Anticuerpos conjugados a fármaco: la nueva generación de terapias biotecnológicas contra el cáncer / Antibody-drug conjugates: the new generation of biotechnological therapies against cancer

Resumen Los anticuerpos terapéuticos son proteínas recombinantes empleadas en el tratamiento del cáncer. Existe una nueva generación de anticuerpos monoclonales con actividad contra las células cancerosas, conocidos como anticuerpos conjugados a fármacos. Estas moléculas están integradas por tres elementos: un anticuerpo monoclonal, un fármaco citotóxico con alta potencia y un enlazador químico que los une. El anticuerpo reconoce antígenos tumorales, por lo que permite la entrega dirigida del agente citotóxico hacia las células cancerosas. Tras el reconocimiento de su antígeno, el anticuerpo conjugado a fármaco es endocitado por las células blanco, donde se induce la degradación lisosomal de la fracción proteica y se libera el fármaco citotóxico. En el presente artículo se revisan las características generales de los anticuerpos conjugados a fármacos y se describe la evidencia clínica de la eficacia y seguridad de los primeros cuatro aprobados por las agencias reguladoras de Estados Unidos y Europa.

Abstract Therapeutic antibodies are recombinant proteins used in the treatment of cancer. There is a new generation of monoclonal antibodies with activity against cancer cells, known as antibody-drug conjugates. These molecules are made up of three elements: a monoclonal antibody, a highly potent cytotoxic drug, and a chemical linker that binds them together. The antibody recognizes tumor antigens, thereby allowing targeted delivery of the cytotoxic agent to cancer cells. After recognizing its antigen, the antibody-drug conjugate is endocytosed by the target cells, where the protein fraction is degradated into lysosomes, releasing the cytotoxic drug. This article reviews antibody-drug conjugates general characteristics and describes the clinical evidence of efficacy and safety of the first four approved by regulatory agencies in the United States and Europe.

Vacunas terapéuticas antitumorales basadas en células dendríticas / Dendritic cell-based therapeutic cancer vaccines

En los últimos años la inmunoterapia ha revolucionado el tratamiento de pacientes con cáncer avanzado. El mayor conocimiento de la biología tumoral y de la inmunología ha permitido desarrollar tratamientos racionales manipulando el sistema inmunitario con importante impacto clínico. Entre otras estrategias de inmunoterapia contra el cáncer se ha explorado el uso de vacunas terapéuticas basadas en células dendríticas (CD). Las CD son células de origen hematopoyético, que expresan constitutivamente moléculas presentadoras de antígeno, y son funcionalmente las inductoras más potentes de la activación y proliferación de linfocitos T a los que presentan antígenos. Los linfocitos T CD8+ proliferan y adquieren capacidad citotóxica cuando reconocen su antígeno específico presentado en la superficie de CD, aunque solo algunos tipos de CD pueden presentar antígenos internalizados desde el exterior celular a precursores de linfocitos T citotóxicos (a esta función se la llama presentación cruzada). Explotar la inducción de una respuesta inmunitaria adaptativa eficaz se considera una buena opción por su especificidad y prolongada duración de la respuesta. Las CD, gracias a su particular capacidad de presentación antigénica y de estimulación linfocitaria, son capaces de revertir la respuesta inmunitaria antitumoral deficiente que presentan algunos pacientes con cáncer. Las CD se pueden obtener a partir de distintas fuentes, empleando diversos protocolos para generar diferenciación y maduración, y se administran por diversas vías como son subcutánea, intravenosa o intranodal. La gran variedad de protocolos en los que se aplican las CD explica los resultados clínicos tan heterogéneos que se han comunicado hasta la fecha.

