Activation of host lymphocytes cultured with cancer cells treated with neuraminidase

Sweet escape: sialic acids in tumor immune evasion

Sialic acids represent a family of sugar molecules derived from neuraminic acid that frequently terminate glycan chains and contribute to many biological processes. Already five decades ago, aberrantly high expression of sialic acids has been proposed to protect cancer cells from recognition and eradication by the immune system. Today, increased understanding at the molecular level demonstrates the broad immunomodulatory capacity of tumor-derived sialic acids that is, at least in part, mediated through interactions with immunoinhibitory Siglec receptors. Here we will review current studies from a sialic acid sugar perspective showing that tumor-derived sialic acids disable major killing mechanisms of effector immune cells, trigger production of immune suppressive cytokines and dampen activation of antigen-presenting cells and subsequent induction of anti-tumor immune responses. Furthermore, strategies to modulate sialic acid expression in cancer cells to improve cancer immunotherapy will be discussed.

Altered reactivity for A, B, H antigens in transitional cell carcinomas of the urinary bladder. A study of the mechanisms involved

Transitional cell carcinomas (TCCs) of the urinary bladder show variable blood group (BG) antigen reactivity even in the non-invasive stage. A correlation exists between the tumor reactivity and subsequent clinical course: when the expected BG antigen(s) is retained, the clinical course is favorable; absence of the expected antigen(s) denotes an aggressive potential. In the present study we investigated some of the possible mechanisms of altered BG antigen reactivity in TCCs. It was found that the "loss" of A, B, H reactivity is a quantitative phenomenon and the threshold for positive reactions depends on the method of tissue processing and the titer of the antisera. Thus, in the 35 cases studied, paraffin processing resulted in reduced reactivity compared to fresh-frozen tissue sections. The reactivity of tumors that appeared positive when tested with undiluted antisera was found reduced when quantitatively compared to that of normal mucosa from the same individual. Excessive or inappropriate sialylation does not appear to be responsible for the reduced BG antigen reactivity of the tumors. In fact, TCCs (9 cases) had significantly reduced sialic acid content compared to normal bladder mucosae (6 cases) regardless of their A, B, H reactivity and neuraminidase did not change their reactions for BG antigens. In addition, spontaneous unmasking of the Thomsen-Friedenreich (T) antigen was observed in invasive tumors that were negative for the expected BG antigen(s). Tumors from patients of blood group A or B often showed increased reactivity for the H antigen, although their A or B antigen was reduced or absent. In view of the known biosynthetic sequence from H to A and B substances, these observations suggest a specific biochemical defect in the tumors.

VCN-releasable sialic acid and gangliosides in human neuroblastomas

The ganglioside pattern and VCN-releasable sialic acid residues of six human neuroblastomas were studied. There was no correlation between VCN-releasable sialic acid and prognosis. The ganglioside patterns were more complex in those cases with an expected good prognosis as reflected by the presence of trisialoganglioside. The complexity of the ganglioside pattern did not always correlate with the histologic grade of the tumor. These results suggest the ganglioside pattern may serve as a chemical marker for predicting the prognosis in patients with neuroblastomas.

Neuraminidase and tumor immunotherapy

Preliminary results of first clinical studies with the enzyme neuraminidase call attention to a new kind of cancer treatment. This promising approach to tumor immunotherapy was entered into the clinical phase as a consequence of successful experimental studies in tumor-bearing mice, rats and dogs. In this review, the presently known and essential results of experimental and clinical studies on tumor immunotherapy by means of neuraminidase are presented as well as some necessary and critical considerations in this context. Moreover, out of a broad variety of results of biochemical and biological in vitro studies, it was attempted to select the more essential knowledge which could contribute to a better understanding of the still rather unclear in vivo mode of action of the enzyme neuraminidase. In a first brief paragraph (1.0), the biochemically characteristic data of the enzyme neuraminidase is presented. In the second section (2.0), the basic knowledge about the effects of neuraminidase on cell behavior is rather amply contained. Here, on the one hand, the biophysical and biochemical alterations are mentioned, the so-called ""unmasking'' effects are reconsidered and, on the other hand, the effects on the immunologically responding cell are discussed. In a third section (3.0), the diverse findings from animal experiments using neuraminidase-treated tumor cells are confronted, whereby tumor transplantation experiments and tumor therapy experiments are dealt with separately. The last section (4.0) reports about the first clinical studies with neuraminidase-treated autologous as well as homologous tumor cells, which partly brought about rather surprising and astonishing success. On the basis of recent findings by the study group of the authors, the more prior and sometimes discrepant results of various groups are critically considered. The problems of alteration of antigenicity and of other properties of cells through splitting off membrane-bound neuraminic acid, the facts of adjuvanticity of neuraminidase itself, the relation of successful therapy to dose dependency as well as the relation of undesirable methods for tumor mass reduction to the immunological responsiveness of the tumor bearer were especially looked into.

