Preclinical evaluation of combined TKI-258 and RAD001 in hepatocellular carcinoma

Comparison of the Effects of Dovitinib and Bevacizumab on Reducing Neovascularization in an Experimental Rat Corneal Neovascularization Model

PURPOSE

To compare the inhibitory effects of dovitinib and bevacizumab for treatment of corneal neovascularization (CNV).

METHODS

Thirty-nine adult female Sprague Dawley rats weighing 180 to 250 g were used. CNV was induced by silver nitrate in the right eye of each rat. After the chemical burn, the animals were randomized into 5 groups. Group 1 did not receive any chemical substance. Group 2 received dimethyl sulfoxide, group 3 received bevacizumab 5 mg/mL, group 4 received dovitinib 5 mg/mL, and group 5 received bevacizumab 5 mg/mL + dovitinib 5 mg/mL topically administered twice daily for 14 days. On the 14th day, slit-lamp examination was performed, and anterior segment photographs were taken. The corneal neovascular area was measured on photographs as the percentage of the cornea's total area using computer imaging analysis. The corneal sections were stained with hematoxylin and eosin for histopathological examination.

RESULTS

A statistically significant decrease in the percentage of CNV was found in all treatment groups (group 3, group 4, and group 5) compared with the control group (group 1) (P < 0.01). A statistically significant difference in the percentage of CNV was found among group 3, group 4, and group 5 (P = 0.003). The percentage of CNV in group 4 was significantly higher than that in group 3 and group 5 (P1 = 0.004; P2 = 0.006). There was no statistically significant difference in the percentage of CNV between group 3 and group 5 (P = 0.228).

CONCLUSIONS

Dovitinib is a newly developed multitargeted tyrosine kinase inhibitor. Topical administration of dovitinib effectively inhibited CNV, but this effect of dovitinib was found less than topical bevacizumab.

Evolving Significance and Future Relevance of Anti-Angiogenic Activity of mTOR Inhibitors in Cancer Therapy

mTOR inhibitors have demonstrated remarkable anti-tumor activity in experimental models, mainly by reducing cancer cell growth and tumor angiogenesis. Their use in cancer patients as monotherapy has, however, generated only limited benefits, increasing median overall survival by only a few months. Likewise, in other targeted therapies, cancer cells develop resistance mechanisms to overcome mTOR inhibition. Hence, novel therapeutic strategies have to be designed to increase the efficacy of mTOR inhibitors in cancer. In this review, we discuss the present and future relevance of mTOR inhibitors in cancer therapy by focusing on their effects on tumor angiogenesis.

mTOR inhibition reduces growth and adhesion of hepatocellular carcinoma cells in vitro

Mechanistic target of rapamycin (mTOR) signaling is typically increased in hepatocellular carcinoma (HCC). A panel of HCC cell lines (HepG2, Hep3B and HuH6) was exposed to various concentrations of the mTOR inhibitors, everolimus and temsirolimus, in order to investigate their effects on cell growth, clonal formation, cell cycle progression, and adhesion and chemotactic migration using MTT and clonal cell growth assays, fluorometric detection of cell cycle phases and a Boyden chamber assay. In addition, integrin α and β adhesion receptors were analyzed by flow cytometry and blocking studies using function blocking monoclonal antibodies were conducted to explore functional relevance. The results demonstrated that everolimus and temsirolimus significantly suppressed HCC cell growth and clonal formation, at 0.1 or 1 nM (depending on the cell line). In addition, the number of cells in G0/G1 phase was increased in response to drug treatment, whereas the number of G2/M phase cells was decreased. Drug treatment also considerably suppressed HCC cell adhesion to immobilized collagen. Integrin profiling revealed strong expression of integrin α1, α2, α6 and β1 subtypes; and integrin α1 was upregulated in response to mTOR inhibition. Suppression of integrin α1 did not affect cell growth; however, it did significantly decrease adhesion and chemotaxis, with the influence on adhesion being greater than that on motility. Due to a positive association between integrin α1 expression and the extent of adhesion, whereby reduced receptor expression was correlated to decreased cell adhesion, it may be hypothesized that the adhesion‑blocking effects of mTOR inhibitors are not associated with mechanical contact inhibition of the α1 receptor but with integrin α1‑dependent suppression of oncogenic signaling, thus preventing tumor cell‑matrix interaction.