In recent years immunotherapy has revolutionized the treatment of patients with advanced cancer. The increased knowledge in the tumor immune-biology has allowed developing rational treatments by manipulation of the immune system with significant clinical impact. This rapid development has significantly changed the prognosis of many tumors without treatment options up to date. Other strategies have explored the use of therapeutic vaccines based on dendritic cells (DC) by inducing antitumor immunity. DC are cells of hematopoietic origin, constitutively expressing molecules capable to present antigens, that are functionally the most potent inducers of the activation and proliferation of antigen specific T lymphocytes. The CD8+ T cells proliferate and acquire cytotoxic capacity after recognizing their specific antigen presented on the surface of DC, although only some types of DC can present antigens internalized from outside the cell to precursors of cytotoxic T lymphocytes (this function is called cross-presentation) requiring translocation mechanisms of complex antigens. The induction of an effective adaptive immune response is considered a good option given its specificity, and prolonged duration of response. The DC, thanks to its particular ability of antigen presentation and lymphocyte stimulation, are able to reverse the poor antitumor immune response experienced by patients with cancer. The DC can be obtained from various sources, using different protocols to generate differentiation and maturation, and are administered by various routes such as subcutaneous, intravenous or intranodal. The wide variety of protocols resulted in heterogeneous clinical responses.

Construction of a fusion plasmid containing the PSCA gene and cytotoxic T-lymphocyte associated antigen-4 (CTLA-4) and its anti-tumor effect in an animal model of prostate cancer

Cytotoxic T lymphocyte-associated antigen-4 (CTLA-4) is a negative regulator of T cell activation, which competes with CD28 for B7.1/B7.2 binding, and which has a greater affinity. Fusion of specific antigens to extracellular domain of CTLA4 represents a promising approach to increase the immunogenicity of DNA vaccines. In this study, we evaluated this interesting approach for CTLA4 enhancement on prostate stem cell antigen (PSCA)-specific immune responses and its anti-tumor effects in a prostate cancer mouse model. Consequently, we constructed a DNA vaccine containing the PSCA and the CTLA-4 gene. Vaccination with the CTLA4-fused DNA not only induced a much higher level of anti-PSCA antibody, but also increased PSCA-specific T cell response in mice. To evaluate the anti-tumor efficacy of the plasmids, murine models with PSCA-expressing tumors were generated. After injection of the tumor-bearing mouse model, the plasmid carrying the CTLA4 and PSCA fusion gene showed stronger inhibition of tumor growth than the plasmid expressing PSCA alone. These observations emphasize the potential of the CTLA4-fused DNA vaccine, which could represent a promising approach for tumor immunotherapy.

Immunodetection of myeloid and plasmacytoid dendritic cells in mammary carcinomas of female dogs / Imunodetecção de células dendríticas mieloides e plasmocitoides nos carcinomas mamários em cadelas

Dendritic cells have attracted great interest from researchers as they may be used as targets of tumor immune evasion mechanisms. The main objective of this study was to evaluate the relationship between the dendritic cells (DCs) subpopulation in simple type mammary carcinomas in female dogs. Two groups of samples were used: the control group consisted of 18 samples of mammary tissue without changes and the tumor group with 26 simple type mammary carcinomas. In these groups, we evaluated the immunodetection of immature and mature myeloid DCs, plasmacytoid DCs and MHC-II. In mammary tumor, mature myeloid DCs predominated in the peritumoral region, while immature myeloid DCs and plasmacytoid DCs were evident in the intratumoral region. Immunostaining of MHC-II was visualized in mammary acini (control group), in tumor cells and inflammatory infiltration associated with tumors. The comparison between the control and tumor groups showed a statistically significant difference between immature myeloid DCs, mature myeloid DCs and plasmacytoid DCs. The immunodetection of MHC-II was not significant when comparing the groups. The predominance of immature DCs in the tumor group is possibly related to an inefficient immune response, promoting the development and survival of tumor cells. The presence of plasmacytoid DCs in the same group suggests a worse prognosis for female dogs with mammary tumors. Therefore, the ability of differentiation of canine dendritic cells could be influenced by neoplastic cells and by the tumor microenvironment...

