Size and Concentration of Cell-Free DNA Measured Directly from Blood Plasma, without Prior DNA Extraction.

Cell-free DNA in human blood plasma (cfDNA) is now widely used and studied as a biomarker for several physiological and pathological situations. In addition to genetic and epigenetic alterations that provide information about the presence and the nature of non-constitutive DNA in the body, cfDNA concentration and size distribution may potentially be independent biomarkers suitable for monitoring at-risk patients and therapy efficacy. Here, we describe a simple, in-line, method, which measures cfDNA concentration and size distribution from only a few microliters of plasma without the need to extract and/or concentrate the DNA prior to the analysis. This method is based on a dual hydrodynamic and electrokinetic actuation, adapted for samples containing salts and proteins such as biological fluids. The method provides analytical performances equivalent to those obtained after purification and concentration of cfDNA, with a precision of ∼1% for size features and of 10-20% for the concentrations of the different size fractions. We show that concentration and size distribution of cfDNA analyzed from plasma can differentiate advanced lung cancer patients from healthy controls. This simple and cost-effective method should facilitate further investigations into the potential clinical usefulness of cfDNA size profiling.

Epigenetically regulated PCDHB15 impairs aggressiveness of metastatic melanoma cells.

The protocadherin proteins are cell adhesion molecules at the crossroad of signaling pathways playing a major role in neuronal development. It is now understood that their role as signaling hubs is not only important for the normal physiology of cells but also for the regulation of hallmarks of cancerogenesis. Importantly, protocadherins form a cluster of genes that are regulated by DNA methylation. We have identified for the first time that PCDHB15 gene is DNA-hypermethylated on its unique exon in the metastatic melanoma-derived cell lines and patients' metastases compared to primary tumors. This DNA hypermethylation silences the gene, and treatment with the DNA demethylating agent 5-aza-2'-deoxycytidine reinduces its expression. We explored the role of PCDHB15 in melanoma aggressiveness and showed that overexpression impairs invasiveness and aggregation of metastatic melanoma cells in vitro and formation of lung metastasis in vivo. These findings highlight important modifications of the methylation of the PCDHß genes in melanoma and support a functional role of PCDHB15 silencing in melanoma aggressiveness.

Switch to fulvestrant and palbociclib versus no switch in advanced breast cancer with rising ESR1 mutation during aromatase inhibitor and palbociclib therapy (PADA-1): a randomised, open-label, multicentre, phase 3 trial.

