Roman Perez-Soler

Erlotinib, an effective epidermal growth factor receptor tyrosine kinase inhibitor, induces p27KIP1 up-regulation and nuclear translocation in association with cell growth inhibition and G1/S phase arrest in human non-small-cell lung cancer cell lines.

Erlotinib, a small-molecule epidermal growth factor receptor (EGFR) tyrosine kinase inhibitor, has been shown to have potent antitumor effects against human non-small-cell lung cancer (NSCLC) cell growth; however, the mechanism of such an effect is not elucidated. Here, we demonstrate that erlotinib-induced cell growth inhibition in EGFR high-expressing human H322 NSCLC cells was accompanied by G1/S phase arrest, which was largely caused by a decrease in expression of G1/S-related cyclins, suppression of activities of cyclin-dependent kinase (CDK) 2 and CDK4, induction of CDK inhibitor p27KIP1, and retinoblastoma hypophosphorylation. To further understand the role of p27KIP1 in G1/S arrest and cell growth inhibition by erlotinib, we determined its effect on the expression of p27KIP1 at transcriptional and posttranscriptional levels. Studies using real-time reverse transcription-polymerase chain reaction analysis and p27 promoter-driven luciferase reporter showed that erlotinib treatment resulted in the promotion of p27 gene transcription. In addition, erlotinib treatment led to an increase in p27KIP1 half-life by inhibiting p27KIP1 phosphorylation at Thr187 and by down-regulating Skp2 expression. Furthermore, immunofluorescence staining and cell fractionation showed that erlotinib treatment led to p27KIP1 translocation to the nucleus. Knockdown of p27KIP1 expression with p27KIP1 small interfering RNA significantly abrogated erlotinib-induced G1 phase arrest and cell growth inhibition, suggesting that induction of p27KIP1 is required for G1 arrest and cell growth inhibition by erlotinib. It is noteworthy that we found that G1 arrest and p27KIP1 up-regulation by erlotinib occurred in the tested sensitive cell lines but to a lesser extent in the resistant cell lines. Taken together, these results suggest that erlotinib inhibits human NSCLC cell growth predominantly by inducing p27KIP1 expression and by suppressing cell-cycle events involved in the G1/S transition.

The Autophagy Inhibitor Chloroquine Overcomes the Innate Resistance of Wild-Type EGFR Non-Small-Cell Lung Cancer Cells to Erlotinib

Introduction: The epidermal growth factor receptor (EGFR) inhibitor erlotinib is much less effective in non–small-cell lung cancer (NSCLC) tumors with wild-type EGFR, than in tumors with activating EGFR mutations. Autophagy is a tightly regulated lysosomal self-digestion process, which may alternatively promote cell survival or type II cell death. This study assessed the role of autophagy in erlotinib-mediated cytotoxicity. Methods: We used wild-type EGFR erlotinib-sensitive and erlotinib-resistant NSCLC cell lines to determine whether inhibiting autophagy by a therapeutic agent potentiated the antitumor activity of erlotinib in vitro and in vivo. Results: Erlotinib at a clinically relevant concentration (2 &mgr;M) induced autophagy in NSCLC cells with wild-type EGFR, and the degree of induction was greater in cells that were resistant than sensitive, suggesting that autophagy is cytoprotective. This was confirmed by knockdown of the autophagy-related gene Atg-5, and by using the autophagy inhibitor chloroquine (CQ), both of which increased the cytotoxicity of erlotinib. The synergistic activity of CQ was not because of the potentiation of erlotinib’s effects on autophagy, cell-cycle arrest, and inhibition of both EGFR or downstream signaling of EGFR. Rather, CQ markedly activated apoptosis in the cells. The ability of CQ to potentiate the antitumor activity of erlotinib was also seen in mice bearing NSCLC tumor xenografts. Conclusions: The ability to adapt to anti-EGFR therapy by triggering autophagy may be a key determinant for resistance to erlotinib in wild-type EGFR NSCLC. Inhibition of autophagy by CQ represents a novel strategy to broaden the spectrum of erlotinib efficacy in wild-type EGFR NSCLC tumors.

