SPANISH NATIONAL CANCER RESEARCH CENTRE, CNIO 21ANNUAL REPORT 2020 20

Molecular oncology PrograMMe | TELOmERES ANd TELOmERASE GROUPBasic research

oVerVieW

We study the mechanisms by which tumour cells are immortal and normal cells are mortal. Immortality is one of the most universal characteristics of cancer cells. The enzyme telomerase is present in more than 95% of all types of human cancers and absent in normal cells in the body. Telomeres are nucleoprotein complexes located at the ends of chromosomes, essential for chromosome protection and genomic stability. Progressive shortening of telomeres associated with organism ageing leads to ageing. When telomeres are altered, adult stem cells have a maimed regenerative capacity.

Our research focuses on :

ɗ Generating mouse models to validate telomeres and telomerase as therapeutic targets for cancer and age-related diseases.

ɗ Interplay between telomeres and DNA repair pathways. ɗ Role and regulation of non-coding telomeric RNAs or

TERRA. ɗ Testing telomerase gene therapy in “ telomere syndromes ”

and age-related diseases. ɗ Role of telomerase and telomeres in adult stem cell biology

and in nuclear reprogramming of differentiated cells to iPS cells.

“ We have shown that the targeting of telomere maintenance mediated through the microRNA miR-490 could be therapeutically important in the treatment of glioblastoma.”

TELOMERES AND TELOMERASE GROUP

Maria A. BlascoGroup Leader

Staff ScientistsIsabel López de Silanes, Rosa M. Marión, Paula Martínez

Post-Doctoral FellowsGiuseppe Bosso, João Tiago Carvalho Jordão ( since December ), Buyun Ma ( since November ), Sergio Piñeiro, Sarita Saraswati

Graduate StudentsJosé Carlos González, Paula Infantes, Óscar Laguía ( since November ), Jessica Louzame, Amparo Sánchez ( since October ), Raúl Sánchez

TechniciansAna Guío ( TS )*, Rosa M. Serrano

*Titulado Superior ( Advanced Degree )

Visiting StudentsAlejandro Bernardo

( January-February ) ( Bachelor’s Student, University of Oviedo, Spain ), Sarah M. Gutiérrez ( until June ) ( BS Thesis, Complutense University of Madrid, Spain ), Aristeidis Michail ( until March ) ( Erasmus Fellowship, National and Kapodistrian University

of Athens, Athens, Greece ), M. José Romero ( July-August ) ( Summer Traineeship, Universitat Autònoma de Barcelona, Spain ), Irene Sánchez ( since September ) ( Bachelor’s Student, University of Huddersfield, UK )

SPANISH NATIONAL CANCER RESEARCH CENTRE, CNIO 23ANNUAL REPORT 2020 22

Molecular oncology PrograMMe | TELOmERES ANd TELOmERASE GROUPBasic research

Telomerase treatment prevents lung fibrosis associated with physiological ageing

Idiopathic pulmonary fibrosis ( IPF ) is a potentially lethal disease associated with certain mutations or advanced age, currently lacking a cure. We had shown that specific induction of telomere dysfunction alveolar type II ( ATII ) cells sufficed to induce progressive and lethal pulmonary fibrosis in mice, demonstrating that dysfunctional telomeres ATII cells are at the origin of IPF. We had also demonstrated that the presence of short telomeres in lung cells triggered IPF in telomerase-deficient mice upon treatment with a low dose of the lung-damaging agent bleomycin. We had also shown that treatment with a telomerase gene therapy that activated telomerase in the lungs stopped lung fibrosis progression in these mice. Evidence from human patients and mouse models with short telomeres indicates that short/dysfunctional telomeres are at the origin of IPF.

It remained unknown whether physiological ageing leads to short telomeres in the lung, and whether this increases the risk of IPF with ageing. We have now found that physiological ageing in wild-type mice leads to telomere shortening and a reduced proliferative potential of ATII cells and club cells, increased cellular senescence and DNA damage, increased fibroblast activation and collagen deposits, and impaired lung biophysics, suggestive of a fibrosis-like pathology. Treatment of ageing wild-type ( FIGURE 2 ) and telomerase-deficient mice with telomerase gene therapy prevented the onset of lung profibrotic pathologies. Short telomeres associated with physiological ageing are at the origin of IPF ; a potential treatment for IPF based on telomerase activation would be of interest both for patients with telomerase mutations and sporadic cases of IPF associated with physiological ageing. s

research highlighTs

Short telomeres mice need active mTOR pathway for survival

The mechanistic target of rapamycin ( mTOR ) pathway is a central regulator of cell growth and metabolism. A variety of signals, including growth factors and nutrients, regulate mTOR activity. Inhibition of this nutrient-sensing pathway is considered a therapeutic target to delay ageing and age-related pathologies. mTOR exists in two distinct complexes, mTORC1 and mTORC2, each with different substrates and activities. Of the two, mTORC1 is the only one sensitive to acute rapamycin treatment.

Genetic or pharmacological inhibition of mTORC1 with rapamycin, or with rapamycin-derived compounds, delays ageing and increases the lifespan of mice. There is evidence suggesting that lifespan extension by dietary restriction may partly arise from mTORC1 inhibition. Rapamycin significantly decreases cancer incidence in wild-type mice and it also has immunosuppressant properties.

