Expression of integrin receptors on 45 clinical neuroblastoma specimens

Immunohistological expression of integrins has been analyzed on 45 neuroblastoma specimens representative of the different clinical and histological forms of the tumor. None of the specimens expressed the α 5 chain of the integrins. The β 1 chain was expressed on all specimens, the α 1 chain on 44 specimens and the α 3 chain on 42; the 4 specimens which lacked α 1 or α 3 were stage‐4 neuroblastomas. The α 2 chain was expressed on 18 specimens, and the α 6 chain on 17;15 reacted with both. Their reactivity was related to the maturation of the tumor rather than the stage of the disease: they were expressed on lowgrade, well‐differentiated specimens; stage 3‐4 neuroblastoma specimens analyzed at diagnosis were negative, but usually expressed both chains when analyzed after in vivo differentiation by chemotherapy. α v reacted with 18 specimens and β 3 with 12, without strict relation with the stage of the disease and/or its degree of differentiation; 9 well‐differentiated specimens expressed the β 4 chain; only 4 well‐differentiated specimens expressed the α 4 chain. The 4 specimens which lacked α 1 ‐β 1 or α 3 ‐β 1 expression had n‐ myc amplification, whereas those which expressed either α 4 , β 4 , β 3 , or α v had no amplification. Furthermore, the expression of the 3 heterodimers α 4 ‐β 1 , α v ‐β 3 and α 6 ‐β 4 was essentially observed on primary tumors which developed in the mediastinum. The expression of α 2 ‐β 1 and α 6 ‐β 1 was observed on both n‐ myc ‐positive and ‐negative specimens. β 1 and α 3 , were diffusely expressed on all counterparts of these tumors, from undifferentiated neuroblasts to ganglion and Schwann cells. The α 1 chain reacted with undifferentiated and intermediate neuroblasts as well as with Schwann cells, but ganglion cells were negative. α 2 and α 6 chains were negative on undifferentiated neuroblasts, variably expressed on intermediate neuroblasts, and restricted to Schwann cells in ganglioneuroma. The expression of α 4 and β 4 was restricted to Schwann cells. α v and β 3 occasionally reacted with undifferentiated and intermediate neuroblasts; α v was strongly positive on Schwann cells but negative on ganglion cells, whereas β 3 was positive on both neuronal and non‐neuronal populations.