Dovitinib enhances temozolomide efficacy in glioblastoma cells

The multikinase inhibitor and FDA‐approved drug dovitinib (Dov) crosses the blood–brain barrier and was recently used as single drug application in clinical trials for GB patients with recurrent disease. The Dov‐mediated molecular mechanisms in GB cells are unknown. We used GB patient cells and cell lines to show that Dov downregulated the stem cell protein Lin28 and its target high‐mobility group protein A2 (HMGA2). The Dov‐induced reduction in pSTAT3^Tyr705 phosphorylation demonstrated that Dov negatively affects the STAT3/LIN28/Let‐7/HMGA2 regulatory axis in GB cells. Consistent with the known function of LIN28 and HMGA2 in GB self‐renewal, Dov reduced GB tumor sphere formation. Dov treatment also caused the downregulation of key base excision repair factors and O⁶‐methylguanine‐DNA‐methyltransferase (MGMT), which are known to have important roles in the repair of temozolomide (TMZ)‐induced alkylating DNA damage. Combined Dov/TMZ treatment enhanced TMZ‐induced DNA damage as quantified by nuclear γH2AX foci and comet assays, and increased GB cell apoptosis. Pretreatment of GB cells with Dov (‘Dov priming’) prior to TMZ treatment reduced GB cell viability independent of p53 status. Sequential treatment involving ‘Dov priming’ and alternating treatment cycles with TMZ and Dov substantially reduced long‐term GB cell survival in MGMT+ patient GB cells. Our results may have immediate clinical implications to improve TMZ response in patients with LIN28⁺/HMGA2⁺GB, independent of their MGMT methylation status.

PI3K Inhibitors Synergize with FGFR Inhibitors to Enhance Antitumor Responses in FGFR2mutant Endometrial Cancers

Improved therapeutic approaches are needed for the treatment of recurrent and metastatic endometrial cancer. Endometrial cancers display hyperactivation of the MAPK and PI3K pathways, the result of somatic aberrations in genes such as FGFR2, KRAS, PTEN, PIK3CA, and PIK3R1 The FGFR2 and PI3K pathways, have emerged as potential therapeutic targets in endometrial cancer. Activation of the PI3K pathway is seen in more than 90% of FGFR2^mutant endometrial cancers. This study aimed to examine the efficacy of the pan-FGFR inhibitor BGJ398 with pan-PI3K inhibitors (GDC-0941, BKM120) and the p110α-selective inhibitor BYL719. We assessed synergy in three FGFR2^mutant endometrial cancer cell lines (AN3CA, JHUEM2, and MFE296), and the combination of BGJ398 and GDC-0941 or BYL719 showed strong synergy. A significant increase in cell death and decrease in long-term survival was seen when PI3K inhibitors were combined with BGJ398. Importantly, these effects were seen at low concentrations correlating to only partial inhibition of AKT. The combination of BGJ398 and GDC-0941 showed tumor regressions in vivo, whereas each drug alone only showed moderate tumor growth inhibition. BYL719 alone resulted in increased tumor growth of AN3CA xenografts but in combination with BGJ398 resulted in tumor regression in both AN3CA- and JHUEM2-derived xenografts. These data provide evidence that subtherapeutic doses of PI3K inhibitors enhance the efficacy of anti-FGFR therapies, and a combination therapy may represent a superior therapeutic treatment in patients with FGFR2^mutant endometrial cancer. Mol Cancer Ther; 16(4); 637-48. ©2017 AACR.

Design, synthesis, and biological evaluation of 3-vinyl-quinoxalin-2(1H)-one derivatives as novel antitumor inhibitors of FGFR1

FGFR1 is well known as a molecular target in anticancer drug design. TKI258 plays an important role in RTK inhibitors. Utilizing TKI258 as a lead compound that contains a quinazolinone nucleus, we synthesized four series of 3-vinyl-quinoxalin-2(1H)-one derivatives, a total of 27 compounds. We further evaluated these compounds for FGFR1 inhibition ability as well as cytotoxicity against four cancer cell lines (H460, B16-F10, Hela229, and Hct116) in vitro. Some compounds displayed good-to-excellent potency against the four tested cancer cell lines compared with TKI258. Structure–activity relationship analyses indicated that small substituents at the side chain of the 3-vinyl-quinoxalin-2(1H)-one were more effective than large substituents. Lastly, we used molecular docking to obtain further insight into the interactions between the compounds and FGFR1.

Role of the fibroblast growth factor receptor axis in cholangiocarcinoma

Advanced cholangiocarcinoma (CCA) is a highly lethal disease with limited therapeutic options beyond cytotoxic chemotherapy. Molecular profiling of CCA has provided insights into the pathogenesis of this disease and identified potential therapeutic targets. The fibroblast growth factor receptor (FGFR) axis is important for maintaining tissue homeostasis. Aberrations in FGFR activity have been implicated in the development and progression of CCA and other malignancies, which has generated significant interest in exploring FGFR's therapeutic potential. FGFR2 fusion events are present in up to 17% of intrahepatic CCAs and appear to predict sensitivity to FGFR inhibitors even after progression on chemotherapy. These observations have led to a clinical trial evaluating FGFR inhibition in patients with CCA enriched for FGFR alterations. This review summarizes current knowledge about the role of the FGFR pathway in cholangiocarcinogenesis and ongoing work in developing FGFR-directed therapies as an antineoplastic strategy for CCA.

mTOR inhibitor therapy: Does it prevent HCC recurrence after liver transplantation?

