Prospective generation of PDTX (patient derived tumor xenografts) and molecular profiling of NSCLC (non small cell lung cancer)

Abstract

Background: The generation of “xeno-patients” is a valuable tool to prospectively reproduce in vivo molecular mechanisms underpinning cancer progression, by recapitulating human cancer heterogeneity. Furthermore, this method allows to overcome intrinsic limitations of in vitro models. In NSCLC, xeno-patiens have been described from early and late stages, with heterogeneous results. The project aims to confirm the reliability of this model in NSCLC and to prospectively characterize their genetic profile. Materials and methods: From February 2014 to September 2016, 125 early stage (I-III) NSCLC patients who underwent radical lung resection and 14 metastatic NSCLC patients were enrolled. Written informed consent was required. Fresh intact tissue (from surgery or radio-guided biopsy) was collected and kept in serum free medium, embedded in 20% matrigel and subcutaneously engrafted into NSG and NOD SCID mice, within 24 hours from sample collection. Next Generation Sequencing was conduced on explanted paraffin embedded samples after first passage. Multigenic mutational analysis of hot spot regions of 52 genes (Oncomine Focus Assay) was conducted on 21 out of 30 engrafted samples. Results: The engrafted samples were 125 from radical lung resections and 14 from TC-guided biopsies. Histologically, early stages samples were found as adenocarcinoma (65%), squamous carcinoma (28%), sarcomatoid carcinoma (2%), LCNEC (3%) and carcinoid (2%). In late stage samples, the main observed histological subtypes were adenocarcinoma (43%), squamous carcinoma (21%) and SCLC (14%). The engraftment rate was equal to 23.2% in surgical samples and 7.1% in biopsy samples. Engraftment was significantly higher in squamous histology (p < 0.005) without correlation with clinical characteristics (age, sex, smoking status, stage). NGS showed high concordance between cancer tissue and corresponding PDTX in terms of polymorphic and mutational variants. Non-synonimous somatic variants were found to overlap in tumors and PDTX, whereas low allelic frequency variants (<10%) were lost in PDTX. In the PDTX transition new somatic variants were not acquired; in six cases, the PDTX showed higher allelic frequency of mutated oncogenic drivers (KRAS, PIK3CA, FGFR2, MET). Conclusions: NGS showed high concordance between NSCLC samples and PDTX, retaining their genetic characteristics. These data confirm the reliability of this model in NSCLC, providing the rationale for further population-based translational studies.