Targeting the EGFR and the PKB pathway in cancer

Investigating the structural basis of piperine targeting AKT1 against prostate cancer through in vitro and molecular dynamics simulations

AkT1, significantly impacts many tumours cell functions, like transcription, apoptosis, glucose metabolism, cell proliferation, and cell migration. For tumours to develop and spread, aberrant activation of AKT1 is essential. Therefore, a major focus of molecularly targeted PCa treatment is AKT1. The present study investigates the effect of piperine compared to SDF using in-vitro studies, viz colony formation assay, comet assay and AKT1 gene expression studies using human PCa cell line PC3. A cluster of approximately at least 50 cells constitutes a colony. The clonogenic assay showed that the number and size of colonies significantly decreased when treated with compounds (SDF and piperine) in comparison to the untreated cells which effectively proliferated to form more colonies. Piperine treatment showed significant inhibition of colony formation than SDF. Effective genotoxicity was observed in piperine-treated PC3 cells with an increased Tail length of 120 µm and it was moderately observed in SDF with a Tail length of 30 µm treated on PC3 cells. The control group did not show any considerable genotoxicity with a Tail length of 6 µm. Our data, both in vitro and in silico, suggested that piperine would be a good starting point for developing novel drugs for the treatment of PCa. The downstream functions of Akt1 may be inhibited by these effects, which could impede the proliferation of PCa cells. High stability of the piperine-AKT1 complex was found by the MD simulation. Higher hydrophilic residues like Lys268 and Ser205 at the active pocket may be the cause of the binding stability. Overall, the observed results confirmed the anti-PCa effect of piperine by causing effective DNA damage and proved to be genotoxic in nature against the human PCa. These effects may impede the downstream activities of Akt1 and result in PCa cell growth regression.Communicated by Ramaswamy H. Sarma.

Traditional Chinese medicine for colorectal cancer treatment: potential targets and mechanisms of action

Colorectal cancer (CRC) is a disease with complex pathogenesis, it is prone to metastasis, and its development involves abnormalities in multiple signaling pathways. Surgery, chemotherapy, radiotherapy, target therapy, and immunotherapy remain the main treatments for CRC, but improvement in the overall survival rate and quality of life is urgently needed. Traditional Chinese medicine (TCM) has a long history of preventing and treating CRC. It could affect CRC cell proliferation, apoptosis, cell cycle, migration, invasion, autophagy, epithelial-mesenchymal transition, angiogenesis, and chemoresistance by regulating multiple signaling pathways, such as PI3K/Akt, NF-κB, MAPK, Wnt/β-catenin, epidermal growth factor receptors, p53, TGF-β, mTOR, Hedgehog, and immunomodulatory signaling pathways. In this paper, the main signaling pathways and potential targets of TCM and its active ingredients in the treatment of CRC were systematically summarized, providing a theoretical basis for treating CRC with TCM and new ideas for further exploring the pathogenesis of CRC and developing new anti-CRC drugs.

Analyzing Kinase Similarity in Small Molecule and Protein Structural Space to Explore the Limits of Multi-Target Screening

While selective inhibition is one of the key assets for a small molecule drug, many diseases can only be tackled by simultaneous inhibition of several proteins. An example where achieving selectivity is especially challenging are ligands targeting human kinases. This difficulty arises from the high structural conservation of the kinase ATP binding sites, the area targeted by most inhibitors. We investigated the possibility to identify novel small molecule ligands with pre-defined binding profiles for a series of kinase targets and anti-targets by in silico docking. The candidate ligands originating from these calculations were assayed to determine their experimental binding profiles. Compared to previous studies, the acquired hit rates were low in this specific setup, which aimed at not only selecting multi-target kinase ligands, but also designing out binding to anti-targets. Specifically, only a single profiled substance could be verified as a sub-micromolar, dual-specific EGFR/ErbB2 ligand that indeed avoided its selected anti-target BRAF. We subsequently re-analyzed our target choice and in silico strategy based on these findings, with a particular emphasis on the hit rates that can be expected from a given target combination. To that end, we supplemented the structure-based docking calculations with bioinformatic considerations of binding pocket sequence and structure similarity as well as ligand-centric comparisons of kinases. Taken together, our results provide a multi-faceted picture of how pocket space can determine the success of docking in multi-target drug discovery efforts.

Phosphorylation Sites in Protein Kinases and Phosphatases Regulated by Formyl Peptide Receptor 2 Signaling

FPR1, FPR2, and FPR3 are members of Formyl Peptides Receptors (FPRs) family belonging to the GPCR superfamily. FPR2 is a low affinity receptor for formyl peptides and it is considered the most promiscuous member of this family. Intracellular signaling cascades triggered by FPRs include the activation of different protein kinases and phosphatase, as well as tyrosine kinase receptors transactivation. Protein kinases and phosphatases act coordinately and any impairment of their activation or regulation represents one of the most common causes of several human diseases. Several phospho-sites has been identified in protein kinases and phosphatases, whose role may be to expand the repertoire of molecular mechanisms of regulation or may be necessary for fine-tuning of switch properties. We previously performed a phospho-proteomic analysis in FPR2-stimulated cells that revealed, among other things, not yet identified phospho-sites on six protein kinases and one protein phosphatase. Herein, we discuss on the selective phosphorylation of Serine/Threonine-protein kinase N2, Serine/Threonine-protein kinase PRP4 homolog, Serine/Threonine-protein kinase MARK2, Serine/Threonine-protein kinase PAK4, Serine/Threonine-protein kinase 10, Dual specificity mitogen-activated protein kinase kinase 2, and Protein phosphatase 1 regulatory subunit 14A, triggered by FPR2 stimulation. We also describe the putative FPR2-dependent signaling cascades upstream to these specific phospho-sites.

An Activating Mutation in ERK Causes Hyperplastic Tumors in a scribble Mutant Tissue in Drosophila

Receptor tyrosine kinase signaling plays prominent roles in tumorigenesis, and activating oncogenic point mutations in the core pathway components Ras, Raf, or MEK are prevalent in many types of cancer. Intriguingly, however, analogous oncogenic mutations in the downstream effector kinase ERK have not been described or validated in vivo To determine if a point mutation could render ERK intrinsically active and oncogenic, we have assayed in Drosophila the effects of a mutation that confers constitutive activity upon a yeast ERK ortholog and has also been identified in a few human tumors. Our analyses indicate that a fly ERK ortholog harboring this mutation alone (RolledR80S), and more so in conjunction with the known sevenmaker mutation (RolledR80S+D334N), suppresses multiple phenotypes caused by loss of Ras-Raf-MEK pathway activity, consistent with an intrinsic activity that is independent of upstream signaling. Moreover, expression of RolledR80S and RolledR80S+D334N induces tissue overgrowth in an established Drosophila cancer model. Our findings thus demonstrate that activating mutations can bestow ERK with pro-proliferative, tumorigenic capabilities and suggest that Drosophila represents an effective experimental system for determining the oncogenicity of ERK mutants and their response to therapy.

