It has been described that auto-antibodies are elicited during the transition from benign neoplasm or chronic inflammatory disease to malignancy [55]. death was evaluated by Newman-Keuls test. == Results == No significant humoral response was observed to CEA, EGFR and ErbB2 in CRC patients. Conversely, 7 out of 67 CRC patient sera reacted to ribosomal P proteins. The prevalence of P proteins auto-antibodies in CRC patients was significant. Five patients showed restricted P0 immunoreactivity, while two patients reacted simultaneously to all P proteins. The C-22 P0 epitope was homogenously expressed both in malignant tumors and the adjacent mucosa, but the intensity of expression was higher in the tumor. Starved colon cancer cells showed a higher C-22 Vincristine sulfate P0 epitope plasma membrane expression compared to control cells. MAb 2B2 inhibited colon cancer cell growth and induced cell death in a dose dependent manner. == Conclusions == Our study shows a spontaneous humoral immune response to ribosomal P0 protein in CRC patients and the inhibition ofin vitrocancer cell growth after C-22 P0 epitope targeting. The ribosomal P0 protein might be a useful immunological target in CRC patients. Keywords:Ribosomal P proteins, Colon cancer, Immune response, Antibodies == Background == Colorectal cancer (CRC) is the most common form of cancer among those that affect the gastrointestinal tract and represents the third most frequent malignancy in men and the second in women [1,2]. Despite advances in diagnosis and therapy, the survival rate of CRC depends on the stage being 90% for stage I and II, and <11% for stage IV [1,3]. The process of CRC carcinogenesis is usually a multistep process characterized by mutations of several genes, which lead to an invasive and drug resistant-phenotype of the tumor [4-8]. The identification of molecular and immunological targets is essential for Vincristine sulfate improving diagnostic and therapeutic strategies for CRC management. Tumor antigens expressed by cancer cells are able to elicit spontaneous immune response in cancer patients [9]. Many auto-antibodies have been proposed as diagnostic or prognostic markers in cancer patients although they recognize self-antigens that are overexpressed in tumors [10-14]. It is worth of note that the repertoire of auto-antibodies found in cancer patients partly covers that detected in patients with autoimmune diseases [9]. In Vincristine sulfate addition, auto-antibodies represent useful serological markers in the diagnosis of the autoimmune disease [9]. The immune identification of self-antigens in cancer patients might have significant repercussions that go beyond the discovery of novel biomarkers, since auto-antibodies found in cancer patients can target crucial molecules involved in the carcinogenesis process [15]. Several tumor associated antigens have been shown to be useful in CRC patients. Among them, the most common is the carcinoembryonic antigen (CEA), a glycosylated membrane-bound protein of 180 kDa expressed in a high percentage Mouse monoclonal to Chromogranin A of several carcinomas, including colorectal, gastric, pancreatic, non-small cell lung and breast carcinomas. The high level tumor expression of CEA and its release in the blood make CEA suitable for using it Vincristine sulfate as tumor marker, especially in patients with CRC [16,17]. Other CRC tumor markers include circulating RNA, MicroRNA, mutated DNA (APC, K-RAS, p53), aberrant methylated markers, CA 19-9, TPA, CA 72-4 and cytokeratin fragments [18-20]. The expression of the epidermal growth factor receptor (EGFR) and human epidermal growth factor receptor 2 (HER2 or ErbB2) are associated with poor prognosis in sporadic CRC, thus representing two important prognostic markers in addition to be employed for targeted-therapy [21,22]. The ribosomal P proteins (P0, 38 kDa; P1, 19 kDa; P2, 17 kDa) are involved in the formation of the ribosomal stalk of the 60 S ribosomal subunit in eukaryotic cell, in which they regulate protein synthesis [23-27]. Recently, we exhibited the spontaneous immunogenicity of the ribosomal P0 protein in head and neck, in breast and prostate cancer patients and the overexpression of the carboxyl-terminal epitope of P0 (C-22 P0) in head and neck and breast carcinomas [28-30].The immunodominant C-22 P0 epitope was found to be located within the 22 amino acid C-terminal peptide shared by all three P proteins [31,32]. P0 exists as a free protein in the cytoplasm and on the surface of cancer cells [28,33] and appears to promote tumor formation [34]. Auto-antibodies against P proteins have been identified for the first time in systemic lupus erythematosus (SLE) [35]. It was also found that the mRNA level of the P0 was greater in.