Jayoung Song

Anti-proliferative activity and suppression of P-glycoprotein by (-)-antofine, a natural phenanthroindolizidine alkaloid, in paclitaxel-resistant human lung cancer cells.

Multidrug resistance (MDR) is a major obstacle in effective chemotherapy for cancer patients. The expression of P-glycoprotein (P-gp) in cancer cells is highly correlated with resistance to chemotherapeutic drugs. (-)-Antofine, a phenanthroindolizidine alkaloid derived from Cynanchum paniculatum, inhibits the growth of various human cancer cells. In this study, we further explored the potential of (-)-antofine to overcome the resistance induced by anti-cancer drugs. To this end, we established the paclitaxel-resistant human lung cancer cell line A549-PA by gradually exposing A549 cells to increasing concentrations of paclitaxel. As a result, the A549-PA cells acquired resistance against paclitaxel treatment and had an IC50 that was more than 200 times that of the parental A549 cells. (-)-Antofine, however, effectively suppressed the growth of both the parental and drug-resistant cells. Additional studies revealed that the anti-proliferative activity of (-)-antofine in A549-PA cells is accompanied by a down-regulation of P-gp mRNA and protein expression. The effect of reversing the multidrug resistance of A549-PA cells via (-)-antofine treatment was demonstrated an increase in intracellular rhodamine-123 accumulation, measured using FACS analysis. These findings suggest an additional chemotherapeutic value of (-)-antofine, that is, regulation of cancer cell drug resistance, in addition to its antitumor effect.

Design, Synthesis, and Biological Activity of Sulfonamide Analogues of Antofine and Cryptopleurine as Potent and Orally Active Antitumor Agents

Due to their profound antiproliferative activity and unique mode of action, phenanthroindolizidine and phenanthroquinolizidine alkaloids, represented by antofine and cryptopleurine, have attracted attention recently as potential therapeutic agents. We have designed, synthesized, and evaluated the methanesulfonamide analogues of these natural alkaloids with the hope of improving their druglikeness. The analogues showed enhanced growth inhibition of human cancer cells compared with the parent natural products. In particular, a methanesulfonamide analogue of cryptopleurine (5b) exhibited improved bioavailability and significant antitumor activity, which suggests that 5b is a promising new anticancer agent. Our studies suggest that the inhibition of cancer cell growth by 5b is associated with the induction of G0/G1 cell cycle arrest via nicotinamide N-methyltransferase-dependent JNK activation in Caki-1 renal cancer cells. In addition, compound 5b significantly inhibited the migration and invasion of Caki-1 cancer cells by modulating the p38 MAPK signaling pathway.

Synthesis and Biological Evaluation of Carbocyclic Analogues of Pachastrissamine

A series of carbocyclic analogues of naturally-occurring marine sphingolipid pachastrissamine were prepared and biologically evaluated. The analogues were efficiently synthesized via a tandem enyne/diene-ene metathesis reaction as a key step. We found that the analogue 4b exhibited comparable cytotoxicity and more potent inhibitory activity against sphingosine kinases, compared to pachastrissamine. Molecular modeling studies were conducted to provide more detailed insight into the binding mode of 4b in sphingosine kinase. In our docking model, pachastrissamine and 4b were able to effectively bind to the binding pocket of sphingosine kinase 1 as co-crystalized sphingosine. However, 4b showed a hydrophobic interaction with Phe192, which suggests that it contributes to its increased inhibitory activity against sphingosine kinase 1.

Design, synthesis, and evaluation of a water-soluble antofine analogue with high antiproliferative and antitumor activity.

New water soluble antofine C-13a analogues were designed, synthesized, and evaluated for antiproliferative activity against cancer cells. Particularly, (-)-(R)-13a-hydroxymethylantofine ((-)-(R)-4b) demonstrated notable growth inhibition against a panel of human cancer cell lines. This growth inhibition was associated with the arrest of the cell cycle in the G0/G1 phases and suppression of mTOR signaling in human lung A549 cancer cells. Compound (-)-(R)-4b also overcame paclitaxel-resistance in human lung cancer cells (A549-Pa) by suppressing P-glycoprotein expression. Furthermore, compound (-)-(R)-4b significantly inhibited the tumor growth of A549 and A549-Pa xenografts in a nude mouse model, which suggests it is a promising novel antitumor agent with sufficient aqueous solubility.

