Design, synthesis, and evaluation of cisplatin-containing EGFR targeting bioconjugates as potential therapeutic agents for brain tumors.

The aim of this study was to evaluate four different platinated bioconjugates containing a cisplatin (cis-diamminedichloroplatinum [cis-DDP]) fragment and epidermal growth factor receptor (EGFR)-targeting moieties as potential therapeutic agents for the treatment of brain tumors using a human EGFR-expressing transfectant of the F98 rat glioma (F98EGFR) to assess their efficacy. The first two bioconjugates employed the monoclonal antibody cetuximab (C225 or Erbitux(®)) as the targeting moiety, and the second two used genetically engineered EGF peptides. C225-G5-Pt was produced by reacting cis-DDP with a fifth-generation polyamidoamine dendrimer (G5) and then linking it to C225 by means of two heterobifunctional reagents. The second bioconjugate (C225-PG-Pt) employed the same methodology except that polyglutamic acid was used as the carrier. The third and fourth bioconjugates used two different EGF peptides, PEP382 and PEP455, with direct coordination to the Pt center of the cis-DDP fragment. In vivo studies with C225-G5-Pt failed to demonstrate therapeutic activity following intracerebral (ic) convection-enhanced delivery (CED) to F98EGFR glioma-bearing rats. The second bioconjugate, C225-PG-Pt, failed to show in vitro cytotoxicity. Furthermore, because of its high molecular weight, we decided that lower molecular weight peptides might provide better targeting and microdistribution within the tumor. Both PEP382-Pt and PEP455-Pt bioconjugates were cytotoxic in vitro and, based on this, a pilot study was initiated using PEP455-Pt. The end point for this study was tumor size at 6 weeks following tumor cell implantation and 4 weeks following ic CED of PEP455-Pt to F98 glioma-bearing rats. Neuropathologic examination revealed that five of seven rats were either tumor-free or only had microscopic tumors at 42 days following tumor implantation compared to a mean survival time of 20.5 and 26.3 days for untreated controls. In conclusion, we have succeeded in reformatting the toxicity profile of cis-DDP and demonstrated the therapeutic efficacy of the PEP455-Pt bioconjugate in F98 glioma-bearing rats.

Neuro-endocrine neoplasms as a result of gene desuppression rather than of a specific cell type of origin.

Neuroendocrine differentiation more closely approximates a process of acquisition of features that ambiguously recapitulate certain cellular biologic properties that transgress normal lines of differentiation as these are generally recognized. In fact, it might be more realistic to consider neuroendocrine tumors the result of a process of progressive desuppression via pathways of altered gene expression that would perhaps reflect basic and dynamic aspects of neoplastic transformation and progression in general. In a final analysis, the character and degree of differentiation of a neoplasm might actually often constitute an anomalous combination of features outside the range of normal differentiation pathways and more an expression of an assorted mixture of partially suppressed or desuppressed gene expression profiles as these affect neoplastic cell pathobiology.

Are tau and alpha synuclein filamentous inclusions in neurons and glia analogous to accumulation of myosin/actin filaments in myofiber hypertrophy?

Degenerative disruption of neuronal networks would appear to constitute a pathogenetic series of mechanisms that would adequately account for the effects of neurodegeneration in its full complexity clinically and pathologically beyond any consideration of the neuron as the basic unit of involvement. In this sense, neurodegeneration as reflected in terms of neurofibrillary tangles and Lewy bodies might actually be a process of integral tau opathy and synucleinopathy that in probably multiple different ways in the individual patient contributes to a disruption of neuronal interactions as an integral neuronal network. In terms therefore of aggregation of neurofilaments or of synuclein filaments it might be valid to consider simple biophysical phenomena of inclusion body formation in neurons directly analogous to myosin/actin accumulation in myofibers in an overall common system of neuronal and myofiber biology and pathobiology.

The malignant transformation event as a clonal transformation of apoptosis to anti-apoptosis pathways and of cell cycle dynamics.

