Failure of cancer vaccines: the significant limitations of this approach to immunotherapy

Immunotherapy has always represented a very attractive fourth-modality therapeutic approach, especially in light of the many shortcomings of conventional surgery, radiation, and chemotherapies in the management of cancer. Subsets of neoplastically transformed cells have been shown to (re-)express on their surface molecules which are not typically present on the surface of neighboring normal cells. In some instances, especially in malignant melanomas, cytotoxic T lymphocytes (CTLs) directed against such tumor associated antigens (TAAs) have been isolated. The cancer vaccine approach to therapy is based on the notion that the immune system could possibly mount a rejection strength response against the neoplastically transformed cell conglomerate. However, due to the low immunogenicity of TAAs, downregulation of MHC molecules, the lack of adequate costimulatory molecule expression, secretion of immunoinhibitory cytokines, etc., such expectations are rarely fulfilled. Various approaches have been explored ranging from the use of irradiation inactivated whole-cell vaccines derived from both autologous and allogeneic tumors (even tumor cell lines), and genetically modified versions of such cellular vaccines which aim at correcting costimulatory dysfunction or altering the in situ humoral milieu to aid immune recognition and activation. Anti-idiotype vaccines, based on cancer cell associated idiotypes, have also been explored which aim at increasing immunogenicity through in vivo generation of vigorous immune responses. Dendritic cell (DC) vaccines seek to improve the presentation of TAAs to naive T lymphocytes. Unfortunately, there is always the possibility of faulty antigen presentation which could result in tolerance induction to the antigens contained within the vaccine, and subsequent rapid tumor progression. The theoretical basis for all of these approaches is very well founded. Animal models, albeit highly artificial, have yielded promising results. Clinical trials in humans, however, have been somewhat disappointing. Although general immune activation directed against the target antigens contained within the cancer vaccine has been documented in most cases, reduction in tumor load has not been frequently observed, and tumor progression and metastasis usually ensue, possibly following a slightly extended period of remission. The failure of cancer vaccines to fulfill their promise is due to the very relationship between host and tumor: through a natural selection process the host leads to the selective enrichment of clones of highly aggressive neoplastically transformed cells, which apparently are so dedifferentiated that they no longer express cancer cell specific molecules. Specific activation of the immune system in such cases only leads to lysis of the remaining cells expressing the particular TAAs in the context of the particular human leukocyte antigen (HLA) subclass and the necessary costimulatory molecules. The most dangerous clones of tumor cells however lack these features and thus the cancer vaccine is of little use. The use of cancer vaccines seems, at present, destined to remain limited to their employment as adjuvants to both traditional therapies and in the management of minimal residual disease following surgical resection of the primary cancer mass.

Immunocytochemical detection of homeobox B3, B4, and C6 gene product expression in lung carcinomas

The so-called homebox (HOX) was described as a highly conserved DNA motif of 183 base pairs, encoding the 61 amino acid DNA-binding homeodomain. Numerous HOX genes have subsequently been shown to bind to DNA and regulate the transcription of other genes. In humans the class I HOX genes are placed in four clusters on different chromosomes. The order of the genes within each of these clusters is evolutionarily conserved to a high degree and suggests that such an organization may be essential in the function of these genes during normal embryo- and histogenesis. Re-expression of HOX gene products has been reported in a wide variety of neoplastically transformed cells and it seems very likely that the HOX genes represent yet another class of oncofetal antigens involved in both normal development and cellular carcinogenesis, as well as tumor progression. The expression pattern of three homeobox gene products (HOX-B3, HOX-B4, and HOX-C6), all shown to be involved in lung tissue development, was examined immunocytochemically, in human lung carcinoma (LC) tissues. In all observed LC cases, HOX-C6 was present in over 60% of neoplastic cells (+3) demonstrating a medium grade (B and C) staining intensity. A smaller number of neoplastically transformed epithelial cells also expressed the proteins HOX-B3 and -B4 (10% to 60% or +2 to +3 and a medium grade staining intensity or B and C). The significance of these novel oncofetal antigens in tumor cell biology and as target molecules in the immunotherapy of lung carcinomas should be established by future studies.

Homeobox B3, B4, and C6 gene product expression in osteosarcomas as detected by immunocytochemistry

Osteosarcoma (OS) is a malignant neoplastic disease of the bone, of mesenchymal origin and with considerable morphologic heterogeneity, consisting of malignant stoma with evidence of malignant osteoid, bone and/or cartilage production. The mammalian homeobox (HOX) represents a highly conserved DNA motif of 183 base pairs, encoding the 61 amino acid DNA-binding homeodomain, through which the HOX gene products regulate the transcription of other genes involved in onto- and histogenesis. Re-expression of HOX proteins has been identified in a wide variety of neoplastically transformed cell types and it seems that the HOX genes represent yet another family of oncofetal antigens involved in both normal development and oncogenesis, as well as tumor tissue progression. During this study, the expression pattern of three HOX gene products (HOX-C6, -B3, and -B4) was examined immunocytochemically in human osteosarcoma (OS) tissues. In all observed (16/16) OS cases, HOX-C6 was present in over 90% of the neoplastically transformed cells (+4), demonstrating a high to medium grade (A to B) staining intensity. Similar results were obtained in OS cells for the other two observed proteins (HOX-B3 and -B4; over 90% or +4 and a high to medium grade staining intensity or A and B). The significance of the expression of class I HOX proteins in the pathobiology, diagnosis and prognostication of human OS should be established by further investigations.