Oncogenic DIRAS3 promotes malignant phenotypes of glioma by activating EGFR-AKT signaling

Epidermal growth factor receptor (EGFR)-Akt signaling cascade activation plays a pivotal role in gliomas malignant phenotype, especially in Classical and Mesenchymal subtype gliomas. However, the molecules and mechanisms underlying regulate and maintain the activation of EGFR-AKT signaling remains unclear. Previously reports showed that DIRAS3 inhibits cell proliferation and induces autophagy in ovarian, breast, lung and prostate cancers, which is heterozygosity loss or down-regulated in aforementioned cancers and functionally as a tumor suppressor, whereas the role of DIRAS3 in glioma is still veiled. Here, in this study, we investigated the biological function and role of DIRAS3 in gliomas, and found that DIRAS3 is up-regulated in gliomas and is positively correlated with poor prognosis of glioma patients, meanwhile, over-expressed DIRAS3 promotes glioma cells proliferation and invasion. Further mechanistic study showed that the expression level of DIRAS3 in Classical and Mesenchymal subtype GBMs is higher, and over-expression of DIRAS3 promotes EGFR-AKT signaling activation at the downstream of EGFR and increases AKT phosphorylation, meanwhile suppression of AKT by MK-2206 reverses the tumor promoting function of DIRAS3. Taken together, these findings reveal a novel oncogenic role of DIRAS3 in the development and progression of glioma, which suggest that DIRAS3 could serve as a potential diagnostic marker and a promising therapeutic target of gliomas.

TIMP-1 is under regulation of the EGF signaling axis and promotes an aggressive phenotype in KRAS-mutated colorectal cancer cells: a potential novel approach to the treatment of metastatic colorectal cancer

It is now widely accepted that therapeutic antibodies targeting epidermal growth factor receptor (EGFR) can have efficacy in KRAS wild-type advanced colorectal cancer (CRC) patients. What remains to be ascertained is whether a subgroup of KRAS-mutated CRC patients might not also derive benefit from EGFR inhibitors. Metalloproteinase inhibitor 1 (TIMP-1) is a pleiotropic factor predictive of survival outcome of CRC patients. Levels of TIMP-1 were measured in pre-treatment plasma samples (n = 426) of metastatic CRC patients randomized to Nordic FLOX (5-fluorouracil and oxaliplatin) +/− cetuximab (NORDIC VII study). Multivariate analysis demonstrated a significant interaction between plasma TIMP-1 protein levels, KRAS status and treatment with patients bearing KRAS mutated tumors and high TIMP-1 plasma level (> 3rd quartile) showing a significantly longer overall survival if treated with cetuximab (HR, 0.48; 95% CI, 0.25 to 0.93). To gain mechanistic insights into this association we analyzed a set of five different CRC cell lines. We show here that EGFR signaling induces TIMP-1 expression in CRC cells, and that TIMP-1 promotes a more aggressive behavior, specifically in KRAS mutated cells. The two sets of data, clinical and in vitro, are complementary and support each other, lending strength to our contention that TIMP- 1 plasma levels can identify a subset of patients with KRAS-mutated metastatic CRC that will have benefit from EGFR-inhibition therapy.

Dehydroglyasperin D Inhibits the Proliferation of HT-29 Human Colorectal Cancer Cells Through Direct Interaction With Phosphatidylinositol 3-kinase

Background:

Despite recent advances in therapy, colorectal cancer still has a grim prognosis. Although licorice has been used in East Asian traditional medicine, the molecular properties of its constituents including dehydroglyasperin D (DHGA-D) remain unknown. We sought to evaluate the inhibitory effect of DHGA-D on colorectal cancer cell proliferation and identify the primary signaling molecule targeted by DHGA-D.

Methods:

We evaluated anchorage-dependent and -independent cell growth in HT-29 human colorectal adenocarcinoma cells. The target protein of DHGA-D was identified by Western blot analysis with a specific antibody, and direct interaction between DHGA-D and the target protein was confirmed by kinase and pull-down assays. Cell cycle analysis by flow cytometry and further Western blot analysis was performed to identify the signaling pathway involved.

Results:

DHGA-D significantly suppressed anchorage-dependent and -independent HT-29 colorectal cancer cell proliferation. DHGA-D directly suppressed phosphatidylinositol 3-kinase (PI3K) activity and subsequent Akt phosphorylation and bound to the p110 subunit of PI3K. DHGA-D also significantly induced G1 cell cycle arrest, together with the suppression of glycogen synthase kinase 3β and retinoblastoma phosphorylation and cyclin D1 expression.

Conclusions:

DHGA-D has potent anticancer activity and targets PI3K in human colorectal adenocarcinoma HT-29 cells. To our knowledge, this is the first report to detail the molecular basis of DHGA-D in suppressing colorectal cancer cell growth.

Growth factor expression mediates resistance to EGFR inhibitors in head and neck squamous cell carcinomas

OBJECTIVES

Epidermal growth factor receptor (EGFR)-targeted therapy is frequently used in the treatment of advanced head and neck squamous cell carcinoma (HNSCC). However, constitutive or acquired resistance is common and underlying resistance mechanisms remain poorly understood. We investigated the expression levels of growth factors (GF) in tumor-associated stroma and tumor from HNSCC patients and determined the influence of GFs on EGFR inhibitor efficacy in vitro.

MATERIALS AND METHODS

The Chicago HNC Genomic Cohort (CHGC) was queried for GF and receptor tyrosine kinase (RTK) expression. Viability assays were used to evaluate the effect of EGFR inhibition (gefitinib), GF treatment, or both in HNSCC cell lines. Caspase-based assays were used to measure apoptotic activity. Expression of RTKs was determined and correlated with GF treatment effects.

RESULTS

Amphiregulin (AREG), transforming growth factor (TGFβ1), insulin like growth factor (IGF1), fibroblast growth factors (FGF1/FGF2) and the corresponding RTKs were highly expressed in 30-50% of HNSCC, and expression was usually concurrent. While EGFR inhibition was markedly efficacious in HNC cell lines (HN5/HN13/H400/SCC61), co-treatment with most GFs increased viability up to 100%. Only TGFβ1 treatment was additive to EGFR inhibition. GFs also reduced apoptotic effects of EGFR inhibition. RTK expression showed strong positive correlation with respective GF treatment effect for IGF1-IGF1R, less strong for HGF-MET/AREG-EGFR and a moderate negative correlation for TGFβ1-TGFBR1/2.

CONCLUSION

High expression of GFs/RTKs occurs in HNSCC. Co-expression is common. GF expression contributes to EGFR inhibition resistance in our model system, and may be a common mechanism of constitutive or acquired resistance to EGFR inhibition in HNSCC.

