MODULATION OF ALPHA(1)BETA(1), ALPHA(2)BETA(1), AND ALPHA(3)BETA(1) INTEGRIN HETERODIMERS DURING HUMAN NEUROBLASTOMA CELL-DIFFERENTIATION

Two human neuroblastoma cell lines, LAN-5 and GI-CA-N, have been analy zed for their capability to adhere to different extracellular matrix ( ECM) components. The GI-CA-N cells adhered to all the tested substrate s: laminin (LN), type I and type IV collagen (Coll I, Coll IV), vitron ectin (VN), and fibronectin (FN). Conversely LAN-5 cells weakly attach ed to FN and VN, whilst adhesion on LN and Coll I and IV was strong an d induced a rapid elongation of cell processes. By means of RT-PCR and immunoprecipitation we showed that the integrin pattern of these two lines was different and could explain their diversity in adhesion capa bility. Both cell lines express a large amount of the beta1 integrin s ubunit, associated with different alpha chains, probably responsible f or their adhesion to some ECM proteins. After treatment of LAN-5 cells with biological differentiating agents, such as gamma-interferon, alo ne or in combination with tumour necrosis factor-alpha, (TNF-alpha), o r retinoic acid, the levels of alpha1beta1, alpha2beta1, and alpha3bet a1 integrin expression were enhanced, while the amount of alpha(v) rem ained constant. In contrast, treatment of LAN-5 cells with TNF-alpha, that did not induce any maturation, or starvation in 2% foetal calf se rum, that inhibited cell proliferation without affecting neural differ entiation, did not induce any change in the integrin assessment. Messe nger-RNAs for the two alpha6 isoforms, A and B, were present in both c ell lines. However, in LAN-5 cells, the protein product was neither de tectable nor inducible by differentiation. Our results confirm the spe cific modulation of the alpha1beta1 integrin expression in human neuro nal development, and show, for the first time, the involvement of alph a2beta1, and alpha3beta1 heterodimers in this maturational process.