BACKGROUND: In advanced oestrogen receptor-positive, HER2-negative breast cancer, acquired resistance to aromatase inhibitors frequently stems from ESR1-mutated subclones, which might be sensitive to fulvestrant. The PADA-1 trial aimed to show the efficacy of an early change in therapy on the basis of a rising ESR1 mutation in blood (bESR1mut), while assessing the global safety of combination fulvestrant and palbociclib. METHODS: We did a randomised, open-label, phase 3 trial in 83 hospitals in France. Women aged at least 18 years with oestrogen receptor-positive, HER2-negative advanced breast cancer and an Eastern Cooperative Oncology Group performance status of 0-2 were recruited and monitored for rising bESR1mut during first-line aromatase inhibitor (2·5 mg letrozole, 1 mg anastrozole, or 25 mg exemestane, orally once per day, taken continuously) and palbociclib (125 mg orally once per day on days 1-21 of a 28-day cycle) therapy. Patients with newly present or increased bESR1mut in circulating tumour DNA and no synchronous disease progression were randomly assigned (1:1) to continue with the same therapy or to switch to fulvestrant (500 mg intramuscularly on day 1 of each 28-day cycle and on day 15 of cycle 1) and palbociclib (dosing unchanged). The randomisation sequence was generated within an interactive web response system using a minimisation method (with an 80% random factor); patients were stratified according to visceral involvement (present or absent) and the time from inclusion to bESR1mut detection (<12 months or ≥12 months). The co-primary endpoints were investigator-assessed progression-free survival from random assignment, analysed in the intention-to-treat population (ie, all randomly assigned patients), and grade 3 or worse haematological adverse events in all patients. The trial is registered with Clinicaltrials.gov (NCT03079011), and is now complete. FINDINGS: From March 22, 2017, to Jan 31, 2019, 1017 patients were included, of whom 279 (27%) developed a rising bESR1mut and 172 (17%) were randomly assigned to treatment: 88 to switching to fulvestrant and palbociclib and 84 patients to continuing aromatase inhibitor and palbociclib. At database lock on July 31, 2021, randomly assigned patients had a median follow-up of 35·3 months (IQR 29·2-41·4) from inclusion and 26·0 months (13·8-34·3) from random assignment. Median progression-free survival from random assignment was 11·9 months (95% CI 9·1-13·6) in the fulvestrant and palbociclib group versus 5·7 months (3·9-7·5) in the aromatase inhibitor and palbociclib group (stratified HR 0·61, 0·43-0·86; p=0·0040). The most frequent grade 3 or worse haematological adverse events were neutropenia (715 [70·3%] of 1017 patients), lymphopenia (66 [6·5%]), and thrombocytopenia (20 [2·0%]). The most common grade 3 or worse adverse events in step 2 were neutropenia (35 [41·7%] of 84 patients in the aromatase inhibitor and palbociclib group vs 39 [44·3%] of 88 patients in the fulvestrant and palbociclib group) and lymphopenia (three [3·6%] vs four [4·5%]). 31 (3·1%) patients had grade 3 or worse serious adverse events related to treatment in the overall population. Three (1·7%) of 172 patients randomly assigned had one serious adverse event in step 2: one (1·2%) grade 4 neutropenia and one (1·2%) grade 3 fatigue among 84 patients in the aromatase inhibitor and palbociclib group, and one (1·1%) grade 4 neutropenia among 88 patients in the fulvestrant and palbociclib group. One death by pulmonary embolism in step 1 was declared as being treatment related. INTERPRETATION: PADA-1 is the first prospective randomised trial showing that the early therapeutic targeting of bESR1mut results in significant clinical benefit. Additionally, the original design explored in PADA-1 might help with tackling acquired resistance with new drugs in future trials. FUNDING: Pfizer.

Early Steps of Resistance to Targeted Therapies in Non-Small-Cell Lung Cancer.

Lung cancer is the leading cause of cancer-related deaths among men and women worldwide. Epidermal growth factor receptor-tyrosine kinase inhibitors (EGFR-TKIs) are effective therapies for advanced non-small-cell lung cancer (NSCLC) patients harbouring EGFR-activating mutations, but are not curative due to the inevitable emergence of resistances. Recent in vitro studies suggest that resistance to EGFR-TKI may arise from a small population of drug-tolerant persister cells (DTP) through non-genetic reprogramming, by entering a reversible slow-to-non-proliferative state, before developing genetically derived resistances. Deciphering the molecular mechanisms governing the dynamics of the drug-tolerant state is therefore a priority to provide sustainable therapeutic solutions for patients. An increasing number of molecular mechanisms underlying DTP survival are being described, such as chromatin and epigenetic remodelling, the reactivation of anti-apoptotic/survival pathways, metabolic reprogramming, and interactions with their micro-environment. Here, we review and discuss the existing proposed mechanisms involved in the DTP state. We describe their biological features, molecular mechanisms of tolerance, and the therapeutic strategies that are tested to target the DTP.

Real-Time Detection of ESR1 Mutation in Blood by Droplet Digital PCR in the PADA-1 Trial: Feasibility and Cross-Validation with NGS.

