Prior xenograft step enables a higher generation rate of novel human colon cancer cell lines derived from both primary tumors and liver metastases.

Abstract

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Only 29 colon cancer cell lines are disposable at the ATCC collection and none of those cell lines originated from liver metastasis. Obtaining representative human colon cancer cell lines from fresh tumor is technically difficult but mandatory for performing either fundamental or translational research on this frequent malignant disease. The present study demonstrates that a prior xenograft step leads to a more efficient in vitro cell line establishment in comparison to direct establishment from fresh tumors (p<0.05). From 26 tumor specimens, we successfully established 20 tumor xenografts in nude mice (77%) and amongst 19 of these xenografts, 9 (47%) led to cell lines, including 4 from liver metastasis. In contrast, only 3 out of 31 tumor specimens (9.7%) grew immediately in cell culture, all of these 3 later cell lines originated from primary tumors. In order to compare major phenotypic and genotypic characteristics of novel human colon cancer cell lines derived from the same tumor fragment and established either directly or after a xenograft step, two cell lines designated CT320 and CT320X6 and generated respectively from a fresh tumor and from its xenograft, were extensively studied. Both cell lines displayed a similar morphology in 2-D monolayer and were able to form compacted 3-D spheroids. CT320X6 grew faster than CT320 in 2-D and CT320 was more sensitive to 5FU, CPT11 and L-OHP than CT320X6. CT320 and CT320X6 showed a common core of karyotype alterations and distinctive additional chromosomal aberrations. Expression levels of 66 genes selected for their implication in oncogenesis evaluated by real-time quantitative PCR were found statistically correlated, whatever the in vitro culture model. Taken together, these data indicate that these two cell lines are distinct but closely related. In conclusion, xenotransplantation in nude mice of human tumor fragments prior to establishment of cell lines allows generating numerous human cancer cell lines from both primary colon cancer and liver metastases. These novel cell lines derived from both primary colon cancers and liver metastases might reproduce the diversity of colon cancer diseases and offer additional opportunities for investigating these malignancies.