As células dendríticas têm despertado grande interesse dos pesquisadores, pois podem ser alvo dos mecanismos de evasão imune do tumor. O objetivo principal deste estudo foi avaliar a relação entre as subpopulações de células dendríticas (DCs) nos carcinomas mamários do tipo simples em cadelas. Dois grupos de amostras foram utilizados, o grupo controle composto por 18 amostras de tecido mamário sem alterações e o grupo tumor com 26 carcinomas mamários do tipo simples. Nestes grupos foram avaliadas a imunodetecção de DCs mieloides imaturas e maduras, DCs plasmocitoides e de MHC-II. Nas mamas com tumor, as DCs mieloides maduras predominaram na região peritumoral, enquanto que as DCs mieloides imaturas e as DCs plasmocitoides foram evidentes na região intratumoral. A imunomarcação do MHC-II foi visualizada nos ácinos mamários (grupo controle), nas células tumorais e no infiltrado inflamatório associado aos tumores. Na comparação entre os grupos controle e tumor houve diferença estatística significativa entre as DCs mieloides imaturas, DCs mieloides maduras e DCs plasmocitoides. A imunodetecção de MHC-II não foi significativa na comparação entre os grupos. A predominância de DCs imaturas no grupo tumor, possivelmente, está relacionada com uma resposta imune ineficiente, favorecendo o desenvolvimento e a sobrevivência das células tumorais. A presença das DCs plasmocitoides no mesmo grupo sugere um prognóstico pior para cadelas com tumores de mama. Portanto, a capacidade de diferenciação das células dendríticas caninas poderia ser influenciada pelas células neoplásicas e pelo microambiente tumoral...

Paracoccidioidoyycosis: challenges in the develpment of a vaccine against an eendemic mycosis in the americas / Paracoccidioidomicose: desafios no desenvolvimento de uma vacina contra micose endêmica nas Américas

SUMMARYParacoccidioidomycosis (PCM), caused by Paracoccidioides spp, is an important endemic mycosis in Latin America. There are two recognized Paracoccidioides species, P. brasiliensis and P. lutzii, based on phylogenetic differences; however, the pathogenesis and disease manifestations of both are indistinguishable at present. Approximately 1,853 (~51,2%) of 3,583 confirmed deaths in Brazil due to systemic mycoses from 1996-2006 were caused by PCM. Antifungal treatment is required for patients with PCM. The initial treatment lasts from two to six months and sulfa derivatives, amphotericin B, azoles and terbinafine are used in clinical practice; however, despite prolonged therapy, relapses are still a problem. An effective Th1-biased cellular immune response is essential to control the disease, which can be induced by exogenous antigens or modulated by prophylactic or therapeutic vaccines. Stimulation of B cells or passive transference of monoclonal antibodies are also important means that may be used to improve the efficacy of paracoccidioidomycosis treatment in the future. This review critically details major challenges facing the development of a vaccine to combat PCM.

RESUMOA paracoccidioidomicose (PCM), causada por Paracoccidioides spp, é importante micose endêmica na América Latina. Com base em diferenças filogenéticas, existem duas espécies reconhecidas de Paracoccidioides, P. brasiliensis e P. lutzii, no entanto, a patogênese e as manifestações clínicas de ambas são indistinguíveis atualmente. Aproximadamente 1853 (~51,2%) de 3583 mortes confirmadas, atribuídas a micoses sistêmicas de 1996-2006, no Brasil foram causadas por PCM. Tratamento antifúngico é necessário para pacientes com PCM. O tratamento inicial dura de dois a seis meses e derivados de sulfa, anfotericina B, azóis e terbinafina são utilizados na prática clínica; no entanto, apesar da terapêutica prolongada, as recaídas ainda são um problema. Uma resposta imune celular eficaz, tendendo a Th1, é essencial para controlar a doença que pode ser induzida por antígenos exógenos, ou moduladas por vacinas profiláticas ou terapêuticas. A estimulação de células B ou a transferência passiva de anticorpos monoclonais também são meios importantes que podem ser utilizados para melhorar a eficácia do tratamento da paracoccidioidomicose no futuro. Esta revisão detalha criticamente os principais desafios que o desenvolvimento de uma vacina para combater a PCM enfrenta.