Colonic type adenocarcinoma of male urethra

A case of rare primary adenocarcinoma of the bulbomembranous portion of the male urethra is presented. The histological and immunohistochemical characteristics of this tumor are identical to those of colon adenocarcinomas. The pathogenesis can be explained either by neoplastic degeneration of globet cells found in the urethral epithelium or by malignant degeneration of persistent glandular elements that are embryonal residues. The patient was successfully treated with transurethral prostatectomy and with a high dose of radiation therapy.

Immunocytochemical detection of the homeobox B3, B4, and C6 gene products in childhood medulloblastomas/primitive neuroectodermal tumors

The homeobox was originally described as a conserved DNA motif of about 180 base pairs. The protein domain encoded by the homeobox, the homeodomain, is thus about 60 amino acids long. The homeodomain is a DNA-binding domain, and many homeobox genes have now been shown to bind to DNA and regulate the transcription of other genes. Thus homeodomain proteins are basically transcription factors, most of which play a role in development. The homeobox genes seem to represent another class of oncofetal antigens involved in both normal development and carcinogenesis, as well as tumor progression. It has been shown that HOX-B3 and HOX-B4 are preferentially expressed in primitive CD34+, lineage-committed hematopoietic stem cells (HSCs) in human bone marrow. HOX-B3 overexpression in HSCs causes defective lymphoid development and progressive myeloproliferation, while HOX-B4 leads to selective expansion of HSCs without altering their differentiation. The HOX-C6 gene product leads to cell differentiation in neuroblastomas, while also being associated with the neoplastically transformed mammary cell phenotype and progression in primary cutaneous lymphomas. The expression pattern of these three homeobox gene products (HOX-B3, HOX-B4, and HOX-C6) was examined immunocytochemically in childhood MEDs/PNETs employing an indirect alkaline phosphatase conjugated technique on formalin-fixed, paraffin-embedded tissue sections. Strong staining intensity (A, B) of HOX-B3 and HOX-B4 was registered in all MEDs/PNETs, with immunoreactivity in between 50% and 90% (+3), but usually over 90% (+4) of the tumor cells. HOX-C6 was detected at medium intensity (mostly B) in 50% to 90% (+3) of the MED/PNET cells. This report is the first to describe the expression of these three homeobox gene products in MEDs/PNETs, and provides further evidence for the role of these proteins in the progression of human malignancies. The value of these genes and proteins in the early diagnosis and possible treatment of various human neoplasms, including childhood brain tumors, should be assessed in further immunocytochemical and molecular biological experiments.

Immunocytochemical detection of the homeobox B3, B4, and C6 gene products within the human thymic cellular microenvironment

The homeobox (HOX) was originally described as a conserved DNA motif of about 180 base pairs. The protein domain encoded by the homeobox, the homeodomain, is thus about 60 amino acids long. The homeodomain is a DNA-binding domain, and many homeobox genes have now been shown to bind to DNA and regulate the transcription of other genes. Thus homeodomain proteins are basically transcription factors, most of which play a role in development. The homeobox genes seem to represent another class of oncofetal antigens involved in both normal development and carcinogenesis, as well as tumor progression. The expression pattern of three homeobox gene products (HOX-B3, HOX-B4, and HOX-C6) was examined immunocytochemically in human thymuses of different ages and developmental stages (prenatal: 16 weeks and postnatal: 3 years, 5 years, and 21 years) employing an indirect alkaline phosphatase conjugated antigen detection technique on formalin-fixed, paraffin-embedded tissue sections. The immunoreactivity was located in the thymic RE cellular network (cortical and medullar), showing different intensity (+3 to +4 or 50% to 90% and over 90% in the prenatal thymic tissue and +2 to +3 or 50% to 90% during the three different postnatal stages). Intense expression was identified in the thymic medulla, including very strong immunoreactivity in the immigrating, committed hematopoietic stem cells (HSCs) present within the interlobular connective tissue (ICT). Strong presence of the HOX-B3 and HOX-B4 proteins was detected in the thymic Hassall's bodies (HBs), suggesting an intensive functional activity of the RE cells present within these unique formations within the thymic medulla. The precise role of these and other HOX gene products in the various steps of intrathymic T lymphopoieis should be elucidated through further basic molecular biological research.

Controversies on the prognostic significance of tumor infiltrating leukocytes in solid human tumors

We have performed immunophenotypical (IP) analyses of tumor infiltrating leukocytes (TIL) in both childhood brain tumors (medulloblastomas[MEDs]/primitive neuroectodermal tumors [PNETs] and astrocytomas [ASTRs]) and malignant melanomas (both primary and metastatic) employing a well-characterized library of monoclonal antibodies (MoABs) directed against leukocyte differentiation/activation associated antigens. The antigens were detected by an indirect, biotinstreptavidin conjugated alkaline phosphatase (AP) immunocytochemical technique. Our systematic cell-surface antigen expression profile analysis of 76 primary childhood brain tumors (34 MEDs/PNETs and 42 ASTRs) identified CD8+ CTL in 58/76 brain tumors. CD4+, MHC class II restricted helper lymphocytes were present in 65/76 brain tumors and represented 1-10% of the observed cells. Macrophages were present in 74/76 childhood brain tumor cases observed by us. Leukocyte common antigen (LCA) expression was demonstrated in all 76 brain tumors studied. MoAB UJ 308 detected the presence of premyelocytes and mature granulocytes in 60/76 brain tumors. They were localized perivascularly, within the tumor tissue, or close to necrotic regions. Natural killer (NK) cells were not defined in the childhood brain tumors observed in this study. The IP characteristics of the heterogeneous leukocytic infiltrate of 30 primary (PMs) and 10 metastatic melanomas (MMs) was also investigated by us. We established the presence of some type of melanoma infiltrating host's immunological effector cells in all 40 observed melanoma cases. More specifically, we found NK cells, macrophages and granulocytes in 30/30 PMs and 10/10 MMs. These effector cells represented the vast majority (> 80%) of the melanoma infiltrating immunocompetent cells. T lymphocytes were observed in 20/30 PMs and 6/10 MMs, but their numbers represented only between 5% to 10% of the heterogeneous leukocytic infiltrate. B cells were found in 22/30 PMs and 8/10 MMs, their numbers representing less than 5%. Presence of cells of the dendritic reticulum, involved in antigen presentation was not determined in any of the observed PMs and MMs. The notion that infiltration of the neoplastically transformed mass of cells by TIL is always a prognostically positive phenomenon has changed in recent years as research on extracellular matrix remodeling and angiogenesis have identified numerous secreted factors which are common to both neoplastically transformed cells and infiltrating leukocytes.

