Ross A. Soo

Isolation and retrieval of circulating tumor cells using centrifugal forces

Presence and frequency of rare circulating tumor cells (CTCs) in bloodstreams of cancer patients are pivotal to early cancer detection and treatment monitoring. Here, we use a spiral microchannel with inherent centrifugal forces for continuous, size-based separation of CTCs from blood (Dean Flow Fractionation (DFF)) which facilitates easy coupling with conventional downstream biological assays. Device performance was optimized using cancer cell lines (> 85% recovery), followed by clinical validation with positive CTCs enumeration in all samples from patients with metastatic lung cancer (n = 20; 5–88 CTCs per mL). The presence of CD133+ cells, a phenotypic marker characteristic of stem-like behavior in lung cancer cells was also identified in the isolated subpopulation of CTCs. The spiral biochip identifies and addresses key challenges of the next generation CTCs isolation assay including antibody independent isolation, high sensitivity and throughput (3 mL/hr); and single-step retrieval of viable CTCs.

A common BIM deletion polymorphism mediates intrinsic resistance and inferior responses to tyrosine kinase inhibitors in cancer

Tyrosine kinase inhibitors (TKIs) elicit high response rates among individuals with kinase-driven malignancies, including chronic myeloid leukemia (CML) and epidermal growth factor receptor–mutated non–small-cell lung cancer (EGFR NSCLC). However, the extent and duration of these responses are heterogeneous, suggesting the existence of genetic modifiers affecting an individuals response to TKIs. Using paired-end DNA sequencing, we discovered a common intronic deletion polymorphism in the gene encoding BCL2-like 11 (BIM). BIM is a pro-apoptotic member of the B-cell CLL/lymphoma 2 (BCL2) family of proteins, and its upregulation is required for TKIs to induce apoptosis in kinase-driven cancers. The polymorphism switched BIM splicing from exon 4 to exon 3, which resulted in expression of BIM isoforms lacking the pro-apoptotic BCL2-homology domain 3 (BH3). The polymorphism was sufficient to confer intrinsic TKI resistance in CML and EGFR NSCLC cell lines, but this resistance could be overcome with BH3-mimetic drugs. Notably, individuals with CML and EGFR NSCLC harboring the polymorphism experienced significantly inferior responses to TKIs than did individuals without the polymorphism (P = 0.02 for CML and P = 0.027 for EGFR NSCLC). Our results offer an explanation for the heterogeneity of TKI responses across individuals and suggest the possibility of personalizing therapy with BH3 mimetics to overcome BIM-polymorphism–associated TKI resistance.

Glycine Decarboxylase Activity Drives Non-Small Cell Lung Cancer Tumor-Initiating Cells and Tumorigenesis

Identification of the factors critical to the tumor-initiating cell (TIC) state may open new avenues in cancer therapy. Here we show that the metabolic enzyme glycine decarboxylase (GLDC) is critical for TICs in non-small cell lung cancer (NSCLC). TICs from primary NSCLC tumors express high levels of the oncogenic stem cell factor LIN28B and GLDC, which are both required for TIC growth and tumorigenesis. Overexpression of GLDC and other glycine/serine enzymes, but not catalytically inactive GLDC, promotes cellular transformation and tumorigenesis. We found that GLDC induces dramatic changes in glycolysis and glycine/serine metabolism, leading to changes in pyrimidine metabolism to regulate cancer cell proliferation. In the clinic, aberrant activation of GLDC correlates with poorer survival in lung cancer patients, and aberrant GLDC expression is observed in multiple cancer types. This link between glycine metabolism and tumorigenesis may provide novel targets for advancing anticancer therapy.

Structural, Biochemical, and Clinical Characterization of Epidermal Growth Factor Receptor (EGFR) Exon 20 Insertion Mutations in Lung Cancer.