Increased circulating macrophage migration inhibitory factor levels are associated with coronary artery disease

BACKGROUND: To evaluate the macrophage migration inhibitory factor and E-selectin levels in patients with acute coronary syndrome. MATERIALS/METHODS: We examined the plasma migration inhibitory factor and E-selectin levels in 87 patients who presented with chest pain at our hospital. The patients were classified into two groups according to their cardiac status. Sixty-five patients had acute myocardial infarction, and 22 patients had non-cardiac chest pain (non-coronary disease). We designated the latter group of patients as the control group. The patients who presented with acute myocardial infarction were further divided into two subgroups: ST-elevated myocardial infarction (n = 30) and non-ST elevated myocardial infarction (n = 35). RESULTS: We found higher plasma migration inhibitory factor levels in both acute myocardial infarction subgroups than in the control group. However, the E-selectin levels were similar between the acute myocardial infarction and control patients. In addition, we did not find a significant difference in the plasma migration inhibitory factor levels between the ST elevated myocardial infarction and NST-elevated myocardial infarction subgroups. DISCUSSION: The circulating concentrations of migration inhibitory factor were significantly increased in acute myocardial infarction patients, whereas the soluble E-selectin levels were similar between acute myocardial infarction patients and control subjects. Our results suggest that migration inhibitory factor may play a role in the atherosclerotic process. .

Regulatory B cells present in lymph nodes draining a murine tumor

In cancer, B cells have been classically associated with antibody secretion, antigen presentation and T cell activation. However, a possible role for B lymphocytes in impairing antitumor response and collaborating with tumor growth has been brought into focus. Recent reports have described the capacity of B cells to negatively affect immune responses in autoimmune diseases. The highly immunogenic mouse tumor MCC loses its immunogenicity and induces systemic immune suppression and tolerance as it grows. We have previously demonstrated that MCC growth induces a distinct and progressive increase in B cell number and proportion in the tumor draining lymph nodes (TDLN), as well as a less prominent increase in T regulatory cells. The aim of this research was to study B cell characteristics and function in the lymph node draining MCC tumor and to analyze whether these cells may be playing a role in suppressing antitumor response and favoring tumor progression. Results indicate that B cells from TDLN expressed increased CD86 and MHCII co-stimulatory molecules indicating activated phenotype, as well as intracellular IL-10, FASL and Granzyme B, molecules with regulatory immunosuppressive properties. Additionally, B cells showed high inhibitory upon T cell proliferation ex vivo, and a mild capacity to secrete antibodies. Our conclusion is that even when evidence of B cell-mediated activity of the immune response is present, B cells from TDLN exhibit regulatory phenotype and inhibitory activity, probably contributing to the state of immunological tolerance characteristic of the advanced tumor condition.

Identification of Pancreatic Cancer-Associated Tumor Antigen from HSP-Enriched Tumor Lysate-Pulsed Human Dendritic Cells

PURPOSE: Vaccine strategies utilizing dendritic cells (DCs) to elicit anti-tumor immunity are the subject of intense research. Although we have shown that DCs pulsed with heat-treated tumor lysate (HTL) induced more potent anti-tumor immunity than DCs pulsed with conventional tumor lysate (TL), the underlying molecular mechanism is unclear. In order to explore the molecular basis of this approach and to identify potential antigenic peptides from pancreatic cancer, we analyzed and compared the major histocompatibility complex (MHC) ligands derived from TL- and HTL-pulsed dendritic cells by mass spectrophotometry. MATERIALS AND METHODS: Human monocyte-derived dendritic cells were pulsed with TL or HTL prior to maturation induction. To delineate differences of MHC-bound peptide repertoire eluted from DCs pulsed with TL or HTL, nanoflow liquid chromatography-electrospray ionization-tandem mass spectrometry (nLC-ESI-MS-MS) was employed. RESULTS: HTL, but not TL, significantly induced DC function, assessed by phenotypic maturation, allostimulation capacity and IFN-gamma secretion by stimulated allogeneic T cells. DCs pulsed with TL or HTL displayed pancreas or pancreatic cancer-related peptides in context of MHC class I and II molecules. Some of the identified peptides had not been previously reported as expressed in pancreatic cancer or cancer of other tissue types. CONCLUSION: Our partial lists of MHC-associated peptides revealed the differences between peptide profiles eluted from HTL-and TL-loaded DCs, implying that induced heat shock proteins in HTL chaperone tumor-derived peptides enhanced their delivery to DCs and promoted cross-presentation by DC. These findings may aid in identifying novel tumor antigens or biomarkers and in designing future vaccination strategies.

