Allogeneic Lymphocyte Therapy - Rationale

The centerpiece of cancer immunotherapy at Oasis of Hope is known as "allogeneic lymphocyte therapy". The regimen which we employ was developed over a quarter of a century ago by an insightful Japanese physician, Dr. Masaru Kondo, who proved to be far ahead of his time. Dr. Kondo reported that his therapy could achieve significant tumor shrinkage (objective response) in 30% of his patients with disseminated disease.1 For an immunotherapy, this is almost unprecedented – a stimulated immune system is known to have the capacity to prevent or slow the formation of new metastases, but immune-mediated regression of pre-existing tumors has been thought to be a very rare occurrence.

Perhaps for this reason, as well as the fact that the mechanistic basis of Kondo's therapy was then poorly understood, the relatively few cancer scientists who became aware of Dr. Kondo's work presumably thought that his claims were "too good to be true", and thus failed to test or implement them. Fortunately, within the last several years, cancer scientists have demonstrated that allogeneic lymphocyte therapy can work in tumor-bearing rodents, and have made great strides in defining the mechanisms responsible for its efficacy.2-4

For optimal efficacy, the administration of allogeneic lymphocytes must be preceded by a short course of low-dose cyclophosphamide. The purpose of this cyclophosphamide – too mild to provoke side effects – is not to attack the cancer directly (indeed, the drug used may be one to which the cancer is resistant), but rather to kill selectively certain "suppressor" immune cells (now known as Treg lymphocytes) that act to suppress the formation or activity of lymphocytes capable of attacking the cancer.5-8 In this way, the immune system can be primed to respond aggressively to the stimulus provided by the infused lymphocytes. The reason why Treg cells may be easier to kill than most other immune cells is that they tend to multiply at a high rate; chemotherapy often selectively targets rapidly multiplying cells.

One or two days after this preliminary course of cyclophosphamide is completed, the lymphocytes are administered. These lymphocytes are obtained from 100 milliters of blood, donated by a healthy young person not related to the patient; a standard technique known as leukophoresis is used to separate these lymphocytes from other blood components. Approximately 50-70 million of these lymphocytes are infused intravenously into the patient; few if any side effects are noted. This protocol – a preliminary round of low-dose chemotherapy followed by lymphocyte infusion – is repeated once per month for three months. If it appears to be efficacious, the therapy can be repeated later at longer intervals. It is desirable to employ a different lymphocyte donor each time the therapy is administered, since otherwise the patient may generate antibodies which can attack the infused lymphocytes and limit their capacity to stimulate an immune response against the cancer.

How does such a simple therapy work? Its efficacy is rooted in a phenomenon known as "the allogeneic effect".4, 9 T lymphocytes have the ability to recognize a very broad range of foreign proteins (antigens), but, at least initially, only a very tiny fraction of lymphocytes can recognize a given antigen. However, a relatively high proportion of lymphocytes are pre-programmed to recognize the so-called "histocompatibility antigens" (derived from HLA proteins) that are different than those on one's own cells. When a patient receives an organ transplant from a donor that has not been carefully matched, a large number of his lymphocytes quickly recognize the foreign histocompatibility antigens expressed by the transplanted organ; this results in rapid rejection of the organ if strong immunosuppressive drugs are not administered concurrently. This marked tendency of T lymphocytes to recognize and react to foreign histocompatibility antigens is known as "alloreactivity". The lymphocytes infused in Dr. Kondo's therapy are said to be "allogeneic" because they express different histocompatibility antigens than the patient, and thus recognize the patient's histocompatibility antigens as foreign.

Dr. Ephraim Fuchs and colleagues of Johns Hopkins Medical School have recently demonstrated, working with tumor-bearing rodents, how the phenomenon of alloreactivity can be employed to generate a strong anti-cancer immune response.2 Direct attack of tumor cells by the infused lymphocytes (known as a "graft-versus-host response") plays little if any role in the efficacy of this strategy. Rather, the major efficacy reflects the fact that infused T helper lymphocytes (bearing the marker CD4+) are capable of greatly boosting the activity of the patient's "antigen-presenting cells" (dendrites), owing to the fact that a high proportion of these infused helper lymphocytes can recognize the histocompatibility antigens expressed by these dendrites.

