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 amplification, were evaluated for their integrin expression patterns as cultured cells, as well as their nude mouse-borne tumors obtained after subcutaneous (ectopic) or adrenal gland (orthotopic) injection. IMR-32 and LaN1 cells (with amplified N-myc) do not express any of the common integrin subunits that recognize fibronectin or collagens, as determined by immunoprecipitation of cell extracts with specific monoclonal antibodies; the same was true for all subcutaneous or adrenal tumors from IMR-32 or LaN1, indicating that they are not essential during primary tumor formation at either site. SK-N-SH cells (with diploid N-myc) express 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 first-round subcutaneous and adrenal tumor cell populations, as well as in second-round subcutaneous tumors derived from a first-round subcutaneous 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 subcutaneous primary tumor formation. Integrin patterns were also evaluated by fluorescence-activated cell sorting. SK-N-SH and its derivative tumors expressed heterogeneous amounts of beta 1 and alpha 2 at the cell surface, while only subcutaneous tumor cells expressed alpha V. Parental SK-N-SH cells contained two subpopulations, half of which expresses alpha 3, while the other half does not; all subcutaneous tumor cells retained this two-subpopulation pattern, indicating that primary tumor formation does not lead to clonal dominance of alpha 3- or alpha 3+ cell types in larger primary tumors. While these results suggest a correlation between N-myc amplification and down-regulation of integrin expression in neuroblastoma, they demonstrate conservation of integrin expression during two rounds of primary tumor formation at ectopic or orthotopic sites in a mouse model system, induction and/or selection for alpha V beta 1 expression at the subcutaneous site, and clonal heterogeneity in alpha 3 beta 1 expression throughout primary tumor development.
Department of Molecular Biology and Microbiology, Case Western Reserve University, School of Medicine, Cleveland, Ohio 44106.
K S
KS
Flickinger
R
R
Judware
R
R
Lechner
W G
WG
Carter
L A
LA
Culp
D000818:Animals; D000911:Antibodies, Monoclonal; D002460:Cell Line; D005260:Female; D005784:Gene Amplification; D016259:Genes, myc; D006801:Humans; D016023:Integrins / Q000032:analysis / Q000096:biosynthesis*; D046911:Macromolecular Substances; D051379:Mice; D008819:Mice, Nude; D009447:Neuroblastoma / Q000378:metabolism* / Q000473:pathology; D014183:Transplantation, Heterologous; D014407:Tumor Cells, Cultured
D000911:Antibodies, Monoclonal; D016023:Integrins; D046911:Macromolecular Substances