The role of the reticulo-epithelial (RE) cell network in the immuno-neuroendocrine regulation of intrathymic lymphopoiesis

The thyrnus provides an optimal cellular and humoral microenvironment for the development of immunocompetent T lymphocytes. Although yolk sac derived pre-T, committed hematopoietic stem cells enter the thymus using a homing receptor, the immigration process also requires secretion of a peptide, called thymotaxin by the cells of the reticulo-epithelial (RE) network of the thymic cellular microenvironment. The thymic RE cells are functionally specialized based on their location within the thymic microenvironment. Thus, although subcapsular, cortical, and medullary RE cells are derived from a common, endodermal in origin epithelial precursor cell, their unique location within the gland causes their specialization in terms of their immunophenotypical and in situ physiological properties. The subcapsular, endocrine, RE cell layer (giant or nurse cells) is comprised of cells filled with PAS positive granules, which also express A2B5/TE4 cell surface antigens and MHC Class I (HLA A, B, C) molecules. In contrast to the medullary RE cells, these subcapsular nurse cells also produce thymosins beta 3 and beta 4. The thymic nurse cells (TNCs) display a neuroendocrine cell specific immunophenotype (IP): Thy-1+, A2B5+, TT+, TE4+, UJ13/A+, UJ127.11+, UJ167.11+, UJ181.4+, and presence of common leukocyte antigen (CLA+). Medullar RE cells display MHC Class II (HLA-DP, HLA-DQ, HLA- DR) molecule restriction. These cells also contain transforming growth factor (TGF)-beta type II receptors and are involved in the positive selection of T cells. Transmission electronmicroscopic (TEM) observations have defined four, functional subtypes of medullary RE cells: undifferentiated squamous, villous and cystic. All subtypes were connected with desmosomes. The secreted thy nic hormones, thymulin, thymosin-alpha 1 and thymopoietin (its short form, thymopentin or TP5) were detected immunocytochemically to be produced by RE cells. Thymic RE cells also produce numerous cytokines including IL-1, IL-6, G-CSF, M-CSF, and GM-CSF molecules that likely are important in various stages of thymocyte activation and differentiation. The co-existence of pituitary hormone and neuropeptide secretion [growth hormone (GH), prolactin (PRL), adrenocorticotropic hormone (ACTH), thyroid stimulating hormone (TSH), triiodothyronine (T3), somatostatin, oxytocin (OT), follicle stimulating hormone (FSH), luteinizing hormone (LH), arginine vasopressin (AVP), growth hormone releasing hormone (GHRH), corticotropin releasing hormone (CRH), nerve growth factor (NGF), vasoactive intestinal peptide (VIP), pro-enkephalin (pro-enk), and beta-endorphin (beta-end)], as well as production of a number of interleukins and growth factors and expression of receptors for all, by RE cells is an unique molecular biological phenomenon. The thymic RE cell network is most probably comprised of cells organized into sub-networks--functional units composed of RE cells with differing hormone production/hormone receptor expression profiles, involved in the various stages of T lymphocyte maturation. Furthermore, it is quite possible that even on the level of individual RE cells, the numerous projections associated with a single cell, which engulf developing lymphocytes, nurturing and guiding them in their maturation, may differ in their hormone production and/or hormone receptor expression profile, thus allowing a single cell to be involved in distinct, separate steps of the T cell maturation process. Based on our systematic observations of the thymus in humans and other mammalian species, we suggest that the thymic RE cells represent an extremely important cellular and humoral network within the thymic microenvironment and are involved in the homeopathic regulation mechanisms of the multicellular organism, in addition to the presentation of various antigens to developing lymphocytes, and providing growth regulatory signals which may range from stimulatory to apoptotic signaling within the thymus. (ABSTRACT TRUNCA

Importance of treatment of depression in assuring the most efficacious management of Parkinson's disease

Parkinson's disease (PD) is characterized by pathological changes which include degeneration of dopaminergic neurons in the substantia nigra pars compacta coupled with intracytoplasmic inclusions known as Lewy bodies. Neurodegeneration and Lewy bodies can also be found in the locus coeruleus, nucleus basalis, hypothalamus, cerebral cortex, cranial nerve motor nuclei, and central and peripheral components of the autonomic nervous system. PD progression is associated with the development of dementia, autonomic dysfunction, and postural instability, which do not respond well to conventional therapy. Therapeutic efforts aimed at preventing or at least delaying PD progression by reducing the overload of iron and generation of ROS, correcting the zinc deficiency may be of great benefit. Current pharmacotherapy of PD, in addition to symptomatic L-dopa treatment, includes the neuroprotective strategies with dopamine agonists, monoamine oxidase-B inhibitors (MAO-B), glutamate antagonists, catechol O-methyltransferase (COMT) inhibitors and other antioxidants or free radical scavengers. Depression, anxiety disorder and stress are all associated with PD and it is therefore necessary to include treatment regimens for these ailments in addition to the traditional pharmacotherapy for the symptoms of PD, as well as the neuroprotective measures noted above, in order to ensure the greatest possible benefit to PD patients.

