Prostate cancer chemotherapy in the era of targeted therapy

Dual-modified PCL-PEG nanoparticles for improved targeting and therapeutic efficacy of docetaxel against colorectal cancer

Polycaprolactone-poly (ethylene glycol) block copolymer (PCL-PEG) based nanoparticles were prepared for the intravenous administration of docetaxel (DTX). PCL-PEG-Tyr and PCL-PEG-Ang were synthesized by using tyrosine (Tyr) and angiopep-2 (Ang) as coupling ligands, and dual-modified PCL-PEG-based nanoparticles (PCL-PEG-Tyr/Ang) were prepared. The physicochemical properties, in vitro drug release, in vitro cytotoxicity, in vitro cellular uptake efficiency, in vivo biodistribution and in vivo antitumor efficacy of PCL-PEG-based nanoparticles were investigated. The PCL-PEG-based nanoparticles were spherical with a mean diameter of 100 nm and high encapsulation efficiencies (> 85%). The results of in vitro drug release showed that the PCL-PEG-based nanoparticles loaded with DTX had sustained-release characteristics. For in vitro cytotoxicity tests, the dual-modified PCL-PEG-based nanoparticles (PCL-PEG-Tyr/Ang) demonstrated the minimum IC50 value (2.94 µg/mL) compared with other PCL-PEG-based nanoparticles. In addition, the cellular uptake of coumarin-6 (C6) in HT29 cells was observed and determined in the PCL-PEG-Tyr/Ang nanoparticles group, which was significantly higher than that in the other PCL-PEG-based groups and C6 solution group. The results of in vivo imaging showed that dual-modified PCL-PEG nanoparticles had better tumor targeting than the other PCL-PEG-based nanoparticles. In the HT29 tumor-xenografted nude mice model, DTX-loaded PCL-PEG-Tyr/Ang nanoparticles also had a significantly higher inhibitory efficacy on tumor growth than Taxotere®-treated group. These results indicated that the dual-modified PCL-PEG-based nanoparticles (PCL-PEG-Tyr/Ang) could be a promising anticancer drug delivery system.

3D-QSAR and Molecular Docking Studies on Design Anti-Prostate Cancer Curcumin Analogues

BACKGROUND

Prostate cancer is one of the most common tumors in the world and the fifth leading cause of male cancer death. Although the treatment of localized androgen-dependent prostate cancer has been successful, the efficacy of androgen-independent metastatic disease is limited. Curcumin, a natural product, has been found to inhibit the proliferation of prostate cancer cells.

OBJECTIVE

To design curcumin analogs with higher biological activity and lower toxicity and side effects for the treatment of prostate cancer.

METHODS

In this study, the three dimensional-quantitative structure activity relationship (3DQSAR) and molecular docking studies were performed on 34 curcumin analogs as anti-prostate cancer compounds. We introduced OSIRIS Property Explorer to predict drug-related properties of newly designed compounds.

RESULTS

The optimum CoMSIA model exhibited statistically significant results: the cross-validated correlation coefficient q2 is 0.540 and non-cross-validated R2 value is 0.984. The external predictive correlation coefficient Rext 2 is 0.792. The information of structure-activity relationship can be obtained from the CoMSIA contour maps. In addition, the molecular docking study of the compounds for 3ZK6 as the protein target revealed important interactions between active compounds and amino acids.

CONCLUSION

Compound 28i may be a new type of anti-prostate cancer drug with higher biological activity and more promising development.

