Investigational platelet-derived growth factor receptor kinase inhibitors in breast cancer therapy

Introduction: Aberrant regulation of platelet-derived growth factors (PDGFs) and their receptors (PDGFR) has been shown to be involved in many solid tumors, including breast cancer. PDGFR-α and PDGFR-β expressions were documented in breast cancer and are correlated with tumor aggressiveness and metastasis. Preclinical evidence further suggests tumor stimulatory roles of PDGFRs expressed by tumor stroma cells and indicates a deleterious effect of stromal PDGFRs on intratumoral drug uptake.

Areas covered: This review summarizes the present understanding of PDGF signaling in breast cancer based on experimental studies and available clinical trials. It also provides a critical discussion of selected ongoing clinical trials in patients with breast cancer involving PDGFR inhibition with tyrosine kinase inhibitors, specifically in endocrine responsive breast cancer.

Expert opinion: An increased molecular understanding of response and resistance mechanisms to endocrine therapy will be essential for therapeutic advances in PDGFR-directed cancer therapy. Future developments in the field will rely on clinical studies where prospective analyses of target expression in breast cancer cells and in the tumor stroma are included. More selective PDGFR inhibitors with reduced side effects will be crucial for combinatorial therapies. Development of sensitive diagnostics is of critical importance for patient selection and monitoring of therapeutic effects.     

Targeting platelet-derived growth factor receptor β inhibits the proliferation and motility of human pterygial fibroblasts

ABSTRACT

Background: Pterygium, a common eye disease with high postoperative recurrence, lacks effective therapeutic strategies. Therefore, it’s urgent to identify specific targets to develop rationally targeted molecular drugs for the pterygial therapy.

Methods: The cell proliferation and motility were studied in both the primary human pterygial fibroblasts (hPFs) and an ex vivo pterygium model. hPFs transfected with the pCMV3-PDGFRB plasmid, PDGFRB siRNA and CRISPR/Cas9 system were used to determine the role of PDGFR-β in pterygial fibroblasts functions. Western blotting, immunohistochemistry and immunofluorescence were performed to evaluate the expression of the key proteins.

Results: PDGFR-β expression in the pterygial stroma and primary hPFs was significantly higher than that in the conjunctiva and human conjunctival fibroblasts. PDGF-BB promoted the proliferation, migration and invasion of hPFs, which can be significantly suppressed by sunitinib via inhibition of the PDGFR-β/extracellular signal-regulated kinase (ERK) pathway. In the ex vivo model, the knockout of PDGFRB and sunitinib treatment blocked the proliferation and motility of fibroblasts in the pterygial stroma via the suppression of PDGFR-β/ERK pathway.

Conclusion: This study demonstrates that PDGFR-β may be a potential therapeutic target for pterygium, and inhibition of PDGFR-β by sunitinib is a promising and effective approach for pterygium treatment.     

Sorafenib in liver cancer

Introduction: With growing knowledge of the molecular pathway of carcinogenesis, targeted therapies have become the ‘blue ocean' of cancer treatment. sorafenib is an oral multikinase inhibitor that targets Raf/mitogen-activated protein (MAP) kinase/extracellular signal-regulated kinase (ERK) (Raf/MEK/ERK) and several tyrosine kinases (VEGFR-2, VEGFR-3, PDGFR-β) that has shown efficacy in hepatocellular carcinoma (HCC).

Areas covered: An updated summary of the preclinical and clinical experience with sorafenib in HCC is presented in this paper. Data are based on abstracts from international conferences and journal articles found in a PubMed search of literature published up to December 2011.

Expert opinion: Based on favorable data from preclinical and clinical trials, sorafenib has been approved as a standard therapy in advanced HCC. However, further efforts to understand the additional roles of sorafenib in the treatment of HCC are still necessary. Data for sorafenib will guide the development of new drugs for the treatment of HCC.     

Targeting integrins in hepatocellular carcinoma

Introduction: Integrins, which are heterodimeric membrane glycoproteins, consist of a family of cell-surface receptors mediating cell–matrix and cell–cell adhesion. Analysis of tumor-associated integrins has revealed an important relationship between integrins and tumor development, bringing new insights into integrin-based cancer therapies. Hepatocellular carcinoma (HCC) is one of the most malignant tumors worldwide and integrins appeal to be a novel group of potential therapeutic targets for HCC.

