Metastatic heterogeneity in a spontaneously metastatic HSV-2 induced hamster fibrosarcoma: association of phenotypic and genotypic properties with metastatic potential

Abstract

A spontaneously metastatic tumour of hamsters and cell lines derived from its in vivo metastatic deposits, or from in vitro cloning were compared for immunobiological and genotypic variation and correlation sought with regard to metastatic potential. Cell lines were established from seven individual lung metastases following primary tumour resection of the parent (HSV-2-333-2-26) cell line. When inoculated subcutaneously, and upon resection of the subsequent tumour mass, four cell lines (MetA, MetB, MetE and MetF) demonstrated greater, one similar (MetG) and two (MetC and MetD) less metastatic capacity compared with the parent tumour line. In further studies cell lines were established in vitro by single cell cloning of the parent tumour either by limiting dilution or soft agar cloning. In vivo tumour resection experiments showed eight cell lines (S4, S7, S4A, S7A, S7B, C1.1, C1.4 and C1.5) to have an increased metastatic potential and five cell lines (S8, S9, S8B, S9D and S9E) a decreased metastatic potential compared to the parental line. Karyotypic analysis of the cells revealed that all highly metastatic cell lines were of a near diploid genotype, whilst non- and weakly metastatic cell lines, including the parental line, were aneuploid or near tetraploid. The immunobiological characteristics of these cell lines was studied. Assessment of in vivo immunogenicity showed that eight clones (MetA, MetB, MetE, MetF, S7A, C1.1, C1.4 and C1.5) were non-immunogenic whilst the parental tumour line and three clones (MetC, MetD and MetG) exhibited a strong transplantation rejection antigen; immunogenicity showed an inverse correlation with metastatic potential. Susceptibility to NK cytolysis was demonstrated for cell lines exhibiting a weak or non-metastatic/immunogenic phenotype. The origin of metastatic variants and their association with genotype and immunobiological properties is discussed.