B7-H4 is a potential prognostic biomarker of prostate cancer

B7-H4 is a member of B7 family which regulates immune responses by delivering costimulatory signals. However, it negatively regulates T cell-mediated immunity and may play an important role in tumor immune evasion. Although several studies have been reported that expression of B7-H4 is elevated in the several types of human cancer with a poor clinical outcome, its clinical significance in the prostate cancer (PCa) has not been well studied. In this study, we investigated the clinical significance of B7-H4 in human PCa and determined if B7-H4 expression is associated with the cancer cell stemness in PCa. Our studies show that expression of B7-H4 is correlated with the pathologic tumor (pT) stage and the clinical stage of PCa. The Kaplan-Meier survival analysis revealed that PCa patients with high expression of B7-H4 exhibits a shorter overall survival (OS) rate. Univariate and multivariate Cox regression analysis indicated that B7-H4 is an independent poor prognostic factor of PCa. In addition, the expression of B7-H4 is correlated with the cancer cell stemness associated genes expression in PCa. Further, our studies show that B7-H4 regulates cancer cell stemness associated genes expression and effects on the cell cycle and PI3K/Akt signaling related genes expression in PCa. These results indicate that B7-H4 expression is associated with cancer cell stemness, and B7-H4 is a potential prognostic biomarker and a therapeutic target of PCa.

Pharmacokinetic studies of a novel tubulin inhibitor SK1326 in rat plasma by UPLC-MS/MS

A sensitive method for quantitation of SK1326 in rat plasma has been established using ultra-performance liquid chromatography-electrospray ionization tandem mass spectrometry (UPLC-ESI/MS/MS). SK1326 and the internal standard (tramadol) in plasma sample were extracted using acetonitrile. A centrifuged upper layer was then evaporated and reconstituted with a mobile phase of 0.5% formic acid-acetonitrile (35:65, v/v). The reconstituted samples were injected into a C₁₈ reversed-phase column. Using MS/MS in the multiple reaction monitoring mode, SK1326 and tramadol were detected without severe interference from the rat plasma matrix. SK1326 produced a protonated precursor ion ([M + H]⁺ ) at m/z 432.3 and a corresponding product ion at m/z 114.4. The internal standard produced a protonated precursor ion ([M + H]⁺ ) at m/z 264.4 and a corresponding product ion at m/z 58.1. Detection of SK1326 in rat plasma by the UPLC-ESI/MS/MS method was accurate and precise with a quantitation limit of 1.0 ng/mL. The validation, reproducibility, stability and recovery of the method were evaluated. The method has been successfully applied to pharmacokinetic studies of SK1326 in rat plasma. The pharmacokinetic parameters of SK1326 were evaluated after intravenous (at a dose of 10 mg/kg) and oral (at a dose of 20 mg/kg) administration of SK1326 in rats. After oral administration (20 mg/kg) of SK1326, the F (fraction absorbed) value was ~77.1%.

Targeting the androgen receptor (AR) with AR degradation enhancer ASC-J9® led to increase docetaxel sensitivity via suppressing the p21 expression

Chemotherapy with docetaxel remains the effective therapy to suppress castration resistant prostate cancer (CRPC) in some patients. However, most chemotherapy with docetaxel eventually fails with the development of docetaxel resistance after 18-weeks of treatment. Here we found docetaxel treatment might have an adverse effect of increasing the androgen receptor (AR) protein level in the CRPC cells, and combining docetaxel with anti-AR therapy using AR-shRNA or the AR degradation enhancer ASC-J9® may increase docetaxel sensitivity to better suppress the CRPC cell growth. Mechanism dissection found docetaxel might have the adverse effect of increasing the AR protein stability via suppressing the AR ubiquitination due to the increased AR phosphorylation. The consequence of such increased AR protein may then lead to increase p21 expression via transcriptional regulation. Preclinical studies with in vitro cells lines also demonstrated that targeting AR with ASC-J9® led to suppressing the AR-increased p21 expression to improve the docetaxel sensitivity in the CRPC cells that already developed docetaxel resistance. Together, these results suggest that a combined therapy of docetaxel and ASC-J9® is a novel therapy to better suppress CRPC in patients that already developed docetaxel resistance.