Areas covered: This review summarizes the current knowledge of integrins involved in HCC and the potential of integrin-targeted drugs in HCC therapy. A brief introduction on the structure, biological function and regulatory mechanism of integrins is given. The distinct expression patterns and biological functions of HCC-associated integrins are described. Finally, the current situation of integrin-based therapies in HCC and other tumor types are extensively discussed in the light of their implications in preclinical and clinical trials.

Expert opinion: To date, increasing numbers of integrin-targeted drugs are undergoing development and they exhibit diverse effects in cancer clinical trials. Tumor heterogeneity should be emphasized in developing effective integrin-targeted drugs specific for HCC. A better understanding of how integrins cooperatively function in HCC will assist in designing more successful integrin-targeted therapeutic drugs and corresponding approaches.     

The predictive value of chromosome 8p deletion for metastasis of hepatocellular carcinoma: a summary of works in 10 years

Hepatocellular carcinoma (HCC) represents an extremely poor prognostic cancer, which is mainly due to the high frequency of metastasis/recurrence after surgical operation. Exploring the molecular mechanisms involved in HCC metastasis could be helpful in the prediction and early diagnosis of HCC recurrence and could also provide new therapeutic targets for HCC metastasis. In the recent decade, we analyzed the genomic aberrations of the clinical specimens, as well as the metastatic models and cell lines of human HCC to identify the genetic markers related to HCC metastasis and to verify their clinical values in the prediction and control of metastasis of HCC. Using the comparative genomic hybridization (CGH) technique, we compared the differences of chromosomal aberrations between primary HCC tumors and their matched metastatic lesions, and found that chromosome 8p deletions might contribute to HCC metastasis. This novel finding was further confirmed by comparison between nude mice models of HCC with different metastatic potentials. By the more sensitive genome-wide microsatellite analysis, 8p deletion was defined to 8p23.3 and 8p11.2, which are two likely regions harboring metastasis-related genes of HCC. Using ‘8p-specific’ microarrays, two novel metastatic suppressors (HTPAP and MRSA) were identified, and were proven to suppress in vitro invasion and in vivo metastasis of HCC. Clinical studies indicate that 8p deletion detected in HCC or circulating plasma DNA of patients is a useful predictor for metastatic recurrence and prognosis, even for patients with early stage HCC. These novel findings are regarded as important advances in the study of the molecular mechanisms of HCC metastasis, which provide not only a holistic view on the molecular cytogenetic bases of HCC metastasis, but also candidate regions for further study to identify metastatic suppressor genes.     

Substitutes for blood

Introduction: Hepatocellular carcinoma (HCC) is often fatal due to local growth inside the liver and its unique arterial vascularization provides the basis for transarterial therapies. Around 35% of patients are diagnosed at stages in which transarterial therapies are indicated as first-line therapy; many others are treated after recurrence or progression to surgery or percutaneous ablation. However, the scientific evidence supporting the use of transarterial therapy is heterogeneous and certainly weak for several subgroups. New developments have emerged in the last decade.

Areas covered: This review discusses the scientific evidence supporting the use of transarterial therapies for patients with HCC, including chemoembolization with conventional materials or drug-eluting beads, and internal radiation procedures such as the injection radioactive lipiodol or radioembolization with ⁹⁰Y-loaded microspheres. The literature on clinical development of transarterial therapies for HCC has been reviewed since 1990.

Expert opinion: Transarterial chemoembolization has been shown to improve the survival of those patients with unresectable, mostly viral-related HCC who have a preserved liver function and low tumor burden. Recently developed devices and procedures, particularly drug-eluting beads and radioactive microspheres, may further improve the clinical outcome of patients receiving transarterial therapies. Combination with antiangiogenic agents is an appealing approach that should be explored.     