The clinical actionability of circulating tumor DNA requires sensitive detection methods with a short turnaround time. In the PADA-1 phase 3 trial (NCT03079011), metastatic breast cancer patients treated with an aromatase inhibitor and palbociclib were screened every 2 months for activating ESR1 mutations in blood (bESR1mut). We report the feasibility of the droplet digital polymerase chain reaction (ddPCR) and cross-validation with next-generation sequencing (NGS). bESR1mut testing was centralized in two platforms using the same ddPCR assay. Results were reported as copies/mL of plasma and mutant allele frequency (MAF). We analyzed 200 positive ddPCR samples with an NGS assay (0.5-1% sensitivity). Overall, 12,552 blood samples were collected from 1017 patients from 83 centers. Among the 12,525 available samples with ddPCR results, 11,533 (92%) were bESR1mut-negative. A total of 267 patients newly displayed bESR1mut (26% patients/2% samples) with a median copy number of 14/mL (range: 4-1225) and a median MAF of 0.83% (0.11-35), 648 samples (20% patients/5% samples) displayed persistent bESR1mut, and 77 (<1%) samples encountered a technical failure. The median turnaround time from blood drawing to result notification was 13 days (Q1:9; Q3:21 days). Among 200 ddPCR-positive samples tested, NGS detected bESR1mut in 168 (84%); 25 of the 32 cases missed by NGS had low MAF and/or low coverage. In these 200 samples, bESR1mut MAF by both techniques had an excellent intraclass correlation coefficient (ICC = 0.93; 95% CI [0.85; 0.97]). These results from a large-scale trial support the feasibility and accuracy of real-time bESR1mut tracking by ddPCR, opening new opportunities for therapeutic interventions.

Randomised, open-label, multicentric phase III trial to evaluate the safety and efficacy of palbociclib in combination with endocrine therapy, guided by ESR1 mutation monitoring in oestrogen receptor-positive, HER2-negative metastatic breast cancer patients: study design of PADA-1.

INTRODUCTION: The combination of a CDK4/6 inhibitor with an aromatase inhibitor (AI) has recently become the gold standard for AI-sensitive first line treatment of oestrogen receptor-positive (ER+) HER2-negative (HER2-) advanced breast cancer. However, most patients receiving this combination will ultimately progress and require further therapies.Several studies have demonstrated that the onset of a ESR1 gene mutation lead to AIs resistance in the advanced setting. ESR1 mutations can be detected in circulating tumour DNA (ctDNA) using a digital PCR assay. Our study aims to prove the clinical efficacy of periodic monitoring for emerging or rise of ESR1 mutations in ctDNA to trigger an early change from AI plus palbociclib to fulvestrant plus palbociclib treatment while assessing global safety. METHODS: PADA-1 is a randomised, open-label, multicentric, phase III trial conducted in patients receiving AI and palbociclib as first line therapy for metastatic ER +HER2- breast cancer. 1000 patients will be included and treated with palbociclib in combination with an AI. Patients will be screened for circulating blood ESR1 mutation detection at regular intervals. Patients for whom a rising circulating ESR1 mutation is detected without tumour progression (up to N=200) will be randomised (1:1) between (1) Arm A: no modification of therapy; and (2) Arm B: palbociclib in combination with fulvestrant, a selective ER down-regulator. At tumour progression, an optional crossover will be offered to patients randomised in arm A. The coprimary endpoints are (1) Grade ≥3 haematological toxicities and their associations with baseline characteristics and (2) progression-free survival in randomised patients. ETHICS AND DISSEMINATION: The study has been approved by the French medicines agency (ANSM) and by an ethics committee (ref 01/17_1 CPP Ouest-IV Nantes) in January 2017. The trial results will be published in academic conference presentations and international peer-reviewed journals. TRIAL REGISTRATION NUMBERS: EudraCT: 2016-004360-18; NCT03079011.

How far we have come targeting BRAF-mutant non-small cell lung cancer (NSCLC).

The advent of high-throughput sequencing has allowed to profoundly interrogate the molecular landscape of non-small cell lung cancer (NSCLC) in the last years. These findings constitute the opportunity to better stratify these patients in order to address specific treatments to well-defined oncogene-restricted subgroups. Among them, BRAF-mutated lung cancers represent around 4% of NSCLC, thus identifying a clinically relevant population that should be aptly managed. Pivotal phase II trials have demonstrated the efficacy of combinatorial treatment - dabrafenib plus trametinib, targeting both BRAF and MEK - for patients harboring V600E mutations, making this specific BRAF alteration a mandatory requirement in the genetic portrait of advanced non-squamous lung cancer patients. However, around half of BRAF+ NSCLC patients remain orphan of targeted approaches. Here we review the available evidence, mainly from a clinical perspective, of therapeutic strategies for both V600E and non-V600 patients, in terms of small molecule, immune checkpoint inhibitors and forthcoming integrated strategies. Looking at on-going clinical trials, a special attention is dedicated to emergent molecules and combinatorial strategies that not only will improve outcomes of classical V600E, but also will make concrete the chance of tailored treatments for the majority of BRAF-mutated patients.