Luteolin attenuates Wnt signaling via upregulation of FZD6 to suppress prostate cancer stemness revealed by comparative proteomics

The mechanisms underlying luteolin-induced inhibition of prostate cancer (PCa) stemness have remained elusive. Here, we report that luteolin suppresses PCa stemness through Wnt signaling by upregulation of FZD6 (frizzled class receptor 6). Luteolin inhibits PCa cell proliferation, migration, self-renewal as well as the expression of prostate cancer stem cell markers in vitro. Through iTRAQ-based quantitative proteomics study, we identified 208 differentially expressed proteins in luteolin-treated PC-3 cells. Subsequent mechanistic analysis revealed that luteolin inhibits Wnt signaling by transcriptional upregulation of FZD6, and thereby suppressing the stemness of PCa cells. Furthermore, we identified FZD6 as a tumor suppressor that can abolish PCa stemness. In summary, our findings demonstrate that suppression of Wnt signaling by upregulation of FZD6 is a mechanism underlying luteolin-induced inhibition of PCa stemness. Our work suggests a new therapeutic strategy against human prostate cancer caused by aberrant activation of Wnt signaling.

Effects of Cinnamon (C. zeylanicum) Bark Oil Against Taxanes-Induced Damages in Sperm Quality, Testicular and Epididymal Oxidant/Antioxidant Balance, Testicular Apoptosis, and Sperm DNA Integrity

The aim of this study was to investigate whether cinnamon bark oil (CBO) has protective effect on taxanes-induced adverse changes in sperm quality, testicular and epididymal oxidant/antioxidant balance, testicular apoptosis, and sperm DNA integrity. For this purpose, 88 adult male rats were equally divided into 8 groups: control, CBO, docetaxel (DTX), paclitaxel (PTX), DTX+PTX, DTX+CBO, PTX+CBO, and DTX+PTX+CBO. CBO was given by gavage daily for 10 weeks at the dose of 100 mg/kg. DTX and PTX were administered by intraperitoneal injection at the doses of 5 and 4 mg/kg/week, respectively, for 10 weeks. DTX+PTX and DTX+PTX+CBO groups were treated with DTX during first 5 weeks and PTX during next 5 weeks. DTX, PTX, and their mixed administrations caused significant decreases in absolute and relative weights of all reproductive organs, testosterone level, sperm motility, concentration, glutathione level, and catalase activity in testicular and epididymal tissues. They also significantly increased abnormal sperm rate, testicular and epididymal malondialdehyde level, apoptotic germ cell number, and sperm DNA fragmentation and significantly damaged the histological structure of testes. CBO consumption by DTX-, PTX-, and DTX+PTX-treated rats provided significant ameliorations in decreased relative weights of reproductive organs, decreased testosterone, decreased sperm quality, imbalanced oxidant/antioxidant system, increased apoptotic germ cell number, rate of sperm with fragmented DNA, and severity of testicular histopathological lesions induced by taxanes. In conclusion, taxanes cause impairments in sperm quality, testicular and epididymal oxidant/antioxidant balance, testicular histopathological structure, and sperm DNA integrity, and long-term CBO consumption protects male reproductive system of rats.

Preparation and characterization of self-assembled nanoparticles based on low-molecular-weight heparin and stearylamine conjugates for controlled delivery of docetaxel

Low-molecular-weight heparin (LMWH)–stearylamine (SA) conjugates (LHSA)-based self-assembled nanoparticles were prepared for intravenous delivery of docetaxel (DCT). 1-Ethyl-3-(3-dimethylaminopropyl) carbodiimide and N-hydroxysuccinimide were used as coupling agents for synthesis of LHSA conjugates. The physicochemical properties, in vitro antitumor efficacy, in vitro cellular uptake efficiency, in vivo antitumor efficacy, and in vivo pharmacokinetics of LHSA nanoparticles were investigated. The LHSA nanoparticles exhibited a spherical shape with a mean diameter of 140–180 nm and a negative surface charge. According to in vitro release and in vivo pharmacokinetic test results, the docetaxel-loaded LHSA5 (LMWH:SA =1:5) nanoparticles exhibited sustained drug release profiles. The blank LHSA nanoparticles demonstrated only an insignificant cytotoxicity in MCF-7 and MDAMB 231 human breast cancer cells; additionally, higher cellular uptake of coumarin 6 (C6) in MCF-7 and MDAMB 231 cells was observed in the LHSA5 nanoparticles group than that in the C6 solution group. The in vivo tumor growth inhibition efficacy of docetaxel-loaded LHSA5 nanoparticles was also significantly higher than the Taxotere^®-treated group in the MDAMB 231 tumor-xenografted mouse model. These results indicated that the LHSA5-based nanoparticles could be a promising anticancer drug delivery system.

