Clinical promise of tumour immunology

Glutamatergic system components as potential biomarkers and therapeutic targets in cancer in non-neural organs

Glutamate is one of the most abundant amino acids in the blood. Besides its role as a neurotransmitter in the brain, it is a key substrate in several metabolic pathways and a primary messenger that acts through its receptors outside the central nervous system (CNS). The two main types of glutamate receptors, ionotropic and metabotropic, are well characterized in CNS and have been recently analyzed for their roles in non-neural organs. Glutamate receptor expression may be particularly important for tumor growth in organs with high concentrations of glutamate and might also influence the propensity of such tumors to set metastases in glutamate-rich organs, such as the liver. The study of glutamate transporters has also acquired relevance in the physiology and pathologies outside the CNS, especially in the field of cancer research. In this review, we address the recent findings about the expression of glutamatergic system components, such as receptors and transporters, their role in the physiology and pathology of cancer in non-neural organs, and their possible use as biomarkers and therapeutic targets.

SARS-CoV-2 Spike Protein-Induced Interleukin 6 Signaling Is Blocked by a Plant-Produced Anti-Interleukin 6 Receptor Monoclonal Antibody

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), the causative agent of the current COVID-19 pandemic, has caused more than 4.5 million deaths worldwide. Severe and fatal cases of COVID-19 are often associated with increased proinflammatory cytokine levels including interleukin 6 (IL-6) and acute respiratory distress syndrome. In this study, we explored the feasibility of using plants to produce an anti-IL-6 receptor (IL-6R) monoclonal antibody (mAb) and examined its utility in reducing IL-6 signaling in an in vitro model, which simulates IL-6 induction during SARS-CoV-2 infection. The anti-IL6R mAb (IL6RmAb) was quickly expressed and correctly assembled in Nicotiana benthamiana leaves. Plant-produced IL6RmAb (pIL6RmAb) could be enriched to homogeneity by a simple purification scheme. Furthermore, pIL6RmAb was shown to effectively inhibit IL-6 signaling in a cell-based model system. Notably, pIL6RmAb also suppressed IL-6 signaling that was induced by the exposure of human peripheral blood mononuclear cells to the spike protein of SARS-CoV-2. This is the first report of a plant-made anti-IL-6R mAb and its activity against SARS-CoV-2-related cytokine signaling. This study demonstrates the capacity of plants for producing functionally active mAbs that block cytokine signaling and implies their potential efficacy to curb cytokine storm in COVID-19 patients.

Increased NY-ESO-1 expression and reduced infiltrating CD3+ T cells in cutaneous melanoma

NY-ESO-1 is a cancer-testis antigen aberrantly expressed in melanomas, which may serve as a robust and specific target in immunotherapy. NY-ESO-1 antigen expression, tumor features, and the immune profile of tumor infiltrating lymphocytes were assessed in primary cutaneous melanoma. NY-ESO-1 protein was detected in 20% of invasive melanomas (16/79), rarely in in situ melanoma (1/10) and not in benign nevi (0/20). Marked intratumoral heterogeneity of NY-ESO-1 protein expression was observed. NY-ESO-1 expression was associated with increased primary tumor thickness (P = 0.007) and inversely correlated with superficial spreading melanoma (P < 0.02). NY-ESO-1 expression was also associated with reduced numbers and density of CD3+ tumor infiltrating lymphocytes (P = 0.017). When NY-ESO-1 protein was expressed, CD3+ T cells were less diffusely infiltrating the tumor and were more often arranged in small clusters (P = 0.010) or as isolated cells (P = 0.002) than in large clusters of more than five lymphocytes. No correlation of NY-ESO-1 expression with gender, age, tumor site, ulceration, lymph node sentinel status, or survival was observed. NY-ESO-1 expression in melanoma was associated with tumor progression, including increased tumor thickness, and with reduced tumor infiltrating lymphocytes.

Cancer vaccines: Where are we going?

