MHC 1 levels tied to colorectal cancer prognosis

Downregulation of major histocompatibility complex (MHC) class 1 molecules appears to be associated with a poor prognosis in patients with colorectal cancer, UK researchers report in the January 1st issue of the International Journal of Cancer.

Senior investigator Dr. Lindy G. Durrant told Reuters Health that “these studies show that the immune system can control tumor growth. However, due to genetic instability within tumors, they can downregulate molecules, thus avoiding immune recognition and becoming more aggressive.””Immune recognition molecules such as MHC 1 are therefore excellent markers to (select) patients for aggressive new therapies, which may result in better survival from cancer.”Dr. Durrant of the University of Nottingham and colleagues note that although these molecules appear to play a central role in modulating immune response to tumors, evidence on the impact of MHC class I loss is scarce.To investigate further, the researchers examined more than 450 tumor samples from patients undergoing surgical resection of histologically proven primary colorectal cancer.The team found that high levels of MHC class I expression as well as absence of such expression was associated with similar disease-specific survival times. However, low levels of expression were associated with significantly reduced survival times and were an independent marker of poor prognosis.The researchers note that the difference is most marked in patients with earlier stage disease. This suggests that “an immune response is occurring, which may eliminate circulating tumor cells and prevent the development of metastases.”Patients with downregulated expression may derive greater benefit from adjuvant chemotherapy, the researchers note. Patients with normal levels “would appear to be good candidates for T-cell based vaccine strategies.”(Source: Int J Cancer 2006;118:6-10: Reuters Health: Oncolink: January 2006.)