TAPCells, the Chilean dendritic cell vaccine against melanoma and prostate cancer

Here we summarize 10 years of effort in the development of a biomedical innovation with global projections. This innovation consists of a novel method for the production of therapeutic dendritic-like cells called Tumor Antigen Presenting Cells (TAPCells®). TAPCells-based immunotherapy was tested in more than 120 stage III and IV melanoma patients and 20 castration-resistant prostate cancer patients in a series of phase I and I/II clinical trials. TAPCells vaccines induced T cell-mediated memory immune responses that correlated with increased survival in melanoma patients and prolonged prostate-specific antigen doubling time in prostate cancer patients. Importantly, more than 60% of tested patients showed a Delayed Type Hypersensitivity (DTH) reaction against the lysates, indicating the development of anti-tumor immunological memory that correlates with clinical benefits. The in vitro analysis of the lysate mix showed that it contains damage-associated molecular patterns such as HMBG-1 protein which are capable to improve, through Toll-like receptor-4, maturation and antigen cross-presentation of the dendritic cells (DC). In fact, a Toll-like receptor-4 polymorphism correlates with patient clinical outcomes. Moreover, Concholepas concholepas hemocyanin (CCH) used as adjuvant proved to be safe and capable of enhancing the immunological response. Furthermore, we observed that DC vaccination resulted in a three-fold increase of T helper-1 lymphocytes releasing IFN-γ and a two-fold increase of T helper-17 lymphocytes capable of producing IL-17 in DTH+ with respect to DTH- patients. Important steps have been accomplished for TAPCells technology transfer, including patenting, packaging and technology assessment. Altogether, our results indicate that TAPCells vaccines constitute an exceptional Chilean national innovation of international value.

Glioma Stem Cell-Targeted Dendritic Cells as a Tumor Vaccine Against Malignant Glioma

PURPOSE: Cancer stem cells have recently been thought to be closely related to tumor development and reoccurrence. It may be a promising way to cure malignant glioma by using glioma stem cell-targeted dendritic cells as a tumor vaccine. In this study, we explored whether pulsing dendritic cells with antigens of glioma stem cells was a potent way to induce specific cytotoxic T lymphocytes and anti-tumor immunity. MATERIALS AND METHODS: Cancer stem cells were cultured from glioma cell line U251. Lysate of glioma stem cells was obtained by the repeated freezing and thawing method. Dendritic cells (DCs) were induced and cultured from the murine bone marrow cells, the biological characteristics were detected by electron microscope and flow cytometry. The DC vaccine was obtained by mixing DCs with lysate of glioma stem cells. The DC vaccine was charactirizated through the mixed lymphocyte responses and cell killing experiment in vitro. Level of interferon-gamma (IFN-gamma) in the supernatant was checked by ELISA. RESULTS: After stimulation of lysate of glioma stem cell, expression of surface molecules of DC was up-regulated, including CD80, CD86, CD11C and MHC-II. DCs pulsed with lysate of glioma stem cells were more effective than the control group in stimulating original glioma cells-specific cytotoxic T lymphocytes responses, killing glioma cells and boosting the secretion of IFN-gamma in vitro. CONCLUSION: The results demonstrated DCs loaded with antigens derived from glioma stem cells can effectively stimulate naive T cells to form specific cytotoxic T cells, kill glioma cells cultured in vitro.

