Abstract 583: Colorectal cancer cell lines recapitulate molecular and pharmacological features of clinical samples
Authors: Picco Gabriele , Russo Mariangela , Cancelliere Carlotta , Buscarino Michela , Isella Claudio , Lamba Simona , Martinoglio Barbara , Di Nicolantonio Federica , Bardelli Alberto , Medico Enzo 
Published: August 2015

Abstract
Colorectal Cancer (CRC) is characterized by wide genetic, biological and clinical heterogeneity. Oncogenic events, such as KRAS, NRAS and BRAF mutations, are known negative biomarker of response to EGFR targeted therapies. In addition to mutational analysis, transcriptional profiling has been recently exploited to identify distinct CRC molecular subtypes, associated with biological and clinical features such as cell of origin, microsatellite instability, prognosis and response to treatments. Detailed analysis of the relationships between the subtypes and clinical/biological features requires a large panel of preclinical models closely recapitulating the molecular heterogeneity of CRC. To this aim, we assembled a large collection of 151 CRC cell lines. For each line, we: (i) verified genetic identity by short tandem repeat (STR) analysis; (ii) assessed microsatellite instability (MSI) status; (iii) sequenced mutational hotspots in the KRAS, BRAF, NRAS and PIK3CA genes; (iv) performed microarray-based global mRNA expression profiling; (v) evaluated sensitivity to the EGFR-targeting drug cetuximab. STR analysis revealed that some cell lines previously thought to be unrelated are indeed derived from the same individual. This result was confirmed by cell line hierarchical clustering based on mRNA expression profiles. Overall, the mutational landscape of the compendium was concordant with what observed in patients (mutation rates: KRAS = 47%; BRAF = 17%; NRAS = 0.7%; PIK3CA = 18%). Similarly, sensitivity to cetuximab was confined to lines without RAS or BRAF mutations. Gene expression profiling was exploited to assign cell lines to molecular subtypes, according to five different published transcriptional classifiers. We found that all molecular subtypes previously identified in CRC patients were robustly maintained in the lines. Moreover, significant overlaps were detected between individual subtypes across distinct classifiers. Subtype-specific molecular and pharmacological associations previously defined in CRC samples were largely recapitulated in the compendium. In particular, MSI+ cells were significantly enriched in inflammatory and goblet subtypes and less prevalent in the Transit Amplifying (TA) and Stem groups. Cell lines carrying BRAF mutations clustered in the inflammatory subtype, while RAS mutations were equally distributed among all subtypes. Notably, in TA lines without RAS or BRAF mutations, the fraction of cetuximab-sensitive cells was strongly enriched (56%), confirming clinical data and indicating that addiction to the EGFR pathway is an intrinsic feature of this CRC subtype. In conclusion, our results describe a powerful preclinical resource reflecting the molecular and functional heterogeneity of CRC, which can be used to explore multidimensional information of potential clinical relevance.
Citation Format: Gabriele Picco, Mariangela Russo, Carlotta Cancelliere, Michela Buscarino, Claudio Isella, Simona Lamba, Barbara Martinoglio, Federica Di Nicolantonio, Alberto Bardelli, Enzo Medico. Colorectal cancer cell lines recapitulate molecular and pharmacological features of clinical samples. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 583. doi:10.1158/1538-7445.AM2015-583