Three
complementary DNA encoding
S19 ribosomal protein (S19),
laminin-
binding protein (LBP), and HLA class I (HLA-I) genes were isolated from a colon
tumor-enriched subtraction library. To evaluate this
mRNA expression, surgically removed colon
tumors as well as matched normal tissue and human colon
carcinoma cell lines showing various differentiation states, anchorage dependence, and proliferation states were examined by Northern blot analysis. The
mRNA level of S19
mRNA (0.6 kilobase) was higher in primary colon
carcinoma tissue than in matched normal colon tissue in 5 of 6 cases. In 2 of 4 cases, the expression of LBP
mRNA (1.2 kilobases) was higher in
carcinoma than in normal tissue. In 12 human colon cell lines, the level of LBP
mRNA was higher in poorly differentiated cells. On the other hand, HLA-I
mRNA (1.7 kilobases) was higher in well-differentiated cells. Although the S19
mRNA was expressed in both well- and poorly differentiated cells, a concomitant increase with
tumor progression was observed in two pairs of cell lines derived from the same patients (SW480 and SW620; COLO201 and COLO205). Anchorage dependence of
butyrate-treated HT29 colon
carcinoma cells was correlated with lower levels of S19 and LBP mRNAs and higher levels of HLA-I
mRNA expression compared with untreated cells. While the expression of S19 and LBP mRNAs was not changed due to cell growth states, HLA-I
mRNA levels were found to be low in proliferating HT29 cells but highly induced in contact-inhibited cells. In summary, therefore, high expression of S19 and LBP combined with low expression of HLA-I were well correlated with colon
carcinoma cells of higher malignant potential.