Optimal standard regimen and predicting response to docetaxel therapy

The purpose of this research is optimizing and predicting the potent activity of docetaxel through an efficient regimen to settle down a new protocol for the treatment of cancer. Effectiveness of docetaxel was examined in vivo in several mouse models engrafted either subcutaneously or intravenously with several types of cell lines. The effects of 147-5040mg/L of docetaxel in treatments of different regimens in those xenograft growths were monitored and quantified to identify energy of those doses as described before in earlier studies. Mock processes were performed on untreated groups of mice for controls. Docetaxel had significant influence on all sizes of treated tumors compared to the control animals. The longer the induced tumor doubling time intraday to more than half the time period from the start of therapy to the time of delivery of the dose, the higher the energy of docetaxel doses and hence the effectiveness of the treatment and vice versa. The energy yield by drug doses in optimal standard regimens was perfectly power correlated (r=1) with the drug dose. An efficient dose-energy model with a perfect fit (R(2)=1) estimating the energy yield by docetaxel doses in optimal standard regimens has been established to administer the personalized dose. Administration of docetaxel doses should be patient-specific and sufficient for the suggested regimen. Time periods from the start of therapy to the time of dose delivery of the efficient regimen are shorter than twice the tumor doubling time intraday on time of dose delivery. Patients with tumors of lower mitotic index may particularly benefit more from optimal standard regimens, whereas metronomic regimens would be more efficient in patients with tumors of higher mitotic index that need lower doses of docetaxel.

Oxidative stress induced in rat liver by anticancer drugs doxorubicin, paclitaxel and docetaxel

PURPOSE

Oxidative stress generated by anticancer drugs in non-targeted tissues, is considered as a significant factor responsible for their severe side effects, e.g. cardiotoxicity, neurotoxicity and hepatotoxicity. Lack of data on the effect of concurrent administration of commonly used anticancer drugs: doxorubicin (DOX), paclitaxel (PTX) and docetaxel (DTX) on normal tissue, prompted us to examine the markers of oxidative stress in the liver of rats treated with these drugs.

MATERIAL/METHODS

Male Wistar rats of average weight 200 g were injected intraperitoneally (i.p.) with 10 mg/kg of body weight (b.w.) of DOX, PTX and DTX. The drugs were given alone or in combinations DOX+taxane. The activities of superoxide dismutase (SOD), catalase (CAT), low molecular weight and total thiols and thiobarbituric acid-reactive substances (TBARS) were estimated.

RESULTS

Combination of two drugs generated greater changes than single agents. Concurrent administration of DOX and PTX increased SOD activity and TBARS, decreased the amount of low molecular weight and total thiols, but did not cause any changes in the activity of catalase. Combination of DOX and DTX induced similar changes except for the activity of catalase, which decreased after the treatment. Of the three drugs only DTX significantly decreased the activity of SOD. However, both taxanes increased the activity of catalase. Although a decrease in concentration of -SH groups, depletion of glutathione and an increase of TBARS were observed after treatment with single drugs, the changes were not statistically significant.

CONCLUSION

Concurrent administration of DOX and taxane induced enhanced oxidative stress in comparison to single drugs, which suggests their synergistic prooxidant mode of action in liver.

FOXM1 and its oncogenic signaling in pancreatic cancer pathogenesis

Pancreatic cancer is a devastating disease with an overall 5-year survival rate less than 5%. Multiple signaling pathways are implicated in the pathogenesis of pancreatic cancer, such as Wnt/β-catenin, Notch, Hedgehog, hypoxia-inducible factor, signal transducer and activator of transcription, specificity proteins/Krüppel-like factors, and Forkhead box (FOX). Recently, increasing evidence has demonstrated that the transcription factor FOXM1 plays important roles in the initiation, progression, and metastasis of a variety of human tumors, including pancreatic cancer. In this review, we focus on the current understanding of the molecular pathogenesis of pancreatic cancer with a special focus on the function and regulation of FOXM1 and rationale for FOXM1 as a novel molecular target for pancreatic cancer prevention and treatment.