Inhibitory effect of antibodies against human chorionic gonadotropin on the growth of colorectal tumour cells.

Human chorionic gonadotropin (hCG) was initially believed to be secreted exclusively by the embryo with its primary function being “rescue” of the corpus luteum. However, recently it has been found that the hormone (or its individual subunits) is also secreted by many cancers and that in many cases secretion is associated with poor patient prognosis. In this study, we assessed the presence of hCG in colorectal cancer cells (CCL-253) and evaluated the anti-tumour effects of anti-hCG antibodies in vitro and in vivo. Anti-hCG antibodies were reactive with CCL-253, as revealed by confocal immunoflourescence microscopy; both cell surface and intracellular expression were observed. Western blot analysis showed that antibodies appeared to interact with several moieties, indicating a level of cross-reactivity. Anti-hCG antiserum specifically reduced the viability of tumor cells and the addition of complement increased in vitro anti-tumor effects. In nude mice implanted with CCL-253 cells, administration of anti-hCG antiserum caused a significant reduction in tumor volume; all treated animals survived, while mortality was observed in control animals. Results suggest that anti-hCG antibodies can mediate significant anti-tumor activity both in vitro and in vivo and lend support to the rationale of anti-hCG immunization in the therapy of gonadotropin- sensitive cancers.

In vitro induction of anterior gradient-2-specific cytotoxic T lymphocytes by dendritic cells transduced with recombinant adenoviruses as a potential therapy for colorectal cancer

Anterior gradient-2 (AGR2) promotes tumor growth, cell migration, and cellular transformation, and is one of the specific mRNA markers for circulating tumor cells in patients with gastrointestinal cancer. We investigated the feasibility of AGR2 as a potent antigen for tumor immunotherapy against colorectal cancer (CRC) cells using dendritic cells (DCs) transduced with a recombinant adenovirus harboring the AGR2 gene (AdAGR2). DCs transduced with a recombinant adenovirus encoding the AGR2 gene (AdAGR2/DCs) were characterized. These genetically-modified DCs expressed AGR2 mRNA as well as AGR2 protein at a multiplicity of infection of 1,000 without any significant alterations in DC viability and cytokine secretion (IL-10 and IL-12p70) compared with unmodified DCs as a control. In addition, AdAGR2 transduction did not impair DC maturation, but enhanced expression of HLA-DR, CD80, and CD86. AdAGR2/DCs augmented the number of IFN-gamma-secreting T-cells and elicited potent AGR2-specific cytotoxic T lymphocytes capable of lysing AGR2-expressing CRC cell lines. These results suggest that AGR2 act as a potentially important antigen for immunotherapy against CRC in clinical applications.

Relationship between ganglioside expression and anti-cancer effects of the monoclonal antibody against epithelial cell adhesion molecule in colon cancer

The human colorectal carcinoma-associated GA733 antigen epithelial cell adhesion molecule (EpCAM) was initially described as a cell surface protein selectively expressed in some myeloid cancers. Gangliosides are sialic acid-containing glycosphingolipids involved in inflammation and oncogenesis. We have demonstrated that treatment with anti-EpCAM mAb and RAW264.7 cells significant inhibited the cell growth in SW620 cancer cells, but neither anti-EpCAM mAb nor RAW264.7 cells alone induced cytotoxicity. The relationship between ganglioside expression and the anti-cancer effects of anti-EpCAM mAb and RAW264.7 was investigated by high-performance thin-layer chromatography. The results demonstrated that expression of GM1 and GD1a significantly increased in the ability of anti-EpCAM to inhibit cell growth in SW620 cells. Anti-EpCAM mAb treatment increased the expression of anti-apoptotic proteins such as Bcl-2, but the expression of pro-apoptotic proteins Bax, TNF-alpha, caspase-3, cleaved caspase-3, and cleaved caspase-8 were unaltered. We observed that anti-EpCAM mAb significantly inhibited the growth of colon tumors, as determined by a decrease in tumor volume and weight. The expression of anti-apoptotic protein was inhibited by treatment with anti-EpCAM mAb, whereas the expression of pro-apoptotic proteins was increased. These results suggest that GD1a and GM1 were closely related to anticancer effects of anti-EpCAM mAb. In light of these results, further clinical investigation should be conducted on anti-EpCAM mAb to determine its possible chemopreventive and/or therapeutic efficacy against human colon cancer.