Shikonin and its derivatives inhibit the epidermal growth factor receptor signaling and synergistically kill glioblastoma cells in combination with erlotinib

Overexpression and mutation of the epidermal growth factor receptor (EGFR) gene play a causal role in tumorigenesis and resistance to treatment of glioblastoma (GBM). EGFR inhibitors such as erlotinib are currently used for the treatment of GBM; however, their efficacy has been limited due to drug resistance. New treatment strategies are therefore urgently needed. Shikonin, a natural naphthoquinone, induces both apoptosis and necroptosis in human glioma cells, but the effectiveness of erlotinib-shikonin combination treatment as well as the underlying molecular mechanisms is unknown yet. In this study, we investigated erlotinib in combination with shikonin and 14 shikonin derivatives in parental U87MG and transfected U87MG.ΔEGFR GBM cells. Most of the shikonin derivatives revealed strong cytotoxicity. Shikonin together with five other derivatives, namely deoxyshikonin, isobutyrylshikonin, acetylshikonin, β,β-dimethylacrylshikonin and acetylalkannin showed synergistic cytotoxicity toward U87MG.ΔEGFR in combination with erlotinib. Moreover, the combined cytotoxic effect of shikonin and erlotinib was further confirmed with another three EGFR-expressing cell lines, BS153, A431 and DK-MG. Shikonin not only dose-dependently inhibited EGFR phosphorylation and decreased phosphorylation of EGFR downstream molecules, including AKT, P44/42MAPK and PLCγ1, but also together with erlotinib synergistically inhibited ΔEGFR phosphorylation in U87MG.ΔEGFR cells as determined by Loewe additivity and Bliss independence drug interaction models. These results suggest that the combination of erlotinib with shikonin or its derivatives might be a potential strategy to overcome drug resistance to erlotinib.

Survival-apoptosis associated signaling in GNE myopathy-cultured myoblasts

GNE Myopathy (GNEM) is a neuromuscular disorder caused by mutations in the GNE gene. It is a slowly progressive distal and proximal muscle weakness sparing the quadriceps. In this study, we applied our model of mutated M743T GNE enzyme skeletal muscle-cultured myoblasts and paired healthy controls to depict the pattern of signaling proteins controlling survival and/or apoptosis of the PI3K/AKT, BCL2, ARTS/XIAP pathways, examined the effects of metabolic changes/stimuli on their expression and activation, and their potential role in GNEM. Immunoblot analysis of the GNEM myoblasts indicated a notable increased level of activated PTEN and PDK1 and a trend of relative differences in the expression and activation of the examined signaling molecules with variability among the cultures. ANOVA analysis showed a highly significant interaction between the level of PTEN and the patients groups. In parallel, the interaction between the level of BCL2, BAX and PTEN with the specific PI3K/AKT inhibitor-LY294002 was highly significant for BCL2 and nearly significant for PTEN and BAX. The pattern of the ARTS/XIAP signaling proteins of GNEM and the paired controls was variable, with no significant differences between the two cell types. The response of the GNEM cells to the metabolic changes/stimuli: serum depletion and insulin challenge, as indicated by expression of selected signaling proteins, was variable and similar to the control cells. Taken together, our observations provide a clearer insight into specific signaling molecules influencing growth and survival of GNEM muscle cells.

Phase I safety and pharmacokinetic study of the PI3K/mTOR inhibitor SAR245409 (XL765) in combination with erlotinib in patients with advanced solid tumors

INTRODUCTION

The primary objectives of this phase I study were to evaluate the safety and maximum tolerated dose (MTD) of SAR245409, a pan-class I phosphatidylinositol 3-kinase (PI3K)/mammalian target of rapamycin inhibitor, combined with erlotinib in patients with advanced solid tumors.

METHODS

Forty-six patients with advanced solid tumors were enrolled. Patients with lung cancer (n = 37) had received an epidermal growth factor receptor (EGFR) inhibitor before study entry. SAR245409 30, 50, 70, or 90 mg once daily (QD) or 20 or 30 mg twice daily (BID) was administered, in combination with erlotinib 100 mg QD, in 28-day cycles. Dose escalation of SAR245409 followed a standard 3 + 3 design. Patients were evaluated for adverse events (AEs). Additional evaluations included pharmacokinetics, pharmacodynamic effects on PI3K and EGFR/mitogen-activated protein kinase signaling pathways in tumor and skin samples, and tumor response.

RESULTS

The MTDs of SAR245409, in combination with erlotinib 100 mg QD, were 70 mg QD and 20 mg BID. The most frequently reported treatment-related AEs (any grade) were diarrhea (35%), rash (35%), and nausea (28%). No treatment-related AE occurred at grade 3/4 in more than one patient (2.2%). No major pharmacokinetic interaction between SAR245409 and erlotinib was noted. Suppression of PI3K and EGFR/mitogen-activated protein kinase signaling pathway biomarkers was observed in skin and tumor samples. Stable disease was the best overall response reported, occurring in 12 of 32 (37.5%) evaluable patients.

CONCLUSION

MTDs of SAR245409 and erlotinib were below the single-agent doses of either agent, despite the lack of major pharmacokinetic interaction.

An in silico protocol for identifying mTOR inhibitors from natural products

The mammalian target of rapamycin (mTOR) is an anti-cancer target. In this study, we propose an in silico protocol for identifying mTOR inhibitors from the ZINC natural product database. First, a three-dimensional quantitative structure-activity relationship pharmacophore model was built based on known mTOR inhibitors. The model was validated with an external test set, Fischer's randomization method, a decoy set and pharmacophore mapping conformation testing. The results showed that the model can predict the mTOR inhibition activity of the tested compounds. Virtual screening was performed based on the best pharmacophore model, and the results were then filtered using a molecular docking approach. In addition, molecular mechanics/generalized born surface area analysis was used to refine the selected candidates. The top 20 natural products were selected as potential mTOR inhibitors, and their structural scaffolds could serve as building blocks in designing drug-like molecules for mTOR inhibition.

EGFR phosphorylation of DCBLD2 recruits TRAF6 and stimulates AKT-promoted tumorigenesis

Aberrant activation of EGFR in human cancers promotes tumorigenesis through stimulation of AKT signaling. Here, we determined that the discoidina neuropilin-like membrane protein DCBLD2 is upregulated in clinical specimens of glioblastomas and head and neck cancers (HNCs) and is required for EGFR-stimulated tumorigenesis. In multiple cancer cell lines, EGFR activated phosphorylation of tyrosine 750 (Y750) of DCBLD2, which is located within a recently identified binding motif for TNF receptor-associated factor 6 (TRAF6). Consequently, phosphorylation of DCBLD2 Y750 recruited TRAF6, leading to increased TRAF6 E3 ubiquitin ligase activity and subsequent activation of AKT, thereby enhancing EGFR-driven tumorigenesis. Moreover, evaluation of patient samples of gliomas and HNCs revealed an association among EGFR activation, DCBLD2 phosphorylation, and poor prognoses. Together, our findings uncover a pathway in which DCBLD2 functions as a signal relay for oncogenic EGFR signaling to promote tumorigenesis and suggest DCBLD2 and TRAF6 as potential therapeutic targets for human cancers that are associated with EGFR activation.