Lyso-thermosensitive liposomal doxorubicin: a novel approach to enhance efficacy of thermal ablation of liver cancer

Background: Hepatocellular carcinoma (HCC) is the fourth leading cause of cancer death worldwide. No more than 30% of HCC patients receive curative treatment. Factors limiting curative therapy include tumor size and degree of liver impairment. Objective: To develop a cure for medium (3.1 – 5.0 cm) and large ( > 5 cm) tumors in seriously impaired livers. Method: Combine radiofrequency ablation (RFA) with lyso-thermosensitive liposomal doxorubicin (LTLD). Results/conclusions: RFA is used safely in patients with medium/large tumors and severe liver impairment; unclear tumor margins limit its curative efficacy. LTLD concentrates in the liver, where the anti-HCC chemotherapeutic, doxorubicin, is released into tumor margins by hyperthermia. RFA/LTLD can treat Child-Pugh class A-B patients with tumors up to 7 cm, a substantial increase in curable patients.     

Axitinib for renal cell carcinoma

Background: The approval of sunitinib, sorafenib and temsirolimus has dramatically altered the management of renal cell carcinoma (RCC). Bevacizumab plus IFN may also be added to the therapeutic armamentarium. Axitinib (AG-013736) is an oral and selective tyrosine kinase inhibitor. Objective: Data supporting the development of axitinib for RCC are reviewed. Methods: Preclinical and clinical data available for axitinib for RCC are presented. Results: Axitinib inhibits VEGFR-1, VEGFR-2 and VEGFR-3 with picomolar potencies, and PDGFR-α, PDGFR-β and c-kit with nanomolar potencies. Phase II clinical trials of axitinib in pretreated RCC following sorafenib or cytokine treatment have demonstrated promising activity accompanied by a favorable toxicity profile. Further development of axitinib for RCC is warranted.     

PTEN and TRAIL genes loaded zein nanoparticles as potential therapy for hepatocellular carcinoma

Gene therapy is one of the recent approaches in treatment of hepatocellular carcinoma (HCC). Development of a vector or vehicle that can selectively and efficiently deliver the gene to target cells with minimal toxicity is an urgent demand. In the present study, phosphatase and tensin homolog (PTEN) and tumor necrosis factor (TNF)-related apoptosis-inducing ligand (TRAIL) genes were loaded to zein nanoparticles (ZNPs). The formulated PTEN and TRAIL-loaded ZNPs were tested for their in vitro and in vivo potential antitumor efficacy using liver tumor cells (HepG2) and HCC-induced rats as animal model. Also, mRNA expression of p53, VGEF and MMP-2 were carried out as markers of apoptosis, angiogenesis and metastasis in animal liver tissues. The results of the study showed that both PTEN and TRAIL-loaded ZNPs proved anti-proliferative activity against HepG2 cell lines with IC₅₀ values of 0.09, 0.25?µg/ml, respectively. In vivo assay confirmed decrease in mRNA expression of both VEGF and MMP-2 with increased in P53 expression level in liver tissues of the treated animals. Therefore, authors introduced new integration between gene therapy and nanotechnology in the form of PTEN and TRAIL-loaded ZNPs that proved potential to be used in gene therapy for the treatment of HCC.     

Effectiveness of localized ultrasound-targeted microbubble destruction with doxorubicin liposomes in H22 mouse hepatocellular carcinoma model

Objective: In order to increase local drug concentration and reduce systemic side effects of liver cancer chemotherapy, it is desirable to develop novel non-invasive technologies for drug targeting, such as ultrasound-targeted microbubble destruction (UTMD).

Methods: H22 hepatocellular carcinoma (HCC) xenograft transplantation model was generated in UTMD study. BALB/c mice were randomly divided into six groups: doxorubicin HCl liposomal injection (DOX), DOX?+?US, UTMD, DOX?+?UTMD, H22 liver tumor control (CH control) and blank control group. The therapeutic schedule started on day 4 after tumor inoculation.

Results: Average survival time of the animal model was approximately 18?d. The UTMD therapy parameters were optimized in the H22 mouse model to be: microbubble (MB) diameter, 2.30?±?0.25?μm; MB density, 4.0?×?10⁹ bubbles/ml; treatment dose, 0.2?ml per 20?g mouse body weight; sonication frequency, 1.3?MHz; and sonication power, 2.06?W/cm². Mice treated with DOX?+?UTMD had the smallest tumor volume and weight (p?<?0.001), and the highest tumor inhibition rate (p?<?0.01), intratumoral DOX concentration (p?<?0.001) and survival rate among all tumor-burden groups (p?<?0.001). Cell viability in different treatment groups was also assessed using a 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay.

