Good bacteria help fight cancer: Resident gut bacteria can affect patient responses to cancer immunotherapy (see the Perspective by Jobin). Routy et al. show that antibiotic consumption is associated with poor response to immunotherapeutic PD-1 blockade. They profiled samples from patients with lung and kidney cancers and found that nonresponding patients had low levels of the bacterium Akkermansia muciniphila . Oral supplementation of the bacteria to antibiotic-treated mice restored the response to immunotherapy. Matson et al. and Gopalakrishnan et al. studied melanoma patients receiving PD-1 blockade and found a greater abundance of “good” bacteria in the guts of responding patients. Nonresponders had an imbalance in gut flora composition, which correlated with impaired immune cell activity. Thus, maintaining healthy gut flora could help patients combat cancer. Science , this issue p. 91 , p. 104 , p. 97 ; see also p. 32

Purpose: Circulating tumor cells (CTCs) may have utility as surrogate biomarkers and “virtual” biopsies. We report the clinical significance and molecular characteristics of CTCs and CTC clusters, termed circulating tumor microemboli (CTM), detected in patients with small-cell lung cancer (SCLC) undergoing standard treatment. Patients and Methods: Serial blood samples from 97 patients receiving chemotherapy were analyzed using EpCam-based immunomagnetic detection and a filtration-based technique. Proliferation status (Ki67) and apoptotic morphology were examined. Associations of CTC and CTM number with clinical factors and prognosis were determined. Results: CTCs were present in 85% of patients (77 of 97 patients) and were abundant (mean ± standard deviation = 1,589 ± 5,565). CTM and apoptotic CTCs were correlated with total CTC number and were detected in 32% and 57% of patients, respectively. Pretreatment CTCs, change in CTC number after one cycle of chemotherapy, CTM, and apoptotic CTCs were independent prognostic factors. Overall survival was 5.4 months for patients with ≥ 50 CTCs/7.5 mL of blood and 11.5 months (P < .0001) for patients with less than 50 CTCs/7.5 mL of blood before chemotherapy (hazard ratio = 2.45; 95% CI, 1.39 to 4.30; P = .002). Subpopulations of apoptotic and of proliferating solitary CTCs were detected, whereas neither were observed within cell clusters (CTM), implicating both protection from anoikis and relative resistance to cytotoxic drugs for cells within CTM. Conclusion: Both baseline CTC number and change in CTC number after one cycle of chemotherapy are independent prognostic factors for SCLC. Molecular comparison of CTCs to cells in CTM may provide novel insights into SCLC biology.

Purpose: Lung cancer is the leading cause of cancer-related death worldwide. Non–small-cell lung cancer (NSCLC) lacks validated biomarkers to predict treatment response. This study investigated whether circulating tumor cells (CTCs) are detectable in patients with NSCLC and what their ability might be to provide prognostic information and/or early indication of patient response to conventional therapy. Patients and Methods: In this single-center prospective study, blood samples for CTC analysis were obtained from 101 patients with previously untreated, stage III or IV NSCLC both before and after administration of one cycle of standard chemotherapy. CTCs were measured using a semiautomated, epithelial cell adhesion molecule–based immunomagnetic technique. Results: The number of CTCs in 7.5 mL of blood was higher in patients with stage IV NSCLC (n = 60; range, 0 to 146) compared with patients with stage IIIB (n = 27; range, 0 to 3) or IIIA disease (n = 14; no CTCs detected). In univariate analysis, progression-free survival was 6.8 v 2.4 months with P < .001, and overall survival (OS) was 8.1 v 4.3 months with P < .001 for patients with fewer than five CTCs compared with five or more CTCs before chemotherapy, respectively. In multivariate analysis, CTC number was the strongest predictor of OS (hazard ratio [HR], 7.92; 95% CI, 2.85 to 22.01; P < .001), and the point estimate of the HR was increased with incorporation of a second CTC sample that was taken after one cycle of chemotherapy (HR, 15.65; 95% CI, 3.63 to 67.53; P < .001). Conclusion: CTCs are detectable in patients with stage IV NSCLC and are a novel prognostic factor for this disease. Further validation is warranted before routine clinical application.

Epithelial circulating tumor cells (CTCs) are detectable in patients with non-small cell lung cancer (NSCLC). However, epithelial to mesenchymal transition, a widely reported prerequisite for metastasis, may lead to an underestimation of CTC number. We compared directly an epithelial marker-dependent (CellSearch) and a marker-independent (isolation by size of epithelial tumor cells [ISET]) technology platform for the ability to identify CTCs. Molecular characteristics of CTCs were also explored. Paired peripheral blood samples were collected from 40 chemonäive, stages IIIA to IV NSCLC patients. CTCs were enumerated by Epithelial Cell Adhesion Molecule-based immunomagnetic capture (CellSearch, Veridex) and by filtration (ISET, RareCell Diagnostics). CTCs isolated by filtration were assessed by immunohistochemistry for epithelial marker expression (cytokeratins, Epithelial Cell Adhesion Molecule, epidermal growth factor receptor) and for proliferation status (Ki67). CTCs were detected using ISET in 32 of 40 (80%) patients compared with 9 of 40 (23%) patients using CellSearch. A subpopulation of CTCs isolated by ISET did not express epithelial markers. Circulating tumor microemboli (CTM, clusters of ≥ 3 CTCs) were observed in 43% patients using ISET but were undetectable by CellSearch. Up to 62% of single CTCs were positive for the proliferation marker Ki67, whereas cells within CTM were nonproliferative. Both technology platforms detected NSCLC CTCs. ISET detected higher numbers of CTCs including epithelial marker negative tumor cells. ISET also isolated CTM and permitted molecular characterization. Combined with our previous CellSearch data confirming CTC number as an independent prognostic biomarker for NSCLC, we propose that this complementary dual technology approach to CTC analysis allows more complete exploration of CTCs in patients with NSCLC.

Purpose: Introduced in 1987, platinum-based chemotherapy remains standard of care for small cell lung cancer (SCLC), a most aggressive, recalcitrant tumor. Prominent barriers to progress are paucity of tumor tissue to identify drug targets and patient-relevant models to interrogate novel therapies. Following our development of circulating tumor cell patient–derived explants (CDX) as models that faithfully mirror patient disease, here we exploit CDX to examine new therapeutic options for SCLC. Experimental Design: We investigated the efficacy of the PARP inhibitor olaparib alone or in combination with the WEE1 kinase inhibitor AZD1775 in 10 phenotypically distinct SCLC CDX in vivo and/or ex vivo. These CDX represent chemosensitive and chemorefractory disease including the first reported paired CDX generated longitudinally before treatment and upon disease progression. Results: There was a heterogeneous depth and duration of response to olaparib/AZD1775 that diminished when tested at disease progression. However, efficacy of this combination consistently exceeded that of cisplatin/etoposide, with cures in one CDX model. Genomic and protein analyses revealed defects in homologous recombination repair genes and oncogenes that induce replication stress (such as MYC family members), predisposed CDX to combined olaparib/AZD1775 sensitivity, although universal predictors of response were not noted. Conclusions: These preclinical data provide a strong rationale to trial this combination in the clinic informed by prevalent, readily accessed circulating tumor cell–based biomarkers. New therapies will be evaluated in SCLC patients after first-line chemotherapy, and our data suggest that the combination of olaparib/AZD1775 should be used as early as possible and before disease relapse. Clin Cancer Res; 24(20); 5153–64. ©2018 AACR.