Characterization of the activity of the PI3K/mTOR inhibitor XL765 (SAR245409) in tumor models with diverse genetic alterations affecting the PI3K pathway

Activation of the PI3K (phosphoinositide 3-kinase) pathway is a frequent occurrence in human tumors and is thought to promote growth, survival, and resistance to diverse therapies. Here, we report pharmacologic characterization of the pyridopyrimidinone derivative XL765 (SAR245409), a potent and highly selective pan inhibitor of class I PI3Ks (α, β, γ, and δ) with activity against mTOR. Broad kinase selectivity profiling of >130 protein kinases revealed that XL765 is highly selective for class I PI3Ks and mTOR over other kinases. In cellular assays, XL765 inhibits the formation of PIP(3) in the membrane, and inhibits phosphorylation of AKT, p70S6K, and S6 phosphorylation in multiple tumor cell lines with different genetic alterations affecting the PI3K pathway. In a panel of tumor cell lines, XL765 inhibits proliferation with a wide range of potencies, with evidence of an impact of genotype on sensitivity. In mouse xenograft models, oral administration of XL765 results in dose-dependent inhibition of phosphorylation of AKT, p70S6K, and S6 with a duration of action of approximately 24 hours. Repeat dose administration of XL765 results in significant tumor growth inhibition in multiple human xenograft models in nude mice that is associated with antiproliferative, antiangiogenic, and proapoptotic effects.

Plasma YKL-40 in patients with metastatic colorectal cancer treated with first line oxaliplatin-based regimen with or without cetuximab: RESULTS from the NORDIC VII Study

Background

We aim to test the hypothesis that high plasma YKL-40 is associated with short progression-free survival (PFS) and overall survival (OS) in patients with metastatic colorectal cancer (mCRC) treated with first-line oxaliplatin and 5-flourouracil with or without cetuximab.

Patients and Methods

A total of 566 patients in the NORDIC VII Study were randomized 1∶1∶1 to arm A (Nordic FLOX), arm B (Nordic FLOX + cetuximab), or arm C (Nordic FLOX + cetuximab for 16 weeks followed by cetuximab alone as maintenance therapy). Pretreatment plasma samples were available from 510 patients. Plasma YKL-40 was determined by ELISA and dichotomized according to the age-corrected 95% YKL-40 level in 3130 healthy subjects.

Results

Pretreatment plasma YKL-40 was elevated in 204 patients (40%), and median YKL-40 was higher in patients with mCRC than in healthy subjects (age adjusted, P<0.001). Patients with elevated YKL-40 had shorter PFS than patients with normal YKL-40 (7.5 vs. 8.2 months; hazard ratio (HR)  = 1.27 95% confidence interval (CI) 1.05–1.53 P = 0.013) and shorter OS (16.8 vs. 23.9 months; HR = 1.33, 1.04–1.69, P = 0.024). Multivariate Cox analysis demonstrated that elevated pretreatment YKL-40 was an independent biomarker of short OS (HR = 1.12, 1.01–1.25, P = 0.033). The ratio of the updated plasma YKL-40 (i.e. level after 1, 2, 8 weeks of treatment, and at end of treatment compared to the baseline level) was associated with OS (HR = 1.27, 1.06–1.52, P = 0.011).

Conclusions

Plasma YKL-40 is an independent prognostic biomarker in patients with mCRC treated with first-line oxaliplatin-based therapy alone or combined with cetuximab.

The role of epidermal growth factor receptor in prognosis and treatment of gastric cancer

Despite tremendous efforts to reduce deaths due to gastric cancer, it represents the second leading cause of cancer-related deaths worldwide. EGF receptor (EGFR) plays important roles in gastric carcinogenesis by regulation of cell cycle, angiogenesis and apoptosis. This review evaluates the functions, mechanisms and clinical uses of EGFR in gastric cancer. Although EGFR targeted single therapy shows limited effect, the combination of EGFR targeted agents with traditional chemotherapy regimens may bring about important progress in cancer therapy. More clinical trials should be performed to clarify both the prognostic and therapeutic value of EGFR in gastric cancer.

Phase I safety, pharmacokinetic, and pharmacodynamic study of SAR245408 (XL147), an oral pan-class I PI3K inhibitor, in patients with advanced solid tumors

PURPOSE

SAR245408 is a pan-class I phosphoinositide 3-kinase (PI3K) inhibitor. This phase I study determined the maximum tolerated dose (MTD) of two dosing schedules [first 21 days of a 28-day period (21/7) and continuous once-daily dosing (CDD)], pharmacokinetic and pharmacodynamic profiles, and preliminary efficacy.

EXPERIMENTAL DESIGN

Patients with refractory advanced solid malignancies were treated with SAR245408 using a 3 + 3 design. Pharmacokinetic parameters were determined after single and repeated doses. Pharmacodynamic effects were evaluated in plasma, hair sheath cells, and skin and tumor biopsies.

RESULTS

Sixty-nine patients were enrolled. The MTD of both schedules was 600 mg; dose-limiting toxicities were maculopapular rash and hypersensitivity reaction. The most frequent drug-related adverse events included dermatologic toxicities, diarrhea, nausea, and decreased appetite. Plasma pharmacokinetics showed a median time to maximum concentration of 8 to 22 hours, mean terminal elimination half-life of 70 to 88 hours, and 5- to 13-fold accumulation after daily dosing (first cycle). Steady-state concentration was reached between days 15 and 21, and exposure was dose-proportional with doses up to 400 mg. SAR245408 inhibited the PI3K pathway (∼40%-80% reduction in phosphorylation of AKT, PRAS40, 4EBP1, and S6 in tumor and surrogate tissues) and, unexpectedly, also inhibited the MEK/ERK pathway. A partial response was seen in one patient with advanced non-small cell lung cancer. Eight patients were progression-free at 6 months. Pharmacodynamic and clinical activity were observed irrespective of tumor PI3K pathway molecular alterations.

CONCLUSIONS

SAR245408 was tolerable at doses associated with PI3K pathway inhibition. The recommended phase II dose of the capsule formulation is 600 mg administered orally with CDD.