Conclusion: An improved antitumor effect was observed with the combination therapy of DOX and UTMD, as compared with treatment with DOX, DOX?+?US or UTMD, which implicates a novel approach for HCC treatment.     

Targeting the extracellular signature of metastatic colorectal cancers

Background: Colorectal cancer is a leading cause of tumor death, a consequence primarily of the spreading of malignant cells to liver and lung. Despite a range of interventions for liver metastases, the present knowledge of few specific molecular targets may contribute to late diagnosis and poorly effective therapy. Objective: To review the most innovative methodology employed to profile the signature(s) of metastatic colorectal cancer (mCRC) and to address diagnostic/therapeutic agents. Methods: A broad range Medline search was conducted, with particular attention to the search terms ‘liver metastasis signature’, in combination with ‘targeting’ and ‘nanotechnology’. Results/conclusions: Studies aimed at the discovery of molecular signatures of cancers and metastasis are ongoing; the future of cancer/metastasis targeting is nanoparticle-mediated drug delivery.     

Chrysanthemum boreale flower floral water inhibits platelet-derived growth factor-stimulated migration and proliferation in vascular smooth muscle cells

Abstract

Context: Chrysanthemum boreale Makino (Compositae) (CBM) is a traditional medicine that has been used for the prevention or treatment of various disorders; it has various properties including antioxidation, anti-inflammation, and antitumor.

Objective: The present study was designed to explore the in vitro effect of CBM flower floral water (CBMFF) on atherosclerosis-related responses in rat aortic smooth muscle cells (RASMCs).

Materials and methods: CBMFF was extracted from CBM flower by steam distillation and analyzed using gas chromatography–mass spectrometry. The anti-atherosclerosis activity of CBMFF was tested by estimating platelet-derived growth factor (PDGF)-BB (10?ng/mL)-induced proliferation and migration levels and intracellular kinase pathways in RASMCs at CBMFF concentrations of 0.01–100?μM and analyzing ex vivo aortic ring assay.

Results: Gas chromatography–mass spectrometry showed that the CBMFF contained a total of seven components. The CBMFF inhibits PDGF-BB-stimulated RASMC migration and proliferation (IC₅₀: 0.010?μg/mL). Treatment of RASMCs with PDGF-BB induced PDGFR-β phosphorylation and increased the phosphorylations of MAPK p38 and ERK1/2. CBMFF addition prevented PDGF-BB-induced phosphorylation of these kinases (IC₅₀: 008 and 0.018?μg/mL, for p38 MAPK and ERK1/2, respectively), as well as PDGFR-β (IC₅₀: 0.046?μg/mL). Treatment with inhibitors of PDGFR, P38 MAPK, and ERK1/2 decreased PDGF-BB-increased migration and proliferation in RASMCs. Moreover, the CBMFF suppressed PDGF-BB-increased sprout outgrowth of aortic rings (IC₅₀: 0.047?μg/mL).

Discussion and conclusion: These results demonstrate that CBMFF may inhibit PDGF-BB-induced vascular migration and proliferation, most likely through inhibition of the PDGFR-β-mediated MAPK pathway; therefore, the CBMFF may be promising candidate for the development of herbal remedies for vascular disorders.     

Regulation of PKB/Akt-pathway in the chemopreventive effect of lactoferrin against diethylnitrosamine-induced hepatocarcinogenesis in rats

