PTEN (phosphatase and tensin homolog), a tumor suppressor frequently mutated in human cancer, has various cytoplasmic and nuclear functions. PTEN translocates to the nucleus from the cytoplasm in response to oxidative stress. However, the mechanism and function of the translocation are not completely understood. In this study, topotecan (TPT), a topoisomerase I inhibitor, and cisplatin (CDDP) were employed to induce DNA damage. The results indicate that TPT or CDDP activates ATM (ATM serine/threonine kinase), which phosphorylates PTEN at serine 113 and further regulates PTEN nuclear translocation in A549 and HeLa cells. After nuclear translocation, PTEN induces autophagy, in association with the activation of the p-JUN-SESN2/AMPK pathway, in response to TPT. These results identify PTEN phosphorylation by ATM as essential for PTEN nuclear translocation and the subsequent induction of autophagy in response to DNA damage.

Harmine, a β-carboline alkaloid isolated from the seeds of Peganum harmala, possesses both antitumor and anti‑nociceptive effects and inhibits human DNA topoisomerase. However, no detailed data are available concerning the mechanisms of harmine in human colorectal carcinoma SW620 cells. In the present study, we demonstrated that harmine inhibited the proliferation of SW620 cells in a dose-dependent manner using MTT and clone formation assays, and the IC50 value of harmine on the growth inhibition of SW620 cells for 48 h was 5.13 µg/ml. PI staining showed that harmine altered the cell cycle distribution by decreasing the proportion of cells in the G0-G1 phase and increasing the proportion in the S and G2-M phase. The expression level of cyclin D1 was decreased, while the expression of cyclin A, E2 and B1, CDK1/cdc2, Myt-1 and p-cdc2 (Tyr15) were increased, which was in accordance with the S and G2/M phase arrest. Hoechst 33258 staining revealed nuclear fragmentation, chromosomal condensation and cell shrinkage in the SW620 cells treated with harmine. Flow cytometry revealed that the percentage of apoptotic sub-G1 cells increased from 7.19 to 26.58%, while in the control group, sub-G1 cells only increased from 1.53 to 1.60%. Furthermore, early and late apoptotic cells were increased from 11.96 to 26.38% when incubated with the indicated concentration of harmine for 48 h, while in the control group, <8% of cells underwent apoptosis. JC-1 staining revealed that harmine decreased mitochondrial transmembrane potential (ΔΨm). The apoptosis of SW620 cells was also detected by western blot analysis, showing caspase-3 and -9, and PARP activation; the downregulation of Bcl-2, Mcl-1, Bcl-xL; and the upregulation of Bax. The expression of p-ERK, p-Akt (Ser473) and p-Akt (Thr308) was inhibited, and phosphorylation of downstream targets of Akt, such as p-FoxO3a and p-GSK‑3β were also attenuated. In conclusion, harmine induces cell cycle arrest and mitochondrial pathway-mediated cellular apoptosis in SW620 cells via inhibition of the Akt and ERK signaling pathways.

Norcantharidin, a low-toxic analog of the active anticancer compound cantharidin in Mylabris, can inhibit proliferation and induce apoptosis of multiple types of cancer cells. However, the anticancer activities of norcantharidin with respect to neuroblastoma, and its underlying mechanisms, have not been investigated. Therefore, our study was designed to determine the efficacy of norcantharidin on SK-N-SH neuroblastoma cell death and to elucidate detailed mechanisms of activity. In the present study, norcantharidin suppressed the proliferation and cloning ability of SK-N-SH cells in a dose-dependent manner, apparently by reducing the mitochondrial membrane potential and arresting SK-N-SH cells at the G2/M stage, accompanied by elevated expressions of p21 and decreased expressions of cyclin B1 and cell division control 2. Treatment by norcantharidin induced significant mitophagy and autophagy, as demonstrated by a decrease in Translocase Of Outer Mitochondrial Membrane 20 (TOM20), increased beclin1 and LC3-II protein expression, reduced protein SQSTM1/p62 expression, and accumulation of punctate LC3 in the cytoplasm of SK-N-SH cells. In addition, norcantharidin induced apoptosis through regulating the expression of B-cell lymphoma 2–associated X protein/B-cell lymphoma 2 and B-cell lymphoma 2–associated X protein/myeloid cell leukemia 1 and activating caspase-3 and caspase-9–dependent endogenous mitochondrial pathways. We also observed an increase in phosphor–AMP-activated protein kinase accompanied with a decrease in phosphor-protein kinase B and mammalian target of rapamycin expression after treatment with norcantharidin. Subsequent studies indicated that norcantharidin participates in cellular autophagy and apoptosis via activation of the c-Jun NH2-terminal kinases/c-Jun pathway. In conclusion, our results demonstrate that norcantharidin can reduce the mitochondrial membrane potential, induce mitophagy, and subsequently arouse cellular autophagy and apoptosis; the AMP-activated protein kinase, protein kinase B/mammalian target of rapamycin, and c-Jun NH2-terminal kinases/c-Jun signaling pathways are widely involved in these processes. Thus, the traditional Chinese medicine norcantharidin could be a novel therapeutic strategy for treating neuroblastoma.