Crystal structure and detailed analysis of different EGFR mutants explain why some mutations in exon 20 make lung cancers resistant to EGFR inhibitors and others make them more sensitive. A Crystal Clear Cause of Drug Resistance Epidermal growth factor receptor (EGFR) tyrosine kinase inhibitors (TKIs) are used to treat a variety of cancers, including non–small cell lung cancer. EGFR mutations have a wide range of effects on the success of TKI treatment in this cancer type, with some sensitizing the tumors to TKI inhibitors and others making them resistant to targeted therapy. For example, most of the mutations in exon 20, a relatively common mutation site, prevent cancer cells from responding to EGFR inhibitors. Here, Yasuda and co-workers determined the crystal structure of EGFR with an exon 20 mutation and used a combination of kinetic studies and structural analysis to elucidate the mechanism for these mutants’ differential sensitivity to TKIs. The findings of Yasuda et al. clarify the reasons for the drug resistance of most exon 20 mutations and show the mechanism for the rare mutation in the same exon that increases tumors’ sensitivity to treatment. In addition to explaining which of the mutants are resistant to targeted inhibition of EGFR and the reasons for this phenomenon, this work could help with the development of future therapeutics. By taking advantage of the crystal structure and detailed insights into the function of mutant EGFR, researchers may be able to design drugs that exploit the unique structural features of resistant mutants and specifically target them for treatment. Epidermal growth factor receptor (EGFR) gene mutations (G719X, exon 19 deletions/insertions, L858R, and L861Q) predict favorable responses to EGFR tyrosine kinase inhibitors (TKIs) in advanced non–small cell lung cancer (NSCLC). However, EGFR exon 20 insertion mutations (~10% of all EGFR mutations) are generally associated with insensitivity to available TKIs (gefitinib, erlotinib, and afatinib). The basis of this primary resistance is poorly understood. We studied a broad subset of exon 20 insertion mutations, comparing in vitro TKI sensitivity with responses to gefitinib and erlotinib in NSCLC patients, and found that most are resistant to EGFR TKIs. The crystal structure of a representative TKI-insensitive mutant (D770_N771insNPG) reveals an unaltered adenosine triphosphate–binding pocket, and the inserted residues form a wedge at the end of the C helix that promotes the active kinase conformation. Unlike EGFR-L858R, D770_N771insNPG activates EGFR without increasing its affinity for EGFR TKIs. Unexpectedly, we find that EGFR-A763_Y764insFQEA is highly sensitive to EGFR TKIs in vitro, and patients whose NSCLCs harbor this mutation respond to erlotinib. Analysis of the A763_Y764insFQEA mutant indicates that the inserted residues shift the register of the C helix in the N-terminal direction, altering the structure in the region that is also affected by the TKI-sensitive EGFR-L858R. Our studies reveal intricate differences between EGFR mutations, their biology, and their response to EGFR TKIs.

Fibroblast Growth Factor Receptor 1 Gene Amplification Is Associated With Poor Survival and Cigarette Smoking Dosage in Patients With Resected Squamous Cell Lung Cancer