A biocompatible in vivo ligation reaction and its application for noninvasive bioluminescent imaging of protease activity in living mice

The discovery of biocompatible reactions had a tremendous impact on chemical biology, allowing the study of numerous biological processes directly in complex systems. However, despite the fact that multiple biocompatible reactions have been developed in the past decade, very few work well in living mice. Here we report that D-cysteine and 2-cyanobenzothiazoles can selectively react with each other in vivo to generate a luciferin substrate for firefly luciferase. The success of this "split luciferin" ligation reaction has important implications for both in vivo imaging and biocompatible labeling strategies. First, the production of a luciferin substrate can be visualized in a live mouse by bioluminescence imaging (BLI) and furthermore allows interrogation of targeted tissues using a "caged" luciferin approach. We therefore applied this reaction to the real-time noninvasive imaging of apoptosis associated with caspase 3/7. Caspase-dependent release of free D-cysteine from the caspase 3/7 peptide substrate Asp-Glu-Val-Asp-D-Cys (DEVD-(D-Cys)) allowed selective reaction with 6-amino-2-cyanobenzothiazole (NH(2)-CBT) in vivo to form 6-amino-D-luciferin with subsequent light emission from luciferase. Importantly, this strategy was found to be superior to the commercially available DEVD-aminoluciferin substrate for imaging of caspase 3/7 activity. Moreover, the split luciferin approach enables the modular construction of bioluminogenic sensors, where either or both reaction partners could be caged to report on multiple biological events. Lastly, the luciferin ligation reaction is 3 orders of magnitude faster than Staudinger ligation, suggesting further applications for both bioluminescence and specific molecular targeting in vivo.

Pluronic P105/F127 mixed micelles for the delivery of docetaxel against Taxol-resistant non-small cell lung cancer: optimization and in vitro, in vivo evaluation

The aim of this work was to establish a novel polymeric mixed micelle composed of Pluronic P105 and F127 copolymers loaded with the poorly soluble antitumor drug docetaxel (DTX) against Taxol-resistant non-small cell lung cancer. A central composite design was utilized to optimize the preparation process, helping to improve drug solubilization efficiency and micelle stability. Prepared by a thin-film hydration method, the average size of the optimized mixed micelle was 23 nm, with a 92.40% encapsulation ratio and a 1.81% drug-loading efficiency. The optimized formulation showed high storage stability in lyophilized form, with 95.7% of the drug content remaining after 6 months’ storage at 4°C. The in vitro cytotoxicity assay showed that the IC50 values for Taxotere^® and mixed micelles were similar for A549, while on A549/Taxol cell lines, DTX-loaded P105/F127 mixed micelles showed a superior hypersensitizing effect; their IC50 value (0.059 μg/mL) was greatly reduced compared to those of Taxotere injections (0.593 μg/mL). The in vivo pharmacokinetic study showed that the mixed-micelle formulation achieved a 1.85-fold longer mean residence time in circulation and a 3.82-fold larger area under the plasma concentration-time curve than Taxotere. In addition, therapeutic improvement of mixed micelles in vivo against A549/Taxol was obtained. The tumor inhibition rate of the micelles was 69.05%, versus 34.43% for Taxotere (P < 0.01). Therefore, it could be concluded from the results that DTX-loaded P105/F127 mixed micelles might serve as a potential antitumor drug delivery system to overcome multidrug resistance in lung cancer.

Determination of docetaxel in rat plasma and its application in the comparative pharmacokinetics of Taxotere and SID530, a novel docetaxel formulation with hydroxypropyl-β-cyclodextrin

