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Aberrant activation of the PI3K pathway is one of the commonest oncogenic events in human cancer. AKT is a key mediator of PI3K oncogenic function, and as such, it has been intensively pursued as a therapeutic target. Despite the high frequency of AKT activation in... Show less

Background

Targeting AKT suppresses tumor growth through inducing apoptosis, however, during which whether other forms of cell death occurring is poorly understood.

Methods

The effects of increasing PARP1 dependent cell death (parthanatos) induced by inhibiting AKT on cell proliferation were determined by CCK-8 assay, colony formation assay, Hoechst 33,258 staining and analysis of apoptotic cells by flow cytometry. For the detailed mechanisms during this process, Western blot analysis, qRT-PCR analysis, immunofluorescence and co-immunoprecipitation were performed. Moreover, the inhibition of tumor growth by inducing p53/SIRT6/PARP1-dependent parthanatos was further verified in the xenograft mouse model.

Results

For the first time, we identified that inhibiting AKT triggered parthanatos, a new form of regulated cell death, leading to colon cancer growth suppression. For the mechanism investigation, we found that after pharmacological or genetic AKT inhibition, p53 interacted with SIRT6 and PARP1 directly to activate it, and promoted the formation of PAR polymer. Subsequently, PAR polymer transported to outer membrane of mitochondria and resulted in AIF releasing and translocating to nucleus thus promoting cell death. While, blocking PARP1 activity significantly rescued colon cancer from death. Furthermore, p53 deletion or mutation eliminated PAR polymer formation, AIF translocation, and PARP1 dependent cell death, which was promoted by overexpression of SIRT6. Meanwhile, reactive oxygen species production was elevated after inhibition of AKT, which might also play a role in the occurrence of parthanatos. In addition, inhibiting AKT initiated protective autophagy simultaneously, which advanced tumor survival and growth.

Conclusion

Our findings demonstrated that AKT inhibition induced p53-SIRT6-PARP1 complex formation and the activation of parthanatos, which can be recognized as a novel potential therapeutic strategy for cancer. Video Abstract. Show less

Oxaliplatin is a platinum analog that can interfere with DNA replication and transcription. Continuous exposure to oxaliplatin results in chemoresistance; however, this mechanism is not well known. In this study, oxaliplatin-resistant (OR) colorectal cancer (CRC) cells of HCT116, HT29, SW480 and SW620 were established by gradually increasing the drug concentration to 2.5 µM. The inhibitory concentrations of cell growth by 50% (IC50 ) of oxaliplatin were 4.40–12.7-fold significantly higher in OR CRC cells as compared to their respective parental (PT) CRC cells. Phospho-Akt and phospho-mammalian target of rapamycin (mTOR) decreased in PT CRC cells but was overexpressed in OR CRC cells in response to oxaliplatin. In addition, an oxaliplatin-mediated decrease in phospho-AMP-activated protein kinase (AMPK) in PT CRC cells induced autophagy. Contrastingly, an increased phospho-AMPK in OR CRC cells was accompanied by a decrease in LC3B, further inducing the activity of glycolytic enzymes, such as glucose transporter 1 (GLUT1), 6-phosphofructo2-kinase/fructose-2,6-bisphosphatase 3 (PFKFB3) and phosphofructokinase 1 (PFK1), to mediate cell survival. Inhibition of AMPK in OR CRC cells induced autophagy through inactivation of Akt/mTOR pathway and a decrease in GLUT1, PFKFB3, and PFK1. Collectively, targeting AMPK may provide solutions to overcome chemoresistance in OR CRC cells and restore chemosensitivity to anticancer drugs. Human Colorectal Cancer. Biomedicines 2022, 10, 2690. Show less

The phosphatidylinositol-3 kinase (PI3K)-AKT pathway is one of the most commonly dysregulated pathways in all of cancer, with somatic mutations, copy number alterations, aberrant epigenetic regulation and increased expression in a number of cancers. The carefully maintained homeostatic balance of cell division and growth on one hand, and programmed cell death on the other, is universally disturbed in tumorigenesis, and downstream effectors of the PI3K-AKT pathway play an important role in this disturbance. With a wide array of downstream effectors involved in cell survival and proliferation, the well-characterized direct interactions of AKT make it a highly attractive yet elusive target for cancer therapy. Here, we review the salient features of this pathway, evidence of its role in promoting tumorigenesis and recent progress in the development of therapeutic agents that target AKT. Show less

Chemokine receptor CCR7 directs mature dendritic cells (mDCs) to secondary lymph nodes where these cells regulate the activation of T cells. CCR7 also promotes survival in mDCs, which is believed to take place largely through Akt-dependent signaling mechanisms. We have analyzed the involvement of the AMP-dependent kinase (AMPK) in the control of CCR7-dependent survival. A pro-apoptotic role for AMPK is suggested by the finding that pharmacological activators induce apoptosis, whereas knocking down of AMPK with siRNA extends mDC survival. Pharmacological activation of AMPK also induces apoptosis of mDCs in the lymph nodes. Stimulation of CCR7 leads to inhibition of AMPK, through phosphorylation of Ser-485, which was mediated by G(i)/Gβγ, but not by Akt or S6K, two kinases that control the phosphorylation of AMPK on Ser-485 in other settings. Using selective pharmacological inhibitors, we show that CCR7-induced phosphorylation of AMPK on Ser-485 is mediated by MEK and ERK. Coimmunoprecipitation analysis and proximity ligation assays indicate that AMPK associates with ERK, but not with MEK. These results suggest that in addition to Akt-dependent signaling mechanisms, CCR7 can also promote survival of mDCs through a novel MEK1/2-ERK1/2-AMPK signaling axis. The data also suggest that AMPK may be a potential target to modulate mDC lifespan and the immune response. Show less