Tumour markers and their role in Cancer diagnostics

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Tumour markers and their role in Cancer diagnostics

Amra Iuoop

BIO 01/181010

HND Biomedical sciences

BMS

30 June 2012

Cancer, or a neoplasm, is best defined by the British oncologist Willis (Robbins, 2010), “A neoplasm is an abnormal mass of tissue, the growth of which exceeds and is uncoordinated with that of the normal tissues and persists in the same manner after cessation of the stimuli which evoked the change”.

Tumour markers, also called serum markers or biomarkers, are metabolized molecular products that are secreted by neoplastic tissue and biochemically processed in cells or body fluids (Cortez, 2011). They are secreted by normal cells as well as by cancer cells; nevertheless the quantity is usually quite high in cancerous conditions.

Consequently, the presence of a malignant tumour can be identified more or less by the detection of a specific tumour marker. Tumour markers are reckoned to be useful in the following (Sharma, 2009):

Screening: Identification of seemingly healthy people who perhaps have a high risk of developing cancer.

Diagnosis: Identification of a disease on the knowledge extent of clinical findings and laboratory tests.

Staging and treatment planning. Planning of the treatment course after identification of the cancer’s stage.

Monitoring: Determination of the cancer’s response to treatment.

Prognosis: Predication of possible outcome or progress of the cancer.

Recurrence. Reappearance of the cancer after successful treatment.

The National Cancer Institute (2011) states that tumour markers are represented by various chemical groups: including hormones, antigens, amino and nucleic acids, enzymes, polyamines, and specific cell membrane proteins and lipids. Alterations in gene expression and nuclear matrix proteins are revealed as a new class of tumour markers. The former is seen in chronic myeloid leukemia and the latter is presented as markers in bladder and prostate cancers (Keesee, 1996). These tumour markers can be found in blood, urine, saliva, stool, tissues (tumour or otherwise), or bodily fluids of certain patients with cancer (Schrohl, 2003). In fact, Henry Bence-Jones described the first tumour marker in 1846 from patients with multiple myeloma, when he observed the precipitation of a protein from their acidified urine (Hajdu, 2006).

Screening

Screening of cancer allows early detection of cancer, prior to exposition of any symptoms. This allows easy treatment and recovery of the patient, as the tumour is less expected to have spread. A perfect tumour marker would aid screening of a particular type of cancer for all people, plus the tumour marker must be present only in the presence of a malignant tumour. Unfortunately studies have proved that such tumour markers do not exist (Sharma, 2009). Research has reveal that prostate-specific antigen (PSA) is the most common marker for its use in screening for prostate cancer, due to the presence of sufficient specificity and sensitivity of the antigen (Parekh, 2007). Its clinical use as a marker for prostate cancer was first reported by Papsidero (1980) after it was identified in 1971 during an experiment aiding forensic circumstances. An elevation in the serum PSA level is proportional to the presence of prostate cancer, yet its limitations are; i) its occasional absence even in the presence of prostate cancer and ii) high serum levels in the presence of other prostate disorders (Thompson, 2004).

A variety of techniques are available for the detection of tumour markers. Immunohistochemistry allows the detection of any antigen or protein based markers, with the use of monoclonal antibodies. However, a more specific technique would be the use of molecular techniques: Polymerase Chain Reaction (PCR) and Reverse-Transcriptase Polymerase Chain Reaction (RT-PCR), for the detection of DNA and RNA, respectively; thus making it possible to even study minute amount of gene expression and metastasis (Lindblom, 2000). Fluorescence in situ hybridization (FISH) is also a molecular technique for the detection of chromosomal abnormalities, with the utilization of fluorescently labeled DNA probes for detection. Urothelial carcinoma, seen in the bladder, is one of the tumours that may be diagnosed through FISH, which basically detects the presence of the exfoliated carcinoma cells in the urine (Halling, 2006).

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Diagnosis

Diagnosis of cancer is not independently possible with the use of tumour markers, due to their elevation in nonmalignant conditions occasionally; it is rather accompanied with other clinical parameters such as histopathological biopsies or radiological imaging. Thus tumour markers combined with other diagnostic modalities mostly distinguish between benign and malignant conditions. Diagnosis aids in treatment on the particular cancer, since the tumour marker occasionally reveal the origin of cancer. Two such markers are Alpha-fetoprotein (AFP) and CA 125. Elevated levels of AFP, an oncofetal protein, allow the diagnosis of hepatocellular carcinoma in the liver. It is necessary to ...

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