Longikaurin A, a natural ent-kaurane, suppresses stemness in nasopharyngeal carcinoma cells

Longikaurin A, a natural ent-kaurane, suppresses proliferation, invasion and tumorigenicity in oral squamous cell carcinoma cell by via inhibiting PI3K/Akt pathway in vitro and in vivo

Background: Longikaurin A (LK-A), a naturally occurring ent-kaurane diterpenoid, has been identified as a promising anti-cancer agent. This study aims to elucidate the anti-tumorigenic effects of LK-A on oral squamous cell carcinoma (OSCC) cells and to unravel its underlying mechanisms. Methods: In vitro assays, including CCK-8 and EdU, were performed to assess cell viability and proliferation. Transwell migration and invasion assays evaluated cell mobility and invasive potential. Apoptotic effects were analyzed using Annexin V-FITC/PI staining and TUNEL assays. Western blot analysis was conducted to examine protein expression related to cell cycle, apoptosis, and the PI3K/Akt signaling pathway. In vivo experiments involved treating mouse xenograft models with LK-A and evaluating tumor growth and signaling pathway inhibition through immunohistochemistry and Western blot assays. Results: LK-A significantly suppressed cell viability and proliferation in a dose-dependent manner, with IC50 values of 4.36 μM and 4.93 μM at 24 h, and 1.98 μM and 2.89 μM at 48 h for CAL27 and TCA-8113 cells, respectively. EdU assays revealed a reduction in the EdU positive rate, and cell cycle analysis showed G2/M phase arrest. Western blot analysis confirmed decreased expression of CyclinB1 and Cdc2. LK-A significantly inhibited OSCC cell mobility and invasive potential, with downregulation of MMP-2 and MMP-9 expression. Apoptotic effects were confirmed by increased apoptosis, upregulation of Bax and cleaved caspase-3, and downregulation of Bcl-2. LK-A suppressed the PI3K/AKT signaling pathway, as evidenced by reduced phosphorylation of PI3K, AKT, and mTOR. The AKT activator SC79 reversed the antiproliferative and pro-apoptotic effects of LK-A. In vivo, LK-A significantly inhibited tumor growth in mouse xenograft models, with reduced tumor weights and volumes, and no significant loss in body weight. Immunohistochemistry and Western blot assays confirmed the inhibition of p-Akt and Ki-67 expression. Conclusion: These findings suggest that LK-A exerts potent antiproliferative, anti-migratory, and pro-apoptotic effects on OSCC cells through the suppression of the PI3K/AKT signaling pathway, demonstrating its potential as a therapeutic agent for OSCC.

Longikaurin A induces ferroptosis and inhibits glioblastoma progression through DNA methylation - Mediated GPX4 suppression

Glioblastoma (GBM) is the most common primary intracranial tumor highly resistant to conventional clinical chemotherapy. Recently, the induction of ferroptosis is emerging as a putative strategy to treat various tumors. However, the identification of the effective and applicable tumor ferroptosis-inducing agents remains challenging. In this study, we showed that longikaurin A (LK-A), a natural diterpenoid isolated from the medicinal plant Isodon ternifolius with strong anti-GBM capacities, induced remarkable GBM cell ferroptosis along with suppressing the key anti-ferroptosis factor glutathione peroxidase 4 (GPX4). GPX4 promoter contains conserved CpG islands. The LK-A-induced GPX4 suppression coincided with the inhibition of ten-eleven translocation 2 (TET2), a key DNA demethylation enzyme and an increase in the hypermethylation of the GPX4 promoter. Further, LK-A promoted the GBM ferroptotic alterations and inhibited GBM progression in both subcutaneous and orthotopic xenograft mouse models, whereas GPX4 overexpression largely abrogated its anti-GBM effects both in vitro and in vivo, suggesting that LK-A inductions of the DNA methylation-incurred GPX4 suppression and ferroptosis are crucial for its anti-GBM functions. Together, our study has elaborated an important epigenetic pathway of GBM ferroptosis and uncovered a critical pharmacological property of LK-A for treating GBM patients.