Abstract The discovery that the immune system can distinguish molecular targets on cancer cells has led to efforts to develop cancer immunotherapeutics that can improve the recognition and effective elimination of tumor cells. Several types of tumor antigens are recognized by T lymphocytes, which are classified according to patterns of gene expression or protein distribution. Of particular interest is the group of molecules known as cancer-germline or cancer-testis antigens. As the relationship between the immune system and cancer has become clearer, so too have the challenges in designing effective cancer immunotherapeutics: (i) antigens need to be specifically selected based on ideal characteristics, such as tissue distribution that is restricted to tumors; (ii) selected antigens need to be combined with adjuvant agents that enhance their immunogenicity and yield robust responses; (iii) vaccination should be timed to pre-empt the development of regulatory suppressive immune mechanisms; and (iv) if suppressive regulatory mechanisms do arise, specific antagonists may be needed to enhance pro-immune outcomes. These challenges are shaping current and future research in this area.

Inhibitors of melanogenesis increase toxicity of cyclophosphamide and lymphocytes against melanoma cells

High mortality rate for metastatic melanoma is related to its resistant to the current methods of therapy. Melanogenesis is a metabolic pathway characteristic for normal and malignant melanocytes that can affect the behavior of melanoma cells or its surrounding environment. Human melanoma cells in which production of melanin pigment is dependent on tyrosine levels in medium were used for experiments. Peripheral blood mononuclear cells were derived from the buffy coats purchased from Lifeblood Biological Services. Cell pigmentation was evaluated macroscopically, and tyrosinase activity was measured spectrophotometrically. Cell proliferation and viability were measured using lactate dehydrogenase release MTT, [(3)H]-thymidine incorporation and DNA content analyses, and gene expression was measured by real time RT-PCR. Pigmented melanoma cells were significantly less sensitive to cyclophosphamide and to killing action of IL-2-activated peripheral blood lymphocytes. The inhibition of melanogenesis by either blocking tyrosinase catalytic site or chelating copper ions sensitized melanoma cells towards cytotoxic action of cyclophosphamide, and amplified immunotoxic activities of IL-2 activated lymphocytes. Exogenous L-DOPA inhibited lymphocyte proliferation producing the cell cycle arrest in G1/0 and dramatically inhibited the production of IL-1beta, TNF-alpha, IL-6 and IL-10. Thus, the active melanogenesis could not only impair the cytotoxic action of cyclophosphamid but also has potent immunosuppressive properties. This resistance to a chemotherapeutic agent or immunotoxic activity of lymphocytes could be reverted by the action of tyrosinase inhibitors. Thus, the inhibition of melanogenesis might represent a valid therapeutic target for the management of advanced melanotic melanomas.

Potency assays for therapeutic live whole cell cancer vaccines

Therapeutic cancer vaccines are under development with the goal of enhancing the body's immune response to cancer cells sufficient to arrest cancer cell growth. Among the various approaches being used are those based on whole tumor cells. Developing a suitable measure of the potency of such vaccines presents a significant challenge because neither cellular associated markers nor in vivo biological responses that are correlated with efficacy have been identified; nevertheless, manufacturers and regulatory agencies will need to develop methods to evaluate these products. At this moment, the challenge for manufacturers who are developing whole cell vaccines is to demonstrate batch-to-batch consistency for the vaccine used in clinical studies and to show that comparable vaccine batches have the same capacity to achieve an acceptable level of biological activity that may be related to efficacy. This is particularly challenging in that animal models to test that activity do not exist and direct serological or immunological correlates of clinical protection are not available because protection has not yet been established in clinical trials. In the absence of well-defined biological markers and tests for manufacturing consistency, manufacturers and regulators will need to rely heavily on a highly reproducible manufacturing process--the consistency of the process therefore becomes critical. In developing regulatory approaches to whole cell cancer vaccines, the experience from the field of infectious disease vaccines should be examined for general guidance. A framework that draws heavily on the field of infectious disease vaccines is presented and suggests that at this point in the development of this new class of products, it is reasonable to develop data on quantitative antigen expression as a measure of potency with the expectation that when clinical efficacy has been established it will confirm the appropriateness of this approach. But because this will not be known until the end of a pivotal trial, a bioassay should be considered and run in parallel. Several examples of bioassays are presented along with their advantages and disadvantages. The final selection of a potency assay for use in lot release of a commercializable therapeutic whole cell vaccine ultimately will depend on the totality of the data available at the time of approval by regulatory agencies. Based on information currently available, it is likely that quantitative antigen expression or a bioassay could be used to measure potency. If both are determined to be acceptable, the use of quantitative antigen expression could be considered for routine lot release, while the bioassay could be reserved for use as one of the elements in establishing comparability when manufacturing changes are being considered after approval.

