INTEGRIN EXPRESSION IN HUMAN NEUROBLASTOMA-CELLS WITH OR WITHOUT N-MYC AMPLIFICATION AND IN ECTOPIC ORTHOTOPIC NUDE-MOUSE TUMORS/

Three human neuroblastoma cell lines, with or without N-myc amplificat ion, were evaluated for their integrin expression patterns as cultured cells, as well as their nude mouse-borne tumors obtained after subcut aneous (ectopic) or adrenal gland (orthotopic) injection. IMR-32 and L aN1 cells (with amplified N-myc) do not express any of the common inte grin subunits that recognize fibronectin or collagens, as determined b y immunoprecipitation of cell extracts with specific monoclonal antibo dies; the same was true for all subcutaneous or adrenal tumors from IM R-32 or LaN1, indicating that they are not essential during primary tu mor formation at either site. SK-N-SH cells (with diploid N-myc) expre ss beta 1, alpha 2, and alpha 3 subunits of expected sizes (with alpha 2 uncleaved at 145 kDa) but do not express alpha 1, alpha 4, alpha 5, alpha V, or beta 3. This expression pattern was conserved in all firs t-round subcutaneous and adrenal tumor cell populations, as well as in second-round subcutaneous tumors derived from a first-round subcutane ous tumor (no tumors expressed beta 3). One significant difference was noted between subcutaneous and adrenal tumor populations: all first- and second-round subcutaneous tumors expressed high levels of alpha V subunit, while adrenal tumors did not express any alpha V. This result suggests some essential function for alpha V beta 1 during subcutaneo us primary tumor formation. Integrin patterns were also evaluated by f luorescence-activated cell sorting. SK-N-SH and its derivative tumors expressed heterogeneous amounts of beta 1 and alpha 2 at the cell surf ace, while only subcutaneous tumor cells expressed alpha V. Parental S K-N-SH cells contained two subpopulations, half of which expresses alp ha 3, while the other half does not; all subcutaneous tumor cells reta ined this two-subpopulation pattern, indicating that primary tumor for mation does not lead to clonal dominance of alpha 3(-) or alpha 3(+) c ell types in larger primary tumors. While these results suggest a corr elation between N-myc amplification and down-regulation of integrin ex pression in neuroblastoma, they demonstrate conservation of integrin e xpression during two rounds of primary tumor formation at ectopic or o rthotopic sites in a mouse model system, induction and/or selection fo r alpha V beta 1 expression at the subcutaneous site, and clonal heter ogeneity in alpha 3 beta 1 expression throughout primary tumor develop ment. (C) 1994 Academic Press, Inc.