IN VITRO AND IN VIVO STUDY OF MELANOMA TUMOR CELL INVASION AND METASTASIS

Abstract

The correlation of information obtained from in vitro investigations and in vivo experiments has frequently evaded researchers, especially in the area of tumor cell invasion and metastasis. In order to better understand and associate in vitro tumor cell invasion through basement membranes with in vivo tumor metastasis in syngeneic animal models, and the subsequent modulation of these processes, the following studies have been undertaken. Malignant murine melanoma cell lines designated B16F1 and B16F10, syngeneic to the C57BL6 mouse, a melanotic variant of the Cloudman S-91 melanoma cell line (denoted Mel-11a) with the syngeneic host being the DBA/2J mouse, and a malignant human melanoma line referenced as A375P (parental) and A375M (metastatic) were used for this dissertation project. Tumor cells were labeled with either ¹⁴C-thymidine or ¹²⁵I-deoxyuridine using previously established protocols. Radiolabeled tumor cells were introduced into the Membrane Invasion Culture System (MICS) in vitro, a system developed in our lab, and concomitantly into the lateral tail vein by injection or intracutaneously into the appropriate syngeneic host in the presence or absence of such biological response modifying agents as [Nle⁴, D-Phe⁷]-MSH, and α-MSH. The superpotent analogue of α-MSH ([Nle⁴, D-Phe⁷] -MSH) showed a proliferative and survival enhancing effect on tumor metastasis in vivo with no effect on in vitro tumor cell invasion, with similar effects demonstrated by α-MSH. The effects of these melanotropins on spontaneous metastasis formation appears to be negligible. The A375M and A375P human melanoma cells parallel their metastatic profile in vitro when assayed in MICS. In concert with these studies, the development of a control cell line, comprised of neural crest-derived melanocytes, and the study of their subsequent invasiveness in vitro were pursued. The neural crest-derived melanocytes were unable to invade the basement membranes (BM); although co-culturing neural crest cells with B16F10 melanoma cells produced an effect such that the neural crest cells did significantly invade the BMs. These studies demonstrate the ability of the MICS in vitro invasion assay to discriminate between tumor cells with differing metastatic propensities and could possibly be used in future studies to predict the effectiveness of biological response modifying agents in vivo.