Detection of Tumor Recurrence via Circulating Tumor DNA Profiling in Patients with Localized Lung Cancer: Clinical Considerations and Challenges.

Approximately 30% of patients with non-small-cell lung cancer (NSCLC) present with localized/non-metastatic disease and are eligible for surgical resection or other "treatment with curative intent". Due to the high prevalence of recurrence after treatment, adjuvant therapy is standard care for most patients. The effect of adjuvant chemotherapy is, however, modest, and new tools are needed to identify candidates for adjuvant treatments (chemotherapy, immunotherapy, or targeted therapies), especially since expanded lung cancer screening programs will increase the rate of patients detected with localized NSCLC. Circulating tumor DNA (ctDNA) has shown strong potential to detect minimal residual disease (MRD) and to guide adjuvant therapies. In this manuscript, we review the technical aspects and performances of the main ctDNA sequencing platforms (TRACERx, CAPP-seq) investigated in this purpose, and discuss the potential of this approach to guide or spare adjuvant therapies after definitive treatment of NSCLC.

Diagnosis, biology and epidemiology of oligometastatic breast cancer.

Does oligometastatic breast cancer (OMBC) deserve a dedicated treatment? Although some authors recommend multidisciplinary management of OMBC with a curative intent, there is no evidence proving this strategy beneficial in the absence of a randomized trial. The existing literature sheds little light on OMBC. Incidence is unknown; data available are either obsolete or biased; there is no consensus on the definition of OMBC and metastatic sites, nor on necessary imaging techniques. However, certain proposals merit consideration. Knowledge of eventual specific OMBC biological characteristics is limited to circulating tumor cell (CTC) counts. Given the data available for other cancers, studies on microRNAs (miRNAs), circulating tumor DNA (ctDNA) and genomic alterations should be developed Finally, safe and effective therapies do exist, but results of randomized trials will not be available for many years. Prospective observational cohort studies need to be implemented.

Minimal Residual Disease Monitoring Using a 3'ALK Universal Probe Assay in ALK-Positive Anaplastic Large-Cell Lymphoma: ddPCR, an Attractive Alternative Method to Real-Time Quantitative PCR.

In ALK-positive anaplastic large-cell lymphomas, positive qualitative PCR for NPM1-anaplastic lymphoma kinase (ALK) in peripheral blood and/or bone marrow at diagnosis and during treatment are associated with a higher risk of treatment failure. Real-time quantitative PCR allows identification of very high risk patients. However, this latter technique initially designed for patients with lymphomas carrying the most frequent NPM1-ALK translocation necessitates calibration curves, limiting interlaboratory reproducibility. An ALK universal quantitative PCR based on 3'ALK transcript amplification was designed to allow the detection of all ALK fusion transcripts. The absolute concordance of 3'ALK quantitative PCR results were validated with the routine NPM1-ALK qualitative and quantitative PCR on 46 samples. The universality of ALK fusion transcript detection also was validated on TPM3-, ALO17-, and ATIC-ALK-positive samples, and the EML4-ALK-positive cell line. Digital droplet PCR using the 3'ALK universal probe showed highly concordant results with 3'ALK universal quantitative PCR. A major benefit of digital droplet PCR is a reduced experimental set-up compared with quantitative PCR, without generation of standard curves, leading to a reliable protocol for multilaboratory validation in multicenter clinical trials essential for this rare pathology. Our ALK universal method could be used for the screening of ALK fusion transcripts in liquid biopsy specimens of other ALK-positive tumors, including non-small cell lung carcinomas.