PURPOSE To investigate the frequency and the prognostic role of fibroblast growth factor receptor 1 (FGFR1) amplification in patients with surgically resected squamous cell carcinoma of the lung (SCCL) and the association between smoking and FGFR1 amplification. PATIENTS AND METHODS Gene copy number of FGFR1 was investigated in microarrayed tumors from 262 patients with SCCL who had tumor tissue as well as smoking and survival data available. Gene copy number was evaluated by fluorescent in situ hybridization, and an FGFR1-amplified tumor (FGFR1 amp(+)) was prespecified as a tumor with nine or more copies of FGFR1. RESULTS Among 262 patients, the frequency of FGFR1 amp(+) was 13.0%. Patients with FGFR1 amp(+) had significantly shorter disease-free survival (DFS; 26.9 v 94.6 months; P < .001) as well as shorter overall survival (OS; 51.2 v 115.0 months; P = .002) than those without FGFR1 amp(+). Multivariate modeling confirmed that patients with FGFR1 amp(+) had a significantly greater risk of recurrence and death than those without FGFR1 amp(+) after adjusting for sex, smoking status, pathologic stage, and adjuvant chemotherapy (DFS: adjusted hazard ratio [AHR], 2.24; 95% CI, 1.45 to 3.45; P < .001; OS: AHR, 1.83; 95% CI, 1.15 to 2.89; P = .01). The frequency of FGFR1 amp(+) was significantly higher in current smokers than in former smokers and never-smokers (28.9% v 2.5% v 0%; P(trend) < .001). As the smoking dosage increased, so did the incidence of FGFR1 amp(+) (P(trend) = .002). CONCLUSION FGFR1 amplification is an independent negative prognostic factor in surgically resected SCCL and is associated with cigarette smoking in a dose-dependent manner. FGFR1 amplification is a relevant therapeutic target in Asian patients with SCCL.

Prognostic significance of thymidylate synthase, dihydropyrimidine dehydrogenase and thymidine phosphorylase protein expression in colorectal cancer patients treated with or without 5-fluorouracil-based chemotherapy

BACKGROUND Low tumour expression levels of thymidylate synthase (TS), dihydropyrimidine dehydrogenase (DPD) and thymidine phosphorylase (TP) have been linked with improved outcome for colorectal cancer (CRC) patients treated with 5-fluorouracil (5-FU). It is unclear whether this occurs because such tumours have better prognosis or they are more sensitive to 5-FU treatment. PATIENTS AND METHODS Associations between TS, DPD and TP levels, determined by tissue microarrays and immunohistochemistry, and survival was evaluated in 945 CRC patients according to treatment status. RESULTS Low TS and DPD expression associated with worse prognosis in stage II [hazard ratio (HR) = 1.69, 95% confidence interval (CI) (1.09-2.63) and HR = 1.92 (95% CI 1.23-2.94), respectively] and stage III CRC patients treated by surgery alone [HR = 1.39 (95% CI 0.92-2.13) and HR = 1.49 (95% CI 1.02-2.17), respectively]. Low TS, DPD and TP associated with trends for better outcome in stage III patients treated with 5-FU [HR = 0.81 (95% CI 0.49-1.33), HR = 0.70 (95% CI 0.42-1.15) and HR = 0.66 (95% CI 0.39-1.12), respectively]. CONCLUSION Low TS and DPD expression are prognostic for worse outcome in CRC patients treated by surgery alone, whereas low TS, DPD and TP expression are prognostic for better outcome in patients treated with 5-FU chemotherapy. These results provide indirect evidence that low TS, DPD and TP protein expression are predictive of good response to 5-FU chemotherapy.

Activation of IL-6R/JAK1/STAT3 Signaling Induces De Novo Resistance to Irreversible EGFR Inhibitors in Non–Small Cell Lung Cancer with T790M Resistance Mutation

The secondary T790M mutation in epidermal growth factor receptor (EGFR) is the major mechanism of acquired resistance to EGFR tyrosine kinase inhibitors (TKI) in non–small cell lung cancer (NSCLC). Although irreversible EGFR TKIs, such as afatinib or dacomitinib, have been introduced to overcome the acquired resistance, they showed a limited efficacy in NSCLC with T790M. Herein, we identified the novel de novo resistance mechanism to irreversible EGFR TKIs in H1975 and PC9-GR cells, which are NSCLC cells with EGFR T790M. Afatinib activated interleukin-6 receptor (IL-6R)/JAK1/STAT3 signaling via autocrine IL-6 secretion in both cells. Inhibition of IL-6R/JAK1/STAT3 signaling pathway increased the sensitivity to afatinib. Cancer cells showed stronger STAT3 activation and enhanced resistance to afatinib in the presence of MRC5 lung fibroblasts. Blockade of IL-6R/JAK1 significantly increased the sensitivity to afatinib through inhibition of afatinib-induced STAT3 activation augmented by the interaction with fibroblasts, suggesting a critical role of paracrine IL-6R/JAK1/STAT3 loop between fibroblasts and cancer cells in the development of drug resistance. The enhancement of afatinib sensitivity by inhibition of IL-6R/JAK1/STAT3 signaling was confirmed in in vivo PC9-GR xenograft model. Similar to afatinib, de novo resistance to dacomitinib in H1975 and PC9-GR cells was also mediated by dacomitinib-induced JAK1/STAT3 activation. Taken together, these findings suggest that IL-6R/JAK1/STAT3 signaling can be a potential therapeutic target to enhance the efficacy of irreversible EGFR TKIs in patients with EGFR T790M. Mol Cancer Ther; 11(10); 2254–64. ©2012 AACR.

