The immune system during the precancer period: naturally-occurring tumor reactive monoclonal antibodies and urethane carcinogenesis

Inflammation and breast cancer. Balancing immune response: crosstalk between adaptive and innate immune cells during breast cancer progression

Recent insights into the molecular and cellular mechanisms underlying cancer development have revealed that immune cells functionally regulate epithelial cancer development and progression. Moreover, accumulated clinical and experimental data indicate that the outcome of an immune response toward an evolving breast neoplasm is largely determined by the type of immune response elicited. Acute tumor-directed immune responses involving cytolytic T lymphocytes appear to protect against tumor development, whereas immune responses involving chronic activation of humoral immunity, infiltration by Th2 cells, and protumor-polarized innate inflammatory cells result in the promotion of tumor development and disease progression. Herein we review this body of literature and summarize important new findings revealing the paradoxical role of innate and adaptive leukocytes as regulators of breast carcinogenesis.

Paradoxical roles of the immune system during cancer development

The main function of the mammalian immune system is to monitor tissue homeostasis, to protect against invading or infectious pathogens and to eliminate damaged cells. Therefore, it is surprising that cancer occurs with such a high frequency in humans. Recent insights that have been gained from clinical studies and experimental mouse models of carcinogenesis expand our understanding of the complex relationship between immune cells and developing tumours. Here, we examine the paradoxical role of adaptive and innate leukocytes as crucial regulators of cancer development and highlight recent insights that have been gained by manipulating immune responses in mouse models of de novo and spontaneous tumorigenesis.

The interplay between innate and adaptive immunity regulates cancer development

There is increasing clinical and experimental evidence that inflammation and cancer are causally linked. Much progress has been made in understanding how inflammatory cells contribute to cancer development; however, it is still largely unknown which molecular mechanisms are responsible for initiation and maintenance of chronic inflammation associated with developing neoplasms. This review will discuss how the adaptive and innate immune systems interact during physiological and chronic inflammation, with a focus on studies revealing new insights into the role of adaptive immune cells as important regulators of chronic inflammation-associated carcinogenesis. We will speculate on whether current knowledge about the dysregulated interplay between adaptive and innate immunity during chronic inflammatory disorders might be useful in understanding and targeting the underlying mechanisms of chronic inflammation-associated neoplastic progression.

Autoantibody-mediated inhibition of pancreatic cancer cell growth in an athymic (nude) mouse model

INTRODUCTION

Antiribosomal P autoantibodies are detectable in 12-16% of patients with systemic lupus erythematosus.

AIM

To assess whether antiribosomal P autoantibodies could be useful as a novel form of immunotherapy for pancreatic cancer.

METHODOLOGY

Three pancreatic cancer cell lines were incubated with antiribosomal P or normal human immunoglobulin. Viability was assayed with MTT, and apoptosis was detected by TUNEL. MIA PaCa-2 cells were injected into athymic mice. Animals were treated with intraperitoneal antibody or control immunoglobulin. Serum antibody levels were measured by ELISA. Tumor nodule size was measured weekly. Binding of the antibody to tumors was demonstrated with fluorescent microscopy.

RESULTS

Antiribosomal P antibody inhibited pancreatic cancer cell proliferation up to 54.6% (p < 0.01) and was associated with a threefold increase in the rate of apoptosis (p < 0.05). Tumor volume after 4 weeks of treatment was 23.2 mm3, versus 141.5 mm3 for the control group (p < 0.05). Apoptosis rate within the nodules was increased twofold, to 11.4%, in comparison with control (p < 0.05).

CONCLUSION

Antiribosomal P autoantibody at levels similar to those that can exist in SLE inhibits the growth of pancreatic cancer cells, in vitro and in vivo. The mechanism involves surface binding and apoptosis.

