In the war against Plasmodium, humans have evolved to eliminate or modify proteins on the erythrocyte surface that serve as receptors for parasite invasion, such as the Duffy blood group, a receptor for Plasmodium vivax, and the Gerbich-negative modification of glycophorin C for Plasmodium falciparum. In turn, the parasite counters with expansion and diversification of ligand families. The high degree of polymorphism in glycophorin B found in malariaendemic regions suggests that it also may be a receptor for Plasmodium, but, to date, none has been identified. We provide evidence from erythrocyte-binding that glycophorin B is a receptor for the P.

Many mammalian cell types co-express several receptors for the evolutionarily related hematopoietic cytokines of the interleukin (IL) 4 -6 group (1). Moreover, all cell types express gp130, the common signal-transducing subunit of this receptor family. A major unresolved issue is whether the receptors for the individual IL-6 cytokines exert redundant functions because of the involvement of shared subunits, or whether they exert specific actions because of the formation of heteromeric subunit combinations. Gross analyses of cell responses to IL-6 cytokines indicated similar signaling reactions, supporting the notion of redundancy (2, 3). However, the individual receptor forms determine not only the ability of the cells to respond to specific IL-6 cytokines by mediating ligand binding but also the quantitative signaling by the relative expression levels of receptor subunits (4). The model of IL-6 cytokine receptors directing specific action takes into consideration that receptor complexes engage cytoplasmic domains of two signal-transducing subunits with distinct structures and capabilities to communicate to signaling pathways (3, 5). The ligand-dependent association of receptor subunits into signaling-competent complexes leads invariably to the activation of JAKs and to a specific pattern of auto-and trans-tyrosine phosphorylation of kinases, receptor subunits, and interacting proteins, including STATs, Src homology 2-containing phosphatase 2, Src homology 2-containing protein C (SHC) and other adaptor proteins. The receptor proximal events at the plasma membrane and the level of sustained signaling defines the duration and magnitude of cell responses, including transcriptional induction of genes, altered cell morphology, and changes in cell proliferation. Proliferation control by cytokine-activated STAT proteins has gained particular attention in part to explain the role of IL-6 cytokines in tissue damage repair (6 -8) and potential relevance to support tumorigenesis (9, 10). Unexplained thus far is the basis for the divergent outcome of IL-6 cytokine action that, in certain epithelial cell types, yields a suppression of proliferation (11), whereas in other cell types it yields a growth promotion (12, 13). Because the subunits for IL-6 cytokine receptors are encoded by single-copy genes, comparable structures and biochemical actions are expected for the receptor proteins expressed in the various cell types, regardless of the ultimate outcome of cytokine treatment.An independent assessment of receptor signaling specificity among IL-6 cytokine receptors became possible with the identification of IL-31R␣ (gp130-like protein; see Ref. 14) as a member of the IL-6R group that does not engage gp130, but OSMR␤, to form a signaling receptor complex (15,16). Based on the effects of ectopic expression in transgenic mice, IL-31, a CD4 ϩ T-cell-derived cytokine, has been associated with pruritis and dermatitis affecting dermal keratinocytes and dorsal root ganglia (17-19). Because antigenic challenge increased levels of * Th...

The carbohydrate moieties on conjugating with 3-(1′-hexyloxyethyl)-3-devinyl pyropeophorbide-a (HPPH) altered the uptake and intracellular localization from mitochondria to lysosomes. In vitro, HPPH-Gal 9 PDT showed increased PDT efficacy over HPPH-PDT as detectable by the oxidative cross-linking of nonphosphorylated STAT3 and cell killing in ABCG2-expressing RIF cells but not in ABCG2-negative Colon26 cells. This increased efficacy in RIF cells could at least partially be attributed to increased cellular accumulation of 9, suggesting a role of the ABCG2 transporter for which HPPH is a substrate. While such differences in the accumulation in HPPH derivatives by tumor tissue in vivo were not detectable, 9 still showed an elevated light dose-dependent activity compared to HPPH in mice bearing RIF as well as Colon26 tumors. Further optimization of the carbohydrate conjugates at variable treatment parameters in vivo is currently underway.

Signal transducer and activator of transcription 3 (STAT3) is associated with various physiological and pathological functions, mainly as a transcription factor that translocates to the nucleus upon tyrosine phosphorylation induced by cytokine stimulation. In addition, a small pool of STAT3 resides in the mitochondria, where it serves as a sensor for various metabolic stressors including reactive oxygen species (ROS). Mitochondrially localized STAT3 largely exerts its effects through direct or indirect regulation of the activity of the electron transport chain (ETC). It has been assumed that the amounts of STAT3 in the mitochondria are static. We showed that various stimuli, including oxidative stress and cytokines, triggered a signaling cascade that resulted in a rapid loss of mitochondrially localized STAT3. Recovery of the mitochondrial pool of STAT3 over time depended on phosphorylation of Ser727 in STAT3 and new protein synthesis. Under these conditions, mitochondrially localized STAT3 also became competent to bind to cyclophilin D (CypD). Binding of STAT3 to CypD was mediated by the amino terminus of STAT3, which was also important for reducing mitochondrial ROS production after oxidative stress. These results outline a role for mitochondrially localized STAT3 in sensing and responding to external stimuli.