In this study, a sensitive, simple and reliable method for the quantification of docetaxel in rat plasma was developed and validated using liquid chromatography-tandem mass spectrometry (LC-MS/MS). The plasma samples were prepared by protein precipitation, and paclitaxel was used as an internal standard (IS). Chromatographic separation was achieved using a Gemini C(18) column (2.0 × 150 mm, 5 µm) with a mobile phase consisting of 0.1% formic acid-acetonitrile (30:70, v/v). The precursor-product ion pairs used for multiple reaction monitoring were m/z 808.5 → 527.5 (docetaxel) and m/z 854.2 → 286.5 (IS, paclitaxel). A calibration curve for docetaxel was constructed over the range 1-1000 ng/mL. The developed method was specific, precise and accurate, and no matrix effect was observed. The validated method was applied in a comparative pharmacokinetic study in which two docetaxel formulations, SID530, a new parenteral formulation of docetaxel with hydroxypropyl-β-cyclodextrin (HP-β-CD), and Taxotere, were administered to rats at a dose of 5 mg/kg. For SID530 and Taxotere, the mean C(0) values were 1494 and 1818 ng/mL, respectively, and the AUC(last) values were 837 and 755 h ng/mL, respectively. These two formulations did not show any statistical differences with regard to the pharmacokinetic parameters, thus establishing that the SID530 and Taxotere products are pharmacokinetically comparable in male rats.

Racial variation in the cost-effectiveness of chemotherapy for prostate cancer

PURPOSE

Heterogeneity of treatment effects and expenditures impacts the cost-effectiveness of health interventions. This study investigates the variation in costs, effects, and incremental cost-effectiveness ratios (ICERs) associated with chemotherapy in elderly patients with metastatic (M1) prostate cancer (PC) across race/ethnicity subgroups (non-Hispanic whites, non-Hispanic blacks, and others).

STUDY DESIGN

Retrospective observational analysis.

METHODS

We examined patients age 66 years or older, identified by using the linked Surveillance, Epidemiology, and End Results-Medicare data set, who were diagnosed with M1 PC between 2000 and 2005. Cost data on the basis of Medicare reimbursements were available for 36 months after diagnosis. Mean costs and effects (life-years gained [LYG]) were adjusted for censoring. The baseline scenario examined PC-specific medical costs at 24 months and required survival of at least three months. Sensitivity analysis considered sampling uncertainty, selection into treatment, and adjustments to initial model assumptions.

RESULTS

We identified 3,888 patients with M1 PC, of whom 24% (n = 930) received chemotherapy (primarily docetaxel and mitoxantrone). Twenty percent of observations were censored. The full sample ICER was $99,146 per LYG (95% CI, $75,042 to $130,195). Estimates for whites (ICER, $107,095; 95% CI, $78,391 to $148,272), blacks (ICER, $59,887; 95% CI, $22,860 to $121,509), and others (ICER, $123,909; 95% CI, $37,782 to $366,376) suggest considerable variation in the likelihood of chemotherapy being cost-effective. Results were similar in sensitivity analysis.

CONCLUSION

Chemotherapy use in elderly patients with M1 PC is associated with an ICER of $99,146 per LYG. Subgroup analysis revealed heterogeneity in point estimates and considerable statistical uncertainty. To generate a reliable evidence base, efforts to increase the representation of minorities in health care data sets need to continue.

Anti-cancer effect of bee venom in prostate cancer cells through activation of caspase pathway via inactivation of NF-κB

BACKGROUND

Bee venom has been used as a traditional medicine to treat arthritis, rheumatism, back pain, cancerous tumors, and skin diseases. However, the effects of bee venom on the prostate cancer and their action mechanisms have not been reported yet.

METHODS

To determine the effect of bee venom and its major component, melittin on the prostate cancer cells, apoptosis is analyzed by tunnel assay and apoptotic gene expression. For xenograft studies, bee venom was administrated intraperitoneally twice per week for 4 weeks, and the tumor growth was measured and the tumor were analyzed by immunohistochemistry. To investigate whether bee venom and melittin can inactivate nuclear factor kappa B (NF-κB), we assessed NF-κB activity in vitro and in vivo.

