Cancer is a group of more than 100 different diseases characterized by uncontrolled cell growth, local tissue invasion, and distant metastases (Chabner, 2006). It has been difficult to develop a precise definition of cancer. The famous British oncologist Willis defined cancer as "an abnormal mass of tissue whose growth exceeds and is not coordinated with that of normal tissues and persists in the same excessive manner after the cessation of the stimuli which caused the change" ( Cotran et al., 1999). The mechanisms by which cancer occurs are not completely understood. Cancer is thought to develop from cells whose usual mechanisms for controlling proliferation and growth have been altered. Recent evidence reinforces the notion of carcinogenesis as a genetically regulated multistep process (Mediana et al., 2008). The first step in this process is initiation which began with the exposure of cells to carcinogens that lead to genetic damage which, if not repaired, results in irreversible mutations. The mutated cells begin to grow until a colony forms. The second stage is promotion, in which carcinogens or other factors modify the environment in such a way as to favor the growth of a mutated cell population over normal cells. The main difference between these two stages is that the latter is reversible and could therefore be the target of future chemoprevention strategies (Mediana et al., 2008). The next step is the transformation of mutated cells into cancer cells; It may take 5 to 20 years to progress from the benign carcinogenic phase to the fully developed malignant stage, where the cancer can be detected clinically. The final stage called progression, where further genetic changes take place, leading to increased proliferation and metastasis (Weinberg, 1996, Compagni and Christofori, 2000).1.2. Cancer epidemiology: Cancer is a major public health problem in many parts of the world. More than ten million new cases of cancer, with more than six million deaths, were estimated in 2000 (Parkin, 2001). Estimated incidence and mortality figures in 2002 increased markedly, with 10.9 million new cases and 6.7 million deaths from cancer (Parkin et al., 2005). Even in developed countries suffering from cancer, in the United States, 2,677,860 new cases of cancer are expected to be diagnosed in 2009. That same year, more than 562,340 deaths will be due to cancer, this number represents 25% of all deaths and makes cancer the largest number of deaths. a second cause of death after heart disease (Jemal et al..