BackgroundAbnormal activation of protein kinase B (PKB) is associated with many cancers. This makes inhibition of PKB signaling pathway a promising strategy for cancer therapy. Lactoferrin (Lf) has been reported for its inhibition of tumor growth and metastasis, however, the mechanism is not completely understood. Its anti-hepatocarcinogenic activity has not taken the deserved recognition despite the additional advantages of Lf as an antiviral against hepatitis C virus, the main cause of hepatocellular carcinoma (HCC), and as a targeting ligand for delivering chemotherapeutics to hepatoma cells.MethodsThis study evaluated the anti-hepatocarcinogenic effect of Lf, and the role of PKB in this effect using diethylnitrosamine (DENA)-induced HCC rat model, and a primary cell culture prepared from the induced hepatic lesions (DENA?HCC cell culture).ResultsUp-regulation of activated PKB in the hepatocytes of rats with DENA-induced HCC was observed, as measured biochemically in the liver homogenate, and localized immunohistochemically. This was accompanied by increment of hepatocytes proliferation, and expression of vascular endothelial growth factor and endothelial nitric oxide synthase. Involvement of PKB in DENA-induced HCC was confirmed by the observed decrease in cell proliferation in DENA?HCC cell culture that was treated with PKB inhibitor. In Lf-treated rats, a dose-dependent chemopreventive effect was observed, with decreased expression and activation of PKB, amelioration of the other DENA-induced alterations, and stimulation of apoptosis. In vitro, Lf blocked PKB activator-induced cell proliferation.ConclusionThese findings support the chemopreventive activity of Lf against HCC, and suggest regulation of PKB-pathway as a potential mechanism underlying this effect.     

Arsenic trioxide in patients with hepatocellular carcinoma: a phase II trial

Summary Background: Arsenic trioxide induces growth inhibition and apoptosis in human hepatocellular carcinoma (HCC) cell lines. A phase II trial was conducted to evaluate the efficacy and toxicity of single-agent arsenic trioxide in patients with HCC. Methods: Inclusion criteria included advanced HCC patients to whom no standard palliative treatment can be offered, good organ function and liver function reserve. Patients received arsenic trioxide 0.16–0.24 mg/kg per day for 5–6 days per week for 3–4 weeks, followed by one-week rest. Tumor response was assessed every 2 cycles. Primary endpoint was the percentage of patients with 6-month disease stabilization. Results: Twenty-nine patients (median age, 59) with locally advanced or metastatic HCC received a total of 61 cycles (median, 2; range, 1–6). One patient had partial response. Three patients had disease stabilization for at least six months. The 6-month tumor stabilization rate was 14% (95% CI, 1–27). The median overall survival was 4.8 months (95% CI, 1.4–8.2) and one-year survival was 30%. Conclusion: Single-agent arsenic trioxide using this dose schedule is not active against advanced HCC.     

Tyrosine kinase inhibitors to treat liver cancer

Importance of the field: Hepatocellular carcinoma (HCC) is the third most common cause of cancer-related death worldwide. Although patients with early-stage disease have a good prognosis, there has been no effective therapy available for those with advanced disease. Despite the death risk of patients with advanced HCC being reduced with sorafenib therapy, many patients eventually turn out to be refractory to this therapy. Thus, treatment of HCC remains an urgent health concern.

Areas covered in this review: Recent improvement in understanding the pathophysiology of HCC at the molecular level has fostered the development of molecular targeted therapies that specifically block the disrupted pathways.

What the reader will gain: This review summarizes the preclinical and clinical data from 2004 to 2009 on the efficacy and safety of the emerging drug for the treatment of HCC, including small molecule inhibitors (erlotinib, sunitinib, sorafenib, vandetanib, cediranib, brivanib and dovitinib) and the rationale for combination therapies for patients with advanced HCC.

Take home message: Understanding the mechanisms of action, safety and efficacy of these new agents and new methods of combining these drugs may help prolong overall survival of patients with HCC and reduce disease recurrence after surgery or ablative therapies.     

Self-assembled FeS-based cascade bioreactor with enhanced tumor penetration and synergistic treatments to trigger robust cancer immunotherapy

Major challenges for cancer treatment are how to effectively eliminate primary tumor and sufficiently induce immunogenic cell death (ICD) to provoke a robust immune response for metastasis control. Here, a self-assembled cascade bioreactor was developed to improve cancer treatment with enhanced tumor penetration and synergistic therapy of starvation, chemodynamic (CDT) and photothermal therapy. Ultrasmall FeS-GOx nanodots were synthesized with glucose oxidase (GOx) as template and induced by paclitaxel (PTX) to form self-assembling FeS-GOx@PTX (FGP) via hydrophobic interaction. After accumulated at tumor sites, FGP disassembles to smaller FeS-GOx for enhanced deep tumor penetration. GOx maintains high enzymatic activity to catalyze glucose with assistant of oxygen to generate hydrogen peroxide (H₂O₂) as starvation therapy. Fenton reaction involving the regenerated H₂O₂ in turn produced more hydroxyl radicals for enhanced CDT. Following near-infrared laser at 808 nm, FGPs displayed pronounced tumor inhibition in vitro and in vivo by the combination therapy. The consequent increased exposure to calreticulin amplified ICD and promoted dendritic cells maturation. In combination with anti-CTLA4 checkpoint blockade, FGP can absolutely eliminate primary tumor and avidly inhibit distant tumors due to the enhanced intratumoral infiltration of cytotoxic T lymphocytes. Our work presents a promising strategy for primary tumor and metastasis inhibition.     