RESULTS AND CONCLUSIONS

Bee venom (1-10 µg/ml) and melittin (0.5-2.5 µg/ml) inhibited cancer cell growth through induction of apoptotic cell death in LNCaP, DU145, and PC-3 human prostate cancer cells. These effects were mediated by the suppression of constitutively activated NF-κB. Bee venom and melittin decreased anti-apoptotic proteins but induced pro-apoptotic proteins. However, pan caspase inhibitor abolished bee venom and melittin-induced apoptotic cell death and NF-κB inactivation. Bee venom (3-6 mg/kg) administration to nude mice implanted with PC-3 cells resulted in inhibition of tumor growth and activity of NF-κB accompanied with apoptotic cell death. Therefore, these results indicated that bee venom and melittin could inhibit prostate cancer in in vitro and in vivo, and these effects may be related to NF-κB/caspase signal mediated induction of apoptotic cell death.

Sunitinib: a multitargeted receptor tyrosine kinase inhibitor in the era of molecular cancer therapies

Sunitinib is an oral oxindole multitargeted kinase inhibitor that inhibits certain receptor tyrosine kinases (RTKs). These include vascular endothelial growth factor receptors (VEGFR type 1 and 2), platelet-derived growth factor receptors (PDGFR-alpha and PDGFR-beta), stem cell factor receptor (KIT), FMS-like tyrosine kinase-3 (FLT3), glial cell-line derived neurotrophic factor receptor (RET) and the receptor of macrophage-colony stimulating factor (CSF1R). Examination of the antitumor effect of sunitinib in a variety of cell lines in vitro suggested an antiproliferative activity that is dependent on the presence of constitutively active RTK targets. The use of sunitinib as first-line therapy in advanced renal cell carcinoma (RCC) has improved the overall survival compared with that observed after cytokine therapy, while its administration in patients with gastrointestinal stromal tumors (GISTs) after progression or intolerance to imatinib achieved an objective response of 7%. Sunitinib is currently approved for the treatment of GISTs in this setting, and as first-line therapy for the treatment of advanced RCC. The relatively long half-life of sunitinib and its major metabolite allow for a once-daily dosing schedule. An interesting antitumor activity of sunitinib was reported in phase II studies of patients with a variety of malignancies, such as hepatocellular cancer, pancreatic neuroendocrine tumors, and non-small cell lung cancer; results of phase III studies are urgently anticipated. Fatigue is one of the most common adverse effects of sunitinib, as 50-70% of patients with advanced RCC and GIST complained of this adverse effect. Other adverse effects are diarrhea, anorexia, nausea and vomiting, oral changes and bleeding events. Most toxicities are reversible and should not result in discontinuation of sunitinib. If necessary, dose adjustments or interruptions should be made. Hypothyroidism has been described in the first 2 weeks of sunitinib therapy and its incidence increases progressively with the duration of therapy. Sunitinib may exert its hypertensive activity through a direct effect on the vasculature, while its most important cardiac adverse effect is left ventricular dysfunction. A variety of skin adverse effects have been described with the use of sunitinib such as hand-foot syndrome, yellow discoloration of the skin, dry skin, subungual splinter hemorrhages, acral erythema, and generalized skin rashes. Administration of sunitinib in the adjuvant and neoadjuvant setting of patients with RCC and of its combination with chemotherapy and other targeted therapies are currently under intense investigation.

Targeted therapy for gastrointestinal stromal tumors: current status and future perspectives

Gastrointestinal stromal tumors (GISTs) present 80% of gastrointestinal tract mesenchymal tumors, with systemic chemotherapy and radiotherapy being unable to improve survival of patients with advanced disease. The identification of activating mutations in either KIT cell surface growth factor receptor or platelet-derived growth factor receptor alpha, which lead to ligand-independent signal transduction, paved the way for the development of novel agents that selectively inhibit key molecular events in disease pathogenesis. The development of imatinib mesylate in the treatment of metastatic GIST represents a therapeutic breakthrough in molecularly targeted strategies, which crucially improved patients' prognosis while its usefulness in adjuvant and neoadjuvant setting is under study. Sunitinib malate is available in the second-line setting, with ongoing studies evaluating its role in an earlier disease stage, while other targets are under intense investigation in order to enrich the therapeutical armamentarium for this disease. GIST phenotype seems to be an essential indicator of treatment response; thus, obtaining genotype information of each patient may be critical in order to tailor individualized treatment strategies and achieve maximal therapeutic results.