Hepatocellular carcinoma (HCC) is one of the leading causes of cancer-related deaths worldwide. Surgical resection and conventional chemotherapy and radiotherapy ultimately fail due to tumor recurrence and HCC’s resistance. The development of novel therapies against HCC is thus urgently required. The cyclin-dependent kinase (CDK) pathways are important and well-established targets for cancer treatment. In particular, CDK2 is a key factor regulating the cell cycle G1 to S transition and a hallmark for cancers. In this study, we utilized our free and open-source protein-ligand docking software, idock, prospectively to identify potential CDK2 inhibitors from 4,311 FDA-approved small molecule drugs using a repurposing strategy and an ensemble docking methodology. Sorted by average idock score, nine compounds were purchased and tested in vitro. Among them, the anti-psychotic drug fluspirilene exhibited the highest anti-proliferative effect in human hepatocellular carcinoma HepG2 and Huh7 cells. We demonstrated for the first time that fluspirilene treatment significantly increased the percentage of cells in G1 phase, and decreased the expressions of CDK2, cyclin E and Rb, as well as the phosphorylations of CDK2 on Thr160 and Rb on Ser795. We also examined the anti-cancer effect of fluspirilene in vivo in BALB/C nude mice subcutaneously xenografted with human hepatocellular carcinoma Huh7 cells. Our results showed that oral fluspirilene treatment significantly inhibited tumor growth. Fluspirilene (15 mg/kg) exhibited strong anti-tumor activity, comparable to that of the leading cancer drug 5-fluorouracil (10 mg/kg). Moreover, the cocktail treatment with fluspirilene and 5-fluorouracil exhibited the highest therapeutic effect. These results suggested for the first time that fluspirilene is a potential CDK2 inhibitor and a candidate anti-cancer drug for the treatment of human hepatocellular carcinoma. In view of the fact that fluspirilene has a long history of safe human use, our discovery of fluspirilene as a potential anti-HCC drug may present an immediately applicable clinical therapy.

Cyclin-dependent kinase 2 (CDK2) has been reported to be overexpressed in human colorectal cancer; it is responsible for the G1-to-S-phase transition in the cell cycle and its deregulation is a hallmark of cancer. The present study was the first to use idock, a free and open-source protein-ligand docking software developed by our group, to identify potential CDK2 inhibitors from 4,311 US Food and Drug Administration-approved small molecular drugs with a re-purposing strategy. Among the top compounds identified by idock score, nine were selected for further study. Among them, adapalene (ADA; CD271,6-[3-(1-adamantyl)-4-methoxyphenyl]-2-naphtoic acid) exhibited the highest anti-proliferative effects in LoVo and DLD1 human colon cancer cell lines. Consistent with the expected properties of CDK2 inhibitors, the present study demonstrated that ADA significantly increased the G1-phase population and decreased the expression of CDK2, cyclin E and retinoblastoma protein (Rb), as well as the phosphorylation of CDK2 (on Thr-160) and Rb (on Ser-795). Furthermore, the anti-cancer effects of ADA were examined in vivo on xenograft tumors derived from DLD1 human colorectal cancer cells subcutaneously inoculated in BALB/C nude mice. ADA (20 mg/kg orally) exhibited marked anti-tumor activity, comparable to that of oxaliplatin (40 mg/kg), and dose-dependently inhibited tumor growth (P<0.05), while combined administration of ADA and oxaliplatin produced the highest therapeutic effect. To the best of our knowledge, the present study was the first to indicate that ADA inhibits CDK2 and is a potential candidate drug for the treatment of human colorectal cancer.

