Tumor-associated embryonic antigen-expressing vaccines that target CCR6 elicit potent CD8+ T cell-mediated protective and therapeutic antitumor immunity

Despite its potency, the wider use of immunotherapy for B cell malignancies is hampered by the lack of well-defined tumor-specific Ags. In this study, we demonstrate that an evolutionarily conserved 37-kDa immature laminin receptor protein (OFA-iLRP), a nonimmunogenic embryonic Ag expressed by a variety of tumors, is rendered immunogenic if targeted to the APCs using the CCR6 ligands MIP3alpha/CCL20 and mDF2beta. The CCR6 targeting facilitated efficient Ag cross-presentation and induction of tumor-neutralizing CTLs. Although the Ag targeting alone, without activation of dendritic cells (DCs), is proposed to induce tolerance, and MIP3alpha does not directly activate DCs, the MIP3alpha-based vaccine efficiently induced protective and therapeutic antitumor responses. The responses were as strong as those elicited by the OFA-iLRP fusions with moieties that activated DCs and Th1-type cytokine responses, mDF2beta, or mycobacterial Hsp70 Ag. Although the same cDNA encodes the dimerized high-affinity mature 67-kDa mLRP that is expressed in normal tissues to stabilize the binding of laminin to cell surface integrins, the vaccines expressing OFA-iLRP elicited long-term protective CD8(+) T cell-mediated memory responses against syngeneic B cell lymphoma, indicating the potential application of these simple vaccines as preventive and therapeutic formulations for human use.     

CCR4-expressing T cell tumors can be specifically controlled via delivery of toxins to chemokine receptors

Expression of chemokine receptors by tumors, specifically CCR4 on cutaneous T cell lymphomas, is often associated with a poor disease outcome. To test the hypothesis that chemokine receptor-expressing tumors can be successfully controlled by delivering toxins through their chemokine receptors, we have generated fusion proteins designated chemotoxins: chemokines fused with toxic moieties that are nontoxic unless delivered into the cell cytosol. We demonstrate that chemokines fused with human RNase eosinophil-derived neurotoxin or with a truncated fragment of Pseudomonas exotoxin 38 are able to specifically kill tumors in vitro upon internalization through their respective chemokine receptors. Moreover, treatment with the thymus and activation-regulated chemokine (CCL17)-expressing chemotoxin efficiently eradicated CCR4-expressing cutaneous T cell lymphoma/leukemia established in NOD-SCID mice. Taken together, this work represents a novel concept that may allow control of growth and dissemination of tumors that use chemokine receptors to metastasize and circumvent immunosurveillance.     

Human peripheral blood T regulatory cells (Tregs), functionally primed CCR4+ Tregs and unprimed CCR4- Tregs, regulate effector T cells using FasL

Regulatory CD25(+)CD4(+) T cells (Tregs) play an important role in the control of peripheral tolerance. In this study we demonstrate that human peripheral blood Tregs can be divided into two distinct populations based on the expression of CCR4. The majority ( approximately 75%) of freshly isolated Tregs express CCR4 and presumably represent memory-type Tregs. Interestingly, CCR4(-) Tregs require anti-CD3 Ab-mediated activation to acquire a regulatory activity, while CCR4(+) Tregs appear to be already primed to suppress the proliferation of CD8(+) T cells. CCR4 is also expressed on CD25(low)CD4(+) T cells (CCR4(+) non-Tregs) that mostly suppress Th1-type polarization without affecting T cell proliferation, presumably via the production of immunomodulatory cytokines like IL-10. In contrast, CCR4(+) Tregs express FasL to primarily regulate T cell proliferation via a contact-mediated process involving FasL/Fas signaling, a major regulatory pathway of T cell homeostasis. Finally, we also demonstrate that the depletion of CCR4(+) T cells leads to Th1-type polarization of CD4(+) T cells and augmentation of CD8(+) T cell responses to tumor Ags.     

Dual actions of nitric oxide on angiogenesis: possible roles of PKC, ERK, and AP-1

Regulation of angiogenesis by nitric oxide (NO) is controversial since NO has been shown to have both pro- and anti-angiogenic effects. In this study, we examined the effect of the NO donor, S-nitro-N-acetyl-penicillamine (SNAP), on in vitro angiogenesis, and the mechanisms involved: PKC activity, ERK and c-Jun phosphorylation, and AP-1 DNA binding activity, in microvascular endothelial cells. SNAP, at 0.5-4 mM, significantly and dose-dependently inhibited angiogenesis, PKC activity, and ERK and c-Jun phosphorylation up to 80%, 83%, and 63% and 73%, respectively. SNAP at concentrations > 2mM also abolished AP-1 binding activity. Lower concentrations of SNAP (0.1-0.3 mM) significantly increased angiogenesis, PKC activity, and ERK and c-Jun phosphorylation up to 46%, 60%, and 61% and 180%, respectively. These findings indicate that the dual pro- and anti-angiogenic actions of NO are dose-dependent and suggest that they are mediated by PKC and ERK acting on AP-1.     

Prostaglandin E2 transactivates EGF receptor: a novel mechanism for promoting colon cancer growth and gastrointestinal hypertrophy

Prostaglandins (PGs), bioactive lipid molecules produced by cyclooxygenase enzymes (COX-1 and COX-2), have diverse biological activities, including growth-promoting actions on gastrointestinal mucosa. They are also implicated in the growth of colonic polyps and cancers. However, the precise mechanisms of these trophic actions of PGs remain unclear. As activation of the epidermal growth factor receptor (EGFR) triggers mitogenic signaling in gastrointestinal mucosa, and its expression is also upregulated in colonic cancers and most neoplasms, we investigated whether PGs transactivate EGFR. Here we provide evidence that prostaglandin E2 (PGE2) rapidly phosphorylates EGFR and triggers the extracellular signal-regulated kinase 2 (ERK2)--mitogenic signaling pathway in normal gastric epithelial (RGM1) and colon cancer (Caco-2, LoVo and HT-29) cell lines. Inactivation of EGFR kinase with selective inhibitors significantly reduces PGE2-induced ERK2 activation, c-fos mRNA expression and cell proliferation. Inhibition of matrix metalloproteinases (MMPs), transforming growth factor-alpha (TGF-alpha) or c-Src blocked PGE2-mediated EGFR transactivation and downstream signaling indicating that PGE2-induced EGFR transactivation involves signaling transduced via TGF-alpha, an EGFR ligand, likely released by c-Src-activated MMP(s). Our findings that PGE2 transactivates EGFR reveal a previously unknown mechanism by which PGE2 mediates trophic actions resulting in gastric and intestinal hypertrophy as well as growth of colonic polyps and cancers.