MACC1 – a novel target for solid cancers

Introduction: The metastatic dissemination of primary tumors is directly linked to patient survival in many tumor entities. The previously undescribed gene metastasis-associated in colon cancer 1 (MACC1) was discovered by genome-wide analyses in colorectal cancer (CRC) tissues. MACC1 is a tumor stage-independent predictor for CRC metastasis linked to metastasis-free survival.

Areas covered: In this review, the discovery of MACC1 is briefly presented. In the following, the overwhelming confirmation of these data is provided supporting MACC1 as a new remarkable biomarker for disease prognosis and prediction of therapy response for CRC and also for a variety of additional forms of solid cancers. Lastly, the potential clinical utility of MACC1 as a target for prevention or restriction of tumor progression and metastasis is envisioned.

Expert opinion: MACC1 has been identified as a prognostic biomarker in a variety of solid cancers. MACC1 correlated with tumor formation and progression, development of metastases and patient survival representing a decisive driver for tumorigenesis and metastasis. MACC1 was also demonstrated to be of predictive value for therapy response. MACC1 is a promising therapeutic target for anti-tumor and anti-metastatic intervention strategies of solid cancers. Its clinical utility, however, must be demonstrated in clinical trials.     

Placental growth factor in cancer

Introduction: Placental growth factor (PLGF) belongs to the VEGF family, which among the three VEGF receptors binds exclusively to VEGFR1, present on various cell types. Isoform PLGF-2 also binds the neuropilin co-receptors. PLGF is dispensable for development and health but has a prominent role in pathology including cancer. This has triggered the question whether PLGF targeting might offer an alternative to current antiangiogenesis therapy, which encounters problems of refractoriness and acquired resistance.

Areas covered: This article reviews the available literature on the characteristics of PLGF, its role(s) in cancer and the findings on PLGF inhibition in preclinical models with attention to as yet unresolved questions and summarizes data from initial clinical trials.

Expert opinion: Preclinical studies show that inhibition of PLGF, either by genetic inhibition or by pharmacological blockade using distinct independently generated anti-PLGF antibodies, slows down tumor growth and metastasis and even induces regression of pre-existing medulloblastoma, the most frequent brain cancer in children. These promising preclinical findings, together with the acceptable safety profile of anti-PLGF administration in Phase I clinical trials, have attracted attention to PLGF as a potential target for therapy.     

Taking aim at Mer and Axl receptor tyrosine kinases as novel therapeutic targets in solid tumors

Importance of the field: Axl and/or Mer expression correlates with poor prognosis in several cancers. Until recently, the role of these receptor tyrosine kinases (RTKs) in development and progression of cancer remained unexplained. Studies demonstrating that Axl and Mer contribute to cell survival, migration, invasion, metastasis and chemosensitivity justify further investigation of Axl and Mer as novel therapeutic targets in cancer.

Areas covered in this review: Axl and Mer signaling pathways in cancer cells are summarized and evidence validating these RTKs as therapeutic targets in glioblastoma multiforme, NSCLC, and breast cancer is examined. A discussion of Axl and/or Mer inhibitors in development is provided.

What the reader will gain: Potential toxicities associated with Axl or Mer inhibition are addressed. We propose that the probable action of Mer and Axl inhibitors on cells within the tumor microenvironment will provide a therapeutic opportunity to target both tumor cells and the stromal components that facilitate disease progression.

Take home message: Axl and Mer mediate multiple oncogenic phenotypes and activation of these RTKs constitutes a mechanism of chemoresistance in a variety of solid tumors. Targeted inhibition of these RTKs may be effective as anti-tumor and/or anti-metastatic therapy, particularly if combined with standard cytotoxic therapies.