Thiophene Carboxamide Analogs with Long Alkyl Chains Comprising Ethylene Glycol Units Inhibit Glioblastoma Cell Proliferation by Activating AMPK.

Glioblastoma is a refractory malignant tumor that requires novel therapeutic strategies for effective treatment. We have previously reported that JCI-20679 (1), an analog of annonaceous acetogenins, shows potent antitumor activity against glioblastomas. However, the synthesis of 1 requires 23 steps, including 16 steps for the preparation of a tetrahydrofuran (THF) moiety. This study reports the design and synthesis of 11 analogs with a triethylene glycol moiety in place of the THF moiety in 1. Among these, the analog 2k with an n-decyl chain exhibited potent inhibitory activity against the growth of glioblastoma stem cells by inhibiting mitochondrial function and synergistically enhancing the effect of temozolomide (TMZ). Furthermore, 2k significantly suppressed tumor growth without critical toxicity in vivo. Hence, this study presents novel potential anticancer agents and a strategy for the development of these agents that can be produced easily.

Structure-antitumor activity relationship of hybrid acetogenins focusing on connecting groups between heterocycles and the linker moiety.

We studied hybrid molecules of annonaceous acetogenins and mitochondrial complex I-inhibiting insecticides to develop a novel anticancer agent. A structure-antitumor activity relationship study focusing on the connecting groups between the heterocycles and the linker moiety bearing the tetrahydrofuran moiety was conducted. Eleven hybrid acetogenins with 1-methylpyrazole instead of γ-lactone were synthesized and their growth inhibitory activities against 39 human cancer cell lines were evaluated. The nitrogen atom at the 2'-position of the linker moiety was essential for inhibiting cancer growth. The 1-methylpyrazole-5-sulfonamide analog showed potent growth inhibition of NCI-H23, a human lung cancer cell line, in a xenograft mouse assay without critical toxicity. Hence, the results of this study may pave the way for the development of novel anticancer agents, with both selective and broad anticancer activities.

JCI­20679 suppresses the proliferation of glioblastoma stem cells by activating AMPK and decreasing NFATc2 expression levels.

The prognosis of glioblastoma, which is the most frequent type of adult­onset malignant brain tumor, is extremely poor. Therefore, novel therapeutic strategies are needed. Previous studies report that JCI­20679, which is synthesized based on the structure of naturally occurring acetogenin, inhibits mitochondrial complex I and suppresses the growth of various types of cancer cells. However, the efficacy of JCI­20679 on glioblastoma stem cells (GSCs) is unknown. The present study demonstrated that JCI­20679 inhibited the growth of GSCs derived from a transposon system­mediated murine glioblastoma model more efficiently compared with the growth of differentiation­induced adherent cells, as determined by a trypan blue staining dye exclusion test. The inhibition of proliferation was accompanied by the blockade of cell­cycle entry into the S­phase, as assessed by a BrdU incorporation assay. JCI­20679 decreased the mitochondrial membrane potential, suppressed the oxygen consumption rate and increased mitochondrial reactive oxygen species generation, indicating that JCI­20679 inhibited mitochondrial activity. The mitochondrial inhibition was revealed to increase phosphorylated (phospho)­AMPKα levels and decrease nuclear factor of activated T­cells 2 (NFATc2) expression, and was accompanied by a decrease in calcineurin phosphatase activity. Depletion of phospho­AMPKα by knockdown of AMPKß recovered the JCI­20679­mediated decrease in NFATc2 expression levels, as determined by western blotting and reverse transcription­quantitative PCR analysis. Overexpression of NFATc2 recovered the JCI­20679­mediated suppression of proliferation, as determined by a trypan blue staining dye exclusion test. These results suggest that JCI­20679 inhibited mitochondrial oxidative phosphorylation, which activated AMPK and reduced NFATc2 expression levels. Moreover, systemic administration of JCI­20679 extended the event­free survival rate in a mouse model transplanted with GSCs. Overall, these results suggested that JCI­20679 is a potential novel therapeutic agent against glioblastoma.

JCI-20679 suppresses autophagy and enhances temozolomide-mediated growth inhibition of glioblastoma cells.

Glioblastoma, a type of brain cancer, is one of the most aggressive and lethal types of malignancy. The present study shows that JCI-20679, an originally synthesized mitochondrial complex I inhibitor, enhances the anti-proliferative effects of suboptimal concentrations of the clinically used chemotherapeutic drug temozolomide in glioblastoma cells. Analysis of the effects of temozolomide combined with JCI-20679 using isobologram and combination index methods demonstrated that the combination had synergistic effects in murine and human glioblastoma cells. We found that JCI-20679 inhibited the temozolomide-mediated induction of autophagy that facilitates cellular survival. The autophagy induced by temozolomide increased ATP production, which confers temozolomide resistance in glioblastoma cells. JCI-20679 blocked temozolomide-mediated increases in ATP levels and increased the AMP/ATP ratio. Furthermore, JCI-20679 enhanced the therapeutic effects of temozolomide in an orthotopic transplantation model of glioblastoma. These results indicate that JCI-20679 may be promising as a novel agent for enhancing the efficacy of temozolomide against glioblastoma.

Structure-Activity Relationships of Thiophene Carboxamide Annonaceous Acetogenin Analogs: Shortening the Alkyl Chain in the Tail Part Significantly Affects Their Growth Inhibitory Activity against Human Cancer Cell Lines.

In a previous study, we found that the thiophene carboxamide solamin analog, which is a mono-tetrahydrofuran annonaceous acetogenin, showed potent antitumor activity through the inhibition of mitochondrial complex I. In this study, we synthesized analogs with short alkyl chains instead of the n-dodecyl group in the tail part. We evaluated their growth inhibitory activities against human cancer cell lines. We found that the alkyl chain in the tail part plays an essential role in their activity.