Mechanistic Pathways and Molecular Targets of Plant-Derived Anticancer ent-Kaurane Diterpenes

Since the first discovery in 1961, more than 1300 ent-kaurane diterpenoids have been isolated and identified from different plant sources, mainly the genus Isodon. Chemically, they consist of a perhydrophenanthrene subunit and a cyclopentane ring. A large number of reports describe the anticancer potential and mechanism of action of ent-kaurane compounds in a series of cancer cell lines. Oridonin is one of the prime anticancer ent-kaurane diterpenoids that is currently in a phase-I clinical trial in China. In this review, we have extensively summarized the anticancer activities of ent-kaurane diterpenoids according to their plant sources, mechanistic pathways, and biological targets. Literature analysis found that anticancer effect of ent-kauranes are mainly mediated through regulation of apoptosis, cell cycle arrest, autophagy, and metastasis. Induction of apoptosis is associated with modulation of BCL-2, BAX, PARP, cytochrome c, and cleaved caspase-3, -8, and -9, while cell cycle arrest is controlled by cyclin D1, c-Myc, p21, p53, and CDK-2 and -4. The most common metastatic target proteins of ent-kauranes are MMP-2, MMP-9, VEGF, and VEGFR whereas LC-II and mTOR are key regulators to induce autophagy.

Limonin enhances the radiosensitivity of nasopharyngeal carcinoma cells via attenuating Stat3-induced cell stemness

The inhibitory effects of limonin have been disclosed in various tumors, however, its roles in nasopharyngeal carcinoma (NPC) progression are never been revealed. In the current work, we collected NPC cells with a higher stemness compared with bulk cells through isolating the side population (SP) cells. It was found that limonin exhibited a stronger inhibitory effect on SP cells than that in bulk cells, which was evident by a lower IC50 value. Additionally, limonin attenuated the stemness and migration ability of SP cells with the higher stemness, characterized as decreasing the spheroid formation ability, expression of stemness markers and migration ability. Moreover, the proportion of SP cells in G0 phase was remarkably higher than that in bulk cells. Notably, upon limonin treatment, the proportion of SP cells in G0 was decreased and S/G2/M increased. Furthermore, limonin enhanced the radiosensitivity of NPC cells. The mechanistic studies based on RNA-sequencing analysis revealed that limonin inhibited the gene transcription driven by Stat3 (signal transducer and activator of transcription 3) and an activator of Stat3 (Colivelin or IL-6) rescued the inhibitory effects of limonin. Therefore, these results demonstrate that limonin could reduce the stemness of NPC cells and thus the radiosensitivity through suppressing Stat3 transcriptional activity.

Diosgenin increased DDX3 expression in hepatocellular carcinoma

Liver cancer, one of the most common malignant tumors occurred worldwide, has emerged as a main health trouble and accounts for leading cancer-related death. Diosgenin is provided as an important material in the pharmaceutical industry, and is used to manage various medical troubles such as cancer because of its multiple bioactivities. DEAD box polypeptide 3 (DDX3) is involved in cancer biogenesis and modulates cancer progression. However, the role of DDX3 in human hepatocellular carcinoma (HCC) has not been fully understood. In the present study, we investigated the anti-tumor effects of diosgenin on HCC cells and whether DDX3 is involved in its antitumor activity. We observed that diosgenin dramatically inhibited cell proliferation, triggered apoptotic cell death, induced G2/M phase arrest, suppressed cell migration and invasion abilities. Moreover, the expression of DDX3 was measured and the results showed that DDX3 was significantly up-regulated upon diosgenin exposure. All together, our data indicated that diosgenin shows a cytotoxic effect on HCC cells and has potential therapeutic values for HCC patients.

MORF4L1 suppresses cell proliferation, migration and invasion by increasing p21 and E-cadherin expression in nasopharyngeal carcinoma

Mortality factor 4-like 1 (MORF4L1) is a member of a subgroup of histone acetyltransferases and belongs to the mortality factor on chromosome 4 (MORF4) class of proteins. However, the role of MORF4L1 in cancers is largely unknown. Using reverse transcription-quantitative polymerase chain reaction and published datasets, the present study demonstrated that the expression of MORF4L1 is decreased in several cancers, including nasopharyngeal carcinoma (NPC). Additionally, the methylation rate of the promoter of MORF4L1 was identified to be significantly higher in tumour cells than in normal cells. The ectopic expression of MORF4L1 was also revealed to inhibit cell proliferation, colony formation, migration and invasion in NPC, whereas the knockdown of MORF4L1 promoted cell proliferation, colony formation, migration and invasion. Mechanistically, the present study demonstrated that MORF4L1 functions as a tumour suppressor by increasing p21 and E-cadherin levels. These findings may be useful novel targets for treating patients with NPC.