Immunoregulation through IL-10 gene expression and the fate of cytotoxic T lymphocyte-mediated tumor immunotherapy.

Gene analysis of tumor associated antigens revealed that tumor antigens are all normal gene product. Inducing tumor reactive cytotoxic T lymphocytes (CT) in the patients is same as inducing autoimmunity in the patients. Immunosuppressive cytokine interleukin-10 (IL-10) plays an important role in maintaining homeostasis or tolerance. To break the tumor tolerance, blocking and IL-10 secretion or intervention in the pathways of IL-10 gene activation is indeed important.

A Case of Hepatic Angiomyolipoma Mimicking Hepatocellular Carcinoma / 대한소화기학회지

No abstract availble.

Anti-tumor immunostimulatory effect of heat-killed tumor cells

As a part of our ongoing search for a safe and efficient anti-tumor vaccine, we attempted to determine whether the molecular nature of certain tumor antigens would influence immune responses against tumor cells. As compared with freeze-thawed or formaldehyde-fixed tumor antigens, heat-denatured tumor antigens elicited profound anti-tumor immune responses and greatly inhibited the growth of live tumor cells. The heat-denatured tumor antigens induced a substantial increase in the anti-tumor CTL response in the absence of any adjuvant material. This response appears to be initiated by strong activation of the antigen-presenting cells, which may recognize heat-denatured protein antigens. Upon recognition of the heat-denatured tumor antigens, macrophages and dendritic cells were found to acutely upregulate the expression of co-stimulatory molecules such as B7.2, as well as the secretion of inflammatory cytokines such as IL-12 and TNF-alpha. The results of this study indicate that heat-denatured tumor extracts might elicit protective anti-tumor adaptive immune responses and also raise the possibility that a safe and efficient adjuvant-free tumor vaccine might be developed in conjunction with a dendritic cell-based tumor vaccine.

Utilization of antihepatocyte clone OCH1E5 (Hep Par 1) in histological evaluation of liver tumors.

Diagnosis of hepatocellular carcinoma (HCC) is not always easy on simple hematoxylin and eosin (H&E) stain. The diagnostic problems arise when tumor shows pseudoglandular, pleomorphic or clear cell differentiation. Various tumors markers have been described with varying sensitivity and specificity. Monoclonal antibody Hep Par 1 (OCH1E5) which is specific for hepatocytes offers great help in separation of these tumors. The aim of the present study was to determine utility of Hep Par 1 (OCH1E5) in differentiating HCC from metastatic tumors and cholangiocarcinoma. Total of 62 cases of liver tumors obtained from biopsies, resected or autopsy specimens were included in the study. Slides having representative sections were subjected to immunohistochemistry with monoclonal antibody Hep Par 1 (Dako Corp) using avidin biotin technique with primary antibody dilution of 1:40. Adjacent nontumorous hepatocytes were taken as positive control. Slides were examined by experienced pathologist without any information of clinical or H&E diagnosis. Cases were considered positive for Hep Par 1 if tumor cells showed cytoplasmic brown colored granules. The intensity and distribution (diffuse/ focal) of immunoreactivity was noted. Subsequently immunohistochemistry results were correlated with histology and clinical diagnosis. Hep Par 1 antibody was positive in 26 (42 %) and negative in 36 (58 %) liver tumors. On correlating with H&E sections, out of 26 positive cases, 25 (89.2%) were HCC and one was the case of metastasis of mucin secreting adenocarcinoma. From 36 tumors with negative staining 3 were cases of HCC, 27 metastatic adenocarcinomas and 6 cholangiocarcinomas. Only one case of liver metastasis of mucin secreting adenocarcinoma showed positivity. None of the cases of cholangiocarcinoma showed positivity for Hep Par 1. The three HCCs which did not take up staining for Hep Par 1 were 2 cases of moderately differentiated HCC having pseudoglandular pattern and a case of well differentiated HCC with trabecular arrangement. In 11(44%) cases staining was diffuse while in 14 (56%) it was focal but intense. Hep Par 1 is a useful marker in differentiating HCC from metastaic tumors and cholangiocarcinoma with sensitivity and specificity of 89 % and 97 % respectively and positive predictive value of 96 %. However one should be aware of limitations of immunohistochemistry.