Mechanisms of resistance to vascular endothelial growth factor blockade

Angiogenesis is essential for the growth of primary tumors and for their metastasis. This process is induced by factors, such as vascular endothelial growth factors (VEGFs), that bind to transmembrane VEGF receptors (VEGFRs). VEGF‐A is the primary factor involved with angiogenesis; it binds to both VEGFR‐1 and VEGFR‐2. The inhibition of angiogenesis by obstructing VEGF‐A signaling has been investigated as a method to treat solid tumors, but the development of resistance to this blockade has complicated treatment. The major mechanisms of this resistance to VEGF‐A blockade include signaling by redundant receptors, such as the fibroblast growth factors, angiopoietin‐1, ephrins, and other forms of VEGF. Other major mechanisms of resistance are increased metastasis of hypoxia‐resistant tumor cells, recruitment of cell types capable of promoting VEGF‐independent angiogenesis, and increased circulation of nontumor proangiogenic factors. Additional mechanisms of resistance to VEGF‐A blockade include heterogeneity of responsiveness among tumor cells, use of anti‐VEGF‐A agents at insufficient doses or for insufficient duration, altered sensitivity to anti‐VEGF‐A agents by mutations in endothelial cells or vascular remodeling, maintenance of vascular sleeves that allow for easy regrowth of tumor vasculature upon discontinuation of therapy, vascular cooption, and intussusceptive angiogenesis. An understanding of these mechanisms may lead to the development of targeted therapies that overcome this resistance. Some of these approaches include the combined inhibition of redundant angiogenic pathways, proper patient selection for various therapies based on gene expression profiles, blockade of cellular migration by inhibition of colony‐stimulating factor, or the use of agents to disrupt vascular architecture. Cancer 2012;3455–3467.

Erlotinib induces mitochondrial-mediated apoptosis in human H3255 non-small-cell lung cancer cells with epidermal growth factor receptorL858R mutation through mitochondrial oxidative phosphorylation-dependent activation of BAX and BAK.

Epidermal growth factor receptor (EGFR) tyrosine kinase inhibitor erlotinib shows potent antitumor activity in some non-small-cell lung cancer (NSCLC) cell lines and is approved by the Food and Drug Administration as second and third line treatment for NSCLC. However, the molecular mechanisms by which erlotinib induces apoptosis remain to be elucidated. Here, we investigated the effect of erlotinib on apoptotic signal pathways in H3255 cells with the EGFRL858R mutation. Erlotinib induces apoptosis associated with the activation of caspases in a dose- and time-dependent manner. Erlotinib did not alter the expression of apoptotic receptors FAS and tumor necrosis factor-related apoptosis-inducing ligand (TRAIL), although it induced caspase-8 activation and BID cleavage. In addition, cell death caused by erlotinib was not prevented by coincubation with FAS and TRAIL antagonists, ZB-4 monoclonal antibody and TRAIL/Fc recombinant, suggesting that erlotinib-induced apoptosis is not associated with receptor-mediated pathways. Erlotinib induces loss of mitochondrial membrane potential and release of cytochrome c and second mitochondria-derived activator of caspases/direct IAP binding protein with low pI from mitochondria. Furthermore, erlotinib causes BAX translocation to mitochondria, BAX and BAK conformational changes, and oligomerization. Erlotinib did not induce reactive oxygen species generation, and cotreatment with antioxidants did not alter erlotinib-induced activation of BAX and BAK and apoptosis. However, cotreatment with inhibitors of mitochondrial oxidative phosphorylation significantly blocked erlotinib-induced activation of BAX and BAK and cell death. Benzyloxycarbiny-VAD-fluoromethyl ketone had no effect on erlotinib-induced BAX and BAK activation but effectively prevented apoptosis. Overexpression of BCL-2 caused a significant attenuation of erlotinib-induced cell death, but no effect on BAX and BAK activation. Down-regulation of BAX and BAK gene expression with small interfering RNA led to an effective reduction of erlotinib-induced apoptosis. Our data indicate that activation of BAX and BAK plays a critical role in the initiation of erlotinib-induced apoptotic cascades.

Phase II study of the proteasome inhibitor bortezomib (PS-341, Velcade®) in chemotherapy-naïve patients with advanced stage non-small cell lung cancer (NSCLC)