Multiplicity of acquired cross-resistance in paclitaxel-resistant cancer cells is associated with feedback control of TUBB3 via FOXO3a-mediated ABCB1 regulation

Acquired drug resistance is a primary obstacle for effective cancer therapy. The correlation of point mutations in class III β-tubulin (TUBB3) and the prominent overexpression of ATP-binding cassette P-glycoprotein (ABCB1), a multidrug resistance gene, have been protruding mechanisms of resistance to microtubule disruptors such as paclitaxel (PTX) for many cancers. However, the precise underlying mechanism of the rapid onset of cross-resistance to an array of structurally and functionally unrelated drugs in PTX-resistant cancers has been poorly understood. We determined that our established PTX-resistant cancer cells display ABCB1/ABCC1-associated cross-resistance to chemically different drugs such as 5-fluorouracil, docetaxel, and cisplatin. We found that feedback activation of TUBB3 can be triggered through the FOXO3a-dependent regulation of ABCB1, which resulted in the accentuation of induced PTX resistance and encouraged multiplicity in acquired cross-resistance. FOXO3a-directed regulation of P-glycoprotein (P-gp) function suggests that control of ABCB1 involves methylation-dependent activation. Consistently, transcriptional overexpression or downregulation of FOXO3a directs inhibitor-controlled protease-degradation of TUBB3. The functional PI3K/Akt signaling is tightly responsive to FOXO3a activation alongside doxorubicin treatment, which directs FOXO3a arginine hypermethylation. In addition, we found that secretome factors from PTX-resistant cancer cells with acquired cross-resistance support a P-gp-dependent association in multidrug resistance (MDR) development, which assisted the FOXO3a-mediated control of TUBB3 feedback. The direct silencing of TUBB3 reverses induced multiple cross-resistance, reduces drug-resistant tumor mass, and suppresses the impaired microtubule stability status of PTX-resistant cells with transient cross-resistance. These findings highlight the control of the TUBB3 response to ABCB1 genetic suppressors as a mechanism to reverse the profuse development of multidrug resistance in cancer.

The roles of IP3 receptor in energy metabolic pathways and reactive oxygen species homeostasis revealed by metabolomic and biochemical studies

Inositol 1,4,5-trisphosphate receptors (IP(3)Rs) are calcium channels modulating important calcium-mediated processes. Recent studies implicate IP(3)R in cell metabolism, but specific evidence is missing regarding IP(3)Rs effects on actual metabolic pathways and key energy metabolites. Here, we applied metabolomics and molecular biology to compare DT40 cell lines devoid of IP(3)R (KO) and its wild-type (WT) counterpart. NMR and LC-MS metabolomic data showed that the KO cell line has a very different basic energy metabolism from the WT cell line, showing enhanced Warburg effect. In particular, the KO cells exhibited significant perturbation in energy charge, reduced glutathione and NADPH ratios with slower cellular growth rate. Subsequent flow cytometry results showed that the KO cell line has a higher level of general reactive oxygen species (ROS) but has a lower level of peroxynitrites. This ROS disturbance could be explained by observing lower expression of superoxide dismutase 2 (SOD2) and unchanged expression of catalase. The higher ROS seems to be involved in the slower growth rate of the KO cells, with an ROS scavenger increasing their growth rate. However, the KO and WT cell lines did not show any noticeable differences in AMPK and phosphorylated AMPK levels, suggesting possible saturation of AMPK-mediated metabolic regulatory circuit in both cells. Overall, our study reveals IP3Rs roles in ROS homeostasis and metabolic pathways as well as the effects of its KO on cellular phenotypes.

Synthesis and biological evaluation of 2′-substituted-4′-selenoribofuranosyl pyrimidines as antitumor agents

The 2′-substituted-4′-selenoribofuranosyl pyrimidines 3a–3j were synthesized from D-ribose and assayed for anticancer activity. The 2′-azido and 2′-fluoro groups with a ribo configuration were introduced by the regioselective opening of the O2,2′-anhydronucleosides with sodium azide and (HF)x-pyridine, respectively. Among the compounds tested, only 2′-fluoro derivative 3j was found to exhibit significant anticancer activity, but was much less potent than the corresponding 2′-arabino analogue 2c. This study will provide medicinal chemists with the insight into the identification of structural requirements for the anticancer activity for the developments of biologically active nucleosides.Graphical Abstract

Abstract 4235: Anti-proliferative effect of (19Z)-halichondramide from the sponge Chondrosia corticata via G2/M cell cycle arrest and suppression of mTOR signaling in human lung cancer cells