The reciprocal t(8;13) chromosome translocation results in a fusion gene (FUS) in which the N-terminal half of the zinc finger protein ZNF198 is combined with the cytoplasmic domain of the fibroblast growth factor receptor-1 (FGFR1). Expression of FUS is suggested to provide growth-promoting activity to myeloid cells similar to the activity of hematopoietic cytokine receptors. This study determined the specificity of FUS to activate signal transduction pathways. Because no tumor cell line expressing FUS was available, the mode of FUS action was identified in cells transiently and stably transfected with an expression vector for FUS. FUS acted as a constitutively active protein-tyrosine kinase and mediated phosphorylation of STAT1, 3, and 5 but not STAT4 and 6. The same specificity but lower activity was determined for normal FGFR1. STAT activation by FUS, similar to that by interleukin-6-type cytokines, promoted STAT-specific induction of genes. The functionality of FUS, as well as the relative recruitment of STAT isoforms, was determined by the dimerizing function of the zinc finger domain. Replacement of the ZNF198 portion by the Bcr portion as present in the t(8;22) translocation shifted the signaling toward a more prominent STAT5 activation. This study documents that both gene partners forming the fusion oncogene define the activity and the signaling specificity of the proteintyrosine kinase of FGFR1.

We report herein the synthesis and biological efficacy of near-infrared (NIR), bacteriochlorin analogues: 3-(1'-butyloxy)ethyl-3-deacetyl-bacteriopurpurin-18-N-butylimide methyl ester (3) and the corresponding carboxylic acid 10. In in vitro assays, compared to its methyl ester analogue 3, the corresponding carboxylic acid derivative 10 showed higher photosensitizing efficacy. However, due to drastically different pharmacokinetics in vivo, the PS 3 (HPLC purity >99%) showed higher tumor uptake and long-term tumor cure than 10 (HPLC purity >96.5%) in BALB/c mice bearing Colon 26 tumors. Isomerically pure R- and S- isomers of 3 (3a and 3b, purity by HPLC > 99%) under similar treatment parameters showed identical efficacy in vitro and in vivo. In addition, photosensitizer (PS) 3 showed limited skin phototoxicity and provides an additional advantage over the clinically approved chemically complex hematoporphyrin derivative as well as other porphyrin-based PDT agents, which makes 3 a promising dual-function agent for fluorescence-guided surgery with an option of phototherapy of cancer.

Purpose The primary objective was to evaluate safety of 3-(1’-hexyloxyethyl)pyropheophorbide-a (HPPH) photodynamic therapy (HPPH-PDT) for dysplasia and early squamous cell carcinoma of the head and neck (HNSCC). Secondary objectives were the assessment of treatment response and reporters for an effective PDT reaction. Experimental Design Patients with histologically proven oral dysplasia, carcinoma in situ (CiS ) or early stage HNSCC were enrolled in two sequentially conducted dose escalation studies with an expanded cohort at the highest dose level. These studies employed an HPPH dose of 4 mg/m2 and light doses from 50 to 140 J/cm2. Pathologic tumor responses were assessed at 3 months. Clinical follow up range was 5 to 40 months. PDT induced cross-linking of signal transducer and activator of transcription 3 (STAT3) were assessed as potential indicators of PDT effective reaction. Results Forty patients received HPPH-PDT. Common adverse events were pain and treatment site edema. Biopsy proven complete response rates were 46% for dysplasia and CiS, and 82% for SCCs lesions at 140 J/cm2. The responses in the CiS/dysplasia cohort are not durable. The PDT induced STAT3 cross-links is significantly higher (P=0.0033) in SCC than in CiS/dysplasia for all light-doses. Conclusion HPPH-PDT is safe for the treatment of CiS/dysplasia and early stage cancer of the oral cavity. Early stage oral HNSCC appears to respond better to HPPH-PDT in comparison to premalignant lesions. The degree of STAT3 cross-linking is a significant reporter to evaluate HPPH-PDT mediated photoreaction.

We present initial results obtained during the course of a Phase I clinical trial of 2-1[hexyloxyethyl]-2-devinylpyropheophorbide-a (HPPH)-mediated photo-dynamic therapy (PDT) in a head and neck cancer patient. We quantified blood flow, oxygenation and HPPH drug photobleaching before and after therapeutic light treatment by utilizing fast, non-invasive diffuse optical methods. Our results showed that HPPH-PDT induced significant drug photobleaching, and reduction in blood flow and oxygenation suggesting significant vascular and cellular reaction. These changes were accompanied by cross-linking of the signal transducer and activator of transcription 3 (STAT3), a molecular measure for the oxidative photoreaction. These preliminary results suggest diffuse optical spectroscopies permit non-invasive monitoring of PDT in clinical settings of head and neck cancer patients.