The primary objective of this study was to determine the objective response rate of bortezomib as a first-line therapy in patients advanced stage NSCLC. Advanced/metastatic NSCLC patients with measurable disease, adequate organ function, ECOG performance status of 0-2, and no prior chemotherapy for metastatic disease were eligible. Patients received intravenously bolus bortezomib 1.3mg/m(2)/day on days 1, 4, 8 and 11 every 21 days for a maximum of 8 cycles, or until disease progression, or unacceptable toxicity. Tumor response was evaluated after every 2 cycles of therapy. This single-arm phase II study employed the Simons two-stage design. The study was terminated in the first stage after 14 patients enrolled at 4 institutions. No objective response was observed. Three patients (21%) had stable disease and received 8, 6 and 4 cycles of treatment; the duration of stable disease was 11.5, 4.2 and 3.4 months, respectively. Median time to progression was 1.3 months (95% CI, 0.6-3.0 months); median overall survival (OS) was 9.9 months (95% CI, 2.2-27.0 months). Twelve patients received at least one dose of bortezomib. There were no grade 4 toxicities or treatment related deaths. Grade 3 toxicities included fatigue (N=1, 8%), deep vein thrombosis (N=1, 8%) and thrombocytopenia (N=1, 8%). Although well tolerated, bortezomib monotherapy is not active in this cohort of chemotherapy-naïve, metastatic NSCLC.

Molecular pharmacodynamics of PM02734 (elisidepsin) as single agent and in combination with erlotinib; synergistic activity in human non-small cell lung cancer cell lines and xenograft models.

PM02734 (elisidepsin) is a novel marine-derived cyclic peptide belonging to the Kahalalide family of compounds currently under phase I development with early evidence of a positive therapeutic index. The cytotoxicity of PM02734 has been determined in a panel of human NSCLC (non-small cell lung cancer) cell lines. Western blot analysis showed a direct correlation between ErbB3 expression and cell sensitivity to PM02734. Furthermore, PM02734 was more effective in the induction of ErbB3 degradation and dephosphorylation than in that of ErbB2 and ErbB1 in human NSCLC cell lines. The combination of PM02734 and erlotinib was synergistic in all NSCLC cell lines tested, including erlotinib resistant cell lines, with combination indexes ranging between 0.59 and 0.81. The combination of PM02734 and erlotinib was more effective than either drug alone in mice inoculated intravenously (i.v.) with A549 cells. The combination of PM02734 and erlotinib was more effective in inhibiting AKT than either single agent alone in H322 cells. These results have provided a rational basis for an ongoing clinical trial to explore this combination in patients with advanced malignant solid tumours.

RICTOR amplification defines a novel subset of patients with lung cancer who may benefit from treatment with mTORC1/2 inhibitors

UNLABELLED We identified amplification of RICTOR, a key component of the mTOR complex 2 (mTORC2), as the sole actionable genomic alteration in an 18-year-old never-smoker with lung adenocarcinoma. Amplification of RICTOR occurs in 13% of lung cancers (1,016 cases) in The Cancer Genome Atlas and at a similar frequency in an independent cohort of 1,070 patients identified by genomic profiling. In the latter series, 11% of cases harbored RICTOR amplification as the only relevant genomic alteration. Its oncogenic roles were suggested by decreased lung cancer cell growth both in vitro and in vivo with RICTOR ablation, and the transforming capacity of RICTOR in a Ba/F3-cell system. The mTORC1/2 inhibitors were significantly more active against RICTOR-amplified lung cancer cells as compared with other agents targeting the PI3K-AKT-mTOR pathway. Moreover, an association between RICTOR amplification and sensitivities to mTORC1/2 inhibitors was observed. The index patient has been treated with mTORC1/2 inhibitors that led to tumor stabilization for more than 18 months. SIGNIFICANCE RICTOR amplification may define a novel and unique molecular subset of patients with lung cancer who may benefit from treatment with mTORC1/2 inhibitors.

Schedule-dependent interaction between the proteosome inhibitor bortezomib and the EGFR-TK inhibitor erlotinib in human non-small cell lung cancer cell lines

Introduction: Both erlotinib (E) and bortezomib (B) have shown single-agent activity in patients with non-small cell lung cancer. We studied the combination of these two novel biologic agents in vitro using a panel of non-small cell lung cancer cell lines. Methods: The growth inhibitory effect of E and B were determined by MTT assay on seven non-small cell lung cancer cell lines. The data obtained from the growth inhibition assay in response to the combination of E and B were subject to isobologram analysis. The effects of each individual drug as well as combination in different sequences on cell cycle and apoptosis were determined by flow cytometry. Results: Two of seven cell lines are sensitive to E. However, B has narrower range of cytotoxicity. The combination is neither synergistic nor additive in two of four cell lines tested. In H358 bronchoalveolar cell lines, the combination is more active than either agent alone. E causes G1 cell cycle arrest and B causes G2/M cell cycle arrest. In sequential studies, 24-hour previous exposure to E causes G1 arrest and abrogates the cytotoxic effect of B. This is observed in both E-sensitive as well as E-resistant cells and is accompanied by an increase in cell survival and a decrease in apoptosis. Conclusions: The combination of E and B is neither additive nor synergistic in two of four cell lines tested. In H358 bronchoalveolar cell, the combination is more active than either agent alone. The schedule-dependent antagonistic effect of E pre-exposure was observed. E pre-exposure causes G1 cell cycle arrest and abrogates the activity of B. Further in vivo studies of this combination are warranted.

