Cell differentiation enhancement by hydrophilic derivatives of 4,8-dihydrobenzo[1,2-b:5,4-b']dithiophene-4,8-diones in HL-60 leukemia cells

Selective Integrin Ligands Promote Cell Internalization of the Antineoplastic Agent Fluorouracil

Drug conjugates consisting of an antineoplastic drug and a targeting receptor ligand could be effective to overcome the heavy side effects of unselective anticancer agents. To address this need, we report here the results of a project aimed to study agonist and antagonist integrin ligands as targeting head of molecular cargoes for the selective delivery of 5-fluorouracil (5-FU) to cancer or noncancer cells. Initially, two fluorescent β-lactam-based integrin ligands were synthesized and tested for an effective and selective internalization mediated by α4β1 or α5β1 integrins in Jurkat and K562 cells, respectively. No cellular uptake was observed for both fluorescent compounds in HEK293 noncancerous control cells. Afterward, three conjugates composed of the β-lactam-based integrin ligand, suitable linkers, and 5-FU were realized. The best compound E, acting as α5β1 integrin agonist, is able to selectively deliver 5-FU into tumor cells, successfully leading to cancer cell death.

Carboxamide analog ITR-284 evokes apoptosis and inhibits migration ability in human lung adenocarcinoma A549 cells

Lung adenocarcinoma is the most common type of lung cancer and found in both smokers and non-smokers, but the treatment of lung cancer is limited. ITR-284 has been shown to be a potent carboxamide-derived anticancer agent and to induce apoptosis in leukemia and colon cancer cells. However, little is known whether ITR-284 has anticancer activity in human lung adenocarcinoma cells through induction of apoptosis and suppression of migration in vitro. We showed that ITR-284 inhibited human lung cancer A549 cells using the thiazolyl blue tetrazolium bromide (MTT) assay and evoked apoptosis via the cell cycle distribution at S phase arrest. After treatment with 20 nM ITR-284 for 24 h, apoptotic cells were induced and detected by Annexin V-FITC/PI staining. The production of reactive oxygen species (ROS) was dose-dependently increased in A549 cells caused by ITR-284. The results from immunoblotting analysis showed an elevation of protein levels of p53 and phosphorylation of p53 in A549 cells prior to ITR-284 exposure. Additionally, apoptosis-associated proteins such as Bax, cleaved caspase-3 and cleaved PARP were upregulated after ITR-284 treatment. By wound healing assay, low concentrations (1-5 nM) of ITR-284 exerted a greater effect on inhibition of A549 cell migration. The protein levels of E-cadherin and vimentin, which are the epithelial-mesenchymal transition (EMT) markers, were modulated in ITR-284-treated cells assessed by western blot analysis. Taken together, our data suggest that ITR-284 may be an effective anticancer agent for treating lung adenocarcinoma.

Discovery and development of natural product-derived chemotherapeutic agents based on a medicinal chemistry approach

Medicinal plants have long been an excellent source of pharmaceutical agents. Accordingly, the long-term objectives of the author's research program are to discover and design new chemotherapeutic agents based on plant-derived compound leads by using a medicinal chemistry approach, which is a combination of chemistry and biology. Different examples of promising bioactive natural products and their synthetic analogues, including sesquiterpene lactones, quassinoids, naphthoquinones, phenylquinolones, dithiophenediones, neo-tanshinlactone, tylophorine, suksdorfin, DCK, and DCP, will be presented with respect to their discovery and preclinical development as potential clinical trial candidates. Research approaches include bioactivity- or mechanism of action-directed isolation and characterization of active compounds, rational drug design-based modification and analogue synthesis, and structure-activity relationship and mechanism of action studies. Current clinical trial agents discovered by the Natural Products Research Laboratories, University of North Carolina, include bevirimat (dimethyl succinyl betulinic acid), which is now in phase IIb trials for treating AIDS. Bevirimat is also the first in a new class of HIV drug candidates called "maturation inhibitors". In addition, an etoposide analogue, GL-331, progressed to anticancer phase II clinical trials, and the curcumin analogue JC-9 is in phase II clinical trials for treating acne and in development for trials against prostate cancer. The discovery and development of these clinical trial candidates will also be discussed.

2-(1-Hydroxethyl)-4,8-dihydrobenzo[1,2-b:5,4-b']dithiophene-4,8-dione (BTP-11) enhances the ATRA-induced differentiation in human leukemia HL-60 cells

2-(1-Hydroxethyl)-4,8-dihydrobenzo[1,2-b:5,4-b']dithiophene-4,8-dione (BTP-11) is a potent enhancer for all-trans retinoic acid (ATRA)-induced differentiation in HL-60 cells. Combination of BTP-11 and ATRA cut down the concentration of ATRA significantly, and that BTP-11 promoted the progression of ATRA-induced into the terminal granulocytic differentiation. Further, Western blot analysis revealed that combination of BTP-11 and ATRA decreased cyclin D/CDK4 and increased C/EBPvarepsilon protein expression to arrest the cells into G0/G1 phase leading to granulocytic maturation. These results confirmed that BTP-11 is a potent enhancer for ATRA-induced differentiation of HL-60 cells, and the great developmental potential of BTP-11 will be expected.

Synthesis of 1-substituted 3-pyridinylmethylidenylindolin-2-ones and 1-substituted 3-quinolinylmethylidenylindolin-2-ones as the enhancers of ATRA-induced differentiation in HL-60 cells

As part of our continuing search for potential differentiation agents, 1-benzyl-3-(4-pyridinylmethylidenyl)indolin-2-one (14) was selected as lead compound, and its new pyridinyl and quinolinyl analogs were synthesized and evaluated for differentiation-inducing activity toward HL-60 cells. Most of the tested compounds enhanced the ATRA-induced differentiation; among them, 1-(1-phenylethyl)-3-(3-quinolinylmethylidenyl)indolin-2-one (25) was the most promising one. The two isomers, 25Z and 25E; consisting 25 were found to have similar differentiation activity. The combination of 25 with all trans retinoic acid (ATRA) was found to induce complete differentiation of HL-60 cells and arrest the cells in the G(0)/G(1) phase of the cell cycle. Beside its excellent differentiation activity, 25 also exhibited relatively low cytotoxicity toward normal cells. Therefore, compound 25 is recommended as a candidate for further development of novel enhancer of ATRA-induced differentiation in HL-60 cells.