  We investigate gene interaction networks in various cancer cells by spectral
analysis of the adjacency matrices. We observe localization of the networks on
hub genes which have extraordinarily many links. The eigenvector centralities
take finite values only on special nodes when the hub degree exceeds a critical
value $d_c \simeq 40$. The degree correlation function shows the disassortative
behavior in the large degrees, and the nodes whose degrees $d \gtrsim 40$ have
tendencies to link to small degree nodes. The communities of the gene networks
centered at the hub genes are extracted by the amount of node degree
discrepancies between linked nodes. We verify the Wigner-Dyson distribution of
the nearest neighbor eigenvalues spacing distribution $P(s)$ in the small
degree discrepancy communities, and the Poisson $P(s)$ in the communities of
large degree discrepancies including the hubs.
