, and other extracellular stimuli promote intracellular signaling responses by activation of heterotrimeric G proteins. This discrepancy between the rates of GTP hydrolysis measured in vitro and in vivo presaged the existence of proteins that accelerate the deactivation of GTP-bound Gα subunits. In the standard model of GPCR signaling, the duration of heterotrimeric G-protein signaling through effectors is thought to be controlled by the lifetime of the Gα subunit in its GTP-bound form. Regulator of G-protein Signaling (RGS) proteins promote the deactivation step in the heterotrimeric G-protein regulatory cycle, catalyzing GTPase rates in vitro that are consistent with the rates of deactivation of G-protein signaling in vivo. The physiological functions of these proteins continue to be investigated and, in the case of many RGS proteins, include additional functionalities beyond their hallmark capacity to act as GAPs for Gα subunits.

Background: Regulator of G-protein signaling (RGS) proteins have been well-described as accelerators of Ga-mediated GTP hydrolysis (‘‘GTPase-accelerating proteins’’ or GAPs). However, RGS proteins with complex domain architectures are now known to regulate much more than Ga GTPase activity. RGS14 contains tandem Ras-binding domains that have been reported to bind to Rap- but not Ras GTPases in vitro, leading to the suggestion that RGS14 is a Rap-specific effector. However, more recent data from mammals and Drosophila imply that, in vivo, RGS14 may instead be an effector of Ras. Methodology/Principal Findings: Full-length and truncated forms of purified RGS14 protein were found to bind indiscriminately in vitro to both Rap- and Ras-family GTPases, consistent with prior literature reports. In stark contrast, however, we found that in a cellular context RGS14 selectively binds to activated H-Ras and not to Rap isoforms. Co- transfection / co-immunoprecipitation experiments demonstrated the ability of full-length RGS14 to assemble a multiprotein complex with components of the ERK MAPK pathway in a manner dependent on activated H-Ras. Small interfering RNA-mediated knockdown of RGS14 inhibited both nerve growth factor- and basic fibrobast growth factor- mediated neuronal differentiation of PC12 cells, a process which is known to be dependent on Ras-ERK signaling. Conclusions/Significance: In cells, RGS14 facilitates the formation of a selective Ras?GTP-Raf-MEK-ERK multiprotein complex to promote sustained ERK activation and regulate H-Ras-dependent neuritogenesis. This cellular function for RGS14 is similar but distinct from that recently described for its closely-related paralogue, RGS12, which shares the tandem Ras- binding domain architecture with RGS14.

Heterotrimeric G-proteins are a class of signal transduction proteins highly conserved throughout evolution that serve as dynamic molecular switches regulating the intracellular communication initiated by extracellular signals including sensory information. This property is achieved by a guanine nucleotide cycle wherein the inactive, signaling-incompetent Galpha subunit is normally bound to GDP; activation to signaling-competent Galpha occurs through the exchange of GDP for GTP (typically catalyzed via seven-transmembrane domain G-protein coupled receptors [GPCRs]), which dissociates the Gbetagamma dimer from Galpha-GTP and initiates signal transduction. The hydrolysis of GTP, greatly accelerated by "Regulator of G-protein Signaling" (RGS) proteins, returns Galpha to its inactive GDP-bound form and terminates signaling. Through extensive characterization of mammalian Galpha isoforms, the rate-limiting step in this cycle is currently considered to be the GDP/GTP exchange rate, which can be orders of magnitude slower than the GTP hydrolysis rate. However, we have recently demonstrated that, in Arabidopsis, the guanine nucleotide cycle appears to be limited by the rate of GTP hydrolysis rather than nucleotide exchange. This finding has important implications for the mechanism of sugar sensing in Arabidopsis. We also discuss these data on Arabidopsis G-protein nucleotide cycling in relation to recent reports of putative plant GPCRs and heterotrimeric G-protein effectors in Arabidopsis.

Heterotrimeric G-protein Galpha subunits and GoLoco motif proteins are key members of a conserved set of regulatory proteins that influence invertebrate asymmetric cell division and vertebrate neuroepithelium and epithelial progenitor differentiation. GoLoco motif proteins bind selectively to the inhibitory subclass (Galphai) of Galpha subunits, and thus it is assumed that a Galphai.GoLoco motif protein complex plays a direct functional role in microtubule dynamics underlying spindle orientation and metaphase chromosomal segregation during cell division. To address this hypothesis directly, we rationally identified a point mutation to Galphai subunits that renders a selective loss-of-function for GoLoco motif binding, namely an asparagine-to-isoleucine substitution in the alphaD-alphaE loop of the Galpha helical domain. This GoLoco-insensitivity ("GLi") mutation prevented Galphai1 association with all human GoLoco motif proteins and abrogated interaction between the Caenorhabditis elegans Galpha subunit GOA-1 and the GPR-1 GoLoco motif. In contrast, the GLi mutation did not perturb any other biochemical or signaling properties of Galphai subunits, including nucleotide binding, intrinsic and RGS protein-accelerated GTP hydrolysis, and interactions with Gbetagamma dimers, adenylyl cyclase, and seven transmembrane-domain receptors. GoLoco insensitivity rendered Galphai subunits unable to recruit GoLoco motif proteins such as GPSM2/LGN and GPSM3 to the plasma membrane, and abrogated the exaggerated mitotic spindle rocking normally seen upon ectopic expression of wild type Galphai subunits in kidney epithelial cells. This GLi mutation should prove valuable in establishing the physiological roles of Galphai.GoLoco motif protein complexes in microtubule dynamics and spindle function during cell division as well as to delineate potential roles for GoLoco motifs in receptor-mediated signal transduction.

