Hypoxia suppresses conversion from proliferative arrest to cellular senescence
Abstract
Unlike reversible quiescence, cellular senescence is characterized by a large flat cell morphology, β-gal staining and irreversible loss of regenerative (i.e., replicative) potential. Conversion from proliferative arrest to irreversible senescence, a process named geroconversion, is driven in part by growth-promoting pathways such as mammalian target of rapamycin (mTOR). During cell cycle arrest, mTOR converts reversible arrest into senescence. Inhibitors of mTOR can suppress geroconversion, maintaining quiescence instead. It was shown that hypoxia inhibits mTOR. Therefore, we suggest that hypoxia may suppress geroconversion. Here we tested this hypothesis. In HT-p21-9 cells, expression of inducible p21 caused cell cycle arrest without inhibiting mTOR, leading to senescence. Hypoxia did not prevent p21 induction and proliferative arrest, but instead inhibited the mTOR pathway and geroconversion. Exposure to hypoxia during p21 induction prevented senescent morphology and loss of regenerative potential, thus maintaining reversible quiescence so cells could restart proliferation after switching p21 off. Suppression of geroconversion was p53- and HIF-1-independent, as hypoxia also suppressed geroconversion in cells lacking functional p53 and HIF-1α. Also, in normal fibroblasts and retinal cells, hypoxia inhibited the mTOR pathway and suppressed senescence caused by etoposide without affecting DNA damage response, p53/p21 induction and cell cycle arrest. Also hypoxia suppressed geroconversion in cells treated with nutlin-3a, a nongenotoxic inducer of p53, in cell lines susceptible to nutlin-3a-induced senescence (MEL-10, A172, and NKE). Thus, in normal and cancer cell lines, hypoxia suppresses geroconversion caused by diverse stimuli. Physiological and clinical implications of the present findings are discussed.
oncotarget research Zoya Demidenko Dr. Zoya N. Demidenko Zoya N. Demidenko , Ph.D. is Executive Manager of the Oncotarget journal . Oncotarget publishes high-impact research papers of general interest and outstanding significance and novelty in all areas of biology and medicine: in translational, basic and clinical research including but not limited to cancer research, oncogenes, oncoproteins and tumor suppressors, signaling pathways as potential targets for therapeutic intervention, shared targets in different diseases (cancer, benign tumors, atherosclerosis, eukaryotic infections, metabolic syndrome and other age-related diseases), chemotherapy, and new therapeutic strategies. After earning her Ph.D. in molecular biology, Zoya was awarded a Fogarty post-doctoral Fellowship from the National Institutes of Health in Bethesda, MD. After successful completion of post-doctoral training, she continued her professional career at George Washington University and Albert Einstein School of Medicine . In 2005 she cofounded the startup company Oncotarget Inc. which is focused on the development of anti-aging and anti-cancer drugs. Her research interests include signal transduction, cell cycle and cellular senescence, and their pharmacological targeting. In 2009 she cofounded the publishing house Impact Journals which specializes in publishing scientific journals. In 2011 she was selected to be a Member of the National Association of Professional Women .
When people refer to today’s medicine, precision plays one of the most important roles and people’s lives are directly dependent on it. Likewise, any researches related to medicine are necessary to comply with the top standards. The problem today is that any results of researches can be shared online and used as a reference without being thoroughly checked and validated. Mikhail (Misha) Blagosklonny of Oncotarget clearly understood this issue and decided to develop an alternative solution. That’s how a weekly oncology-focused research journal named “Oncotarget” has been established back in 2010. The main principle of this journal is based on Altmetric scores that are used as a quality indicator. That assists both readers and authors to validate publications with Altmetric Article Reports that create “real-time feedback containing data summary related to a particular publication.” Oncotarget website demonstrates a complete publications list with respective scores higher than 100 as well as reports mentioned above. Mikhail (Misha) Blagosklonny proud to share his new approach and hopes it provides the required help to anyone, who has interest in oncology.
“A diagnostic autoantibody signature for primary cutaneous melanoma” has the Altmetric score of 594. This article was published back in 2018 by Oncotarget and written by various experts from Hollywood Private Hospital, Edith Cowan University, Dermatology Specialist Group, St. John of God Hospital and The University of Western Australia. The introduction of the study discusses “recent data shows that Australians are four times more likely to develop a cancer of the skin than any other type of cancer”, and provides an insight on melanoma that “is curable by surgical excision in the majority of cases, if detected at an early stage.”
The publication has got an Altmetric score of 594. Mikhail (Misha) Blagosklonny realizes that majority of readers are aiming to comprehend the very meaning of it. Based on the Altmetric website, the score relates to “how many people have been exposed to and engaged with a scholarly output.” Likewise, the article about melanoma, was utilized for citations in various news articles 69 times. Besides that, it was quoted in 2 online blogs, as well as 25 Tweets on Twitter and 1 Facebook post. FOX23 of Tulsa, Oklahoma has headlined their report on July 20, 2018 as “New blood test could detect skin cancer early”, using the main content of Australia study
Another Oncotarget’s research with a top score of 476, is “Biomarkers for early diagnosis of malignant mesothelioma: Do we need another moon-shot,”. This article has appeared in 60 news stories, 1 online blog post and 6 Twitter posts. The majority of public may have seen a short overview only, however those who visit Mikhail (Misha) Blagosklonny at Oncotarget, do get useful scientific facts. Oncotarget is proud to have the ability to share with online readers this highly appreciated and high-quality information, that is trustworthy and reliable.