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 membrane synthesis. Rapidly growing cells have high numbers of LDLRs, and these proteins have also been detected in neoplastic samples of human colorectal mucosa. Polyamines, putrescine, spermidine, and spermine, play an important role in cellular growth, and studies on colorectal cancers have demonstrated higher polyamine levels in neoplastic mucosa samples than in surrounding mucosa. The aim of this study was to investigate LDLR and polyamine levels in the neoplastic tissue of 43 patients (28 males and 15 females) with colorectal adenocarcinoma, using enzymatic immunoassay and high performance liquid chromatography, respectively. Specimens of neoplastic mucosa were considered LDLR-positive or LDLR-negative when the amount of bound human anti-LDLR antibody detected 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 total polyamines (P < 0.05). These findings, reporting the presence of increased polyamine content in LDLR-positive colorectal neoplastic specimens, suggest an association between LDLR levels and gastrointestinal neoplastic proliferative activity.