Anti-apoptosis, as a more vital aspect of a whole series of progressive steps in carcinogenesis, would appear primarily a phenomenon of variable nonresponsiveness. Programmed cell death, in addition, would appear to affect the individual cell as attributes also of an integral field phenomenon constituted by clones of tumor cells that grow, proliferate and spread. Various modes of development of anti-apoptosis subsequently involving the development of genetic abnormalities would possibly account for transformation as a neoplastic phenomenon. It is in terms of such pathways as telomeric length preservation, of anti-apoptosis as failed activation of apoptosis, and of failed DNA binding events that clonally selected tumor cells would tend to inherently progress to higher grade and stage and to spread systemically. Moreover, clonal and field events would possibly influence in their turn individual cell cyclical activity and programmed cell pathways in neoplastic transformation. Anti-apoptosis would constitute, in fact, a predicted system of pathways that switch from apoptosis as an essential pathway in malignant transformation. Angiogenesis, as a full series of cascade events of a paracrine/autocrine nature, would also participate with anti-apoptosis in a tumor cell cycle transformation that is self-amplifying. Given different modes of how apoptosis would convert to anti-apoptosis in tumorigenesis, perhaps abnormal cell cycle dynamics might also contribute to the evolving nature of such neoplastic transformation.

Dysregulatory dysequilibrium of gene transcription and of nuclear transport in polyglutamine neuro-degeneration.

Polyglutamine neurodegeneration as an essential expansion mutation of the CAG-trinucleotide repeat encoding glutamine would appear to constitute an integral process of aggregation/accumulation that self-propagates a secondary process of possible nuclear sequestration. Within such a scheme of progressive expansion of polyglutamine stretches in strict parallel correlation with increased CAG trinucleotide repeats in genes such as ataxin-7 and its messenger RNA, it would appear that a fundamental relationship of accumulation directly inducing biophysical disruption between nuclear/nucleolar and cytoplasmic protein machineries would constitute a dysfunctional dysequilibrium accounting for self-progressive neuronal degeneration with atrophy of the cerebral cortex and ganglia such as the caudate, that is limited often to specific population groups of neurons. It is for example in terms of Huntington's disease as an autosomal dominant disorder with high penetrance on a background of onset of dementia mainly in the fourth and fifth decades of life that one might conceive of polyglutamine neurodegeneration as fundamentally a developmental disturbance affecting neuronal maturation that accounts for abnormal neurophysiological and biochemical aspects of interaction of nucleus with cytoplasm. Polyglutamine expansion and trinucleotide repeats as both progressive processes of accumulation and synthesis would constitute a complex interplay of inducing and induced effects that both contribute in probably multiple ways to the self-progressive nature of a nuclear sequestration process.

Possible close analogy between HIV and EBV infection and, respectively, induced lymphomas.

Within a system that operatively allows a progressive infection of T-lymphocytes by human immunodeficiency virus (HIV) in a manner that also entails depletion of the T-helper subset with directly resulting severe immunodeficiency, there might also be implicated a form of modulation of effects conducive to neoplastic transformation based on peculiar consequences of lesions induced by HIV integration within the cell genome. It might, in addition, be valid to consider Epstein Barr virus (EBV) as a cause of both B-lymphocyte infection and also of the creation of a whole population of atypical T-lymphocytes as seen in infectious mononucleosis, to constitute a close parallel analogy to HIV; in this manner it might be suggestive also of a series of analogous reactive lymphocytic changes also in AIDS; such a phenomenon might perhaps help account for the emergence in some AIDS patients of a primary Central Nervous System Lymphoma that is virtually always of B-cell derivation, analogous to Burkitt's lymphoma that is also of B-cell origin. In addition, the occurrence of T-cell rich B-cell lymphoma would appear perhaps to constitute a series of phenomena that intricately implicate both B-lymphocyte and T-lymphocyte participation in the genesis even of lymphomatous states as a category.

Beta-amyloidosis as an index of activity of the Alzheimer process rather than as a primary mechanism of neuronal injury in organic dementia.

In simple effective terms, beta-amyloid deposition might actually reflect ongoing activity of the Alzheimer process in a manner not directly related to the actual nature of this Alzheimer process. In a strict sense, perhaps, microglial and astrocytic activation within the possibly additional context of micro-circulatory pathology might actually operate towards the creation of a set of stress-inducing injuries to neurons by such mechanisms as oxidative stress, and also enzymatic release by microglia with phagocytosis within a system that dynamically evolves. In this sense, a central process of neuritic injury would appear to potentially engender a series of secondary mechanisms of injury that contribute and even transform the pathologic process central to neurodegeneration in Alzheimer's. In a real sense, therefore, neuronal cell death would constitute a set of effects that integrally evolve via various pathways that are central or else secondary to active induction and progression of neuritic pathology. In perhaps an overall system of such self-engendered transformation both through primary and secondary series of pathways, beta-amyloid deposition would constitute a visible expression of the Alzheimer process as perhaps significantly related to disease activity per se irrespective of the specific genesis or nature of such disease activity.

Does transmissibility necessarily imply infectivity in spongiform encephalopathy?