Since mTOR inhibitors could represent potential treatments for human patients afflicted with telomere syndromes, we addressed whether rapamycin treatment could ameliorate the premature ageing phenotypes and the decreased longevity of telomerase-deficient mice with short telomeres. We found that while chronic rapamycin treatment in mice with telomeres of normal length inhibits mTOR activity and leads to a decrease of cancer and ageing and to increased survival ( FIGURE 1 ), in telomerase-deficient mice with short telomeres it leads to the upregulation of the mTOR pathway and, quite unexpectedly, to the decreased longevity of these mice, a stark contrast to the lifespan extension observed in similarly treated wild-type mice ( FIGURE 1 ). Altogether, our findings demonstrate that hyperactivation of the mTOR pathway as the consequence of short telomeres constitutes a compensatory survival mechanism. In agreement with this, inhibition of this pathway has deleterious effects in telomerase-deficient mice.

∞ PUBLICATIONS

∞ Callen E, Zong D, Wu W, Wong N, Stanlie A, Ishikawa M, Pavani R, Dumitrache LC, Byrum AK, Mendez-Dorantes C, Martinez P, Canela A, Maman Y, Day A, Kruhlak MJ, Blasco MA, Stark JM, Mosammaparast N, McKinnon PJ, Nussenzweig A ( 2020 ). 53BP1 enforces distinct pre- and post-re-section blocks on homologous recombi-nation. Mol Cell 77, 26-38.e7.

∞ Ferrara-Romeo I, Martinez P, Saraswati S,

Whittemore K, Graña-Castro O, Thelma Poluha L, Serrano R, Hernandez-Enci-nas E, Blanco-Aparicio C, Maria Flores J, Blasco MA ( 2020 ). The mTOR pathway is necessary for survival of mice with short telomeres. Nat Commun 11, 1168.

∞ Fuentes-Fayos AC, Vázquez-Borrego MC, Jiménez-Vacas JM, Bejarano L, Pe-draza-Arévalo S, L-López F, Blanco-Ace-vedo C, Sánchez-Sánchez R, Reyes O, Ventura S, Solivera J, Breunig JJ, Blasco

MA, Gahete MD, Castaño JP, Luque RM ( 2020 ). Splicing machinery dysregula-tion drives glioblastoma development/aggressiveness : oncogenic role of SRSF3. Brain. PMID : 33141183.

∞ Salazar-Roa M, Trakala M, Álvarez-Fernán-dez M, Valdés-Mora F, Zhong C, Muñoz J, Yu Y, Peters TJ, Graña-Castro O, Serrano R, Zapatero-Solana E, Abad M, Bueno MJ, Gómez de Cedrón M, Fernández-Piquer-as J, Serrano M, Blasco MA, Wang DZ,

Clark SJ, Izpisua-Belmonte JC, Ortega S, Malumbres M ( 2020 ). Transient exposure to miR-203 enhances the differentiation capacity of established pluripotent stem cells. EMBO J 39, e104324.

∞ Whittemore K, Blasco MA ( 2020 ). Reply to Udroiu : Interesting mathematical anal-ysis of telomere shortening rate and life span. Proc Natl Acad Sci USA 117, 2250.

∞ Piñeiro-Hermida S, Autilio C, Martínez P, Bosch F, Pérez-Gil J, Blasco MA. Telomer-

ase treatment prevents lung profibrotic pathologies associated with physiological aging ( 2020 ). J Cell Biol 219, e202002120.

∞ Vinchure OS, Whittemore K, Kushwah D, Blasco MA, Kulshreshtha R ( 2020 ). miR-490 suppresses telomere mainte-nance program and associated hallmarks in glioblastoma. Cell Mol Life Sci. PMID : 32970185.

∞ Kordowitzki P, Hamdi M, Derevyanko A, Rizos D, Blasco MA ( 2020 ). The effect

of rapamycin on bovine oocyte matu-ration success and metaphase telomere length maintenance. Aging ( Albany NY ) 12, 7576-7584.

∞ Kordowitzki P, Silanes IL, Guío-Carrión A, Blasco MA ( 2020 ). Dynamics of telomeric repeat-containing RNA expression in early embryonic cleavage stages with regards to maternal age. Aging ( Albany NY ) 12, 15906-15917.

∞ AWARDS AND RECOGNITION

∞ Chair of SOMMa (“ Severo Ochoa ” Centres and “ María de Maeztu ” Units of Excellence Alliance ), Spain.

∞ ERC-Advanced Grant SHELTERINS, Eu-ropean Research Council.

∞ Spin-off company Telomere Therapeutics, a joint venture arising from the labora-tories of Maria A. Blasco at CNIO and of Fàtima Bosch ( Universitat Autònoma de Barcelona ) to develop telomerase-based

gene therapies for the treatment of pul-monary and renal fibrosis, Spain.

∞ Member of the Scientific Advisory Board of the Institute of Genetics and Molecu-lar and Cellular Biology-IGBMC, Illkirch, Strasbourg, France.

∞ Member of the Scientific Advisory Board of the Marseille Cancer Research Centre – CRCM, Marseille, France.

∞ Editorial Board Member, International Journal of Cancer.

FIGURE 1 Opposite outcomes of rapamycin treatment depending on telomere length.

FIGURE 2 Development of ageing-associated initial stages of pulmonary fibrosis in untreated mice ( left ) is

prevented by telomerase gene therapy treatment ( right ).