Clinical pharmacology and pharmacogenetics of gemcitabine

Gemcitabine is a cytotoxic nucleoside analog, which is widely used in the treatment of malignancies. Interindividual differences in gemcitabine pharmacokinetics and pharmacodynamics have been demonstrated. Pharmacogenetic factors may account for a significant proportion of these differences. This review provides an update on the pharmacogenetics of gemcitabine and its influence on gemcitabine efficacy and toxicity.

Nivolumab in NSCLC: Latest evidence and clinical potential

New insight on the interaction between the immune system and tumor has identified the programmed death-1/programmed death-1 ligand pathway to be a key player in evading host immune response. The immune checkpoint modulator, nivolumab (BMS-936558/ONO-4538), is the first PD-1 inhibitor to gain regulatory approval, for the treatment of patients with unresectable melanoma. This review will discuss results from early phase studies of nivolumab in solid tumors including non-small cell lung cancer (NSCLC) as well as studies of nivolumab in combination with chemotherapy, other immune modulators and molecular targeted therapy in patients with NSCLC.

Phase I and Biomarker Study of ABT-869, a Multiple Receptor Tyrosine Kinase Inhibitor, in Patients With Refractory Solid Malignancies

PURPOSE To determine the safety and tolerability of ABT-869 at escalating doses and its effects on biomarkers relevant for antiangiogenic activity in patients with solid malignancies. PATIENTS AND METHODS Patients with solid malignancies refractory to or for which no standard effective therapy exists were enrolled onto escalating-dose cohorts and treated with oral ABT-869 once daily continuously. RESULTS Thirty-three patients were studied at doses of 10 mg/d, 0.1 mg/kg/d, 0.25 mg/kg/d, and 0.3 mg/kg/d. Dose-limiting toxicities in the first cycle (21 days) included grade 3 fatigue in a patient at 10 mg/d, grade 3 proteinuria and grade 3 hypertension in two separate patients at 0.25 mg/kg/d, and grade 3 hypertension and grade 3 proteinuria in two separate patients at 0.3 mg/kg/d, which was the maximum-tolerated dose. Other significant treatment-related adverse events included asthenia, hand and foot blisters, and myalgia. Oral clearance of ABT-869 was linear, with a mean of 2.7 +/- 1.2 L/h and half-life of 18.4 +/- 5.7 hours, with no evidence of drug accumulation at day 15. Two patients with lung cancer and one patient with colon cancer achieved partial response. Stable disease for more than four cycles was observed in 16 patients (48%). Dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI) showed dose-dependent reduced tumor vascular permeability that correlated with drug exposure. By day 15 of treatment, circulating endothelial cells were significantly reduced (P = .007), whereas plasma vascular endothelial growth factor was increased (P = .004). CONCLUSION ABT-869 by continuous once-daily dosing was tolerable at doses </= 0.25 mg/kg/d. Biomarker evidence of antiangiogenic activity and DCE-MRI evidence of tumor antiangiogenesis were observed together with promising clinical activity.