Liquid Biopsy of Non-Plasma Body Fluids in Non-Small Cell Lung Cancer: Look Closer to the Tumor!

Liquid biopsy is a rapidly emerging field due to an increasing number of oncogenic drivers and a better understanding of resistance mechanisms to targeted therapies in non-small cell lung cancer (NSCLC). The sensitivity of the most widely used blood-based assays is, however, limited in particular in cases of low tumor volume where shed of tumor-derived material can be limited. A negative result thus requires biopsy confirmation using minimally invasive sampling procedures that can result in small specimens, which are often not suitable for genotyping. Liquid biopsy is not limited to plasma, and tumor DNA circulating in other body fluids such as urine, pleural fluid, cerebrospinal fluid, or cytology specimen-derived supernatant can be exploited. In comparison to cell blocks, these fluids in close contact to the tumor may contain a more abundant and less analytically demanding tumor DNA. In this review, we discuss the potential applications of circulating tumor DNA derived from cytology samples in NSCLC, from early stage (screening, nodule characterization) to metastatic disease.

Circulating Tumor DNA Genomics Reveal Potential Mechanisms of Resistance to BRAF-Targeted Therapies in Patients with BRAF-Mutant Metastatic Non-Small Cell Lung Cancer.

PURPOSE: The limited knowledge on the molecular profile of patients with BRAF-mutant non-small cell lung cancer (NSCLC) who progress under BRAF-targeted therapies (BRAF-TT) has hampered the development of subsequent therapeutic strategies for these patients. Here, we evaluated the clinical utility of circulating tumor DNA (ctDNA)-targeted sequencing to identify canonical BRAF mutations and genomic alterations potentially related to resistance to BRAF-TT, in a large cohort of patients with BRAF-mutant NSCLC. EXPERIMENTAL DESIGN: This was a prospective study of 78 patients with advanced BRAF-mutant NSCLC, enrolled in 27 centers across France. Blood samples (n = 208) were collected from BRAF-TT-naïve patients (n = 47), patients nonprogressive under treatment (n = 115), or patients at disease progression (PD) to BRAF-TT (24/46 on BRAF monotherapy and 22/46 on BRAF/MEK combination therapy). ctDNA sequencing was performed using InVisionFirst-Lung. In silico structural modeling was used to predict the potential functional effect of the alterations found in ctDNA. RESULTS: BRAFV600E ctDNA was detected in 74% of BRAF-TT-naïve patients, where alterations in genes related with the MAPK and PI3K pathways, signal transducers, and protein kinases were identified in 29% of the samples. ctDNA positivity at the first radiographic evaluation under treatment, as well as BRAF-mutant ctDNA positivity at PD were associated with poor survival. Potential drivers of resistance to either BRAF-TT monotherapy or BRAF/MEK combination were identified in 46% of patients and these included activating mutations in effectors of the MAPK and PI3K pathways, as well as alterations in U2AF1, IDH1, and CTNNB1. CONCLUSIONS: ctDNA sequencing is clinically relevant for the detection of BRAF-activating mutations and the identification of alterations potentially related to resistance to BRAF-TT in BRAF-mutant NSCLC.

Current and future applications of liquid biopsy in nonsmall cell lung cancer from early to advanced stages.

Liquid biopsy refers to the analysis of any tumour-derived material circulating in the blood or any other body fluid. This concept is particularly relevant in lung cancer as the tumour is often difficult to reach and may need an invasive and potentially harmful procedure. Moreover, the multitude of anticancer drugs and their sequential use underline the importance of conducting an iterative assessment of tumour biology. Liquid biopsies can noninvasively detect any targetable genomic alteration and guide corresponding targeted therapy, in addition to monitoring response to treatment and exploring the genetic changes at resistance, overcoming spatial and temporal heterogeneity.In this article, we review the available data in the field, which suggest the potential of liquid biopsy in the area of lung cancer, with a particular focus on cell-free DNA and circulating tumour cells. We discuss their respective applications in patient selection and monitoring through targeted therapy, as well as immune checkpoint inhibitors. The current data and future applications of liquid biopsy in the early stage setting are also investigated.Liquid biopsy has the potential to help manage nonsmall cell lung cancer throughout all stages of lung cancer: screening, minimal residual disease detection to guide adjuvant treatment, early detection of relapse, systemic treatment initiation and monitoring of response (targeted or immune therapy), and resistance genotyping.