Novel insights into the function of the thymic Hassall's bodies

During thymic ontogenesis, the HBs appear when lymphopoiesis is already established and the cortex, medulla and the cortico-medullary junction are capable of conducting the positive and negative selection of T lymphocytes undergoing progressive maturation. The HBs are structurally organized from RE cells, which usually undergo hypertrophy prior to their inclusion in the outer cell layer of the corpuscles. The cellular microenvironment of the thymic medulla is composed of networks of cell types, of a variety of origins, and all of them may participate in the construction of growing, progressive HBs. Histochemically, we detected a rich content of basic non-histone proteins, PAS positive substance (glycogen) and acid mucopolysaccharides within the bodies. Employing the histological stain of Pasini and immunocytochemical methods with monoclonal antidodies (MoABs) AE2 and AE3, high molecular weight (56.5 to 67 kD) basic keratins were defined in human HBs. Employing a panel of MoABs developed against thymic RE cell surface antigens, we observed immunoreactivity localized to the outer cell layer of the HBs with MoABs TE8, TE16 and TE19, while the centrally located cells reacted positively with TE15 and TE19. Immunoreactivity in human skin, employing the TE8, TE16 and TE19 MoABs was also observed in the epidermal granulosa cell layer, while TE15 reacted with cells of the stratum corneum. The presence of endocrine, peptide secreting RE cells within the HBs was defined with the use of MoAB A2B5, which binds to the GQ ganglioside. The hypertrophied, physiologically active RE cells of the peripheral cell layer of the HBs reacted positively with medium to strong intensity when stained with MoABs UJ127.11, J1153, A2B5, 215.D11, and 275.G7. We also observed the expression of transforming growth factor-beta type II receptors in HBs. The recently detected expression of the homobox gene products B3, B4, and C6, transcription factors involved in developmental processes related to hematopoiesis within HBs provides further evidence that HBs are important functional components of the RE network of the thymus which provide developing thymocytes with paracrine and juxtacrine signals to ensure their proper functional maturation during intrathymic lymphopoiesis. Our transmission electronmicroscopical (TEM) studies on HBs determined the existence of groups of RE cells connected to one another by desmosomes. We also observed long cytoplasmic processes originating from medullary RE cells and directly contacting thymic T lymphocytes and accessory antigen presenting cells (macrophages, dendritic cells, interdigitating cells, Langerhans cells, etc.) by the use of scanning electronmicroscopy (SEM). Thus, our results indicate that the HBs are unique, antigenically distinct, functionally active, multicellular components of the nonlymphocytic, cellular micro-environment of the thymic medulla, and participate in the physiological activities of the prenatal and adult thymus.

Review of thymic hormones in cancer diagnosis and treatment

The thymus is an endocrine organ. A unified, physiological concept of humoral regulations of the immune response has emerged in the last three decades. The thymus is the major site of production of immunocompetent T lymphocytes from their hematopoietic stem cells. This complex process required direct cell to cell, receptor based interactions, as well as in situ paracrine information via the numerous cytokines and thymic hormones produced by the cells of thymic microenvironment. Thymic hormones induce in situ T-cell marker differentiation, expression and functions. These polypeptide hormones have also been shown by means of immunocytochemistry to localize in the reticulo-epithelial (RE) cells of the thymic cellular microenvironment. Due to the great complexity of the intrathymic maturation sequence of T lymphocytes and the diverse immunophenotypically unique subpopulations of T lymphocytes, it is quite unlikely that a single thymic humoral factor could control all of the molecular steps and cell populations involved. It is much more likely that an extremely rich and diverse, but genetically determined, milieu is present within the thymus, and that thus the control of intrathymic T lymphocyte maturation and the functional maturation of T cells involves the orchestral interaction of various thymic-specific factors and other molecules during the differentiation process. Thymosin fraction 5 and its constituent peptides influence several properties of lymphocytes including cyclic nucleotide levels, migration inhibitory factor production, T-dependent antibody production, as well as the expression of various cell surface maturation/differentiation markers. Recently, derivatives of thymic hormones, mostly of thymosins, have been detected as products of neoplastically transformed cells and employed in the early diagnosis of neoplasms. In clinical trials, thymic hormones strengthen the effects of immunomodulators in immunodeficiencies, autoimmune diseases, and neoplastic malignancies. Combined chemo-immunotherapeutical anti-cancer treatment seems to be more efficacious than chemotherapy alone, and the significant hematopoietic toxicity associated with most chemotherapeutical clinical trials can be reduced significantly by the addition of immunotherapy.

Papillary microcarcinoma of the thyroid: a clinico-pathologic and prognostic review

Papillary microcarcinoma (PMC) of the thyroid is the most common form of thyroid cancer, which usually remains clinically silent until its incidental histologic diagnosis in autopsy or surgical material. Autopsy incidence varies from 3%-36%. PMC may, however, present with clinical symptoms, the commonest of which is cervical lymphadenopathy with or without palpable thyroid nodules. Other reported presentations include cystic neck mass, pulmonary mass (es), metastases in the skull or vertebral column. The upper limit of size to define PMC is 10 mm in most studies but many studies include lesions up to 15 mm in diameter. Histologic variants include encapsulated and partially encapsulated papillary carcinoma, circumscribed microcarcinoma and occult sclerosing carcinoma. Younger age and size less than 10 mm (< 15 mm in other studies) are considered to be favorable prognostic factors. Size alone, however, cannot be regarded as a determinant of prognosis. Older age, larger tumor size, distant metastases, capsular invasion and multifocality indicate unfavorable prognosis. Loss of heterozygosity (LOH) is an infrequent finding, since small deletions may be missed by southern blot analysis. Activation of oncogenes ret and trk have been reported in papillary carcinoma. Some authors advocate conservative while others favor aggressive therapy including total thyroidectomy with or without Iodine 131ablation. Additional investigative techniques are needed to identify the subset of PMC cases with a potential for aggressive clinical course, thereby targeting more aggressive therapy to an appropriate subset of tumors.

