Cancer immune surveillance is considered to be important in the anti-tumor protection of the host. The growing tumor escapes the immune control under the immunosuppressive conditions. The surgical removal of the tumor may reverse the immunosuppression. The TF antigen and Tn belong to tumor-associated carbohydrate antigens (TACA). TF antigen is implicated in the metastatic spread due to the adhesion of cancer cells to the endothelium. However, the dynamic changes of the level of TF and Tn-antibodies in the serum of patients with cancer and its association with survival have been insufficiently studied.
A research article to be published on July 21, 2008 in the World Journal of Gastroenterology addresses this question. The research team led by Dr. Kurtenkov from National Institute for Health Development (Tallinn, Estonia) have undertaken a long-term follow-up of cancer patients to determine changes in the postoperative level of TF- and Tn antibodies, as well as to elucidate the association of this level with the progression of cancer, and survival. The level of antibodies in serum was determined by the ELISA using synthetic polyacrylamide (PAA) glycoconjugates.
They found that in gastrointestinal cancer, the TF antibody level was found to have elevated significantly after the removal of G3 tumors as compared with the preoperative level (u = 278.5, P < 0.05). After surgery, the TF and Tn antibody level was elevated in the majority of gastric cancer patients (sign test, 20 vs 8, P < 0.05, and 21 vs 8, P < 0.05, respectively). In gastrointestinal cancer, the elevated postoperative level of TF, Tn and Gal antibodies was noted in most patients with G3 tumors (sign test, 22 vs 5, P < 0.01; 19 vs 6, P < 0.05; 24 vs 8, P < 0.01, respectively), but the elevation was not significant in patients with G1 + G2 resected tumors. The postoperative follow-up showed that the percentage of patients with G3 resected tumors of the digestive tract, who had a mean level of anti-TF IgG above the cutoff value (1.53), was significantly higher than that of patients with G1 + G2 resected tumors (chi2 = 3.89, all patients; chi2 = 5.34, patients without regional lymph node metastases; P < 0.05). The percentage of patients with a tumor in stage I, whose mean anti-TF IgG level remained above the cut-off value (1.26), was significantly higher than that of patients with the cancer in stages II I-IV (chi2 = 4.71, gastric cancer; chi2 = 4.11, gastrointestinal cancer; P < 0.05). The correlation was observed to exist between the level of anti-TF IgG and the count of lymphocytes (r = 0.517, P < 0.01), as well as between the level of anti-Tn IgG and that of serum CA 19-9 (r = 0.481, P < 0.05). No positive delayed-type hypersensitivity reaction in skin test challenges with TF-PAA in any of the fifteen patients, including those with a high level of anti-TF IgG, was observed.
Their result indicated that the surgical operation raises the level of anti-carbohydrate IgG in most patients, especially in those with the G3 tumor of the gastrointestinal tract. The stage and morphology-dependent immuneosuppression affects the TF-antibody response and may be one of the reasons for unresponsiveness to the immunization with TF-antigens.