The P110 subunit of PI3-K is a therapeutic target of acacetin in skin cancer

The identification of primary molecular targets of cancer-preventive phytochemicals is essential for a comprehensive understanding of their mechanism of action. In the present study, we investigated the chemopreventive effects and molecular targets of acacetin, a flavonoid found in Robinia p seudoacacia, also known as black locust. Acacetin treatment significantly suppressed epidermal growth factor (EGF)-induced cell transformation. Immunoblot analysis revealed that acacetin attenuated EGF-induced phosphorylation of Akt and p70(S6K), which are downstream effectors of phosphatidylinositol 3-kinase (PI3-K). An immunoprecipitation kinase assay of PI3-K and pull-down assay results demonstrated that acacetin substantially inhibits PI3-K activity by direct physical binding. Acacetin exhibited stronger inhibitory effects against anchorage-dependent and -independent cell growth in cells expressing higher PI3-K activity compared with those exhibiting relatively low PI3-K activity. Binding assay data combined with computational modeling suggest that acacetin binds in an adenosine triphosphate (ATP)-competitive manner with the p110α subunit of PI3-K and interacts with Val828, Glu826, Asp911, Trp760, Ile777, Ile825, Tyr813, Ile910 and Met900 residues. Acacetin was also found to significantly reduce SK-MEL-28 tumor growth and Akt phosphorylation in vivo. Taken together, these results indicate that acacetin is an ATP-competitive PI3-K inhibitor and a promising agent for melanoma chemoprevention.

Akt2 and acid ceramidase cooperate to induce cell invasion and resistance to apoptosis

Both Akt 2 and acid ceramidase (ASAH1) are found aberrantly overexpressed in cancer cells, but whether these two enzymes cooperate to induce malignant transformation is not known. We found that in immortalized, non-transformed cells, ectopic co-expression of Akt2 and ASAH1 is significantly more effective than expression of each gene alone at inducing cell invasion and at conferring resistance to apoptosis. Consistent with these observations, siRNA-mediated depletion of both Akt2 and ASAH1 is much more potent than depleting each alone at inhibiting cell viability/proliferation and cell invasion. Furthermore, pharmacological inhibitors of Akt (TCN or MK-2206) and ASAH1 (B13) synergize to inhibit cell viability/proliferation, and combinations of these drugs are more effective than single-agent treatments at inhibiting cell invasion. Taken together, the results suggest that these two enzymes cooperate to induce malignant transformation and warrant further preclinical studies to evaluate the potential of combining inhibitors of Akt and ASAH1 to treat cancer.

EGF-induced centrosome separation promotes mitotic progression and cell survival

Timely and accurate assembly of the mitotic spindle is critical for the faithful segregation of chromosomes, and centrosome separation is a key step in this process. The timing of centrosome separation varies dramatically between cell types; however, the mechanisms responsible for these differences and its significance are unclear. Here, we show that activation of epidermal growth factor receptor (EGFR) signaling determines the timing of centrosome separation. Premature separation of centrosomes decreases the requirement for the major mitotic kinesin Eg5 for spindle assembly, accelerates mitosis, and decreases the rate of chromosome missegregation. Importantly, EGF stimulation impacts upon centrosome separation and mitotic progression to different degrees in different cell lines. Cells with high EGFR levels fail to arrest in mitosis upon Eg5 inhibition. This has important implications for cancer therapy because cells with high centrosomal response to EGF are more susceptible to combinatorial inhibition of EGFR and Eg5.

Investigation of radiation-induced transcriptome profile of radioresistant non-small cell lung cancer A549 cells using RNA-seq

Radioresistance is a main impediment to effective radiotherapy for non-small cell lung cancer (NSCLC). Despite several experimental and clinical studies of resistance to radiation, the precise mechanism of radioresistance in NSCLC cells and tissues still remains unclear. This result could be explained by limitation of previous researches such as a partial understanding of the cellular radioresistance mechanism at a single molecule level. In this study, we aimed to investigate extensive radiation responses in radioresistant NSCLC cells and to identify radioresistance-associating factors. For the first time, using RNA-seq, a massive sequencing-based approach, we examined whole-transcriptome alteration in radioresistant NSCLC A549 cells under irradiation, and verified significant radiation-altered genes and their chromosome distribution patterns. Also, bioinformatic approaches (GO analysis and IPA) were performed to characterize the radiation responses in radioresistant A549 cells. We found that epithelial–mesenchymal transition (EMT), migration and inflammatory processes could be meaningfully related to regulation of radiation responses in radioresistant A549 cells. Based on the results of bioinformatic analysis for the radiation-induced transcriptome alteration, we selected seven significant radiation-altered genes (SESN2, FN1, TRAF4, CDKN1A, COX-2, DDB2 and FDXR) and then compared radiation effects in two types of NSCLC cells with different radiosensitivity (radioresistant A549 cells and radiosensitive NCI-H460 cells). Interestingly, under irradiation, COX-2 showed the most significant difference in mRNA and protein expression between A549 and NCI-H460 cells. IR-induced increase of COX-2 expression was appeared only in radioresistant A549 cells. Collectively, we suggest that COX-2 (also known as prostaglandin-endoperoxide synthase 2 (PTGS2)) could have possibility as a putative biomarker for radioresistance in NSCLC cells.

Tas13D inhibits growth of SMMC-7721 cell via suppression VEGF and EGF expression

OBJECTIVE

Taspine, isolated from Radix et Rhizoma Leonticis has demosntrated potential proctiective effects against cancer. Tas13D, a novel taspine derivative synthetized by structure-based drug design, have been shown to possess interesting biological and pharmacological activities. The current study was designed to evaluate its antiproliferative activity and underlying mechanisms.

METHODS

Antiproliferative activity of tas13D was evaluated by xenograft in athymic mice in vivo, and by 3-(4, 5-dimethylthiazol-2-yl)-2, 5-diphenyltetrazolium bromide (MTT) and cell migration assays with human liver cancer (SMMC-7721) cell lines in vitro. Docking between tas13D and VEGFR and EGFR was studied by with a Sybyl/Surflex module. VEGF and EGF and their receptor expression was determined by ELISA and real-time PCR methods, respectively.

RESULTS

Our present study showed that tas13D inhibited SMMC-7721 xenograft tumor growth, bound tightly with the active site of kinase domains of EGFR and VEGFR, and reduced SMMC-7721 cell proliferation (IC=34.7 μmol/L) and migration compared to negative controls. VEGF and EGF mRNAs were significantly reduced by tas13D treatment in a dose-dependent manner, along with VEGF and EGF production.

CONCLUSION

The obtained results suggest that tas13D inhibits tumor growth and cell proliferation by inhibiting cell migration, downregulating mRNA expression of VEGF and EGF, and decreasing angiogenic factor production. Tas13D deserves further consideration as a chemotherapeutic agent.

Tyrosine kinase inhibitors: views of selectivity, sensitivity, and clinical performance

With the manufacture of imatinib, researchers introduced tyrosine kinase inhibitors (TKIs) into the clinical setting in 2000 to treat cancers; approximately fifteen other TKIs soon followed. Imatinib remains the most successful agent, whereas all the others have had modest effects on the cancers that they target. The current challenge is to identify the agents that need to be combined with TKIs to maximize their efficacy. One of the most promising approaches is to combine immune therapy with TKI treatment. In this review, the therapeutic potential of TKIs for treatment is discussed.

