Senescence is defined as a stress-induced durable cell cycle arrest. We herein revisit the origin of two of these stresses, namely mitochondrial metabolic compromise, associated with reactive oxygen species (ROS) production, and replicative senescence, activated by extreme telomere shortening. We discuss how replication stress-induced DNA damage of telomeric DNA (telDNA) and mitochondrial DNA (mtDNA) can be considered a common origin of senescence in vitro, with consequences on ageing in vivo. Unexpectedly, mtDNA and telDNA share common features indicative of a high degree of replicative stress, such as G-quadruplexes, D-loops, RNA:DNA heteroduplexes, epigenetic marks, or supercoiling. To avoid these stresses, both compartments use similar enzymatic strategies involving, for instance, endonucleases, topoisomerases, helicases, or primases. Surprisingly, many of these replication helpers are active at both telDNA and mtDNA (e.g., RNAse H1, FEN1, DNA2, RecQ helicases, Top2α, Top2β, TOP3A, DNMT1/3a/3b, SIRT1). In addition, specialized telomeric proteins, such as TERT (telomerase reverse transcriptase) and TERC (telomerase RNA component), or TIN2 (shelterin complex), shuttle from telomeres to mitochondria, and, by doing so, modulate mitochondrial metabolism and the production of ROS, in a feedback manner. Hence, mitochondria and telomeres use common weapons and cooperate to resist/prevent replication stresses, otherwise producing common consequences, namely senescence and ageing.

MiR-422a promotes loco-regional recurrence by targeting NT5E/CD73 in head and neck squamous cell carcinoma

Glioblastoma (GBM) is the most frequent and aggressive type of adult brain tumor. Most GBMs express telomerase; a high level of intra-tumoral telomerase activity (TA) is predictive of poor prognosis. Thus, telomerase inhibitors are promising options to treat GBM. These inhibitors increase the response to radiotherapy (RT), in vitro as well as in vivo. Since typical treatments for GBM include RT, our objective was to evaluate the efficiency of Imetelstat (TA inhibitor) combined with RT. We used a murine orthotopic model of human GBM (N = 8 to11 mice per group) and μMRI imaging to evaluate the efficacy of Imetelstat (delivered by intra-peritoneal injection) alone and combined with RT. Using a clinically established protocol, we demonstrated that Imetelstat significantly: (i) inhibited the TA in the very center of the tumor, (ii) reduced tumor volume as a proportion of TA inhibition, and (iii) increased the response to RT, in terms of tumor volume regression and survival increase. Imetelstat is currently evaluated in refractory brain tumors in young patients (without RT). Our results support its clinical evaluation combined with RT to treat GBM.

PURPOSE: Alkylating agents (ALKY) are the main chemotherapies used for advanced neuroendocrine tumors (NETs). O ⁶ -Methylguanine-DNA methyltransferase (MGMT) status, as proficient (p) or deficient (d), may predict the response to ALKY. PATIENTS AND METHODS: MGMT-NET (ClinicalTrials.gov identifier: NCT03217097 ) was a phase II trial randomly assigning 1:1 for pMGMT or 2:1 for dMGMT-NETs to either ALKY or oxaliplatin (Ox). Inclusion criteria were a confirmed advanced pancreatic, thoracic, or unknown primary NETs with an indication for chemotherapy and tissue available. The primary aim was to detect a difference of 35% between the 3-month objective response rate (ORR) in pMGMT-NETs versus in dMGMT-NETs when treated with ALKY. A biomarker-stratified design was performed to compare ALKY and Ox in the dMGMT and pMGMT strata for the secondary end points. dMGMT was defined using pyrosequencing (PSQ; methylated MGMT ≥9%) and using immunochemistry ( H -score of MGMT <50) when PSQ was not interpretable. RESULTS: From October 2018 to October 2021, 105 patients (55 pancreas, 38 thorax, 12 unknown) started either ALKY (n = 62) or Ox (n = 43). The median age was 63 years (range, 30-84), and 59% were males. NETs were G1 (19%), G2 (69%), or G3 (10%). Among patients with interpretable MGMT status, 56.9% (58 of 102) had a dMGMT-NET. The primary end point was not reached; the 3-month ORR was 10 (29.4%) versus 2 (8%), and the odds ratio was 3.5 (0.58-21.16), P = .172. However, best ORR (18 [52.9%] v 3 [11.5%]) and median progression-free survival (14.6 [95% CI, 7.2 to 22.1] v 11.3 [9.4 to 13.2] months) were higher for dMGMT-NETs versus pMGMT-NETs. MGMT status does not seem to affect the Ox efficacy. CONCLUSION: Despite the fact that the primary end point was not reached, ALKY has clinical activity in patients with dMGMT-NETs.