Genetically engineered monoclonal antibodies for direct anti-neoplastic treatment and cancer cell specific delivery of chemotherapeutic agents

Classical therapeutic modalities such as surgery, radiation, and chemotherapy not only fail to cure the great majority of malignant tumors, but their employment often leads to severe and debilitating side effects. The severe cancer related morbidity is also in direct correlation with the use of x-radiation and chemotherapy, making them less than ideal forms of therapy. The development of hybridoma technology and the advances in monoclonal antibody (MoAB) production have revitalized the initial concept of Ehrlich concerning the existence of cancer cell-targeted, specific "magic bullets". Entirely new approaches to cancer therapy that are neoplastic cell-directed, and specifically lethal to malignant cells and less toxic to normal tissues are being observed and developed, adhering to the old prayer: "Destroy the diseased tissues, preserve the normal." Immunotherapy as a fourth modality of cancer therapy has already been developed and proven to be quite effective. Strategies for the employment of antibodies for anti-cancer immunotherapy include: 1) Immune reaction directed destruction of cancer cells; 2) Interference with the growth and differentiation of malignant cells; 3) Antigen epitope directed transport of anti-cancer agents to malignant cells; 4) Anti-idiotype vaccines; and 5) Development of engineered (humanized) mouse monoclonals for anti-cancer therapy. In addition, a variety of different agents (e.g. toxins, radionuclides, chemotherapeutic drugs) have been conjugated to mouse and human MoABs for selective delivery to cancer cells. Preclinical observations in athymic, nude mice using xenografted human cancers and mouse, anti-human MoABs were more than impressive and have lead to the development of clinical trials. Phase I studies established the safety of employing immunoconjugates in humans, but the in vivo therapeutic results were less impressive. The clinical use of mouse MoABs in humans is limited due to the development of a foreign anti-globulin immune response by the human host. Genetically engineered chimeric human-mouse MoABs have been developed by replacing the mouse Fc region with the human constant region. Moreover, the framework regions of variable domains of rodent immunoglobulins were also experimentally replaced by their human equivalents. These antibodies can also be designed to have specificities and effector functions determined by researchers, which may not appear in nature. The development of antibodies with two binding ends (bispecific antibodies) provided a great improvement in targeting cancer cells. The existing inadequacies of MoABs in immunotherapy may also be improved by increasing their efficiency with chemical coupling to various agents such as bacterial or plant toxins, radionuclides or cytotoxic drugs. The astonishing immunophenotypic (IP) heterogeneity of neoplastically transformed cells, the different cytotoxic activity associated with the moiety linked to given MoABs, and mostly the impressive genetic modulation capabilities of cancer cells still remain as yet unsolved difficulties in the present immunotherapy of human cancer. In writing this review article, one of our main goals is to encourage further clinical research with the use of genetically engineered rodent MoABs and various immunoconjugates in the treatment of human cancer, as well as the combination of such immunotherapy with the three conventional modalities of therapy. Finally, we propose that MoAB-based immunotherapy be accepted as a conventional form of therapy and employed not only in terminal cancer patients but also, for instance, during and following surgical resection.

Involution and neoplasms of the thymus

Mammalian ontogenesis and postnatal histogenesis involves the dynamic and appropriate interaction of two growth related phenomena: progression and regression. The thymus gland is the organ of the mammalian body that exhibits the most profound involution during normal postnatal histogenesis. Involution of the thymus can be compared to similarly regressive processes during the ontogeny of holometabolic insects, as well as to the spontaneous regression of neoplasms. It can be expected that in the future a better understanding of neoplastic regression will result from the comparison of ontogenetic processes from taxonomically far-removed regressive processes, and the evaluation of various factors that promote progression and regression. Furthermore the thymus, as the key organ of the cellular arm of the mammalian immune system, is intimately involved in the determination of the eventual outcome of malignant neoplastic disease. Primary anterior mediastinal tumors comprise a diverse group of neoplasms accounting for 50% of all mediastinal tumor lesions. Thymic carcinomas and thymomas are epithelial neoplasms which can be divided according to clinical behavior into various biological subtypes. A review of the nature of thymic neoplasms, a description of physiologic and accidental involution of the thymus gland, and a discussion of various paraneoplastic disorders, including myesthenia gravis, associated with thymic neoplasms are the aims of this article.

