ABO(H) antigens and beta-2 microglobulin in transitional cell carcinoma. Predictors of response to intravesical bacillus Calmette-Guerin

Cancer Immune Evasion Through Loss of MHC Class I Antigen Presentation

Major histocompatibility class I (MHC I) molecules bind peptides derived from a cell's expressed genes and then transport and display this antigenic information on the cell surface. This allows CD8 T cells to identify pathological cells that are synthesizing abnormal proteins, such as cancers that are expressing mutated proteins. In order for many cancers to arise and progress, they need to evolve mechanisms to avoid elimination by CD8 T cells. MHC I molecules are not essential for cell survival and therefore one mechanism by which cancers can evade immune control is by losing MHC I antigen presentation machinery (APM). Not only will this impair the ability of natural immune responses to control cancers, but also frustrate immunotherapies that work by re-invigorating anti-tumor CD8 T cells, such as checkpoint blockade. Here we review the evidence that loss of MHC I antigen presentation is a frequent occurrence in many cancers. We discuss new insights into some common underlying mechanisms through which some cancers inactivate the MHC I pathway and consider some possible strategies to overcome this limitation in ways that could restore immune control of tumors and improve immunotherapy.

Cell surface carbohydrates as prognostic markers in human carcinomas

Tumour development is usually associated with changes in cell surface carbohydrates. These are often divided into changes related to terminal carbohydrate structures, which include incomplete synthesis and modification of normally existing carbohydrates, and changes in the carbohydrate core structure. The latter includes chain elongation of both glycolipids and proteins, increased branching of carbohydrates in N-linked glycoproteins, and blocked synthesis of carbohydrates in O-linked mucin-like glycoproteins. In mature organisms, expression of distinct carbohydrates is restricted to specific cell types; within a given tissue, variation in expression may be related to cell maturation. Tumour-associated carbohydrate structures often reflect a certain stage of cellular development; most of these moieties are structures normally found in other adult or embryonic tissues. There is no unique tumour carbohydrate structure, since certain structures which are tumour-related in one organ may be normal constituents of other tissues. Tumour-associated carbohydrate changes have been used in the diagnosis of human cancers. Recently, however, it has been demonstrated that the expression of some carbohydrate structures is associated with prognosis. Tn, sialyl-Tn, and T are cell membrane-bound mucin-like carbohydrate structures that may be expressed in tumours due to blocked synthesis of the core carbohydrate chain of mucin-like structures. Their expression is strongly associated with prognosis in certain tumours, but the biological relationship between their expression and tumour progression is at present unknown. The blood group-related carbohydrate structures Le(x), sialyl-Le(x), ABH, and Le(y) are examples of terminal carbohydrate structures which are related to tumour prognosis. These structures are of increasing interest since they may function as adhesion molecules; adhesion of tumour cells to endothelial cells of blood vessels may be mediated by an interaction between sialosyl-Le(x) and E-selectin and studies indicate that Le(y) is related to cell motility. These findings are now the basis for tumour therapeutic experiments.

Prognostic value of an assessment of ABH(0) isoantigens and Thomsen-Friedenreich (TF) antigen expression in patients with urinary bladder tumours

The discriminating and prognostic value of the expression of ABH(0) and TF antigens in tumour cells of 76 patients with urinary bladder tumours was evaluated. In patients with superficial tumours the most frequently defined phenotype was ABH(-) TF(+) and in those with deep tumours ABH(-) TF(-). The lowest frequency of recurrences was seen in patients with TFCr(+) antigenic phenotype and no patient died in this group. The mean lifespan of patients with TF(-) tumours was shorter (21 months) than of those with TF(+) tumours. For detection of tumours with higher risk of recurrences an analysis of the combination of markers revealed to be more predictive than analysis of a single marker.