Background and Aim: Pancreatic cancer is one of the most fatal cancers. Cytotoxic chemotherapy remains the mainstream treatment for unresectable pancreatic cancer. This systematic review evaluated and compared the overall survival (OS) and progression-free survival (PFS) outcomes obtained from recent phase 2 and 3 clinical trials of pancreatic cancer chemotherapy. Materials and methods: Thirty-two studies were included and compared based on chemotherapy agents or combinations used. Additionally, outcomes of first-line versus second-line chemotherapy in pancreatic cancer were compared. Results: In studies that investigated the treatments in adjuvant settings, the highest OS reported was for S-1 in patients, who received prior surgical resection (46.5 months). In neoadjuvant settings, the combination of gemcitabine, docetaxel, and capecitabine prior to the surgical resection had promising outcomes (OS of 32.5 months). In non-adjuvant settings, the highest OS reported was for the combination of temsirolimus plus bevacizumab (34.0 months). Amongst studies that investigated second-line treatment, the highest OS reported was for the combination of gemcitabine plus cisplatin (35.5 months), then temsirolimus plus bevacizumab (34.0 months). Conclusions: There is a need to develop further strategies besides chemotherapy to improve the outcomes in pancreatic cancer treatment. Future studies should consider surgical interventions, combination chemotherapy, and individualized second-line treatment based on the prior chemotherapy.

The 'cross-talk' between different types of neurotransmitters through second messenger pathways represents a major regulatory mechanism in neuronal function. We investigated the effects of activation of protein kinase C (PKC) on cAMPdependent signaling by structurally related human D1-like dopaminergic receptors. Human embryonic kidney 293 (HEK293) cells expressing D1 or D5 receptors were pretreated with phorbol-12-myristate-13-acetate (PMA), a potent activator of PKC, followed by analysis of dopamine-mediated receptor activation using whole cell cAMP assays. Unpredictably, PKC activation had completely opposite effects on D1 and D5 receptor signaling. PMA dramatically augmented agonist-evoked D1 receptor signaling, whereas constitutive and dopamine-mediated D5 receptor activation were rapidly blunted. RT-PCR and immunoblotting analyses showed that phorbol ester-regulated PKC isozymes (conventional: a, bI, bII, c; novel: d, e, g, h) and protein kinase D (PKCl) are expressed in HEK293 cells. PMA appears to mediate these contrasting effects through the activation of Ca 2+ -independent novel PKC isoforms as revealed by specific inhibitors, bisindolylmaleimide I, Gö 6976, and Gö 6983. The finding that cross-talk between PKC and cAMP pathways can produce such opposite outcomes following the activation of structurally similar D1-like receptor subtypes is novel and further strengthens the view that D1 and D5 receptors serve distinct functions in the mammalian nervous and endocrine systems.

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In this study, a cleavable signal peptide fused to the enhanced green fluorescent protein (EGFP) was tagged to the extracellular N-terminus of the human dopamine D2 receptor short and long isoforms (D2S and D2L). Ligand-binding properties of EGFP-tagged receptors were essentially unchanged in comparison to their respective wild-type receptors. The dopamine-mediated activation of both EGFP-D2 isoforms generated a robust inhibition of adenylyl cyclase type 5 in intact cells. In addition, the receptor density of EGFP-D2S and EGFP-D2L in transfected human embryonic kidney 293 (HEK293) cells was not altered when compared to cells transfected with the untagged D2S and D2L. However, the receptor densities of untagged and EGFP-tagged D2L were significantly lower in comparison to those measured with D2S constructs. Moreover, the receptor density of EGFP-D2S and EGFP-D2L was differentially upregulated in cells treated with antipsychotic drugs. As assessed by confocal microscopy, both EGFP-D2 isoforms were present on the cell surface. Notably, in contrast to the predominant plasma membrane localization of EGFP- D2S, EGFP-D2L was visualized both on the plasma membrane and intracellularly before dopamine exposure. Importantly, EGFP-D2S and EGFP-D2L are robustly internalized after dopamine treatment. Overall, our data suggest a differential intracellular sorting of D2S and D2L.