Studies on the mitogenic activity of trypsin, pronase and neuraminidase on human peripheral blood lymphocytes

Human peripheral blood lymphocytes were cultured in the presence of protease (trypsin and pronase) and Vibrio choleraneuraminidase. T and B lymphocyte populations were separated and the effect of these enzymes plus phytohaemagglutin or Tuberculin was studied. The results of these experiments show that proteases moderately stimulate spontaneous deoxynucleic acid synthesis of control cells and potentiate the effect of tuberculin on sensitized cells. These enzymes act specifically on B lymphocytes. Neuraminidase also increases spontaneous deoxyribonucleic acid synthesis of control cells and augments significantly the in vitro response to PPD. There is no additive effect of neuraminidase on phytohaemagglutin stimulated cells. Neuraminidase seems to stimulate specifically T lymphocytes. Some possible mechanisms of action of these enzymes are proposed and discussed.

Lymphocyte stimulation by autologous tumor cells in the presence of serum from the same patient or from healthy donors

Lymphocyte blastogenesis induced by autologous tumor biopsy cells, by allogeneic lymphocytes and by PHA, was performed in the presence of autologous or allogeneic serum collected from normal blood donors. In 13 of the 15 cases lymphocyte stimulation by autologous tumor cells was inhibited in the presence of autologous serum. In contrast, autologous serum somewhat enhanced the blastogenic effect of PHA and allogeneic lymphocytes.

Immunologic approach to cancer therapy

The resistance that many cancer patients show to the progress of their disease, attested to by well documented cases of spontaneous regressions as in neuroblastoma, hypernephroma, choriocarcinoma and malignant melanoma, and the long-term dormancy of multiple metastases seen particularly after removal of a primary mass, can be explained only by host defense mechanisms. Attemps at immunotherapy over the years are reviewed and new directions are presented.

Neuraminidase-mediated augmentation of in vitro immune response of patients with solid tumors

Host blood lymphocytes undergo accentuated blastic transformation when cultured with tumor cells pretreated with neuraminidase. The effect has been observed in 38 patients with such common solid tumors as bronchus carcinoma, skin melanoma, hypernephroma, or adenocarcinoma of the breast, lung, colon, or rectum. Individual response varied but often exceeded response to allogeneic cells. Three patients with glioblastoma of the brain did not respond. Lymphoblastic transformation was not observed in three of four cultures containing benign tumor or in any cultures containing normal tissue analogues of the malignant tumors. A factor in host blood serum inhibiting lymphoblastic transformation correlated to abnormal elevation of serum-bound sialic acid. This blocking factor differed in specificity from enhancing antibody or serum blocking complexes described by other investigators. Blocking effects were observed when the tumor-cell type of a serum donor differed from the cell type of the culture test tumor. Serum with abnormal elevation of bound sialate from a cancerfree human also non-specifically blocked host response to tumor. The blocking effect could be eliminated by partial enzymatic removal of bound sialic acid from serum glycoproteins.

Regeneration of the surface glycoproteins of a transplantable mouse tumor cell after treatment with neuraminidase

Strain A mouse ascites tumor cells that were treated with neuraminidase (EC 3.2.1.18) (these cells show decreased tumor-forming ability in allogeneic C3H mice) rapidly regenerate sialoglycoproteins at the cell surface during culture. The incorporation of labeled D-glucosamine into membrane glycoproteins of cells that were treated or untreated with neuraminidase proceeds at similar rates. Surface glycoproteins that contain sialic acid are synthesized de novo during culture of neuraminidase-treated cells, and in nondividing cells, synthesis is accompanied by turnover of the membrane glycoproteins. The rate of turnover of membrane glycoproteins that lack sialic acid residues is the same as that occurring in non-dividing cells that are not treated with neuraminidase and that are cultured under identical conditions. Turnover of the surface membrane of nondividing cells leads to the accumulation of glycoproteins in the supernatant medium of cell cultures. The rapid regeneration of cell surfaces that contain sialic acid by TA3 cells that were treated with neuraminidase, makes it unlikely that the rejection of these cells in vivo, in C3H mice, is due solely to the induction of a primary immune response to new or to previously concealed antigenic specificities that would be expressed on the surface of the sialic acid-depleted cell.