Growth hormone and colorectal carcinoma: localization of receptors

Growth hormone (GH) plays a crucial role in stimulating and controlling the growth, metabolism and differentiation of many mammalian cell types by modulating the synthesis of multiple mRNA species and a paracrine or autocrine mechanism of action has been proposed. These effects are mediated by the binding of GH to its membrane-bound receptor and involve a phosphorylation cascade that results in the modulation of numerous signaling pathways. To address the side/mode of action through which GH exerts its effects, a panel of well characterized monoclonal antibodies, directed against the hormone binding side of the receptor, was applied to immunohistochemically determine growth hormone receptor (GH-receptor) expression in poorly- moderate- to well differentiated col.orectal adenocarcinomas (n = 40) from the rectum, transverse-, ascending-, descending and sigmoid colons. Of five anti-growth hormone receptor monoclonal antibodies used, human GH- receptor specific Mab 263 consistently resulted in strong receptor expression in colorectal carcinoma tumour cells. Heterogeneity of immunoreactivity was found in primary and secondary tumour lesions with a variable range of positive cells. Staining was mainly intracellular, showing either a monotonous or granular pattern, with some nuclei also reactive. The presence of intracellular GH-receptors has been previously documented and is a result of endoplasmic reticulum and Golgi localization. Immunoreactivity in surface columnar cells, independent from pathological tissue, was weak to moderate. Epithelial cells from normal tissue, adjacent to tumour lesions, were of variable intensity. Goblet and mucous cells located at the crypt base immunostained faintly or were negative for the GH-receptors. Crypt base columnar cells strongly expressed the GH-receptor, but oligomucous cells were less reactive. In conclusion, this study indicates that receptor expression may be associated with malignancy of colorectal carcinoma and supports the hypothesis that GH may act locally in colorectal tissue. The demonstration of the presence of receptors for GH will be useful for site-specific studies of the evolution of gastrointestinal tract tumours, providing valuable information concerning cellular growth kinetics and tumour prognosis. It also raises questions regarding the administration of GH to cancer-induced cachexia patients and the possible oncogenic potential of the GH-receptor.

Neoplasms during the progression of pregnancy

Restricting this review to dealing with pregnancy and its interaction with neoplasms limits us to the child-bearing years. Neoplasms may appear at all stages of species with true tissues and the incidence of malignancy in pregnancy is estimated to be 1:1,000. Almost 50% of these tumors are cervical cancers, followed by breast cancer, with an incidence of approximately 0.03%. The pregnant woman, in the same person, exhibits controlled growth (the pregnancy) and uncontrolled growth (the malignancy). In younger women, the neoplasms represent early stages of biological development and seem to arise practically from all maternal tissues. Geriatric changes in the neoplastic growth processes are missing. This article encompasses a review of the integration of neoplasms, the maternal body, the fetus and the placenta. The morphological and biochemical integration of the different processes is diversified. Mainly, we would like to address the interaction between pregnancy and common human malignancies like breast, cervix, and melanoma, but we will also review rare neoplastic complications. This way it is possible to treat the combined growth processes as they evolve from the initiated sperm, the ovum and continue via the placental development. These processes lead to the fetus and, in the pathological sense, to childhood complications, though most cases develop only portions of the process.

The effects of volatile anesthetic agents on pulmonary surfactant function

The purpose of this article is to review the findings from research directed at understanding the effects of volatile anesthetics on the respiratory surface known as pulmonary surfactant. Anesthetics have long been known to have a disruptive effect on biological membranes. This review will highlight the interactions of volatile anesthetics with pulmonary surfactant. This paper has emphasized the interaction of volatile anesthetics with the pulmonary surfactant monolayer versus the lipid bilayer. The goal of this review is to uncover to what extent this understanding has progressed in forty years. Although the goal is quite broad, the information gathered and the advice given is specific. Theories of anesthesia and surfactant structure and function are summarized and discussed in light of early physico-chemical approaches and extend to an era where powerful new three-dimensional structural techniques can be used to answer this question.

Pathogenesis of thrombotic disorders in patients with cancer

Cancer patients experience several complications during the course of their illness which increase their morbidity and mortality. Thromboembolic phenomena are frequent and important events encountered in these patients. Although the exact mechanisms of thrombosis in this population of patients are largely unknown, speculations regarding the pathogenesis of clotting are presented in this short review. Interactions between elements related to the underlying neoplastic disorder, adherence to the vessel wall by cancer cells, indirect injury of the endothelial tissue, cytokine released by the malignant clone and disturbances in the clotting cascade to mention a few, are thought to be responsible for hypercoaguability in patients with cancer. More experimental and clinical studies are needed to clarify the etiology and management of these serious complications and concomitant diseases. Thrombotic complications are considered the second most common cause of death in patients with underlying malignant disorders. It has been estimated that 15% of patients with cancer will suffer from thromboembolic phenomena during their life (1,2). However, prospective data that examine the exact incidence of these complications are currently unavailable. Few investigators have estimated that the prevalence of serious thrombosis may be up to 50% in post mortem analysis (3).

Apoptosis and pathogenesis of viral hepatitis C--an update

Hepatitis C virus is a major causative agent of chronic liver disease. Viral genotype, mutations, virus-host interaction, expression of viral proteins and host immune-reaction are important factors in the pathogenesis of HCV infection. Precise pathogenesis and perpetuation of hepatocellular injury in hepatitis C viral infection remain unclear. Proposed mechanisms include direct viropathic effect, the host immune response mediated through cytotoxic T lymphocytes, both viropathic and cytopathic effects, and macrophages/monocytes. Apoptosis occurs both in acute or chronic hepatitis and has been suggested to be mediated through Fas antigen. In HCV infection, Fas expression is up-regulated in the liver cells in line with the severity of liver inflammation. When HCV-specific T cells migrate into hepatocytes and recognize the viral antigen via the T cell receptor, they become activated and express Fas ligand that transduces the apoptotic death signal to Fas-bearing hepatocytes resulting in their destruction. Thus, the Fas system plays an important role in liver cell injury by HCV infection. Possible inducers of apoptosis in hepatitis C include cytokines, especially tumor necrosis factor-alpha (TNF-alpha), released by inflammatory cells, and acting through TNF and other cytokine receptors.