Targeted sequencing of plasma cell-free DNA to predict response to PD1 inhibitors in advanced non-small cell lung cancer.

OBJECTIVES: Tumor mutational burden is an emerging biomarker of response to immune checkpoint inhibitors (ICI), whose clinical adoption is challenging. We hypothesized that targeting limited but relevant genetic alterations in plasma cell-free DNA along with early monitoring may non-invasively predict response to ICI in advanced non-small cell lung cancer (NSCLC). MATERIAL AND METHODS: Plasma samples from patients with progressive NSCLC collected before ICI initiation and at 1 month were profiled from responders (R: PFS > 6 months) and non-responders (NR: progressive disease at first evaluation) using amplicon sequencing of hotspots and coding regions from 36 genes. The molecular profile of ctDNA, and its early kinetics were analyzed. RESULTS: 97 patients were analyzed, of which 86 (39 R, 47 NR) were evaluable. Alterations in ctDNA were detectable in 67/86 baseline samples (78%). The detection of a targetable oncogenic driver was associated with a 2 months PFS. The presence of a PTEN or STK11 mutation was correlated with early progression (HR 8.9, p = 0.09 for PTEN, HR 4.7, p = 0.003 for STK11), while transversion mutations (Tv) in KRAS and TP53 predicted better outcomes (HR 0.36, p = 0.011 for TP53 Tv; HR 0.46, p = 0.11 for KRAS Tv). Patients with a low "immune score" (driver and/or PTEN or STK11 mutation and/or without KRAS or TP53 Tv) derived poor outcomes (median PFS 2 months), compared with patients with a high immune score (no driver, no PTEN or STK11 and with KRAS or TP53 Tv (median PFS 14 months, p = 0.0001, HR 2.96). Early changes in the ctDNA allele fraction (AF) of 65 specimens were correlated with clinical outcomes (14 months PFS if AF decreases vs. 2 months if AF increases, p < 0.0001). CONCLUSION: Targeted sequencing of plasma ctDNA and monitoring its early variations can predict response to ICI.

Cytoplasmic p27Kip1 promotes tumorigenesis via suppression of RhoB activity.

The cell cycle inhibitor p27Kip1 is a tumor suppressor via the inhibition of CDK complexes in the nucleus. However, p27 also plays other functions in the cell and may acquire oncogenic roles when located in the cytoplasm. Activation of oncogenic pathways such as Ras or PI3K/AKT causes the relocalization of p27 in the cytoplasm, where it can promote tumorigenesis by unclear mechanisms. Here, we investigated how cytoplasmic p27 participates in the development of non-small cell lung carcinomas. We provide molecular and genetic evidence that the oncogenic role of p27 is mediated, at least in part, by binding to and inhibiting the GTPase RhoB, which normally acts as a tumor suppressor in the lung. Genetically modified mice revealed that RhoB expression is preferentially lost in tumors in which p27 is absent and maintained in tumors expressing wild-type p27 or p27CK- , a mutant that cannot inhibit CDKs. Moreover, although the absence of RhoB promoted tumorigenesis in p27-/- animals, it had no effect in p27CK- knock-in mice, suggesting that cytoplasmic p27 may act as an oncogene, at least in part, by inhibiting the activity of RhoB. Finally, in a cohort of lung cancer patients, we identified a subset of tumors harboring cytoplasmic p27 in which RhoB expression is maintained and these characteristics were strongly associated with decreased patient survival. Thus, monitoring p27 localization and RhoB levels in non-small cell lung carcinoma patients appears to be a powerful prognostic marker for these tumors. Copyright © 2018 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.