Since cyclin‑dependent kinases 4/6 (CDK4/6) play pivotal roles in cell cycle regulation and are overexpressed in human skin cancers, CDK4/6 inhibitors are potentially effective drugs for skin cancer. In the present study, we present a mixed computational and experimental study attempting to repurpose approved small‑molecule drugs as dual CDK4/6 inhibitors for skin cancer treatment. We performed structure‑based virtual screening using the docking software idock, targeting an ensemble of CDK4/6 structures. We identified and selected nine compounds with significant predicted scores, and evaluated their cytotoxic effects in vitro in A375 and A431 human skin cancer cell lines. Rafoxanide was found to exhibit the highest cytotoxic effects (IC50: 1.09 µM for A375 and 1.31 µM for A431 cells). Consistent with the expected properties of CDK4/6 inhibitors, rafoxanide significantly increased the G1 phase population. Notably, we revealed that rafoxanide specifically decreased the expression of CDK4/6, cyclin D, retinoblastoma protein (Rb) and the phosphorylation of CDK4/6 and Rb. Furthermore, the anticancer effect of rafoxanide was demonstrated in vivo in BALB/C nude mice subcutaneously xenografted with human skin cancer A375 cells. Rafoxanide (40 mg/kg, i.p.) exhibited significant antitumor activity, comparable to that of oxaliplatin (5 mg/kg, i.p.). The combined administration of rafoxanide and oxaliplatin produced a synergistic therapeutic effect. To the best of our knowledge, the present study is the first to indicate that rafoxanide inhibits CDK4/6 activity and is a potential candidate drug for the treatment of human skin cancer.

The phosphatidylinositol-3-kinase (PI3K)/AKT signaling pathway plays a pivotal role in many cellular processes, including the proliferation, survival and differentiation of lung cancer cells. Thus, PI3K is a promising therapeutic target for lung cancer treatment. In this study, we applied free and open-source protein-ligand docking software, screened 3167 FDA-approved small molecules, and identified putative PI3Kα inhibitors. Among them, econazole nitrate, an antifungal agent, exhibited the highest activity in decreasing cell viability in pathological types of NSCLC cell lines, including H661 (large cell lung cancer) and A549 (adenocarcinoma). Econazole decreased the protein levels of p-AKT and Bcl-2, but had no effect on the phosphorylation level of ERK. It inhibited cell growth and promote apoptosis in a dose-dependent manner. Furthermore, the combination of econazole and cisplatin exhibited additive and synergistic effects in the H661 and A549 lung cancer cell lines, respectively. Finally, we demonstrated that econazole significantly suppressed A549 tumor growth in nude mice. Our findings suggest that econazole is a new PI3K inhibitor and a potential drug that can be used in lung cancer treatment alone or in combination with cisplatin.

Background : The phosphatidylinositol 3-kinase (PI3K)/AKT signaling pathway is hyperactivated in lung cancer and regulates a broad range of cellular processes, including proliferation, survival, angiogenesis, and metastasis. Thus PI3K is considered a promising target for therapy. To date, PI3K inhibitors have not been approved for lung cancer. Recent studies showed that the antipsychotic agent flupentixol induced apoptosis of lung cancer cell, however the anti-tumor mechanism of flupentixol remains unclear. Methods : (1) The idock software simulated the molecular docking between the PI3Kα protein and flupentixol. (2) Inhibition of PI3Kα by the flupentixol was examined by in vitro kinase assays. (3) The cytotoxicity of flupentixol on the NSCLC cell lines was tested by MTT assays. (4) We treated A549 and H661 cells with flupentixol and then measured the percentage of apoptotic cells by the Annexin V/PI analysis. (5) We investigated the effect of flupentixol on the expression of critical PI3K/AKT signaling pathway proteins, further analyzed on the cleavage of PARP and caspase-3 by Western blotting. (6) BALB/C nude mice were subcutaneously injected with A549 cells to evaluate the effect of flupentixol on the growth of lung carcinoma. Results : Structural analysis of the predicted binding conformation suggested that flupentixol docks to the ATP binding pocket of PI3Kα. Kinase assays demonstrate that flupentixol indeed inhibited the PI3Kα kinase activity. Flupentixol exhibited cytotoxicity in lung cancer cell lines A549 and H661 in a dose- and time-dependent manner. Furthermore, flupentixol more strongly inhibited the phosphorylation of AKT (T308 and S473) and the expression of its downstream target gene Bcl-2 than two known PI3K inhibitors (BYL719 and BKM120). Flupentixol induced apoptosis as measured by PARP and caspase-3 cleavage. Finally, flupentixol significantly suppressed A549 xenograft growth in BALB/C nude mice. Conclusions : Flupentixol could be docked to the PI3Kα protein and specifically inhibit the PI3K/AKT pathway and survival of lung cancer cells in vitro and in vivo . As an old drug, flupentixol is a new PI3K inhibitor that may be used for the treatment of lung cancers.