If these stimulated antigen-presenting cells have assimilated tumor proteins that can be perceived as foreign by the host's immune cells, they then have the capacity to confer strong activation to the patient's own cytotoxic T lymphocytes (bearing the marker CD8+) that are capable of recognizing these tumor proteins. These stimulated cytotoxic T lymphocytes can then directly attack and kill the cancer cells. This strategy is all the more effective because the preliminary chemotherapy has selectively eliminated many of the suppressor lymphocytes which otherwise could have limited the activation or activity of these tumor-directed cytotoxic T lymphocytes. Dendrites activated by infused alloreactive lymphocytes can also markedly enhance the activity of natural killer cells, immune cells which can recognize and attack many cancer cells in a way that is not dependent on the recognition of specific tumor antigens.

At Oasis, we use Dr. Kondo's classic allogeneic lymphocyte therapy in the context of other measures which can boost the efficacy of the anti-cancer immune response, either by amplifying the activation of the cytotoxic T lymphocytes and natural killer cells capable of attacking the cancer, or by blocking strategies which tumors often employ to ward off immune rejection. These measures include melatonin, subcutaneous injections of interleukin-2 (employed with the IRT-IL regimen), high-dose selenium (which Dr. Kondo also used!), spirulina, glutamine, the cox-2 inhibitor diclofenac, and caffeine.

• References
• (1) Kondo M, McCarty MF. Rationale for a novel immunotherapy of cancer with allogeneic lymphocyte infusion. Med Hypotheses 1984 November;15(3):241-77.
• (2) Symons HJ, Levy MY, Wang J, Zhou X, Zhou G, Cohen SE, Luznik L, Levitsky HI, Fuchs EJ. The allogeneic effect revisited: exogenous help for endogenous, tumor-specific T cells. Biol Blood Marrow Transplant 2008 May;14(5):499-509.
• (3) Su X, Guo S, Zhou C, Wang D, Ma W, Zhang S. A simple and effective method for cancer immunotherapy by inactivated allogeneic leukocytes infusion. Int J Cancer 2009 March 1;124(5):1142-51.
• (4) Fabre JW. The allogeneic response and tumor immunity. Nat Med 2001 June;7(6):649-52.
• (5) Brode S, Raine T, Zaccone P, Cooke A. Cyclophosphamide-induced type-1 diabetes in the NOD mouse is associated with a reduction of CD4+CD25+Foxp3+ regulatory T cells. J Immunol 2006 November 15;177(10):6603-12.
• (6) Salem ML, Kadima AN, El-Naggar SA, Rubinstein MP, Chen Y, Gillanders WE, Cole DJ. Defining the ability of cyclophosphamide preconditioning to enhance the antigen-specific CD8+ T-cell response to peptide vaccination: creation of a beneficial host microenvironment involving type I IFNs and myeloid cells. J Immunother 2007 January;30(1):40-53.
• (7) Liu JY, Wu Y, Zhang XS, Yang JL, Li HL, Mao YQ, Wang Y, Cheng X, Li YQ, Xia JC, Masucci M, Zeng YX. Single administration of low dose cyclophosphamide augments the antitumor effect of dendritic cell vaccine. Cancer Immunol Immunother 2007 October;56(10):1597-604.
• (8) Schabowsky RH, Madireddi S, Sharma R, Yolcu ES, Shirwan H. Targeting CD4+CD25+FoxP3+ regulatory T-cells for the augmentation of cancer immunotherapy. Curr Opin Investig Drugs 2007 December;8(12):1002-8.
• (9) Suchin EJ, Langmuir PB, Palmer E, Sayegh MH, Wells AD, Turka LA. Quantifying the frequency of alloreactive T cells in vivo: new answers to an old question. J Immunol 2001 January 15;166(2):973-81.