Similar Datasets
Project description:Oncogenic RAS activation, hypertranscription and transcription-replication conflicts (TRCs) are frequent features of cancer cells that are under investigation for therapeutic targeting. RAS oncogenes promote RNA polymerase activity and hypertranscription for cell growth and proliferation, which can the lead to TRCs. Here, we investigated hypertranscription and replication stress induced by the HRAS and KRAS oncogenes, and their downstream signalling through the MAPK and PI3K pathways. We show that HRAS causes more TRCs than KRAS because HRAS specifically hyperactivates the PI3K-AKT signalling pathway. MAPK signalling is insufficient to cause hypertranscription and TRCs, which require PI3K activity. PI3K hyperactivation was associated with increased E2F and MYC transcription programmes, increased S phase entry, increased nascent transcription of genes encoding ribosome biogenesis factors and expression of small nucleolar RNAs (snoRNAs). Inhibiting S phase entry alone did not rescue hypertranscription and replication stress, which required both MAPK and PI3K signalling. We report that a main downstream effector of PI3K-induced hypertranscription is AKT-mediated phosphorylation of GSK3b, which stabilises MYC. Cancer datasets further support that PI3K mutations may be associated with hypertranscription and replication stress signatures. Our findings suggest a mechanistic explanation for replication stress variability across RAS models and identify potential new predictors of TRCs in cancer.
2026-03-09 | GSE322525 | GEO
Project description:Oncogenic RAS activation, hypertranscription and transcription-replication conflicts (TRCs) are frequent features of cancer cells that are under investigation for therapeutic targeting. RAS oncogenes promote RNA polymerase activity and hypertranscription for cell growth and proliferation, which can the lead to TRCs. Here, we investigated hypertranscription and replication stress induced by the HRAS and KRAS oncogenes, and their downstream signalling through the MAPK and PI3K pathways. We show that HRAS causes more TRCs than KRAS because HRAS specifically hyperactivates the PI3K-AKT signalling pathway. MAPK signalling is insufficient to cause hypertranscription and TRCs, which require PI3K activity. PI3K hyperactivation was associated with increased E2F and MYC transcription programmes, increased S phase entry, increased nascent transcription of genes encoding ribosome biogenesis factors and expression of small nucleolar RNAs (snoRNAs). Inhibiting S phase entry alone did not rescue hypertranscription and replication stress, which required both MAPK and PI3K signalling. We report that a main downstream effector of PI3K-induced hypertranscription is AKT-mediated phosphorylation of GSK3b, which stabilises MYC. Cancer datasets further support that PI3K mutations may be associated with hypertranscription and replication stress signatures. Our findings suggest a mechanistic explanation for replication stress variability across RAS models and identify potential new predictors of TRCs in cancer.
2026-03-09 | GSE322524 | GEO
Project description:PI3K-AKT activation determines oncogenic RAS-induced hypertranscription and replication stress
| PRJNA1430343 | ENA
Project description:PI3K-AKT activation determines oncogenic RAS-induced hypertranscription and replication stress [RNASeq]
| PRJNA1430365 | ENA
Project description:PI3K-AKT activation determines oncogenic RAS-induced hypertranscription and replication stress [ChrRNAseq]
| PRJNA1430363 | ENA
Project description:Cancer cells often experience high basal levels of DNA replication stress (RS), for example due to hyperactivation of oncoproteins like MYC or RAS. Therefore, cancer cells are considered to be sensitive to drugs that exacerbate the level of RS or block the intra S-phase checkpoint. Consequently, RS-inducing drugs including ATR and CHK1 inhibitors are used or evaluated as anti-cancer therapies. However, drug resistance and lack of biomarkers predicting therapeutic efficacy limit efficient use. This raises the question what determines sensitivity of individual cancer cells to RS. Here, we report that oncogenic RAS does not only enhance the sensitivity to ATR/CHK1 inhibitors by directly causing RS. Instead, we observed that HRASG12V dampens the activation of the P53-dependent transcriptional response to drug-induced RS, which in turn confers sensitivity to RS. We demonstrate that inducible expression of HRASG12V sensitized cells to ATR and CHK1 inhibitors. Using RNA-sequencing of FACS-sorted cells we discovered that P53 signaling is the sole transcriptional response to RS. However, oncogenic RAS attenuates the transcription of P53 and TGF-β pathway components which consequently dampens P53 target gene expression. Accordingly, live cell imaging showed that HRASG12V exacerbates RS in S/G2-phase, which could be rescued by stabilization of P53. Thus, our results demonstrate that transcriptional control of P53 target genes is the prime determinant in the response to ATR/CHK1 inhibitors and show that hyperactivation of the MAPK pathway impedes this response. Our findings suggest that the level of oncogenic MAPK signaling could predict sensitivity to intra-S-phase checkpoint inhibition in cancers with intact P53.
| S-EPMC9076537 | biostudies-literature
Project description:The TMPRSS2/ERG gene rearrangement occurs in 50% of prostate tumors and results in expression of the transcription factor ERG, which is normally silent in prostate cells. ERG expression promotes prostate tumor formation and luminal epithelial cell fates when combined with PI3K/AKT pathway activation, however the mechanism of synergy is not known. In contrast to luminal fates, expression of ERG alone in immortalized normal prostate epithelial cells promotes cell migration and epithelial to mesenchymal transition (EMT). Migration requires ERG serine 96 phosphorylation via endogenous Ras/ERK signaling. We found that a phosphomimetic mutant, S96E ERG, drove tumor formation and clonogenic survival without activated AKT. S96 was only phosphorylated on nuclear ERG, and differential recruitment of ERK to a subset of ERG-bound chromatin associated with ERG-activated, but not ERG-repressed genes. S96E did not alter ERG genomic binding, but caused a loss of ERG-mediated repression, EZH2 binding and H3K27 methylation. In contrast, AKT activation altered the ERG cistrome and promoted expression of luminal cell fate genes. These data suggest that, depending on AKT status, ERG can promote either luminal or EMT transcription programs, but ERG can promote tumorigenesis independent of these cell fates and tumorigenesis requires only the transcriptional activation function.