The essential biologic properties inherently acquired subsequent to conformational transformation of the alpha-helical molecular structure of the normal cellular PrPc isoform to the beta-sheet molecular tertiary structure of the abnormal PrPsc associated with a rapidly spreading form of neuronal cell death of spongiform encephalopathy are unknown. However, the vacuolization that chiefly characterizes the morphology of neurons in spongiform encephalopathy might constitute a physical disruption with subsequent rapidly progressive impairment of maintenance of homeostatic viability of neurons due to precisely loss of membrane integrity of the plasmalemma and cell organelles. As far as transmission of the prion particle is concerned, it would appear that active incorporation of this agent under the direction of the affected neuronal cell itself would implicate host attributes as paramount factors determining not only susceptibility to the pathologic effects of the prion particle but also to the mode of such infliction as arising in and constituting spongiform encephalopathy beyond its acquisition and progression. As a single set of acquired circumstances determining both transmissibility and also pathologic lesion creation, the spongiform neuronal change might arise directly from a membrane abnormality of water ingress and egress in and out of the neuron. An excess of water ingress intra-neuronally might actually constitute a phenomenon of active lesion induction even in terms simply of biophysical stress intra-neuronally. In simple terms, an understanding of pathogenesis in spongiform encephalopathy might actually implicate aspects of transmissibility as direct attributes of processes of template replication within a system of utilization and elimination of the prion particle. Indeed, susceptibility to spongiform change might constitute one aspect of a biologic process that arises from conformational change of the prion protein molecule that would in turn result from variable polymorphisms in modes of reactive handling of PrPc and PrPsc by the neurons and other constituent cell elements in the central nervous system.

Is repetitive opportunistic infection in AIDS patients the effective mechanism for neurodegeneration in terms of endlessly amplifying cytokine/chemokine effect?

With strict reference to how AIDS dementia somehow evolves from HIV infection through stages of initial monocyte-macrophage stimulation via a series of transendothelial and infiltrative events, it is perhaps significant to consider systemic body involvement by the HIV-associated processes to culminate in a concerted series of effects involving cascades and amplifications of action of cytokines and chemokines. Indeed, in terms that would implicate neurons only secondarily in AIDS dementia, one might perhaps consider HIV-1-dementia as an effective result of ongoing inflammation in the brain dependent not only on macrophage-microglial activation and replication, but also on glial participation in an overall process particularly conducive to increasing the brain HIV-1 load. In effect, perhaps, HIV encephalitis would constitute a system of mutually self-enhancing series of events ranging from macrophage-monocyte activation and replication on the one hand, and also HIV-1-induced cellular effects on the other that would result in progressively amplifying neuronal injury induced by cytokines and chemokines in AIDS patients suffering from repetitive opportunistic infections.

Viral participation in cellular and microenvironmental transformation and amplification towards malignancy in AIDS patients.

HIV-1 infection would initially predispose to neoplastic transformation in terms of a progressive lymphocytic proliferation followed by the onset of an immunodeficiency state. Both virion genomic integration and also active host cell proliferation would perhaps participate in the establishment of an often multifocal primary CNS lymphoma of AIDS type. Repeated opportunistic infections in AIDS patients tend to especially involve the central nervous system to also carry an increased risk of neoplastic transformation of the reactive B lymphocytes reaching the brain. A microenvironmental set of circumstances in patients with AIDS would predispose to non-Hodgkin's lymphoma largely in terms of an HIV-1 infection that progresses concurrently with evolving cell replication, immunodeficiency, and repeated opportunistic infections as caused by several different potential pathogens. Epstein-Barr virus infection in particular appears closely related to Hodgkin's disease that develops in some AIDS patients. A viral role in the development of lymphomas and of Kaposi sarcoma in HIV-infected individuals would account for neoplastic aggressiveness and for a particular predilection for primary CNS lymphoma. Such a role perhaps implicates viral integration within the genome of host cells that are actively proliferating or else infected by multiple viral pathogens such as EBV, HIV-1, CMV, and Herpes virus.

The focality of the global Alzheimer brain process: is the selective vulnerability of neurons a specific phenomenon of primary neuronal pathobiology?

A focality in the development of a global series of predisposing factors that conditions a progressiveness in the neurodegenerative process of Alzheimer type would appear to arise as a specific lesion of the neuron. Such a neuronal lesion would perhaps disrupt functional connectivity of neuronal networks in a process involving loss of neuronal viability. Indeed, a strict concept of selective vulnerability of neurons in the Alzheimer brain might be simply a preconditioning by microenvironmental factors that interacts with the individual neuron in terms of cellular component depletion or in terms of plasmalemmal disruption. In a final analysis, perhaps, the individual neuron would appear as the essential focus of a process that would account for a conditioning globality of the Alzheimer process that promotes both progressiveness and irreversibility of the brain pathology.

