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 α5 chain of the integrins. The β1 chain was expressed on all specimens, the α1 chain on 44 specimens and the α3 chain on 42; the 4 specimens which lacked α1 or α3 were stage‐4 neuroblastomas. The α2 chain was expressed on 18 specimens, and the α6 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. αv reacted with 18 specimens and β3 with 12, without strict relation with the stage of the disease and/or its degree of differentiation; 9 well‐differentiated specimens expressed the β4 chain; only 4 well‐differentiated specimens expressed the α4 chain. The 4 specimens which lacked α1‐β1 or α3‐β1 expression had n‐myc amplification, whereas those which expressed either α4, β4, β3, or αv had no amplification. Furthermore, the expression of the 3 heterodimers α4‐β1, αv‐β3 and α6‐β4 was essentially observed on primary tumors which developed in the mediastinum. The expression of α2‐β1 and α6‐β1 was observed on both n‐myc‐positive and ‐negative specimens. β1 and α3, were diffusely expressed on all counterparts of these tumors, from undifferentiated neuroblasts to ganglion and Schwann cells. The α1 chain reacted with undifferentiated and intermediate neuroblasts as well as with Schwann cells, but ganglion cells were negative. α2 and α6 chains were negative on undifferentiated neuroblasts, variably expressed on intermediate neuroblasts, and restricted to Schwann cells in ganglioneuroma. The expression of α4 and β4 was restricted to Schwann cells. αv and β3 occasionally reacted with undifferentiated and intermediate neuroblasts; αv was strongly positive on Schwann cells but negative on ganglion cells, whereas β3 was positive on both neuronal and non‐neuronal populations.