| S-EPMC8345871 | biostudies-literature
Project description:Ferroptosis, a form of regulated necrosis driven by iron-dependent peroxidation of phospholipids, is regulated by cellular metabolism, redox homeostasis, and various signaling pathways related to cancer. In this study, we found that activating mutation of phosphatidylinositol 3-kinase (PI3K) or loss of phosphatase and tensin homolog deleted on chromosome 10 (PTEN) function, highly frequent events in human cancer, confers ferroptosis resistance in cancer cells, and that inhibition of the PI3K-AKT-mTOR signaling axis sensitizes cancer cells to ferroptosis induction. Mechanistically, this resistance requires sustained activation of mTORC1 and the mechanistic target of rapamycin (mTOR)C1-dependent induction of sterol regulatory element-binding protein 1 (SREBP1), a central transcription factor regulating lipid metabolism. Furthermore, stearoyl-CoA desaturase-1 (SCD1), a transcriptional target of SREBP1, mediates the ferroptosis-suppressing activity of SREBP1 by producing monounsaturated fatty acids. Genetic or pharmacologic ablation of SREBP1 or SCD1 sensitized ferroptosis in cancer cells with PI3K-AKT-mTOR pathway mutation. Conversely, ectopic expression of SREPB1 or SCD1 restored ferroptosis resistance in these cells, even when mTORC1 was inhibited. In xenograft mouse models for PI3K-mutated breast cancer and PTEN-defective prostate cancer, the combination of mTORC1 inhibition with ferroptosis induction resulted in near-complete tumor regression. In conclusion, hyperactive mutation of PI3K-AKT-mTOR signaling protects cancer cells from oxidative stress and ferroptotic death through SREBP1/SCD1-mediated lipogenesis, and combination of mTORC1 inhibition with ferroptosis induction shows therapeutic promise in preclinical models.
| S-EPMC7733797 | biostudies-literature
Project description:Apoptosis of endothelial cells is a very important event in various diseases and angiogenesis. We recently reported that ras guanyl nucleotide releasing protein 2 (RasGRP2), which is a guanine nucleotide exchange factor, was expressed in the human umbilical vein endothelial cells (HUVECs) and that Rap1 activation by its overexpression inhibited apoptosis by suppressing tumor necrosis factor-α induced-reactive oxygen species (ROS) production. However, other signaling pathways and roles of RasGRP2 not mediated via Rap1 are not well understood. Therefore, we compared the Mock (M) and the RasGRP2-stable overexpression (R) immortalized HUVECs using BAM7 and anisomycin, which are apoptosis inducers. BAM7 and anisomycin induced apoptosis without causing ROS production, and such apoptosis was significantly increased in M cells, but not in R cells. RasGRP2 suppressed BAM7- and anisomycin-induced apoptosis, but not via the Rap1 pathway as observed using Rap1 knockdown. Furthermore, RasGRP2 activated not only Rap1 but also R-Ras, and suppressed apoptosis by activating R-Ras-phosphoinositide 3-kinase (PI3K)-Akt signaling pathway. The phosphorylation of Akt by RasGRP2 inhibited Bax translocation by promoting translocation of hexokinase-2 (HK-2) from cytoplasm to mitochondria. Taken together, it was suggested that RasGRP2 suppresses the Bax activation-induced apoptosis by promoting HK-2 translocation to mitochondria via R-Ras-PI3K-Akt signaling pathway.
| S-EPMC6854084 | biostudies-literature
Project description:Pulmonary fibrosis is characterized by fibroblast proliferation and extracellular matrix remodelling, leading to respiratory insufficiency. The mechanisms underlying this progressive and devastating disease remain unclear. Conditions that can impair the function of the endoplasmic reticulum (ER) cause accumulation of unfolded or misfolded proteins, resulting in ER stress and activation of the unfolded protein response (UPR). ER stress has been implicated in many conditions including cancer, diabetes, obesity, and inflammation. It is also involved in lung fibrosis, through myofibroblastic differentiation of fibroblasts; however, the precise role of ER stress in lung fibrosis is unknown. The current study aimed to investigate the underlying mechanisms of ER stress inhibitors in the treatment of bleomycin-induced lung fibrosis. We demonstrated that bleomycin can activate ER stress associated proteins, including GRP78, CHOP, and ATF-4, both in vitro and in vivo. PI3K/AKT acts upstream of ER stress to affect lung fibroblast proliferation, resulting in bleomycin-induced pulmonary fibrosis. Treatment with ER stress inhibitors or a PI3K inhibitor caused a reduction in fibroblast proliferation and improved pulmonary function. The relationship between PI3K/AKT/mTOR and ER stress in pulmonary fibrosis, and the application of PI3K inhibitors and ER stress inhibitors in the treatment of pulmonary fibrosis require further investigation.
| S-EPMC5660192 | biostudies-literature