An integrin binding-defective mutant of insulin-like growth factor-1 (R36E/R37E IGF1) acts as a dominant-negative antagonist of the IGF1 receptor (IGF1R) and suppresses tumorigenesis but still binds to IGF1R.

Insulin-like growth factor-1 (IGF1) is a major therapeutic target for cancer. We recently reported that IGF1 directly binds to integrins (αvß3 and α6ß4) and induces ternary complex formation (integrin-IGF1-IGF1 receptor (IGF1R)) and that the integrin binding-defective mutant of IGF1 (R36E/R37E) is defective in signaling and ternary complex formation. These findings predict that R36E/R37E competes with WT IGF1 for binding to IGF1R and inhibits IGF signaling. Here, we described that excess R36E/R37E suppressed cell viability increased by WT IGF1 in vitro in non-transformed cells. We studied the effect of R36E/R37E on viability and tumorigenesis in cancer cell lines. We did not detect an effect of WT IGF1 or R36E/R37E in cancer cells under anchorage-dependent conditions. However, under anchorage-independent conditions, WT IGF1 enhanced cell viability and induced signals, whereas R36E/R37E did not. Notably, excess R36E/R37E suppressed cell viability and signaling induced by WT IGF1 under anchorage-independent conditions. Using cancer cells stably expressing WT IGF1 or R36E/R37E, we determined that R36E/R37E suppressed tumorigenesis in vivo, whereas WT IGF1 markedly enhanced it. R36E/R37E suppressed the binding of WT IGF1 to the cell surface and the subsequent ternary complex formation induced by WT IGF1. R36E/R37E suppressed activation of IGF1R by insulin. WT IGF1, but not R36E/R37E, induced ternary complex formation with the IGF1R/insulin receptor hybrid. These findings suggest that 1) IGF1 induces signals under anchorage-independent conditions and that 2) R36E/R37E acts as a dominant-negative inhibitor of IGF1R (IGF1 decoy). Our results are consistent with a model in which ternary complex formation is critical for IGF signaling.

Detection of EGFR Mutations in cfDNA and CTCs, and Comparison to Tumor Tissue in Non-Small-Cell-Lung-Cancer (NSCLC) Patients.

Lung cancer is the leading cause of cancer-related mortality worldwide. Epidermal growth factor receptor (EGFR) tyrosine kinase inhibitor (TKI) therapies, based on the evaluation of EGFR mutations, have shown dramatic clinical benefits. EGFR mutation assays are mainly performed on tumor biopsies, which carry risks, are not always successful and give results relevant to the timepoint of the assay. To detect secondary EGFR mutations, which cause resistance to 1st and 2nd generation TKIs and lead to the administration of a 3rd generation drug, effective and non-invasive monitoring of EGFR mutation status is needed. Liquid biopsy analytes, such as circulating tumor cells (CTCs) and circulating tumor DNA (cfDNA), allow such monitoring over the course of the therapy. The aim of this study was to develop and optimize a workflow for the evaluation of cfDNA and CTCs in NSCLC patients all from one blood sample. Using Vortex technology and EntroGen ctEGFR assay, EGFR mutations were identified at 0.5 ng of DNA (∼83 cells), with a sensitivity ranging from 0.1 to 2.0% for a total DNA varying from 25 ng (∼4 CTCs among 4000 white blood cells, WBCs) to 1 ng (∼4 CTCs among 200 WBCs). The processing of plasma-depleted-blood provided comparable capture recovery as whole blood, confirming the possibility of a multimodality liquid biopsy analysis (cfDNA and CTC DNA) from a single tube of blood. Different anticoagulants were evaluated and compared in terms of respective performance. Blood samples from 24 NSCLC patients and 6 age-matched healthy donors were analyzed with this combined workflow to minimize blood volume needed and sample-to-sample bias, and the EGFR mutation profile detected from CTCs and cfDNA was compared to matched tumor tissues. Despite the limited size of the patient cohort, results from this non-invasive EGFR mutation analysis are encouraging and this combined workflow represents a valuable means for informing therapy selection and for monitoring treatment of patients with NSCLC.

Fast and Label-Free Isolation of Circulating Tumor Cells from Blood: From a Research Microfluidic Platform to an Automated Fluidic Instrument, VTX-1 Liquid Biopsy System.

Tumor tissue biopsies are invasive, costly, and collect a limited cell population not completely reflective of patient cancer cell diversity. Circulating tumor cells (CTCs) can be isolated from a simple blood draw and may be representative of the diverse biology from multiple tumor sites. The VTX-1 Liquid Biopsy System was designed to automate the isolation of clinically relevant CTC populations, making the CTCs available for easy analysis. We present here the transition from a cutting-edge microfluidic innovation in the lab to a commercial, automated system for isolating CTCs directly from whole blood. As the technology evolved into a commercial system, flexible polydimethylsiloxane microfluidic chips were replaced by rigid poly(methyl methacrylate) chips for a 2.2-fold increase in cell recovery. Automating the fluidic processing with the VTX-1 further improved cancer cell recovery by nearly 1.4-fold, with a 2.8-fold decrease in contaminating white blood cells and overall improved reproducibility. Two isolation protocols were optimized that favor either the cancer cell recovery (up to 71.6% recovery) or sample purity (≤100 white blood cells/mL). The VTX-1's performance was further tested with three different spiked breast or lung cancer cell lines, with 69.0% to 79.5% cell recovery. Finally, several cancer research applications are presented using the commercial VTX-1 system.