Biological markers are useful chemicals, which can be endogenous or exogenous such as inulin (Prevot A, et al. , 2002), and can be proteins, receptors, genes etc. They confirm a diagnosis with different degrees of certainty according to their specificity and sensitivity; simply, they are processes which can be measured (Franz K. , 2004). Markers are a response to abnormal cells or dysfunction of organs. They are either released from cells, displayed on cell surfaces, accumulate inside cells, or compounds injected into patients. Three types of markers used in cellular pathology will be discussed below.
Diagnostic markers Diagnostic markers are used to confirm signs and symptoms or provide further evidence that a certain illness exists such as distinguishing a certain cancer from another. Diagnostic markers are commonly employed and are lately being discovered rapidly to aid in diagnosis of specific diseases. In some cases, they are not required as the tumour may be evidently large, whereas in other cases, the tumour may be small or poorly differentiated and presents similar signs and symptoms to other diseases, which is where the diagnostic markers are put best to use.
They are utilised in a wide range from detecting different types of specific cancerous cells. Most basically the results are a verdict of either positive or negative. AKR1B10, being from the aldo-keto reductase family protein (Fukumoto S, et al. , 2005), is greatly expressed in non-small cell lung carcinoma. It is mainly expressed in squamous cell carcinomas.. AKR1B10 is a highly specific marker, which is closely linked to smoking (Fukumoto S, et al. , 2005). AKR1B10 is up regulated in response to cellular stress, involvement in carcinogen metabolism and nuclear receptor signalling (Fukumoto S, et al. 2005). Studies have illustrated that AKR1B10 possibly controls retinoic acid signalling, so has an effect on carcinogenesis process (Fukumoto S, et al. , 2005). Retinoic acid in the cell, which is converted from 9-cis-retinal, all trans-retinal and 13-cis-retinal (Fukumoto S, et al. , 2005) causes the cell to differentiate and become cancerous. AKR1B10 inhibits this cellular differentiation and so is over expressed in these cancerous cells. Therefore, it could be a possible diagnostic marker in detecting lung cancer, in specific, non-small cell lung carcinoma.
This therefore gives it the characteristic of being an efficient differential diagnostic marker. Prognostic markers Prognostic markers provide a risk assessment on the outcome of a disease. Since some diseases may not require treatment, prognostic markers are useful in preventing patients from going through pointless, frustrating and sometimes costly treatments. On the other hand, prognostic markers could also give information, which would necessitate that the patient receives instant medical attention. They are required to add information to the known factors such as age, tumour grade and receptor status.
In other words, the prognostic markers are used for predicting the outcome of the disease. For prognostic evaluation of colorectal cancer, the size of the tumour is critical information. Exostoses (Multiple)-Like 3 (EXTL3), which is the receptor, and its counterpart, Regenerating Islet-Derived 1 Alpha (REG1A), are prognostic markers for colorectal cancer recurrence (Froelich W. , 2006). Both markers are greatly expressed in patients suffering from colorectal tumours with an increased risk or reappearance. These markers may assist in making choices on controlling colorectal cancers.
In comparison to healthy tissue, REG1A is increasingly evident in tumours. The period at which the recurrence happens is related to the amount of expression of REG1A (Froelich W. , 2006), suggesting as REG1A rises, the slighter the chance of survival without the disease. Another attribute is seen when REG1A and EXTL3 expression is greater in tumours with peritoneal carcinomatosis (Froelich W. , 2006). Therefore, these markers are imperative in determining decisions involving avoidance of the cancer chances of recurrence, and its treatment.
From this it is clear that prognostic markers are exclusive in their role compared to diagnostic markers. A diagnostic marker informs the scientist of the presence of the disease, however, prognostic markers that are specific seem to be more useful as they inform scientists of a disease, chance of it occurring again, and its level of severity. Predictive markers As a general case, most anticancer therapies are unpredictable. Predictive markers indicate if a certain treatment should be given, what kind of treatment and weighs the advantages. A response to a certain therapy is foreseen by the use of predictive markers.
In breast cancer, the predictive markers being used are the progesterone receptor and oestrogen receptor (Arpino G, et al. , 2005), which are used by scientist to determine patients with endocrine sensitive breast cancers and who will confidently respond to hormone therapy. HER-2 (epidermal growth factor receptor) is a young predictive marker to determine patients with metastatic disease for treatment with transtuzumab (antibody) (Slamon DJ. , 2001). Depending on the amount of HER-2 expression, the patients are categorised into three different levels and therefore given treatment accordingly.
The patient is unlikely to respond to tamoxifen (Arpino G, et al. , 2005) if HER-2 expression is too high. Patients who have HER-2 over expression show highest recurrences. With early and advanced breast cancer, high amounts of HER-2 can be connected with a decreased chance of response to hormone therapy (Arpino G, et al. , 2005). From the results of these markers, one concludes the exact type of treatment to be administered to a patient. The use of predictive markers saves money and conserves time wasted in the use of painstakingly unnecessary treatment for patients on whom it will have no significant effect.
All three markers require a high sensitivity as their results may either come back negative while a patient may truly have the illness or they may falsely come back positive when the patient might not suffer from any ailment. Therefore, it is of great importance to obviate these mistakes by using specific markers, especially when used in screening of large groups such as breast cancer. Generally biological markers must be simple to measure and detect, able to discover cancer at an early phase, recognize patients at an elevated risk and recognition of possible recurrence.