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Regulation of PTEN translation by PI3K signaling maintains pathway homeostasis.

ABSTRACT: The PI3K pathway regulates cell metabolism, proliferation, and migration, and its dysregulation is common in cancer. We now show that both physiologic and oncogenic activation of PI3K signaling increase the expression of its negative regulator PTEN. This limits the duration of the signal and output of the pathway. Physiologic and pharmacologic inhibition of the pathway reduces PTEN and contributes to the rebound in pathway activity in tumors treated with PI3K inhibitors and limits their efficacy. Regulation of PTEN is due to mTOR/4E-BP1-dependent control of its translation and is lost when 4E-BP1 is deleted. Translational regulation of PTEN is therefore a major homeostatic regulator of physiologic PI3K signaling and plays a role in reducing the pathway activation by oncogenic PIK3CA mutants and the antitumor activity of PI3K pathway inhibitors. However, pathway output is hyperactivated in tumor cells with coexistent PI3K mutation and loss of PTEN function.

SUBMITTER: Mukherjee R

PROVIDER: S-EPMC8384339 | biostudies-literature | 2021 Feb

REPOSITORIES: biostudies-literature

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Regulation of PTEN translation by PI3K signaling maintains pathway homeostasis.

Mukherjee Radha R Vanaja Kiran G KG Boyer Jacob A JA Gadal Sunyana S Solomon Hilla H Chandarlapaty Sarat S Levchenko Andre A Rosen Neal N

Molecular cell 20210201 4

The PI3K pathway regulates cell metabolism, proliferation, and migration, and its dysregulation is common in cancer. We now show that both physiologic and oncogenic activation of PI3K signaling increase the expression of its negative regulator PTEN. This limits the duration of the signal and output of the pathway. Physiologic and pharmacologic inhibition of the pathway reduces PTEN and contributes to the rebound in pathway activity in tumors treated with PI3K inhibitors and limits their efficacy ...[more]

PMID: 33606974

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Project description:Honokiol (HNK) is a small biphenolic compound, which exerts antineoplastic effects in various types of cancer. However, the mechanism underlying the antitumor effects of HNK in osteosarcoma (OS) cells is not yet fully understood. Emerging evidence has indicated that microRNAs (miRNAs/miRs) serve key roles in numerous pathological processes, including cancer. It has previously been reported that Chinese medicinal herbs harbor anticancer properties via modulating miRNA expression. Therefore, the present study aimed to determine whether HNK could suppress OS cell growth by regulating miRNA expression. The 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay and flow cytometric analysis were used to evaluate the cell proliferation and apoptosis in human OS cells after treatment with HNK, respectively. The results demonstrated that HNK inhibits proliferation and induces apoptosis of human OS cells in a dose?dependent manner. Furthermore, HNK?induced apoptosis was characterized by upregulation of proapoptotic proteins, including cleaved?caspase?3, cleaved?poly (ADP?ribose) polymerase and B?cell lymphoma 2 (Bcl?2)?associated X protein, and downregulation of the anti?apoptotic protein Bcl?2. Reverse transcription?quantitative polymerase chain reaction (RT?qPCR) verified that HNK was able to induce aberrant expression of miRNAs in human OS cells, and miR?21 was one of the miRNAs that was most significantly downregulated. To further investigate miR?21 function, the present study validated that HNK reduces miR?21 levels in a dose?dependent manner. In addition, restoration of miR?21 expression abrogated the suppressive effects of HNK on OS cells. Luciferase assay and western blot analysis identified that miR?21 inhibits the expression of phosphatase and tensin homolog (PTEN) by directly targeting its 3'-UTR. Notably, HNK was able to suppress the phosphoinositide 3?kinase (PI3K)/protein kinase B (AKT) signaling pathway; however, it was reactivated by miR?21 overexpression. Taken together, these data indicated that HNK may inhibit proliferation and induce apoptosis of human OS cells by modulating the miR?21/PTEN/PI3K/AKT signaling pathway. Therefore, miR?21 may be considered a potential therapeutic target for the treatment of osteosarcoma with HNK.

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Regulation of PTEN translation by PI3K signaling maintains pathway homeostasis.

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Regulation of PTEN translation by PI3K signaling maintains pathway homeostasis.

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