Chemopreventive strategies for colorectal cancer (CRC) have been extensively studied to prevent the recurrence of adenomas and/or delay their development in the gastrointestinal tract. The non-steroidal anti-inflammatory drugs (NSAIDs) and selective cyclooxygenase (COX)-2 inhibitors have been proven as promising and the most attractive candidates for CRC clinical chemoprevention. The preventive efficacy of these agents is supported by a large number of animal and epidemiological studies which have clearly demonstrated that NSAID consumption prevents adenoma formation and decreases the incidence of, and mortality from CRC. On the basis of these studies, aspirin chemoprevention may be effective in preventing CRC within the general population, while aspirin and celecoxib may be effective in preventing adenomas in patients after polypectomy. Nevertheless, the consumption of NSAID and COX-2 inhibitors is not toxic free. Well-known serious adverse events to the gastrointestinal, renal and cardiovascular systems have been reported. These reports have led to some promising studies related to the use of lower doses and in combination with other chemopreventive agents and shown efficacy. In the intriguing jigsaw puzzle of cancer prevention, we now have a definite positive answer for the basic question "if", but several other parts of the equation-proper patient selection, the ultimate drug, optimal dosage and duration are still missing.

RASSF1A is frequently methylated in ES.

Increased expression of CD24 is seen in a large variety of solid tumors, including up to 90% of gastrointestinal (GI) tumors. Stable derivatives of SW480 colorectal cancer (CRC) cells that overexpress CD24 proliferate faster, and increase cell motility, saturation density, plating efficiency, and growth in soft agar. They also produce larger tumors in nude mice as compared to the parental SW480 cells. Most significantly, even depletion of one copy of the CD24 allele in the APCMin/+ mice of a transgenic mouse model led to a dramatic reduction in tumor burden in all sections of the small intestine. Homozygous deletion of both CD24 alleles resulted in complete abolishment of tumor formation. Moreover, CD24 knockout mice exhibited resistance to chemically induced inflammation‐associated CRC. Finally, a new signal transduction pathway is suggested: namely, CD24 expression downstream to COX2 and PGE2 synthesis, which is directly regulated by β‐catenin. CD24 is shown in vitro and in vivo as being an important oncogene in the gut, and one that plays a critical role in the initiation and progression of carcinogenesis.