Tumor vaccine: current trends in antigen specific immunotherapy.

Effective cancer treatment to prevent the tumor growth as well as to stop its recurrence is the dream of oncologists. Currently available therapeutic measures like, radiotherapy and chemotherapy, often suffer from severe toxicity and lack of specificity of the drug towards tumor cells. Another promising approach is the 'immunotherapy', in which either the immune system is activated by tumor vaccine to combat the tumor growth or antitumor antibodies can be used. Vaccination can stimulate humoral, cellular and innate immune systems to generate various effector molecules, like antibody, cytotoxic T cells, cytokines etc. In antigen specific immunotherapy, the immune system can be stimulated actively by antigen based tumor vaccine to kill only those tumor cells, having expression of the particular tumor associated antigen. Different experimental, preclinical and clinical studies have proved that generated immune responses are effective to restrict the tumor growth. Useful strategies of antigen specific immunotherapy and outcome of various laboratory and clinic based studies are discussed.

Role of natural killer cells in antitumor resistance

Natural killer cells constitute a population of lymphocytes able to non-specifically destroy virus-infected and some kinds to tumor cells. Since this lytic activity was shown by non-immunized animals the phenomenon is denominated natural killer (NK) activity and contrasts with specific cytotoxicity performed by cytolytic T lymphocytes (CTLs) because it does not depends on MHC-restricted peptides recognition. In fact, the main feature of most functional receptors of NK cells (NKRs) is their ability to be inhibited by different kinds of class I MHC antigens. In the middle of the 1950, Burnet and Thomas forged the concept of tumor immunosurveillance and NK cells can be considered one of the main figures in this phenomenon both effector and regulatory functions. In the present review the early studies on the biology of NK cells were revisited and both their antitumor activity and dependence on the activation by cytokines are discussed

Avances en inmunoterapia celular contra el melanoma maligno / Advances in cellular immunotherapy for malignant melanoma

An alternative strategy for cancer treatment is the manipulation of the immune system, denominated cancer immunotherapy. The immunotherapeutical use of cells of the immune system, like dendritic cells (DC), is being explored in different clinical protocols. Recently, we finalized a clinical phase I protocol, for the treatment of malignant melanoma, using DCs loaded with tumor lysates. Our results indicate that the subcutaneous application of DCs do not produce adverse effects. We also observed an increase of tumor specific T lymphocytes precursors in the blood, associated to hypersensitivity reactions (DTH) in 60% of the treated patients. In most cases, an stability in the disease was observed, although without a significant association between vaccination and survival. Additionally, therapies based on Interleukin-2 (IL-2) have been used with relative success in the treatment of some kind of tumors since 1985. However, problems associated to the toxicity of IL-2 still restrict its massive use. Our direct experience with the use of IL-2, indicates that low doses and its subcutaneous application, maintains the beneficial effects for patients, eliminating the adverse effects. Based on the accumulated evidence during last the five years, we decided to implement an optimized clinical protocol, which alternatively combines dendritic cells vaccines with the use of low doses of IL-2 for the reinforcement of the immunological system.