Nucleic acid therapeutics: concepts for targeted delivery to solid tumors

Solid tumors form a heterogeneous group of diseases, although common features such as hyperproliferation, overexpression of certain growth factor receptors and deregulated vessel formation including leaky vasculature give the opportunity to target macromolecular drug and nucleic acid carriers to tumor tissue. Similar to other macromolecular drugs, nucleic acid carriers have to be designed to enable tumor targeting after systemic injection. Chemical modification of nucleic acids makes them resistant towards enzymatic degradation. Cationic lipids or polycations condense nucleic acids into small, virus-like structures and the surface modification with hydrophilic polymers allows passive accumulation in tumor tissue; tumor cell binding ligands allow cellular targeting. To avoid toxic side effects, biodegradable and biocompatible carriers were designed. The design of thermoresponsive gene carriers allowed their selective tumor accumulation by locoregional hyperthermia. As a therapeutic concept, tumor-specific delivery of antitumoral RNA was realized in an orthotopic brain tumor model. The combination of gene- and radio-therapy enabled selective accumulation of radionuclides in tumors and boosted antitumoral effects. Hence, combining a smart delivery concept for nucleic acids with a suitable therapeutic strategy will allow successful treatment of otherwise incurable malignant diseases.

Chk1 phosphorylates the tumour suppressor Mig-6, regulating the activation of EGF signalling

The tumour suppressor gene product Mig-6 acts as an inhibitor of epidermal growth factor (EGF) signalling. However, its posttranslational modifications and regulatory mechanisms have not been elucidated. Here, we investigated the phosphorylation of human Mig-6 and found that Chk1 phosphorylated Mig-6 in vivo as well as in vitro. Moreover, EGF stimulation promoted phosphorylation of Mig-6 without DNA damage and the phosphorylation was inhibited by depletion of Chk1. EGF also increased Ser280-phosphorylated Chk1, a cytoplasmic-tethering form, via PI3K pathway. Mass spectrometric analyses suggested that Ser 251 of Mig-6 was a major phosphorylation site by Chk1 in vitro and in vivo. Substitution of Ser 251 to alanine increased inhibitory activity of Mig-6 against EGF receptor (EGFR) activation. Moreover, EGF-dependent activation of EGFR and cell growth were inhibited by Chk1 depletion, and were rescued by co-depletion of Mig-6. Our results suggest that Chk1 phosphorylates Mig-6 on Ser 251, resulting in the inhibition of Mig-6, and that Chk1 acts as a positive regulator of EGF signalling. This is a novel function of Chk1.

Loss of the ceramide transfer protein augments EGF receptor signaling in breast cancer

Triple-negative breast cancers (TNBC) are especially refractory to treatment due to their negative hormone receptor and ErbB2/HER2 status. Therefore, the identification of cancer-associated deregulated signaling pathways is necessary to develop improved targeted therapies. Here, we show that expression of the ceramide transfer protein CERT is reduced in TNBCs. CERT transfers ceramide from the endoplasmic reticulum to the Golgi complex for conversion into sphingomyelin (SM). We provide evidence that by regulating cellular SM levels, CERT determines the signaling output of the EGF receptor (EGFR/ErbB1), which is upregulated in approximately 70% of TNBCs. CERT downregulation in breast cancer cells enhanced ErbB1 lateral mobility, ligand-induced autophosphorylation, internalization, and chemotaxis. Together, our findings provide a link between lipid metabolism at the Golgi with signaling at the plasma membrane, thereby implicating CERT loss in the progression of TNBCs.

K63-linked ubiquitination in kinase activation and cancer

Ubiquitination has been demonstrated to play a pivotal role in multiple biological functions, which include cell growth, proliferation, apoptosis, DNA damage response, innate immune response, and neuronal degeneration. Although the role of ubiquitination in targeting proteins for proteasome-dependent degradation have been extensively studied and well-characterized, the critical non-proteolytic functions of ubiquitination, such as protein trafficking and kinase activation, involved in cell survival and cancer development, just start to emerge, In this review, we will summarize recent progresses in elucidating the non-proteolytic function of ubiquitination signaling in protein kinase activation and its implications in human cancers. The advancement in the understanding of the novel functions of ubiquitination in signal transduction pathways downstream of growth factor receptors may provide novel paradigms for the treatment of human cancers.

Diallyl trisulfide-induced prostate cancer cell death is associated with Akt/PKB dephosphorylation mediated by P-p66shc

Purpose

P66Shc, an isoform of adaptor proteins, is known to mediate various signals including those leading to apoptosis or cell proliferation. Previously, we have shown that diallyl trisulfide (DATS)-induced prostate cancer cell death was mediated by increased ROS formation. In this study, we investigated the role of p66Shc protein and its serine 36 phosphorylation in DATS induced decrease in prostate cancer cell viability (PC-3).

Methods

PC-3 prostate cancer cells were used in this study. Stable cell lines expressing p66ShcS36A or an empty vector have been obtained. Cell viability, concentration of ROS, changes in P-p66Shc and P-Akt and DNA damage were determined.

Results

We observed that DATS treatment increased p66Shc phosphorylation at serine 36. Importantly, the phosphorylation was abolished by JNK inhibitor SP600125. Cells expressing plasmid-encoded variant of p66ShcS36A showed much higher resistance to DATS-induced cells death. In addition to that, we observed that DATS-induced ROS formation was completely abolished in cells expressing the p66ShcS36A variant. Interestingly, SP600125 proved to prevent DATS-induced Akt inactivation. In order to confirm that the observed effect is related to phosphorylation of p66Shc, we performed experiments on a stable cell line expressing p66ShcS36A. In such cells, DATS-induced Akt dephosphorylation was significantly reduced. On the other hand, hydrogen peroxide induced Akt activation in PC-3 cells, which was abrogated in cells expressing p66ShcS36A.

Conclusions

Our results uncover a novel signaling pathway with p66Shc being indispensable for DATS-induced inactivation of Akt due to hypophosphorylation.

Inhibition of neurotensin receptor 1 selectively sensitizes prostate cancer to ionizing radiation

Radiotherapy combined with androgen depletion is generally successful for treating locally advanced prostate cancer. However, radioresistance that contributes to recurrence remains a major therapeutic problem in many patients. In this study, we define the high-affinity neurotensin receptor 1 (NTR1) as a tractable new molecular target to radiosensitize prostate cancers. The selective NTR1 antagonist SR48692 sensitized prostate cancer cells in a dose- and time-dependent manner, increasing apoptotic cell death and decreasing clonogenic survival. The observed cancer selectivity for combinations of SR48692 and radiation reflected differential expression of NTR1, which is highly expressed in prostate cancer cells but not in normal prostate epithelial cells. Radiosensitization was not affected by androgen dependence or androgen receptor expression status. NTR1 inhibition in cancer cell-attenuated epidermal growth factor receptor activation and downstream signaling, whether induced by neurotensin or ionizing radiation, establish a molecular mechanism for sensitization. Most notably, SR48692 efficiently radiosensitized PC-3M orthotopic human tumor xenografts in mice, and significantly reduced tumor burden. Taken together, our findings offer preclinical proof of concept for targeting the NTR1 receptor as a strategy to improve efficacy and outcomes of prostate cancer treatments using radiotherapy.

