RESUMO
Many tumor cells produce vast amounts of lactate and acid, which have to be removed from the cell to prevent intracellular lactacidosis and suffocation of metabolism. In the present study, we show that proton-driven lactate flux is enhanced by the intracellular carbonic anhydrase CAII, which is colocalized with the monocarboxylate transporter MCT1 in MCF-7 breast cancer cells. Co-expression of MCTs with various CAII mutants in Xenopus oocytes demonstrated that CAII facilitates MCT transport activity in a process involving CAII-Glu69 and CAII-Asp72, which could function as surface proton antennae for the enzyme. CAII-Glu69 and CAII-Asp72 seem to mediate proton transfer between enzyme and transporter, but CAII-His64, the central residue of the enzyme's intramolecular proton shuttle, is not involved in proton shuttling between the two proteins. Instead, this residue mediates binding between MCT and CAII. Taken together, the results suggest that CAII features a moiety that exclusively mediates proton exchange with the MCT to facilitate transport activity.
Assuntos
Neoplasias da Mama/metabolismo , Anidrase Carbônica II/metabolismo , Ácido Láctico/metabolismo , Transportadores de Ácidos Monocarboxílicos/metabolismo , Simportadores/metabolismo , Xenopus laevis/metabolismo , Animais , Transporte Biológico , Neoplasias da Mama/genética , Neoplasias da Mama/patologia , Anidrase Carbônica II/química , Anidrase Carbônica II/genética , Feminino , Humanos , Transportadores de Ácidos Monocarboxílicos/genética , Oócitos/citologia , Oócitos/metabolismo , Conformação Proteica , Prótons , Propriedades de Superfície , Simportadores/genética , Células Tumorais CultivadasRESUMO
PURPOSE: Various studies have shown the importance of the GAIP interacting protein, COOH-terminus (GIPC, also known as Synectin) as a central adaptor molecule in different signaling pathways and as an important mediator of receptor stability. GIPC/Synectin is associated with different growth-promoting receptors such as insulin-like growth factor receptor I (IGF-IR) and integrins. These interactions were mediated through its PDZ domain. GIPC/Synectin has been shown to be overexpressed in pancreatic and breast cancer. The goal of this study was to show the importance of GIPC/Synectin in pancreatic cancer growth and to evaluate a possible therapeutic strategy by using a GIPC-PDZ domain inhibitor. Furthermore, the effect of targeting GIPC on the IGF-I receptor as one of its associated receptors was tested. EXPERIMENTAL DESIGN: The in vivo effects of GIPC/Synectin knockdown were studied after lentiviral transduction of luciferase-expressing pancreatic cancer cells with short hairpin RNA against GIPC/Synectin. Additionally, a GIPC-PDZ--targeting peptide was designed. This peptide was tested for its influence on pancreatic cancer growth in vitro and in vivo. RESULTS: Knockdown of GIPC/Synectin led to a significant inhibition of pancreatic adenocarcinoma growth in an orthotopic mouse model. Additionally, a cell-permeable GIPC-PDZ inhibitor was able to block tumor growth significantly without showing toxicity in a mouse model. Targeting GIPC was accompanied by a significant reduction in IGF-IR expression in pancreatic cancer cells. CONCLUSIONS: Our findings show that targeting GIPC/Synectin and its PDZ domain inhibits pancreatic carcinoma growth and is a potential strategy for therapeutic intervention of pancreatic cancer.
Assuntos
Proteínas Adaptadoras de Transdução de Sinal/antagonistas & inibidores , Antineoplásicos/farmacologia , Oligopeptídeos/farmacologia , Domínios PDZ , Neoplasias Pancreáticas/tratamento farmacológico , Neoplasias Pancreáticas/metabolismo , Proteínas Adaptadoras de Transdução de Sinal/genética , Proteínas Adaptadoras de Transdução de Sinal/metabolismo , Animais , Proliferação de Células/efeitos dos fármacos , Feminino , Técnicas de Silenciamento de Genes , Humanos , Integrinas/metabolismo , Camundongos , Camundongos Nus , Domínios PDZ/efeitos dos fármacos , Neoplasias Pancreáticas/patologia , Receptor IGF Tipo 1/metabolismo , Transdução de SinaisRESUMO
BACKGROUND: The role of tumor associated macrophages (TAMs) in tumor angiogenesis and inflammation and the interactions between TAMs and tumor cells as well as lymphocytes appear to be critical factors in the development and progression of cancer. PATIENTS AND METHODS: Carcinomas of the gastrointestinal tract have been analysed by tissue microarrays. TAMs and vessels were characterized by immunohistochemistry using the antibodies PG-M1, KP1, MRP8, MRP14, MRP8/14 and CD31, CD34, respectively. RESULTS: The number of all macrophages was significantly higher and lymphocyte densities were lower in tumor tissues than in tumor-free tissues. The MRP-antibodies identified a minority population of macrophages and a low numbers of these macrophages tended to occur in more advanced cancers. There was a positive correlation between the number of macrophages and the number of microvessels in all tumors, but no correlation between macrophages and vessel counts in tumor-free tissues. CONCLUSION: The results indicated a suppressed immune response towards the tumors. The observed common characteristics regarding macrophage attraction, lymphocyte suppression and microvessel density suggested that these mechanisms are regulated similarly in all carcinomas of the GI-tract.