Reduced tumorigenicity of threshold syngeneic tumor inocula in xid-bearing mice treated with natural antibodies

Several correlative experimental approaches have provided evidence that polyclonal serum natural antibodies (NAb) participate in the defense against small syngeneic tumor foci in vivo. The threshold subcutaneous tumor inoculum model of incipient neoplasia has consistently revealed an inverse relationship between tumorigenicity in vivo and the NAb binding capacity of the tumor injected or the anti-tumor NAb levels of the recipient animals, including B cell-deficient mice bearing the xid mutation of the CBA/N mouse strain. Now passive i.v. administration of whole normal syngeneic serum NAb in bolus injections, given I each day beginning on day -2, -1 or 0 prior to the threshold s.c. challenge of xid-bearing CBA/N or male (CBA/N x CBA/J)F1 mice with syngeneic RI-28 lymphoma cells, consistently and significantly reduced their tumorigenicity assayed as tumor appearance and latency. Three similar injections of an ammonium sulfate-precipitated fraction of whole serum NAb also reduced tumor frequency and latency, while a combination of purified IgG and IgM NAb reduced the appearance of tumors slightly and increased the survival of recipients. The reconstitution of the xid-defect in anti-tumor NAb provides more direct evidence to substantiate a role for NAb in the defense against early tumor development in vivo and establishes a model for the dissection of the in vivo mechanisms of the NAb anti-tumor activity.

Reactivity and structure of a mouse anti-F(ab')2 IgM. Comparison of its variable region sequences with those of a structurally close polyreactive natural IgM

IE12 is a monoclonal IgM with strong anti-F(ab')2 activity that inhibits the binding of normal mouse IgG to self antigens. In this study, we found that this IgM was also reactive with several monoclonal antibodies (mAbs), myeloma proteins and B lymphocytes from normal BALB/c mouse. The nucleotide sequences of the variable region of the heavy and light chains of IE12 were determined, and compared to those of another mAb already described in the literature. This mAb uses the same light chain and also the same VH, D and JH segments, but unlike IE12, is polyreactive. The comparison of the amino acid composition of these two mAbs and of the computer predictions for their structure and hydrophilicity indicated that the most striking difference between them was located in the third complementarity determining region (CDR3) of the heavy chain. Indeed, they used the same D segment but translated in two different reading frames, leading to different amino acid compositions. The CDR3 of IE12 contains aliphatic amino acids, while that of the polyreactive IgM does not. In addition, IE12 has two prolines, one at each at each extremity of its D segment, that could confer a certain rigidity to this region. Finally, the CDR3 of IE12 is predicted to be hydrophobic, while the one of the polyreactive IgM is predicted to be hydrophilic and more flexible, suggesting that the hydrophilicity and the flexibility of this region might be critical for polyreactivity.

Abnormalities in immune regulation precede the development of multiple myeloma

Immunosuppression of immunoglobulin synthesis seen in patients with multiple myeloma is in part due to immunosuppressive CD5 positive B cells. In a 13 year longitudinal study of an IgA-deficient blood donor who developed multiple myeloma, the presence of immunosuppressive CD5 positive B cells and T cells preceded the diagnosis of overt multiple myeloma and the appearance of immunosuppressive monocytes. These data argue that certain immune defects may be involved in the development of myeloma and are not simply a consequence of overt malignancy.

CD5+ B cells and naturally occurring autoantibodies in cancer patients

We have determined the percentage of CD5+ B lymphocytes in the peripheral blood of cancer patients and healthy controls, using antibodies directed at the CD5 and CD19 (pan-B) markers. The frequencies of CD5+ B cells, expressed as a percentage of total B cells, ranged from 14.3 to 57.5% in the controls and from 14.8 to 82.8% in the patient population. One-third of the cancer patients had frequencies greater than 2 s.d. above the mean of the control population. The CD5+ B cell fraction expressed as a percentage of total lymphocytes was also significantly elevated in this group of cancer patients. These results suggest that the CD5+ B cell compartment may be affected by the malignant process or by the therapy modality employed. The plasma levels of several naturally occurring autoantibodies, the products of the CD5+ B cells, were also assessed in cancer patients and controls. No significant differences were observed when reactivity to several autoantigens was measured. These included nuclear components and phospholipids.