Five oxazole-containing macrolides isolated from the marine sponge Chondrosia corticata were evaluated for their anti-proliferative activity in a panel of human solid cancer cell lines. (19Z)-Halichondramide ((19Z)-HCA), a novel trisoxazole-containing macrolide, exhibited the highest potency among the macrolides, with IC 50 values in the submicro-molar ranges. Prompted by the high potency of growth inhibition of cancer cells, we investigated the mechanism of action of the anti-proliferative activity of (19Z)-HCA in human A549 lung cancer cells. (19Z)-HCA induced cell cycle arrest in the G2/M phase, and this event was highly correlated with the expression of checkpoint proteins, including the up-regulation of p53 and GADD45α and the down-regulation of cyclin B1, cyclin A, CDC2, and CDC25C. In addition, the growth inhibition by (19Z)-HCA was associated with the suppression of mTOR and its downstream effector molecules 4EBP1 and p70S6K. The modulation of mTOR signaling by (19Z)-HCA was found to be mediated by the regulation of upstream proteins, including the down-regulation of Akt and p38 MAPK and the up-regulation of AMPK. These data suggest the potential of (19Z)-HCA to serve as a candidate for cancer chemotherapeutic agents derived from marine organisms by virtue of arresting the cell cycle in the G2/M phase and the modulation of mTOR/AMPK signaling pathways. [Acknowledgements: This work was supported by the MarineBio Research Program (NRF-2013045101) of the National Research Foundation of Korea (NRF) Grant funded by the Korean Government (MEST).] Citation Format: Song Yi Bae, Jayoung Song, Yoonho Shin, Won Kyung Kim, Jedo Oh, Tae Joon Choi, Eun Ju Jeong, So Hyun Park, Eun Jeong Jang, Ji In Kang, Hyen Joo Park, Ji-Young Hong, Gi Dae Kim, Ju-eun Jeon, Jongheon Shin, Sang Kook Lee. Anti-proliferative effect of (19 Z )-halichondramide from the sponge Chondrosia corticata via G2/M cell cycle arrest and suppression of mTOR signaling in human lung cancer cells. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 4235. doi:10.1158/1538-7445.AM2014-4235

A novel selenonucleoside suppresses tumor growth by targeting Skp2 degradation in paclitaxel-resistant prostate cancer

&NA; Prostate cancer (PC) is the most common disease in men over age 50, and its prevalence rate has been gradually increasing since 1980. Taxane‐derived anticancer agents are the primary agents used to treat metastatic prostate cancer patients; however, the side effects and acquired drug resistance limit the success of these therapies. Because there is no specific treatment for paclitaxel‐resistant prostate cancer, it is necessary to develop new targets and therapeutic strategies to overcome the acquired resistance. In this study, the antitumor activity of a novel selenonucleoside (4′‐selenofuranosyl‐2,6‐dichloropurine, LJ‐2618), a third‐generation nucleoside, and its plausible mechanisms of action in paclitaxel‐resistant prostate cancer (PC‐3‐Pa) cells were investigated. The established PC‐3‐Pa cells exhibited over 100‐fold resistance against paclitaxel compared to the paclitaxel‐sensitive PC‐3 cells. LJ‐2618, however, effectively inhibited the proliferation of both cell lines with similar IC50 values in vitro. In PC‐3‐Pa cells, the activated PI3K/Akt signaling pathway was suppressed by LJ‐2618 treatment. In addition, Skp2 was found to be over‐expressed in paclitaxel‐resistant cells, and the transfection of Skp2 siRNA recovered the sensitivity of paclitaxel in PC‐3‐Pa cells. Furthermore, LJ‐2618 significantly down‐regulated Skp2 expression in PC‐3‐Pa cells by promoting degradation and inducing destabilization of Skp2, which triggers G2/M cell cycle arrest. In a xenograft mouse model implanted with PC‐3‐Pa cells, LJ‐2618 (3 or 10 mg/kg) effectively inhibited tumor growth with the enhancement of Skp2 degradation and induction of p27 expression in tumor tissues. These findings suggest that LJ‐2618 may have potential for overcoming paclitaxel resistance via promoting Skp2 degradation and stabilizing p27 expression in PC‐3‐Pa cells. Therefore, the novel selenonucleoside LJ‐2618 may lead to the development of a new treatment strategy for patients with paclitaxel‐resistant, castration‐resistant prostate cancer.

Synthesis, structural characterization and biological evaluation of 4′-C-methyl- and phenyl-dioxolane pyrimidine and purine nucleosides

Nucleoside analogues play an important role in antiviral, antibacterial and antineoplastic chemotherapy. Herein we report the synthesis, structural characterization and biological activity of some 4′-C-methyl- and -phenyl dioxolane-based nucleosides. In particular, α and β anomers of all natural nucleosides were obtained and characterized by NMR, HR-MS and X-ray crystallography. The compounds were tested for antimicrobial activity against some representative human pathogenic fungi, bacteria and viruses. Antitumor activity was evaluated in a large variety of human cancer cell-lines. Although most of the compounds showed non-significant activity, 23α weakly inhibited HIV-1 multiplication. Moreover, 22α and 32α demonstrated a residual antineoplastic activity, interestingly linked to the unnatural α configuration. These results may provide structural insights for the design of active antiviral and antitumor agents.