Growth inhibitors in the treatment of malignant neoplasms

Growth inhibitors are an integral part of the regulatory mechanisms involved in the growth and differentiation of cells and tissues. Aberration in the response to growth inhibitors leads to the escape of the cell from the cell cycle control mechanisms and may lead to the development of malignancies. The inactivation of tumor suppressor genes, activation of oncogenes leads to the acquisition of an invasive and increasingly malignant immunophenotype and secretory profile by transformed cells. The commencement of the complex process of carcinogenesis, and subsequent, rapid tumor growth and progression of mammalian neoplasms depends upon the continuous de novo formation of capillaries (angiogenesis). The generation of a malignant, invasive cellular immunophenotype (CIP) and distant metastases, as aspects of tumor progression, are also NRA-dependent processes. Specific molecules with cytostatic/cytotoxic growth inhibitory effects represent a very diverse group of factors. Growth inhibitors may regulate the cell cycle at various levels, and growth inhibitors comprise a heterogeneous group of agents including cytokines, growth factors, steroid hormones, etc. The phenomenon of multidrug resistance to a wide spectrum of cytostatic/cytotoxic agents has posed a major difficulty in the effective chemotherapeutical treatment of cancer patients. The development of novel therapeutic regimens should be based on the observations of the growth inhibitory profile of the particular malignancy, in addition to its immunophenotype and genotype, and the devisement of 'individualized' combinations of factors, including gene and immuno-therapeutical options, targeting different aspects of the malignant disease.

Loss of heterozygosity in papillary and follicular thyroid carcinoma: a mini review

Inactivation of tumor suppressor genes is an important mechanism in the development of most cancers. This can be detected by determining loss of heterozygosity (LOH) on highly polymorphic loci on chromosomes. Many investigations to determine LOH in papillary and follicular thyroid carcinoma have been performed using bulk tissue which was fresh, snap frozen, or has been formalin-fixed/paraffin-embedded. Loss of heterozygosity is more frequently encountered in follicular than papillary carcinoma. Laser Capture Microdissection (LCM) may be useful to ascertain if there is a pattern of LOH for various histologic forms and variants of thyroid carcinoma.

Independent prognostic role of p16 expression in lung cancer

OBJECTIVES

The cyclin-dependent kinase p16 (also known as Ink4A, Mts1, Cdkn2, and Cdkn4i) has been proposed as a tumor suppressor gene mapped on chromosome segment 9p21. This study evaluated p16 protein expression in 135 lung cancer specimens and investigated potential genetic alterations occurring in this gene.

RESULTS

We found altered p16 immunohistochemical expression to be a frequent event in lung cancer and to be independent of either the histologic type or any other clinical-pathologic feature. Western blot analyses performed on about one third of the specimens correlated highly with these results. In addition, we found p16 immunohistochemical expression to be a favorable prognostic factor in lung cancer in that its reduction or loss correlated with a worse outcome for the patients. Polymerase chain reaction amplification and direct sequencing of p16 exons 1 and 2 revealed no mutations, indicating that p16-altered expression in lung cancer is not necessarily linked to mutational events of these genes.

CONCLUSIONS

We conclude that p16-altered expression is both an independent and frequent event in lung cancer and may have an important role in tumorigenesis and in malignant progression of a significant proportion of these cancers. However, the actual incidence and relevance of p16 mutations in this neoplasm continues to be debated, and its analysis seems inconclusive. Our results suggest a prognostic role for the immunodetection of this protein on formalin-fixed and paraffin-embedded specimens. They further suggest its routine use in the evaluation of the frequently unpredictable behavior of lung cancer.

Fas (APO-1, CD95) receptor expression and new options for immunotherapy in childhood medulloblastomas

Central nervous system (CNS) tumors are the most common solid neoplasms in children. Medulloblastomas (MEDs) resemble embryonic neuroectodermal stem cells and their immature, uncommitted neuronal and glial progeny. Apoptosis is a basic physiological process wherein the cell initiates a sequence of events culminating in the fragmentation of its DNA, nuclear collapse, and finally, disintegration of the cell into small, membrane-bound apoptotic bodies. Expression of Fas (APO-1, CD95) receptor (FasR) and programmed or active cell death (PCD) was studied in childhood MEDs with varying stages of malignancy, and cell differentiation features. The majority of neoplastically transformed, neuroectodermal in origin cells, particularly in MEDs, express FasR, whereas normal cells in the CNS do not. FasR is a transmembrane glycoprotein, which belongs to the nerve growth factor/tumor necrosis factor (NGF/TNF) receptor superfamily. Apoptosis within childhood PNETs/MEDs is triggered by the binding of FasR to its natural ligand (FasL) or by cross-linking with anti-section i FasR antibodies. The resence of FasL has also been detected in childhood glial tumors. Therefore, a spontaneous, cellular immunophenotype (IP) regulatory, intratumoral apoptotic cell death (autocrine suicide) is possible in childhood brain tumors during neoplastic growth and progression. During our systematic immunocytochemical screening, we employed formalin fixed, paraffin-wax embedded tissue sections, as well as frozen sections of 34 primary human childhood PNETs/MEDs. The use of a sensitive, indirect, six step immunoperoxidase or alkaline phosphatase conjugated streptavidin-biotin antigen detection technique, modified by us, provided excellent immunocyto-chemical results. A systematic observation of the presence of apoptosis related markers (especially FasR) and cells in PCD was carried out. A strong expression (intensity of staining: "A"-the highest possible; number of stained neoplastic cells: +3 to +4, between 50% to 90%) of FasR, was detected employing 4 microns thick, formalin fixed, paraffin-wax embedded tissue slides. The panel of normal tissues employed as positive and negative tissue controls demonstrated presence of FasR in the prenatal thymus, mature tonsils and colon epithelium. Certainly, the coexpression of FasR, FasL, and other PCD-related proteins have also been reported in other human malignancies: breast cancer, colorectal carcinomas, large granular lymphocytic leukemia of T or NK cell origin, melanomas, lung, prostate, pancreas, and hepatocellular carcinomas. The coexpression of both FasR and FasL on several neoplastic cell types may represent an effective mechanism for tumor escape of the cellular immunological response of the host. It has been well established that brain tumors and melanomas produce their autocrine FasL, and even become capable of switching their signal transduction from the PCD pathway to a tumor growth, proliferative pathway. It seems that the therapeutical use of FasR-FasL (main apoptotic pathway) represents a new and exciting immunotherapeutical possibility in the treatment of primary childhood neuroectodermal tumors.

