NF1 and cancer: All cancer tissues were grouped into three groups: NF1high, NF1low and NF1negative expression group, the cancer tissues were designated as negative expression when NF1 mRNA was undetectable in cancer samples, the cancer tissues were designed as low expression when NF1 mRNA was detectable but the level was 10-fold lower than that in the adjacent normal tissues, and the cancer tissues were designed as high expression when NF1 mRNA was detectable and the level was either higher than, equal to, or lower (but less than 10-fold difference) than that in the adjacent normal tissues.