Resistance to NK and metastatic potential of fibrosarcoma cells is associated with products encoded by the H-2D region

We have used the murine 3-methylcholanthrene induced T10 fibrosarcoma tumor cell system originating in (C3II/en x C57BL/6)F₁ mice (H-2^b x H-2^k) to elucidate the possible correlation between metastatic potential, expression of individual H-2 antigens and susceptibility to NK cells. Transfection of the non metastatic and NK sensitive IC9 cells (D^b+, K^k-, K^b-, K^k-) with the H-2D^k gene, altered the metastatic phenotype of the parental cells, yet had no effect on the susceptibility of these tumor cells to lysis by NK and did not elicit a specific CTL response in syngeneic hosts. Variants of the metastatic and NK resistant IE7 clone (D^b+, K^k-, K^b-, K^k-), lacking H-2D^k, were selected by treatment with monoclonal anti H-2D^k antibodies and complement. These variants were sensitive to NK and poorly or non metastatic. Transfection of D^k negative variants with the H-2D^k gene, resulted in the isolation of several clones which expressed a wide range of metastatic phenotypes but maintained sensitivity to NK. In addition, by cloning the cDNA of the H-2D^k gene of the metastatic T10-IE7 variant cells and analyzing its nucleotide sequence, we found four single nucleotide changes. Two of them are not expected to alter the encoded amino acids, whereas the others should result in two amino acid substitutions in the alpha-2 domain of the class I H-2K^d protein product. These changes might account, at least partially, for the failure of the transfection of H-2D^k to restore resistance to NK. These results indicate that the H-2D region of the MHC and/or closely linked genes may be involved in the complex interrelationship between susceptibility to NK and metastasis.