Desmoplastic melanoma: comparison of expression of differentiation antigens and cancer testis antigens

Desmoplastic melanoma is a diagnostic and therapeutic challenge. Immunohistochemical analysis with antibodies to melanoma antigens can complement morphologic evaluation. Although staining for S100 protein is generally positive, staining for other melanoma differentiation antigens, particularly gp100, Melan-A/MART1 and tyrosinase, is often negative despite being commonly positive in other melanoma types. A high clinical index of suspicion and better diagnostic techniques are essential as atypical features and incorrect diagnosis can lead to poor clinical outcomes. Antigens associated with melanoma, such as the melanocyte differentiation and cancer testis antigen, may become important targets for immune therapies. We characterized the patterns of antigen expression of desmoplastic melanoma from 32 patients, including gp100, Melan-A/MART-1, tyrosinase, MAGE-A1, MAGE-A4 and NY-ESO-1. Consistent positive staining with S100 was observed. Differentiation antigens were expressed more frequently than cancer testis antigens regardless of the histological subtype of desmoplastic melanoma. When present, cancer testis antigen expression correlated to positive staining with differentiation antigens. The diagnostic yield of desmoplastic melanoma did not increase with the addition of cancer testis antigen typing. Low levels of expression of cancer testis antigen may indicate that they are suboptimal targets for vaccine development in desmoplastic melanoma.

Tumor antigen expression in melanoma varies according to antigen and stage

PURPOSE

Melanoma cells express antigens that can induce T-cell and antibody responses. Obtaining a detailed understanding of antigen expression in primary and metastatic melanoma is essential if these molecules are to be useful targets for immunotherapy of melanoma.

EXPERIMENTAL DESIGN

Malignant melanomas (n = 586) from 426 patients were typed for antigen expression. Multiple samples were available from 86 individuals, enabling analysis of antigen expression patterns over time. Paraffin-embedded samples were tested by immunohistochemistry for the presence of the differentiation antigens: gp100, Melan-A, tyrosinase, and the "cancer/testis" antigens MAGE-A1, MAGE-A4, and NY-ESO-1.

RESULTS

Samples were primary tumors (n = 251), lymph node metastases (n = 174), s.c. metastases (n = 71), and distant metastases (n = 90). The differentiation antigens were strongly expressed in 93% to 95% of tumors regardless of stage. In contrast, the frequency of cancer/testis antigen expression in primary tumors for MAGE-A1, MAGE-A4, and NY-ESO-1 was lower (20%, 9%, and 45%, respectively). MAGE-A1 and MAGE-A4 were acquired with advancing disease (to 51% and 44% in distant metastases, respectively) but not NY-ESO-1, which remained positive in 45%. MAGE-A1 expression was twice as prevalent in ulcerated primaries as in nonulcerated primaries (30% versus 15%; P = 0.006) and in thicker as opposed to thin melanomas (26% versus 10%; P = 0.1).

CONCLUSIONS

This large series describes patterns of antigen expression in melanoma and their evolution over time. This will help inform decisions about selection of patients and target antigens for melanoma immunotherapy clinical trials.

A phase I trial of humanized monoclonal antibody A33 in patients with colorectal carcinoma: biodistribution, pharmacokinetics, and quantitative tumor uptake

PURPOSE

To determine the in vivo characteristics of huA33, a CDR-grafted humanized antibody against the A33 antigen, we have conducted an open-label, dose escalation, biopsy-based phase I trial of huA33 in patients with colorectal carcinoma.

EXPERIMENTAL DESIGN

Patients with colorectal carcinoma were infused with [131I]huA33 (400 MBq: 10 mCi) and [125I]huA33 (40 MBq: 1 mCi) 1 week before surgery. There were four huA33 dose levels (0.25, 1.0, 5.0, and 10 mg/m2). Adverse events, pharmacokinetics, biodistribution, tumor biopsies, and immune responses to huA33 were evaluated.