Immunophenotypical analysis and immunobiology of childhood brain tumors

Cancer associated markers (CAMs) are the biochemical and immunological counterparts of the morphology of neoplasms. The expression of an immunocytochemically defined CAM is related to the tissue of origin and is not a random event. During the past two decades, the use of MoABs against oncofetal, neoplasm associated, cell lineage specific, endothelial, and cell proliferation related antigens in the diagnosis and biological assessment of prognosis in neoplastic disease gained increased importance. A sensitive direct correlation exists between the expression of certain molecules and the development of an invasive, highly malignant immunophenotype (IP) of neoplastic cells, allowing for the occurrence of angiogenesis and metastasis. Our systematic and detailed cellular IP analyses of 82 childhood brain tumors [34 medulloblastomas (MEDs)/primitive neuroectodermal tumors (PNETs), 42 astrocytomas (ASTRs), 5 choroid plexus papillomas (CPPs) and 1 choroid plexus carcinoma (CPC)], was conducted using over 55 MoABs. An indirect, four-step, enzyme linked [alkaline phosphatase (AP) and peroxidase (PO)], biotin-streptavidin based, antigen detection technique was employed. (ABSTRACT TRUNCATED)

Fas (Apo-1, CD95) receptor expression in childhood astrocytomas. Is it a marker of the major apoptotic pathway or a signaling receptor for immune escape of neoplastic cells?

Apoptosis is a physiological process wherein the cell initiates a sequence of events culminating in the fragmentation of its DNA, nuclear collapse, and finally disintegration of the cell into small, membrane-bound apoptotic bodies. Expression of Fas (APO-1, CD95) Receptor (FasR) and programmed or active cell (PCD) death was studied in childhood astrocytomas (ASTRs) with varying stages of malignancy, including pilocytic ASTR, low grade ASTR, anaplastic ASTR, and glioblastoma multiforme (GBM). The great majority of childhood glial tumors, particularly ASTRs express FasR whereas normal cells in the central nervous system (CNS) do not. FasR represents a transmembrane glycoprotein which belongs to the nerve growth factor/tumor necrosis factor (NGF/TNF) receptor superfamily. Apoptosis within ASTRs is triggered by the binding of FasR to its natural ligand (FasL) or by cross-linking with antibodies developed against FasR. Presence of FasL was also detected in childhood glial tumors. The expression of both FasR and FasL was also observed within the same ASTRs. Therefore, spontaneous, IP regulatory, intratumoral apoptotic cell death (autocrine suicide) is possible in childhood glial tumors. During a systematic, immunocytochemical screening of 42 childhood ASTRs tissues divided according to WHO classification: 6 WHO grade I or pilocytic ASTRs; 14 WHO grade II or low grade ASTRs; 16 WHO grade III or anaplastic ASTRs and 6 WHO grade IV or glioblastoma multiforme (GBM), we detected strong expression (intensity of staining: "A"--the highest possible; number of stained cells: +2 to +4, between 20% to 90%) of FasR, employing 4 microns thick, formalin fixed, paraffin-wax embedded tissue slides. FasR was present on 70% to 90% of tumor cells in pilocytic ASTRs, in 50% to 60% of the tumor cells in low grade ASTRs, in between 30% and 40% of the tumor cells in anaplastic ASTRs, and in between 20% to 35% of GBM cells. The panel of normal tissues employed as positive and negative tissue controls demonstrated presence of FasR in the prenatal thymus, mature tonsils and colonic epithelium. The use of a sensitive, indirect, six step immunoperoxidase or alkaline phosphatase conjugated streptavidin-biotin antigen detection technique provided excellent immunocytochemical results. A broad spectrum of neoplastic cells have been identified to express FasR: 1) carcinomas of epithelial origin, such as breast (ductal invasive, lobular invasive, mucinous), renal cell, gastric, colorectal, endometrial, prostate, pancreas, hepatocellular and large cell and squamous cell lung carcinomas: 2) non-epithelial neoplasms such as B cell mediastinal B cell and nodal non-Hodgkin's lymphomas large granular lymphocytic leukemia of T or NK cell origin malignant fibrous histiocytoma, malignant mesothelioma, leiomyosarcoma, epitheloid sarcoma and alveolar soft part sarcoma, as well as melanomas. Flow cytometry studies have also detected FasR expression on cells of adult T cell, and hairy cell leukemias, as well as in chronic B cell lymphocytic leukemia (BCLL). The coexpression of both FasR and FasL on several malignant cell types may represent an effective mechanism of tumor escape from the cellular immunological response of the host. It has been well established that brain tumors and melanomas produce their autocrine FasL, and even become capable of switching the signal transduction associated with FasL-FasR coupling from the PCD pathway to a tumor growth, proliferative pathway. It seems that the therapeutical use of FasR-FasL (main apoptotic pathway) may represent a new and exciting type of immunotherapy in the treatment of primary childhood glial tumors.