Functional genomics screen identifies YAP1 as a key determinant to enhance treatment sensitivity in lung cancer cells

Survival for lung cancer patients remains dismal and is largely attributed to treatment resistance. To identify novel target genes the modulation of which could modify platinum resistance, we performed a high-throughput RNAi screen and identified Yes-associated protein (YAP1), a transcription coactivator and a known oncogene, as a potential actionable candidate. YAP1 ablation significantly improved sensitivities not only to cisplatin but also to ionizing radiation, both of which are DNA-damaging interventions, in non-small cell lung cancer (NSCLC) cells. Overall YAP1 was expressed in 75% of NSCLC specimens, whereas nuclear YAP1 which is the active form was present in 45% of 124 resected NSCLC. Interestingly, EGFR-mutated or KRAS-mutated NSCLC were associated with higher nuclear YAP1 staining in comparison to EGFR/KRAS wild-type. Relevantly, YAP1 downregulation improved sensitivity to erlotinib, an EGFR inhibitor. A pharmacological inhibitor of YAP1 signaling, verteporfin also synergized with cisplatin, radiation and erlotinib in NSCLC cells by potentiating cisplatin and radiation-related double-stranded breaks and decreasing expression of YAP1 and EGFR. Taken together, our study is the first to indicate the potential role of YAP1 as a common modulator of resistance mechanisms and a potential novel, actionable target that can improve responses to platinum, radiation and EGFR-targeted therapy in lung cancer.

Phase-I/II study of bortezomib in combination with carboplatin and bevacizumab as first-line therapy in patients with advanced non-small-cell lung cancer.

Background: This study aimed to establish the maximum tolerated dose (MTD) of weekly bortezomib in combination with fixed standard doses of carboplatin and bevacizumab, and to estimate the efficacy (response rate and progression free survival [PFS]) and safety of combination therapy with carboplatin, bortezomib, and bevacizumab as first-line therapy in patients with advanced non–small-cell lung cancer (NSCLC). Methods: Patients were assigned to three dose levels of weekly bortezomib with the fixed standard doses of carboplatin AUC 6 and bevacizumab (15 mg/kg) every 3 weeks using a standard phase-I design. Bortezomib doses were 1.3 mg/m2, 1.6 mg/m2, and 1.8 mg/m2 weekly on day 1 and day 8 of every 3-week cycle. A maximum of six cycles was administered. Patients with complete, partial response or stable disease were continued on single-agent bevacizumab (15 mg/kg every 3 weeks) as maintenance therapy. In phase II, either level III or MTD was administered to evaluate the efficacy and safety of the combination in first-line treatment of advanced NSCLC. Results: Sixteen patients were enrolled (three, four, and nine patients in dose level I, II, and III, respectively). There was no predefined dose limiting toxicity in cycle 1 in all 16 patients. The recommended phase-II dose is bortezomib 1.8 mg/m2 weekly on day 1 and day 8 in combination with carboplatin AUC 6 and bevacizumab 15 mg/kg on every 21-day cycle. Totally 9 patients were treated at the recommended phase-II dose level. The most common treatment related grade-3/4 toxicities during the subsequent cycles were thrombocytopenia (58%), lymphopenia (25%), neutropenia (12%), and diarrhea (25%). The grade-1/2 neuropathy was seen in 7 out of 16 patients (44%). The response rate, PFS, and overall survival in all patients were 37.5% (95%CI 13.8%–61.2%), 5.0 months (95%CI: 3.1–8.4), 9.9 months (95% CI: 8.2–14.1), and among the 9 patients in phase-II portion are 44% (95%CI 15.3%–77.3%), 5.5 months (95%CI: 3.1–2.2) and 10.9 months (95%CI: 8.0–14.1). Conclusion: The recommended phase-II dose for this combination is: carboplatin AUC 6, bevacizumab 15 mg/kg on day 1 and bortezomib 1.8 mg/m2 on day 1 and day 8 on every 21-day cycle. The regimen was very well tolerated with interesting clinical activity in first-line treatment of NSCLC.