ovarian cancers 34 interferon alpha inducible protein 27 is also shown to be overexpressed in 50 of breast cancers 35 in contrast the cluster of genes overexpressed in lung adenocarcinoma fig2 c middle panel mostly encoded small airway associated proteins and immunologically related proteins the presence of surfactants a2 and b pronapsin a and mucin1 in the cluster reflects the origin of tumors derived from small airway epithelial cells such as type 2 pneumocytes and clara cells 36 37 however high expression of these genes also suggested that these proteins may participate in the tumorigenesis of lung adenocarcinomas indeed mucin1 is also overexpressed in breast cancers and tyrosine phosphorylation of the ct domain of muc 1 mucin leads to activation of a mitogen activated protein kinase pathway through the ras mek erk2 pathway 38 39 furthermore the overexpression of immunoglobulin genes in adenocarcinomas examined may be explained by the extent of b cell infiltration and the presence of antigen presenting cells apc in the adenocarcinomas used for sage analysis however clustering analyses of the sage tags revealed that different tumor types preferentially expressed a different set of cell surface markers squamous cell cancers appeared to overexpress mhc class i and cd71 proteins fig2 c upper panel while adenocarcinomas had a relatively high expression of mhc class ii and cd 74 antigens this gene expression differences in tumors indicated that immuno based cancer therapy might be augmented based on the expression of different tumor surface markers no unexpected many of the genes underexpressed in the primary adenocarcinomas and the a549 adenocarcinoma cell line fig2 c lower panel were those that.