PF-04691502, a potent and selective oral inhibitor of PI3K and mTOR kinases with antitumor activity

Deregulation of the phosphoinositide 3-kinase (PI3K) signaling pathway such as by PTEN loss or PIK3CA mutation occurs frequently in human cancer and contributes to resistance to antitumor therapies. Inhibition of key signaling proteins in the pathway therefore represents a valuable targeting strategy for diverse cancers. PF-04691502 is an ATP-competitive PI3K/mTOR dual inhibitor, which potently inhibited recombinant class I PI3K and mTOR in biochemical assays and suppressed transformation of avian fibroblasts mediated by wild-type PI3K γ, δ, or mutant PI3Kα. In PIK3CA-mutant and PTEN-deleted cancer cell lines, PF-04691502 reduced phosphorylation of AKT T308 and AKT S473 (IC(50) of 7.5-47 nmol/L and 3.8-20 nmol/L, respectively) and inhibited cell proliferation (IC(50) of 179-313 nmol/L). PF-04691502 inhibited mTORC1 activity in cells as measured by PI3K-independent nutrient stimulated assay, with an IC(50) of 32 nmol/L and inhibited the activation of PI3K and mTOR downstream effectors including AKT, FKHRL1, PRAS40, p70S6K, 4EBP1, and S6RP. Short-term exposure to PF-04691502 predominantly inhibited PI3K, whereas mTOR inhibition persisted for 24 to 48 hours. PF-04691502 induced cell cycle G(1) arrest, concomitant with upregulation of p27 Kip1 and reduction of Rb. Antitumor activity was observed in U87 (PTEN null), SKOV3 (PIK3CA mutation), and gefitinib- and erlotinib-resistant non-small cell lung carcinoma xenografts. In summary, PF-04691502 is a potent dual PI3K/mTOR inhibitor with broad antitumor activity. PF-04691502 has entered phase I clinical trials.

Backbone cyclic peptide inhibitors of protein kinase B (PKB/Akt)

Elevated levels of activated protein kinase B (PKB/Akt) have been detected in many types of cancer. Substrate-based peptide inhibitors have the advantage of selectivity due to their extensive interactions with the kinase-specific substrate binding site but often lack necessary pharmacological properties. Chemical modifications of potent peptide inhibitors, such as cyclization, may overcome these drawbacks while maintaining potency. We present an extensive structure-activity relationship (SAR) study of a potent peptide-based PKB/Akt inhibitor. Two backbone cyclic (BC) peptide libraries with varying modes of cyclization, bridge chemistry, and ring size were synthesized and evaluated for in vitro PKB/Akt inhibition. Backbone-to-backbone urea BC peptides were more potent than N-terminus-to-backbone amide BC peptides. Several analogues were up to 10-fold more active than the parent linear peptide. Some activity trends could be rationalized using computational surface mapping of the PKB/Akt kinase catalytic domain. The novel molecules have enhanced pharmacological properties which make them promising lead candidates.

Systems pharmacology

We examine how physiology and pathophysiology are studied from a systems perspective, using high-throughput experiments and computational analysis of regulatory networks. We describe the integration of these analyses with pharmacology, which leads to new understanding of drug action and enables drug discovery for complex diseases. Network studies of drug-target relationships can serve as an indication on the general trends in the approved drugs and the drug-discovery progress. There is a growing number of targeted therapies approved and in the pipeline, which meets a new set of problems with efficacy and adverse effects. The pitfalls of these mechanistically based drugs are described, along with how a systems view of drug action is increasingly important to uncover intricate signaling mechanisms that play an important part in drug action, resistance mechanisms, and off-target effects. Computational methodologies enable the classification of drugs according to their structures and to which proteins they bind. Recent studies have combined the structural analyses with analysis of regulatory networks to make predictions about the therapeutic effects of drugs for complex diseases and possible off-target effects.

Anti-proliferative and apoptotic effects of the novel taspine derivative tas41 in the Caco-2 cell line

Taspine was screened and isolated for the first time from Radix et Rhizoma Leonticis. Tas41 is a novel taspine derivative. We investigated the effects of tas41 on proliferation of the Caco-2 cell line using 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT), a fluorescence-activated cell sorter (FACS), enzyme-linked immunosorbent assay (ELISA), reverse transcription-polymerase chain reaction (RT-PCR) and western blotting (WB). Changes in the cell cycle, apoptosis, activation of caspase-3, caspase-8 and caspase-9, and expressions of vascular endothelial growth factor (VEGF) and epidermal growth factor (EGF) were investigated after Caco-2 cells were treated with tas41. At the same time, expressions of apoptosis protein bcl-2 and bax were determined. Tas41 was found to induce apoptosis in a concentration-dependent manner as confirmed by DNA fragmentation analysis, TUNEL assay and flow cytometry. Protein and mRNA expressions of EGF, VEGF, CDK2, bcl-2 and bax were evaluated by ELISA, WB and RT-PCR. Tas41 had a better anti-proliferative effect than taspine on Caco-2 cells. A DNA ladder and apoptosis was observed, and the increased apoptotic activity by tas41 was accompanied by a decrease in the expression of VEGF protein and mRNA. The activities of caspase-3, caspase-8 and caspase-9 were significantly increased in cells treated with tas41 compared with those in the control group. In addition, protein and mRNA expressions of bcl-2 were decreased, and protein and mRNA expressions of bax were increased. These findings demonstrate that tas41 can inhibit the proliferation of, and induce apoptosis in, Caco-2 cells by activating caspase-3, caspase-8 and caspase-9, downregulating the expressions of VEGF, upregulating the ratio of bax/bcl-2.

Targeting the heparin-binding epidermal growth factor-like growth factor in ovarian cancer therapy

PURPOSE OF REVIEW

Therapeutics targeting the ErbB protein family receptors have not always yielded favorable or successful results in present cancer therapy. This review discusses the possibility of the clinical adaptation of targeting against heparin-binding epidermal growth factor-like growth factor (HB-EGF), one of the ligands of the ErbB system, in ovarian cancer therapy.

RECENT FINDINGS

We have previously described the results of studies concerning roles of HB-EGF in tumor formation in ovarian cancer. In brief, lisophosphatidic acid (LPA) and HB-EGF are predominantly expressed in advanced ovarian cancer, and LPA-induced, a disintegrin and metalloprotease-mediated ectodomain shedding of HB-EGF was found to be critical to tumor formation. We also noted that exogenous expression of HB-EGF enhanced tumor formation but inhibition blocked both extracellular signal-related kinase and serine/threonine protein kinase activation. Finally we investigated the antitumor effects of CRM197 - a specific HB-EGF inhibitor - on ovarian cancer cells by evaluating human ovarian cancer cell proliferation.