RESULTS

There were 12 patients entered into the trial (6 males and 6 females; age range, 39-66 years). No dose-limiting toxicity was observed. The biodistribution of huA33 showed excellent uptake of [131I]huA33 in metastatic colorectal carcinoma. Pharmacokinetic analysis showed no significant difference in terminal half-life (T1/2beta) between dose levels (mean +/- SD, 86.92 +/- 22.12 hours). Modeling of colon uptake of huA33 showed a T1/2 of elimination of 32.4 +/- 8.1 hours. Quantitative tumor uptake ranged from 2.1 x 10(-3) to 11.1 x 10(-3) %ID/g, and tumor/normal tissue and tumor/serum ratios reached as high as 16.3:1 and 4.5:1, respectively. Biosensor analysis detected low-level human anti-human antibody responses in four patients following huA33 infusion.

CONCLUSIONS

huA33 shows selective and rapid localization to colorectal carcinoma in vivo and penetrates to the center of large necrotic tumors, and colon elimination half-life of huA33 is equivalent to basal colonocyte turnover. The excellent targeting characteristics of this humanized antibody indicate potential for the targeted therapy of metastatic colorectal cancer in future trials.

Black tea protects immunocytes from tumor-induced apoptosis by changing Bcl-2/Bax ratio

It is known that cancer is associated with altered immune function. We demonstrated earlier that black tea inhibits tumor growth in a dose-dependent manner. Here, we report that apoptosis was the cause of immunocyte death in Ehrlich's ascites carcinoma (EAC)-bearing mice and anti-tumor dose of black tea restored EAC-induced immunosuppression by inhibiting apoptosis. A search for the molecular mechanism revealed that EAC burden increased the expression of the pro-apoptotic proteins p53 and Bax in splenic lymphocytes although did not change the level of pro-proliferative protein Bcl-2. Interestingly, anti-tumor dose of black tea down-regulated p53, decreased Bax while augmenting Bcl-2 in these cells. As a result, Bcl-2/Bax ratio was increased and the immunocytes were protected from tumor-induced apoptosis. Thus, unlike many other anti-cancer agents, black tea is not only devoid of immunosuppressive effect but also acts as immuno-restorer in tumor-bearing host. These results, thus, raise the possibility of inclusion of black tea in successful therapeutic regimen against cancer.

Rational approaches to human cancer immunotherapy

Over most of the 20th century, immunotherapy for cancer was based on empiricism. Interesting phenomena were observed in the areas of cancer, infectious diseases, or transplantation. Inferences were made and extrapolated into new approaches for the treatment of cancer. If tumors regressed, the treatment approaches could be refined further. However, until the appropriate tools and reagents were available, investigators were unable to understand the biology underlying these observations. In the early 1990s, the first human tumor T cell antigens were defined and dendritic cells were discovered to play a pivotal role in antigen presentation. The current era of cancer immunotherapy is one of translational research based on known biology and rationally designed interventions and has led to a rapid expansion of the field. The beginning of the 21st century brings the possibility of a new era of effective cancer immunotherapy, combining rational, immunological treatments with conventional therapies to improve the outcome for patients with cancer.

Vaccine therapy in melanoma today

Melanoma is the most significant malignant tumor of the melanocyte system. It is characterized by a high malignant potential and an outstanding possibility for giving metastasis. Despite all investigations and progress concerning molecular genetics and immunology melanoma is a therapeutic problem even today. Vaccines are being developed with an intention not only to prevent but also to cure the disease, and the most important aim of clinical trails is to develop corresponding antitumor immunotherapy based on vaccine.

Malignant melanoma

CONTEXT

The rapidly developing fields of melanoma research are revolutionizing the current concepts on melanoma etiology and pathogenesis and are introducing newer diagnostic techniques and potential therapeutic approaches.

OBJECTIVES

To present the most current concepts on the etiology and pathogenesis of melanoma and to introduce the recent diagnostic techniques and the potential therapeutic approaches.

METHODS

Data sources were reports on melanoma published in the English language literature and observations made using specimens available at Harvard University, Johns Hopkins Medical Center, Albany Medical College, Loyola University Medical Center, and University of Tennessee Health Science Center.