Regulator of G-protein signaling (RGS) proteins accelerate GTP hydrolysis by heterotrimeric G-protein alpha subunits and thus inhibit signaling by many G protein-coupled receptors. Several RGS proteins have a multidomain architecture that adds further complexity to their roles in cell signaling in addition to their GTPase-accelerating activity. RGS12 contains a tandem repeat of Ras-binding domains but, to date, the role of this protein in Ras-mediated signal transduction has not been reported. Here, we show that RGS12 associates with the nerve growth factor (NGF) receptor tyrosine kinase TrkA, activated H-Ras, B-Raf, and MEK2 and facilitates their coordinated signaling to prolonged ERK activation. RGS12 is required for NGF-mediated neurite outgrowth of PC12 cells, but not outgrowth stimulated by basic fibroblast growth factor. siRNA-mediated knockdown of RGS12 expression also inhibits NGF-induced axonal growth in dissociated cultures of primary dorsal root ganglia neurons. These data suggest that RGS12 may play a critical, and receptor-selective, role in coordinating Ras-dependent signals that are required for promoting and/or maintaining neuronal differentiation.

Hepatocellular carcinoma (HCC) is one of the most deadly cancers worldwide and has no effective treatment, yet the molecular basis of hepatocarcinogenesis remains largely unknown. Here we report findings from a whole genome sequencing (WGS) study of 88 matched HCC tumour/normal pairs, 81 of which are HBV positive, seeking to identify genetically altered genes and pathways implicated in HBV-associated HCC. We find β-catenin to be the most frequently mutated oncogene (15.9%) and TP53 the most frequently mutated tumour suppressor (35.2%). The Wnt/β-catenin pathway, altered in 62.5% of cases, is likely to act as the major oncogenic driver in HCC. TP53 alterations appear to cause increased levels of genomic arrangement and chromosomal instability. We identified chromothripsis in 5 HCC genomes (5.7%) recurrently affecting chromosomal arms 1q and 8q. We also identified recurrent HBV integration events at the known and putative cancer-related genes such as TERT, MLL4 and CCNE1, which showed upregulated gene expression in tumour versus normal tissue. The frequently altered genes and pathways in HCC reflect classical cancer hallmarks. This study identified several prevalent and actionable mutations that provide a path towards therapeutic intervention of the disease. Citation Format: Mao Mao, Hancheng Zheng, Zhengyan Kan, Jiangchun Xu, Xiao Liu, Shuyu Li, Thomas Barber, Zhuolin Gong, Huan Gao, Ke Hao, Melinda Willard, Robert Hauptschein, Paul Rejto, Julio Fernandez, Guan Wang, Qinghui Zhang, Bo Wang, Ronghua Chen, Jian Wang, Nikki Lee, Wei Zhou, Zhao Lin, Zhiyu Peng, Kang Yi, Shengpei Chen, Lin Li, Xiaomei Fan, Jie Yang, Rui Ye, Jia Ju, Kai Wang, Heather Estrella, Shibing Deng, Ping Wei, Ming Qiu, Isabella Wulur, Jiangang Liu, Mariam Ehsani, Chunsheng Zhang, Andrey Loboda, Wing Kin Sung, Amit Aggarwal, Ronnie Poon, Sheung Tat Fan, Jun Wang, James Hardwick, Christoph Reinhard, Hongyue Dai, Yingrui Li, John Luk. Whole genome sequencing reveals genetic landscape of hepatocellular carcinoma. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr LB-229. doi:10.1158/1538-7445.AM2013-LB-229

Data indicates that focal adhesion kinases (FAKs) play a critical role in cancer. Specifically, accumulating evidence suggests that overexpression and altered activity of FAKs promotes tumorigenesis, metastasis, and correlates with reduced survival. Proline-rich tyrosine kinase 2 (PYK2, FAK2) and its role in physiological processes in bone and inflammatory cellular responses have been well-documented. Recently, the role of PYK2 in the induction of endothelial to mesenchymal transition and cancer progression has emerged. Somatic mutations altering the coding region of PTK2B have been detected in melanoma and lung cancer, but the functional significance of these mutations is unknown. Here we demonstrate that cancer-associated mutations of PYK2 found in malignant melanoma lead to altered protein localization, interactions, and activity, and consequently, abnormal cellular behavior. These findings suggest that somatic mutations in PTK2B may promote tumor progression through deregulated protein activity, and highlight the importance of evaluating PYK2 inhibitors to block both the normal and mutant forms of the kinase. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 100. doi:1538-7445.AM2012-100