Early Circulating Tumour DNA Variations Predict Tumour Response in Melanoma Patients Treated with Immunotherapy.

Antibodies targeting immune checkpoints were recently approved for metastatic melanoma. However, not all patients will respond to the treatment and some will experience grade III-IV immune-related adverse events. Therefore, early identification of non-responder patients would greatly aid clinical practice. Detection of circulating tumour DNA (ctDNA) is a non-invasive approach to monitor tumour response. Digital droplet PCR was used to quantify BRAF and NRAS mutations in the plasma of patients with metastatic melanoma treated with immunotherapy. In 16 patients, ctDNA variations mirrored tumour response (p = 0.034) and ctDNA augmentation during follow-up detected tumour progression with 100% specificity. In 13 patients, early ctDNA variation was associated with clinician decision at first evaluation (p = 0.0046), and early ctDNA increase with shorter progression-free survival (median 21 vs. 145 days; p = 0.001). Monitoring ctDNA variations early during immunotherapy may help clinicians rapidly to discriminate non-responder patients, allow early adaptation of therapeutic strategies, and reduce exposure to ineffective, expensive treatment.

PD-L1 expression in circulating tumor cells of advanced non-small cell lung cancer patients treated with nivolumab.

BACKGROUND: Inhibitors of the PD-1/PD-L1 immune checkpoint have become a standard of care in non-small cell lung cancer (NSCLC). Patient selection, currently based on PD-L1 expression on tumor tissue, is limited by its temporal and spatial heterogeneity. We hypothesized that liquid biopsy with PD-L1 analysis on circulating tumor cells (CTCs) might overcome this limitation. METHODS: Blood samples were prospectively collected from patients with advanced NSCLC before nivolumab treatment and at the time of progression. CTCs were isolated using a cell size-based technology. PD-L1 expression was assessed by immunofluorescence on CTCs and immunohistochemistry on tissue biopsies. RESULTS: 113 specimens from 96 patients were collected. Baseline PD-L1 expression could be assessed on 72% and 93% of tissue and CTC, respectively. CTCs were more frequently found to be PD-L1 positive than tissue (83% vs. 41%) and no correlation was observed between tissue and CTC PD-L1 expression (r = 0.04, p = 0.77). Pre-treatment high CTC number was associated with increased risk of death and progression (HR1.06, p = 0.03 for OS; HR1.05, p = 0.02 for PFS). The presence of pre-treatment PD-L1+CTC was not significantly correlated with outcomes but a higher baseline PD-L1+ CTC number (≥1%) was observed in the "non-responders" group (PFS <6 months) (p = 0.04) and PD-L1+CTC were seen in all patients at progression. CONCLUSION: Assessment of PD-L1 expression in CTCs is feasible and CTCs are more often positive than in tissue. Pre-treatment PD-L1+CTCs are associated with bad prognosis in patients treated with PD-1 inhibitors.

RHOB expression controls the activity of serine/threonine protein phosphatase PP2A to modulate mesenchymal phenotype and invasion in non-small cell lung cancers.

Metastatic dissemination is the cause of death in the vast majority of cancers, including lung cancers. In order to metastasize, tumor cells must undergo a well-known series of changes, however the molecular details of how they manage to overcome the barriers at each stage remain incomplete. One critical step is acquiring the ability to migrate through the extracellular matrix. Loss of expression of the RAS-related small GTPase RHOB is a common feature of lung cancer progression, and we recently reported that this induces an epithelial-to-mesenchymal transition (EMT) that is dependent on SLUG overexpression and E-Cadherin inhibition and is characterized by 3-dimensional cell shape reorganization and the increased invasiveness of bronchial cells. RHOB loss was found to induce AKT1 activation, which in turn activates RAC1 through its GEF TRIO. Further investigation of this pathway revealed that RHOB interacts with and positively regulates PP2A, one of the major cellular serine-threonine phosphatases, by recruiting its regulatory subunit B55. Here we discuss the role of this newly discovered RHOB/PP2A/AKT1/RAC1 pathway in relation to mesenchymal migration and invasion in lung cancer.