RESULTS

Studies on melanoma containing chromosomal or genetic evaluation were selected for further analysis. Current clinical and pathologic categories with the reported genetic abnormalities were related to the latest information on pigment biology. The data extracted were used to develop a conceptual framework on the pathogenesis of melanoma; the generated model was then evaluated and used to suggest potential therapeutic approaches.

CONCLUSIONS

(1) Melanoma is not genetically homogeneous, and the existing differences between the pathologic categories, particularly in areas such as type of growth phase (radial vs vertical growth), total vertical dimension, ulceration of primary tumor, and metastatic process, have profound prognostic and therapeutic implications. (2) Chromosomal aberrations and gene mutations are found in sporadic and familial melanomas; among the most important are those affecting the 9p21, which contains the p16 locus, a site known to be critical for normal progression of the cell cycle. Aberrant p16 expression is associated with more aggressive behavior. (3) Melanoma cells possess a remarkable repertoire of biosynthetic capacities represented by the production of hormones, growth factors, and their receptors that may sustain and accelerate tumor development and progression. For example, expression of the tumoral products alpha-melanocyte-stimulating hormone and adrenocorticotropic hormone is regulated in vitro by ultraviolet light, a known carcinogen. (4) Melanomas differ from other tumors in their intrinsic capability to express melanogenic enzymes with the corresponding structural proteins to actually synthesize melanin. Melanogenesis-related proteins are rapidly entering the clinical arena, being used not only as diagnostic markers, but also as potential targets for melanoma therapy.

Glutamate antagonists limit tumor growth

Neuronal progenitors and tumor cells possess propensity to proliferate and to migrate. Glutamate regulates proliferation and migration of neurons during development, but it is not known whether it influences proliferation and migration of tumor cells. We demonstrate that glutamate antagonists inhibit proliferation of human tumor cells. Colon adenocarcinoma, astrocytoma, and breast and lung carcinoma cells were most sensitive to the antiproliferative effect of the N-methyl-d-aspartate antagonist dizocilpine, whereas breast and lung carcinoma, colon adenocarcinoma, and neuroblastoma cells responded most favorably to the alpha-amino-3-hydroxy-5-methyl-4-isoxazole-propionate antagonist GYKI52466. The antiproliferative effect of glutamate antagonists was Ca(2+) dependent and resulted from decreased cell division and increased cell death. Morphological alterations induced by glutamate antagonists in tumor cells consisted of reduced membrane ruffling and pseudopodial protrusions. Furthermore, glutamate antagonists decreased motility and invasive growth of tumor cells. These findings suggest anticancer potential of glutamate antagonists.

Humanized anti-ganglioside GM2 antibody is effective to induce antibody-dependent cell-mediated cytotoxicity in mononuclear cells from lung cancer patients

Ganglioside GM2 is one of the major gangliosides expressed on the cell surface of human tumors including lung cancer. We have previously reported that a mouse-human chimeric monoclonal antibody (mAb), KM966, against GM2 promotes the lysis of lung cancer cells by human blood mononuclear cells (MNC) of healthy donors. In this study, we examined antibody-dependent cell-mediated cytotoxicity (ADCC) of MNC, using KM966 mAb and its humanized counterpart, KM8969, in 16 lung cancer patients and 18 control patients. The ADCC activity was assessed by 4-h (51)Cr release from GM2 positive SBC-3 small cell lung cancer cells. MNC from lung cancer patients exhibited similar ADCC activity to those from control patients when KM966 and KM8969 were used as mAb. Moreover, effective ADCC activity was observed even in MNC from advanced lung cancer patients. These observations suggest the potential activity of humanized anti-GM2 mAb (KM8969), as well as chimeric KM966, in biological therapy for lung cancer patients.

Adoptive immunotherapy to lower postsurgical recurrence rates of hepatocellular carcinoma: a randomised trial

BACKGROUND

Postsurgical recurrence of hepatocellular carcinoma (HCC) is frequent and fatal. Adoptive immunotherapy is active against HCC. We assessed whether postoperative immunotherapy could lower the frequency of recurrence.