SUMMARY

We discuss alternative strategies to develop the chemotherapeutic agent based on targeting ErbB family ligands rather than their receptors. A phase I study of CRM197 for advanced ovarian cancer has already begun, which is the first approved trial of ErbB-ligand-targeted therapy. We also discuss clinical adaptations based on combination of CRM197 with other conventional chemotherapeutic agents.

From man to mouse and back again: advances in defining tumor AKTivities in vivo

AKT hyperactivation is a common event in human cancers, and inhibition of oncogenic AKT activation is a major goal of drug discovery programs. Mouse tumor models that replicate AKT activation typical of human cancers provide a powerful means by which to investigate mechanisms of oncogenic signaling, identify potential therapeutic targets and determine treatment regimes with maximal therapeutic efficacy. This Perspective highlights recent advances using in vivo studies that reveal how AKT signaling supports tumor formation, cooperates with other mutations to promote tumor progression and facilitates tumor-cell dissemination, focusing on well-characterized prostate carcinoma mouse models that are highly sensitive to AKT activation. The implications of these findings on the therapeutic targeting of AKT and potential new drug targets are also explored.

The role of the focal adhesion protein PINCH1 for the radiosensitivity of adhesion and suspension cell cultures

Focal adhesion (FA) signaling mediated by adhesion to extracellular matrix and growth factor receptors contributes to the regulation of the cellular stress response to external stimuli. Critical to focal adhesion assembly and signaling is the adapter protein PINCH1. To evaluate whether the prosurvival function of PINCH1 in radiation cell survival depends on cell adhesion, we examined PINCH1^fl/fl and PINCH1^−/− mouse embryonic fibroblasts and human cancer cell lines. Here, we found that the enhanced cellular radiosensitivity mediated by PINCH1 depletion observed under adhesion conditions is conserved when cells are irradiated under suspension conditions. This unsuspected finding could not be explained by the observed modification of adhesion and growth factor associated signaling involving FAK, Paxillin, p130^CAS, Src, AKT, GSK3β and ERK1/2 under suspension and serum withdrawal relative to adhesion conditions with serum. Our data suggest that the adapter protein PINCH1 critically participates in the regulation of the cellular radiosensitivity of normal and malignant cells similarly under adhesion and suspension conditions.

Emerging role of Lys-63 ubiquitination in protein kinase and phosphatase activation and cancer development

Ubiquitination is an important post-translational modification that has a pivotal role in numerous biological functions, such as cell growth, proliferation, apoptosis, DNA damage response, innate immune response and neuron degeneration. Although ubiquitination is thought to achieve these functions by targeting proteins for proteasome-dependent degradation, recent studies suggest that ubiquitination also has nonproteolytic functions, such as protein trafficking, kinase and phosphatase activation, which are involved in cell survival and cancer development. These progresses have advanced our current understanding of the novel functions of ubiquitination in signal transduction pathways and may provide novel paradigms for the treatment of human cancers.

Potential role of PI3K inhibitors in the treatment of breast cancer

In recent years, we have witnessed advances in the understanding of molecular events that lead to breast cancer. This knowledge allowed, among other things, the development of novel therapies that target critical pathways involved in this disease. One of these pathways is the PI3K pathway, whose signaling axis has implications on cancer cell growth, survival, motility and metabolism. In the present review, the potential role of PI3K inhibitors in the treatment of breast cancer is discussed. The fast pace of development of these drugs urges the discussion on the advantages and pitfalls of their application and impact in the future therapy of breast cancer.

Coupling of mitochondria to store-operated Ca(2+)-signaling sustains constitutive activation of protein kinase B/Akt and augments survival of malignant melanoma cells

Mitochondria are emerging as a major hub for cellular Ca(2+)-signaling, though their contribution to Ca(2+)-driven growth- and survival-promoting events in cancer is poorly understood. Here employing flow cytometry to monitor mitochondrial and cytosolic Ca(2+), we assessed trans-mitochondrial Ca(2+)-transport and store-operated Ca(2+)-influx (store-operated channels (SOC)) in malignant vs. non-malignant B16BL6 melanoma clones. Remarkably, mitochondrial Ca(2+)-fluxes measured in whole cells or in isolated mitochondria were accelerated in the malignant clones compared to their non-malignant counterpart clones. This coincided with enhanced SOC-mediated Ca(2+)-influx and high levels of constitutively active protein kinase B/Akt (PKB). Interruption of trans-mitochondrial Ca(2+)-transport in the malignant cells with an antagonist of the mitochondrial Na(+)/Ca(2+) exchanger, CGP-37157, abolsihed SOC-mediated Ca(2+)-influx, inactivated PKB, retarded cell growth and increased vulnerability to apoptosis. Similarly, direct SOC blockade by silencing Stim1 inhibited PKB, indicating that the crosstalk between SOC and mitochondria is essential to preserve PKB in constitutively active state. Finally, the retraction of mitochondria from sub-plasmalemmal micro-domains triggered by Fis1 over-expression inhibited SOC-coupled trans-mitochondrial Ca(2+)-flux, Ca(2+)-entry via SOC and PKB activity. Taken together, our data show that in the malignant melanoma cells, the functional and spatial relationship of up-regulated mitochondrial Ca(2+)-transport to the SOC sustains the robust Ca(2+)-responses and down-stream signaling critical for apoptosis-resistance and proliferation.

Plethora of agents, plethora of targets, plethora of side effects in metastatic renal cell carcinoma

The plethora of novel agents recently approved for the management of metastatic renal cell carcinoma (RCC) has changed the therapeutic landscape in this disease. The plethora of targets some of these agents inhibit can result in a wide range of side effects. While these novel therapies can be viewed as inhibitors of angiogenesis that directly or indirectly target the vascular endothelial growth factor (VEGF) pathway, their individual mechanisms of action (MoA) are key to defining their side-effect profiles. Direct VEGF inhibition with the anti-VEGF monoclonal antibody bevacizumab, is primarily associated with side effects related to the precise inhibition of VEGF, such as proteinuria, hypertension and minor bleeding events. In contrast, non-VEGF-related side effects are observed with agents inhibiting multiple receptor tyrosine kinases (sunitinib, sorafenib, axitinib and pazopanib) and mammalian target of rapamycin inhibitors (temsirolimus and everolimus); these include diarrhoea, skin rash, stomatitis, hand-foot skin reaction, hypothyroidism, and haematological and metabolic abnormalities. This review discusses the MoA of these novel therapies and how a greater understanding of MoA may help to predict the range and type of side effects, develop combinations of agents with acceptable tolerability, enable a more rational approach to patient selection, and allow the development of effective side-effect management strategies.