Tumour markers: An overview

Abstract

Tumor Markers comprise a wide spectrum of biomacromolecules synthesized in excess concentration by a wide variety of neoplastic cells. The markers could be endogenous products of highly active metabolic malignant cells or the products of newly switched on genes, which remained unexprssed in early life or newly acquired antigens at cellular and sub-cellular levels. The appearance of tumor marker and their concentration are related to the genesis and growth of malignant tumors in patients. An ideal tumor marker should be highly sensitive, specific, reliable with high prognostic value, organ specificity and it should correlate with tumor stages. However, none of the tumor markers reported to date has all these characteristics. Inspite of these limitations, many tumor markers have shown excellent clinical relevance in monitoring efficacy of different modes of therapies during entire course of illness in cancer patients. Additionally, determination of markers also helps in early detection of cancer recurrence and in prognostication.

Clinically feasible approaches to potentiating cancer cell-based immunotherapies

“…The shared TAAs are divided into 4 subgroups including cancer/testis, oncofetal, differentiation, and overexpressed antigens. Cancer/testis antigens (CTAs) 3 and oncofetal antigens 4 are 2 closely related categories of TAAs encoded by awakened 'silent' genes. In adult organisms, CTAs are normally expressed exclusively in immune privileged organs including the testis and placenta, and they can also be aberrantly expressed in tumor cells.…”

“…The reasons underlying the expression of these genes in tumors have been examined for the MAGE genes, suggesting that the expression is triggered by promoter demethylation, which has a high CpG content. 4 CTAs are highly immunogenic because they are 'unknown' to the immune system and thus are not tolerated. 5 However, very low expression levels of oncofetal antigens have been shown in normal tissues (e.g., fetoprotein is expressed in the liver), in contrast with high expression levels in some cancers or during various non-malignant pathologies.…”

“…5 However, very low expression levels of oncofetal antigens have been shown in normal tissues (e.g., fetoprotein is expressed in the liver), in contrast with high expression levels in some cancers or during various non-malignant pathologies. 4,5 Overexpressed oncofetal antigens are less immunogenic than CTAs because they are presented to the immune system in the neonatal period during the establishment of immune tolerance. Differentiation TAAs exhibit tissue-specific and in some cases differentiation stage-dependent expression patterns.…”

CEA, AFP, CA125, CA153 and CA199 in Malignant Pleural Effusions Predict the Cause

“…Some markers were classified as oncofetal antigens, such as carcinoembryonic antigen (CEA), alphafetoprotein (AFP). Some markers classified as tumor associated antigens are produced by various organs and are not specific to cancer but associated with cancer, such as, cancer antigen (CA) 125, CA153, CA199 (Watanabe, 1996;Malati, 2007). Now, levels of pleural effusion CEA, AFP, CA125, CA153 and CA199 have been assayed in many studies focusing on differentiating benign and malignant pleural effusions (Botte et al, 1990;Cascinu et al, 1997;Porcel et al, 2004;Shitrit et al, 2005;Gaspar et al, 2008;Liang et al, 2008).…”

Optimization of Reference Genes for Normalization of the Quantitative Polymerase Chain Reaction in Tissue Samples of Gastric Cancer

“…The carcinoembryonic antigen (CEA), one of widely used clinical tumor marker (Duffy et al, 2001;Malati et al, 2007;Cidón et al, 2011) was used as validation gene to further analyze the reliability of the internal reference genes. Using GAPDH, beta-actin, RPII and 18sRNA as internal reference genes, the expression of CEA was detected with qRT-PCR in 50 specimens of gastric cancer and peritumoral tissues.…”