METHODS

Between 1992 and 1995, we did a randomised trial in which 150 patients who had undergone curative resection for HCC were assigned adoptive immunotherapy (n=76) or no adjuvant treatment (n=74). Autologous lymphocytes activated vitro with recombinant interleukin-2 and antibody to CD3 were infused five times during the first 6 months. Primary endpoints were time to first recurrence and recurrence-free survival and analyses were by intention to treat.

FINDINGS

76 patients received 370 (97%) of 380 scheduled lymphocyte infusions (mean cell number per patient 7.1x10(10) [SD 2.1]; CD3 and HLA-DR cells 78% [16]), and none had grade 3 or 4 adverse events. After a median follow-up of 4.4 years (range 0.2-6.7), adoptive immunotherapy decreased the frequency of recurrence by 18% compared with controls (45 [59%] vs 57 [77%]) [corrected] patients. Time to first recurrence in the immunotherapy group was significantly longer than that in the control group (48% [37-59] vs 33% [22-43] at 3 years, 38% [22-54] vs 22% [11-34] at 5 years; p=0.008). The immunotherapy group had significantly longer recurrence-free survival (p=0.01) and disease-specific survival (p=0.04) than the control group. Overall survival did not differ significantly between groups (p=0.09).

INTERPRETATION

Adoptive immunotherapy is a safe, feasible treatment that can lower recurrence and improve recurrence-free outcomes after surgery for HCC.

The use of bispecific antibodies in tumor cell and tumor vasculature directed immunotherapy

To overcome dose limiting toxicities and to increase efficacy of immunotherapy of cancer, a number of strategies are under development for selectively redirecting effector cells/molecules towards tumor cells. Many of these strategies exploit the specificity of tumor associated antigen recognition by monoclonal antibodies. Using either hybridoma fusion, chemical derivatization or molecular biology technology, antibodies with dual specificity can be constructed. These so called biospecific antibodies (BsAbs) have been used to redirect the cytolytic activity of a variety of immune effector cells such as cytotoxic T lymphocytes, natural killer cells, neutrophils and monocytes/macrophages to tumor cells. Local administration of BsAbs, either alone or in combination with autologous effector cells, is highly effective in eradicating tumor cells. In contrast, systemic application of BsAb at present is only suitable for adjuvant treatment of minimal residual disease due to poor tumor cell accessibility. As an alternative, angiogenesis related determinants on tumor blood vessels can be exploited for the selective delivery of effector cells/molecules apart from being used to inhibit angiogenesis. Important advantages of this strategy is that the endothelial cell associated target epitope(s) are easy accessible. The dependence of tumor growth on the tumor's blood supply also renders tumor endothelial cells an attractive target for therapy. Although still in its infancy, attacking the tumor's blood supply for example by delivering coagulation factors or toxins, or by BsAb directed immunotherapies holds great promise for antineoplastic therapy.

Accumulation of identical T cells in melanoma and vitiligo-like leukoderma

The cloning of genes encoding melanoma antigens has opened new possibilities for the treatment of patients with cancer; however, most tumor rejection antigens recognized by tumor infiltrating lymphocytes are the products of genes that are also expressed by normal melanocytes. Hence, a large set of antigenic determinants of the self have not induced self-tolerance and these peptide determinants furnish target structures for immune responses directed against tumors. The notion that the immunotherapeutic targets involved in cancer regression comprise normal differentiation antigens is stressed by the association between vitiligo-like leukoderma, due to destruction of normal melanocytes, and melanoma regression, due to destruction of cancer cells. Nevertheless, this is the first report to demonstrate by means of a new technique based on reverse transcription polymerase chain reaction and denaturing gradient gel electrophoresis, the presence of clonally expanded T cells with identical BV regions in areas of destruction of both normal and neoplastic cells.