Background: Norcantharidin (NCTD) is known to impact on cell progression in many cancers; however, its activity in non-small cell lung cancer (NSCLC) has not yet been characterized. In the present study, we set out to determine the cytotoxic effects of NCTD on the proliferation and apoptosis on A549 cells and their underlying mechanisms. Methods: NSCLC cell line A549 cells were cultured. A549 cells were treated with different concentrations of NCTD. Cell proliferation was detected by MTT and cell clone formation assay. Cell cycle and apoptosis were detected by flow cytometry. After A549 cells were treated with NCTD for 24 hours, the mitochondrial membrane potential was measured. The protein expression of Bcl-2, Bax, light chain 3 (LC3), et al. was tested by western blot. The expression of LC3 and Tom20 protein was detected by immunofluorescence. Results: NCTD suppressed the proliferation of NSCLC cells while decreasing mitochondrial membrane potential and inducing G2/M phase arrest. NCTD induced apoptosis, as demonstrated by increased B-cell lymphoma 2/Bcl-2-associated X protein and Bcl-2-associated X protein/myeloid cell leukemia 1 ratios. Aside from autophagy, NCTD induced mitophagy, with an increase in LC3 expression and a decrease in sequestosome 1 (p62) expression in the cytoplasm, accompanied by increased levels of Phospho-adenosine 5’-monophosphate -activated protein kinase (p-AMPK), Phospho-c-Jun NH2-Terminal Kinase (p-JNK), and Phospho-c-jun (p-c-jun) and a decreased level of Phospho-protein kinase B (p-AKT). Conclusions: This study has elucidated that NCTD restrains NSCLC cell progression via regulation of AMPK/mammalian target of rapamycin (mTOR)/uncoordinated 51-like kinase 1 (ULK1)/JNK pathways. This evidence provides insight into a novel treatment for NSCLC.

The aim of the present study was to investigate the inhibitory effect of silibinin on SW1990 pancreatic cancer cells. An MTT assay following silibinin treatment demonstrated an inhibitory effect on AsPC‑1 and SW1990 cells in a dose‑ and time‑dependent manner. Propidium iodide staining analysis identified the cell cycle arrest of G1 phase and western blotting analysis demonstrated that the expression levels of cyclin D1, cyclin E2, cyclin A and cyclin B1 were decreased. The expression of G1‑associated cell cycle‑dependent kinases, cyclin‑dependent kinase (CDK)4 and CDK6, were also decreased, whereas the expression of p15 (p15INK4B) was increased. In addition, after SW1990 cells were incubated with various concentrations of silibinin, early and late apoptotic cells were detected using flow cytometry. Silibinin increased the activities of caspase‑9 and caspase‑3, and subsequent cleavage of poly (ADP‑ribose) polymerase (PARP) was also observed. The expression levels of B‑cell lymphoma (Bcl)‑2, Bcl‑2‑like 1 and myeloid cell leukemia 1 were decreased, whereas the expression of Bcl‑like protein 4 did not alter and the expression levels of Bcl‑2‑like 1 small and Bcl‑2‑like protein 11 were increased. The expression levels of c‑Jun N‑terminal kinase (JNK) and phospho‑JNK were also increased. In conclusion, silibinin inhibited cell proliferation, induced cell cycle G1 arrest via upregulating p15INK4B and induced mitochondrial apoptosis via upregulating JNK/stress‑activated protein kinase (SAPK) signaling pathway in human pancreatic cancer SW1990 cells.