Prevention of hepatocellular carcinoma (HCC) recurrence after liver transplantation is a clinical priority. The importance of the mammalian target of rapamycin (mTOR) pathway in cell growth and survival makes it a logical target for antitumor strategies, as borne out by clinical data in various types of malignancy. A number of studies have indicated that the mTOR inhibitors everolimus and sirolimus suppress cell proliferation and tumor growth in animal models of HCC. Coadministration of an mTOR inhibitor could permit lower dosing of chemotherapeutic agents in HCC management, and trials in non-transplant HCC population are exploring combined used with various agents including sorafenib, the vascular endothelial growth factor inhibitor bevacizumab and conventional agents. In terms of a preventive effect after liver transplantation for HCC, data from retrospective studies and non-randomized prospective analyses in which patients received an mTOR inhibitor with concomitant calcineurin inhibitor therapy have indicated that HCC recurrence rates and overall survival may be improved compared to a standard calcineurin inhibitor regimen. Meta-analyses have supported these findings, but controlled trials are required before any firm conclusions can be drawn. In two of the three randomized trials which have assessed de novo mTOR inhibitor therapy after liver transplantation, there was a numerically lower rate of HCC recurrence by one year post-transplant in patients given an mTOR inhibitor versus the control arm, but absolute numbers were low. Overall, based on the available data from retrospective studies, meta-analyses, and post-hoc assessments of randomized trials, it appears advisable to consider mTOR inhibition-based immunosuppression after transplantation for HCC, particularly in patients who exceed the Milan criteria. Prospective data are awaited.

Efficacy of combination treatment modalities for intermediate and advanced hepatocellular carcinoma: intra-arterial therapies, sorafenib and novel small molecules

Hepatocellular carcinoma (HCC) is a growing epidemic with a high mortality rate and clear need for improved therapies. In patients with Barcelona-Clinic Liver Cancer (BCLC) B and C, treatment with transarterial chemoembolization (TACE) has been the gold standard in therapy as it delays progression; however, recurrence proves common. In the US, transarterial bead embolization (TABE) has uniformly replaced TACE. With this limited armamentarium, there is need for a shift to novel strategies combining different modalities to further improve patient outcomes. Historically, HCC drug discovery concentrated on common features of HCC including its highly vascular nature and dependence on growth factors (GFs). The multikinase inhibitor sorafenib acts on angiogenesis via modulation of vascular endothelial GF expression and was the first step toward systemic targeted therapy against HCC. Sorafenib has provided clinicians with a tool to modestly improve survival by 2-6 months or longer. Despite the progress in survival provided by TACE, TABE and sorafenib independently, rigorous combination clinical trials do not consistently show significant improvement over TACE/TABE monotherapy. Other novel small molecules targeting angiogenesis such as brivanib, linifanib and everolimus have failed or are in development. Anti-HCV treatment became more feasible with the novel direct-acting antiviral agents; with the much higher and more durable treatment responses that they provide, the risk of HCC progression may be reduced. The most effective strategies in developing combination therapies are hampered by the complexities of FDA testing along with intellectual property and economic issues. To achieve significant progress, more basic science studies are necessary to help understand which novel molecules demonstrate the greatest synergy. Individual patient genomic profiling and biomarkers may help guide therapy and improve the clinician's ability to tailor treatment and to know when it could be appropriate to combine systemic therapy with transarterial embolization. Most importantly, partnerships that facilitate testing of novel therapies in intelligently designed trials based on preclinical pharmacokinetics must be established.

Preclinical evaluation of the PI3K-mTOR dual inhibitor PF-04691502 as a novel therapeutic drug in nasopharyngeal carcinoma

Nasopharyngeal carcinoma (NPC) is common in Southeast Asia and over 40% of NPC tissues have PIK3CA amplification. This study characterized the preclinical activity of a novel potent dual PI3K/mTOR inhibitor, PF-04691502, in five NPC cell lines: CNE-1, HK1, CNE-2, HONE-1 and C666-1, in which all of the cell lines possessed basal and activated expression of Akt and p70S6K. Over 80% inhibition of cell growth in all of these cell lines were achieved after 72 h of PF-04691502 incubation and their IC50 were in hundred nanomolar range. CNE-2, HK1 and HONE-1 were selected to further evaluate the effect of PF-04691502 on cell cycle, apoptosis and Akt downstream signaling. PF-04691502 induced G0/G1 cell cycle arrest and apoptosis at 24 h incubation and it significantly abrogated Akt and its downstream signaling by suppressing the expression of p-mTOR, p-p70S6K, p-Akt(S473, T308), p-S6 and p-4E-BP1, suggesting its effectiveness in inhibition of translation and protein synthesis. Anti-proliferation was also observed in 3D culture system and spheroids formation of NPC cell line HONE-1-EBV was strongly inhibited by PF-04691502. Antitumor activity was observed in CNE-2 xenograft in 2 weeks of 10 mg/kg PF-09641502 treatment to tumor bearing athymic nude mice. Both tumor volume and weight in treatment group were significantly lower than those in vehicle group while no obvious body weight decrease was found, suggesting this working dose was effective and well-tolerated. Additive effects were observed in combination of PF-09641502 with either cisplatin or paclitaxel. There were no synergistic effect observed in drug combination but PF-09641502 alone was effective in treating cisplatin resistant cell lines as compared to its parental control. The beneficial effects of PF-09641502 in both in vitro and in vivo studies for NPC warrant a further investigation.