Combination of granulocyte-macrophage colony-stimulating factor (GM-CSF) anf erythropoietin (EPO) for the treatment of advanced non-responsive chronic lymphocytic leukemia

We report the use of a colony-stimulating granulocyte-macrophage factor (GM/CSF) and erythropoietin (EPO) combination as salvage treatment in four heavily-pretreated patients with refractory/ recurrent B-CLL. Induction therapy was subcutaneous GM-CSF 2.5 microg/ kg, and EPO, 150 units/kg both daily for the first 14 d. Maintenance therapy was GM-CSF on days 1, 3 and 5 and Epo on days 2, 4 and 6 at the same doses with weekly recycling. All the patients responded favourably. A significant reduction of lymphocytosis, lymphoadenomegaly, and organomegaly was obtained within one month of therapy. The number of infections and transfusional requirement decreased dramatically. The hemoglobin increased to over 11 g/dl in 3 out of 4 patients. With a median follow-up of 11 months (range 5-13) we observed 4 partial responses (NCI/IWCLL) and only one progression after a 10-month partial response. This combination regimen seems very active, safe and easy to administer. It may represent a promising therapeutical option in heavily pretreated patients. Further clinical and biological studies on a larger cohort of patients are needed to confirm these preliminary data, to clarify the hypothetical interactions between these cytokines and B-CLL cell proliferation pathways, and to establish if this therapy may have an impact on survival.

The effect of skin transplantation on tumor growth in mice

BACKGROUND

Skin allograft is an immunostimulant. Skin allograft activates effector arms of the immune system including the cytotoxic T lymphocytes, activated macrophages, and natural killer cells. These cells may be involved in the destruction of tumor cells.

METHODS

Balb/c mice were divided into the study (n = 10) and control (n = 10) groups. Alloskin grafts 1 cm in diameter from the backs of Swiss albino mice were placed on the backs of balb/c mice (study group). The same size autoskin grafts from the backs of other balb/c mice were used for the control group. Fourteen days after grafting, we inoculated 1,000 Ehrlich ascites tumor cells intraperitoneally into both groups. Two days after tumor inoculation, we used secondary allografts and autografts (which were about 2 to 3 mm in diameter) for the same groups. We followed up graft survival and animal survival in both groups.

RESULTS

All 10 of the autografted mice died between the 18th and 25th days owing to malignancy. In the allografted group, 2 mice died (1 on day 17 and the other on day 23). Allograft rejection had not occurred in these 2 mice at the time of their death. The other 8 mice in the same group rejected allograft, on average within 9 days (9+/-3, median 8). These 8 mice were alive and without apparent health problems during the 4 months of follow-up.

CONCLUSION

Allo-skin graft rejection may help rejection of tumor cells and may be of use in immunotherapy of cancer.

Identification of a 220-kDa membrane tumor-associated antigen by human anti-UK114 monoclonal antibodies selected from the immunoglobulin repertoire of a cancer patient

Human monoclonal antibodies (HuMAb) specific for a 14-kDa perchloric acid-soluble protein (defined as UK114) were produced by somatic fusion of the human-mouse myeloma K6H6/B5 with Epstein-Barr virus-transformed peripheral B lymphocytes from a cancer patient previously treated with UK101 preparations, containing the UK114 protein. Three IgM-secreting clones were selected on the criteria of specificity for the purified UK114 protein immobilized onto plastic and adapted to grow in a serum-free medium. The reactivity of these antibodies showed a broad distribution pattern restricted to fresh tumor tissues and tumor cell lines, mainly of the adenocarcinoma type. None of the normal cells, nonmalignant cell lines, and normal tissues surrounding the neoplastic lesions were reactive. The immunochemical analysis of the target antigens showed that the HuMAb recognize a molecule of 220 kDa selectively expressed by the surface of tumor cells, as well as a cytoplasmic 14-kDa protein. The 220-kDa antigen was different from other tumor-associated antigens with similar molecular mass and, so far, unique. In the presence of human complement, two of three HuMAb are cytotoxic for tumor cells expressing the 220-kDa surface antigen. The tumor specificity and the lytic ability attributed to these HuMAb are promising features for the exploration of future clinical applications.

Antibody-based immunological therapies

Clinical research in the area of antibody-based tumor-targeted therapy has been driven for many years by the prospect of identifying cell surface antigens with sufficient restrictive tissue expression patterns to allow for the selective and specific accumulation of antibody in tumor tissue. Few, if any, such antibody-antigen systems have been identified which can effectively deliver a large fraction of an administered therapeutic agent to metastatic cancer. Despite this limitation, however, a greater understanding of the biological and physiological principles of tumor-targeted therapy has resulted in successful antibody-based therapy of lymphoma, colon cancer and breast cancer in recent clinical trials.