New Variants of B16 Mouse Melanoma: Differentiation and Metastatic Properties

Abstract

A system of tumor transplantation has been developed to select metastatic variants of B16 in mutants of the C57BL/6J black strain of mice. The effects of transplantation into nonagouti a/a and mutant recipients on the production of melanin and on the metastatic potential of tumors were investigated. Transplantation of the pigmented B16 melanoma from a nonagouti black a/a host to a yellow mutant Ay/a recipient resulted in an achromic and metastatic variant melanoma, designated YB16. The amelanotic phenotype occurred consistently after more than ten passages through yellow mice and simultaneously with an increase in the incidence of pulmonary metastases. When YB16 was transplanted back to the nonagouti black a/a host, a second variant, MB16, characterized by its variable pigmentation, was obtained. Pigmented and/or entirely achromic tumors were observed. MB16 was dramatically more metastatic than B16 and YB16 when injected s.c. or i.v. Metastases in the lungs were pigmented and/or achromic. The properties of tumor cells derived from artificially induced metastases were investigated after s.c. and i.v. injections. Whereas the metastatic cells expressed a potent ability to generate metastases when injected s.c., no differences in the incidence of metastases, as compared to the metastatic potential of cells of parental origin, were observed after i.v. injection. In the MB16 variant, there appeared to be an inverse relationship between differentiation (production of melanins) and malignancy. Our results demonstrate that differentiation and metastatic behaviour are dependent on specific mutations in the host environment which generate a pool of tumor cells from which highly metastatic variants can be selected.

Thermochemotherapy for B16 Melanoma: Combination Therapy of Hyperthermia, Melphalan, and CCNU in Mice

“…Metastasizing capacity seems very variable, ranging from nil for Demopoulos et al (1965) to constant for Wosko et al (19841, who observed it exclusively in viscera. In our study it was rarely encountered (in 3.3% of animals) and then always in viscera as Aubert et al (1989) recently observed. This low incidence, compared with the work of Wosko et al (1984), might be due to the different transplant technique; however, it also differs from the high percentages obtained by Kancklertz and Chapman (1986), who used the same implant technique, the same number of cells, and a tumoral line obtained from the same Centre as ours.…”

Differentiation of New Metastatic Variants of B16 Melanoma Under Different Culture Conditions

“…The B16 control melanoma and its YB16 and MB16 metastatic variants (MMB16 melanotic and AMB16 amelanotic tumors), which were generated in our laboratory, have been described previously (Aubert et al, 1989). lhmors were removed under sterile conditions and adapted to growth in vitro in Falcon plastic T30 tissue-culture flasks.…”

“…Correlations in vitro and in vivo between hormonal regulation of melanogenesis and metastatic potential have been demonstrated by us and by others (Bennett et al, 1986;Niles and Makarski, 1978;Voulot et al, 1985). Recently, we obtained new metastatic YB16, MMB16, and AMB16 variants of the B16 melanoma in vivo in agouti and non-agouti mice as a result of a multistep protocol for increasing metastatic capac-ity (Aubert et al, 1989). The purpose of the present study was to examine differences in the extent of differentiation of tumors, in terms of production of pigment in tumors and pulmonary metastases, as indicated by ultrastructural morphological features and biochemical markers.…”