LOW-DENSITY-LIPOPROTEIN RECEPTORS AND POLYAMINE LEVELS IN HUMAN COLORECTAL ADENOCARCINOMA

The low density lipoprotein receptor (LDLR) is a cell surface protein that binds with LDL, providing the cell with cholesterol for new membr ane synthesis. Rapidly growing cells have high numbers of LDLRs, and t hese proteins have also been detected in neoplastic samples of human c olorectal mucosa. Polyamines, putrescine, spermidine, and spermine, pl ay an important role in cellular growth, and studies on colorectal can cers have demonstrated higher polyamine levels in neoplastic mucosa sa mples than in surrounding mucosa. The aim of this study was to investi gate LDLR and polyamine levels in the neoplastic tissue of 43 patients (28 males and 15 females) with colorectal adenocarcinoma, using enzym atic immunoassay and high performance liquid chromatography, respectiv ely. Specimens of neoplastic mucosa were considered LDLR-positive or L DLR-negative when the amount of bound human anti-LDLR antibody detecte d was equal or higher or lower than the cut-off value (0.5 ng of bound anti-LDLR Ab/mg protein), respectively. Twenty-one subjects were LDLR -positive and 22 LDLR-negative. Polyamine levels (nmol/g tissue) were higher in LDLR-positive specimens; this increase was significant for t otal polyamines (P < 0.05). These findings, reporting the presence of increased polyamine content in LDLR-positive colorectal neoplastic spe cimens, suggest an association between LDLR levels and gastrointestina l neoplastic proliferative activity.