Neuroinflammation as the proximate cause of signature pathogenic pattern progression in amyotrophic lateral sclerosis, AIDS, and multiple sclerosis.

The realization of injury to large motor neurons is embedded within contextual reference to the parallel pathways of apoptosis and necrosis of system-patterned evolution. A widespread loss of cell components occurs intracellularly and involves a reactive participation to a neuroinflammation that potentially is immunologically definable. In such terms, sporadic and hereditary forms of amyotrophic sclerosis are paralleled by the components of a reactive nature that involve the aggregation of proteins and conformational misfolding on the one hand and a powerful oxidative degradation that overwhelms the proteasome clearance mechanisms. In such terms, global participation is only one aspect of a disorder realization that induces the development of the defining systems of modulation and of injury that involves the systems of consequence as demonstrated by the overwhelming immaturity of the molecular variants of mutated superoxide dismutase. It is further to such processes of neuroinflammatory consequence that the immune system is integral to the reactive involvement of neurons as patterns of disease recognition and as the system biology of prevalent voluntarily motor character. It is highly significant to recognize various inflammatory states in the nervous system as prototype variability in phenotype expression and as incremental progression in pathogenesis. In fact a determining definition of amyotrophic lateral sclerosis is an incremental phenotype modulation within the pathways of the consequential loss and depletion of motor cell components in the first instance. Neuroinflammation proves a pattern of the contextual spread of such pathogenic progression in the realization of end-stage injury states involving neurons and neuronal networks.

Given dimensions of neoplastic events as aberrantly operative alternative splicing.

The provision of dynamic splicing events constitutes the reflected nature of neoplasia that locally infiltrates and systemically spreads in terms of evolutionary attributes of the primary and various secondary pathways in malignant transformation. The significant diversity in molecular characterization of the given tumor lesion would adaptively conform to dynamics of splicing as enhanced or silenced exons of the premessenger RNA molecule. The proteins synthesized are in turn potential modifiers in further gene expression within such contexts as RNA:protein and RNA:DNA binding events. The recognition of pathways of incremental scope would underline the development of lesions, such as tumors, as multiple alternative splicing phenomena primarily affecting molecular physicochemical identity. It is within contexts of operative intervention and modification that the real identity of the malignant neoplastic process arises, within terms of reference of contextual splicing events. Disrupted gene expression is thus a referential pathway in the modification of splicing that may prove constitutive or alternative, in first instance, but also aberrant as the lesion progresses locally and systemically.

A primary dysregulation in the immunoregulatory role of the intestinal mucosal epithelial cell in inflammatory bowel disease pathogenesis? Biology of inflammatory response as tissue pattern entities in Crohn's versus ulcerative colitis.

Within a framework of dual involvement of mucosa and submucosa on the one hand, and of the muscularis propria of the bowel wall on the other, it might be valid to consider involvement of the vascular supply as the essential means in itself of not only causing the morphologic lesions in inflammatory bowel disease, but also especially in accounting for persisting patterns of inflammatory response both in ulcerative colitis and in Crohn's disease. Inflammatory bowel disease as a group constitutes a spectrum of biologic and pathobiologic manifestations in terms not only of inflammatory involvement of the bowel wall but also in terms of how the bowel in its turn deals with inflammation as a pathologic lesion in its own right. Parameters of inflammatory bowel activity transcend simple concepts of etiology and pathogenesis as applicable to category disorders such as infections or bowel ischemia. Indeed, the strictly characterized initiation of the inflammatory bowel response as a function of defective regulation of the antigenicity of the luminal contents on the one hand, and on interactions between nitric oxide and free oxygen radicals on the other, might help determine a persistence of tissue damage in inflammatory bowel disease that is either relapsing/remitting or chronic in progression. In a final analysis, perhaps, there might be involved a single central form of pathway induction of dysregulated immune reactivity arising from an early disturbance in activation patterns as induced by the onset of luminal antigenicity at an early or specific-stage, further characterized perhaps by specific forms of intestinal epithelial defects of the bowel mucosa in patients subsequently developing inflammatory bowel disease. Specific genetic markers for disease susceptibility and for therapeutic responsiveness are particularly of interest. The Nucleotide binding oligomerization Domain 2 (NOD2) would recognize microbial lipopolysaccharide or else mark systemic responses to pathogens that are pathogenic to evolving inflammatory bowel disease.