TGS1 mediates 2,2,7-trimethyl guanosine capping of the human telomerase RNA to direct telomerase dependent telomere maintenance

Pathways that direct the selection of the telomerase-dependent or recombination-based, alternative lengthening of telomere (ALT) maintenance pathway in cancer cells are poorly understood. Using human lung cancer cells and tumor organoids we show that formation of the 2,2,7-trimethylguanosine (TMG) cap structure at the human telomerase RNA 5′ end by the Trimethylguanosine Synthase 1 (TGS1) is central for recruiting telomerase to telomeres and engaging Cajal bodies in telomere maintenance. TGS1 depletion or inhibition by the natural nucleoside sinefungin impairs telomerase recruitment to telomeres leading to Exonuclease 1 mediated generation of telomere 3′ end protrusions that engage in RAD51-dependent, homology directed recombination and the activation of key features of the ALT pathway. This indicates a critical role for 2,2,7-TMG capping of the RNA component of human telomerase (hTR) in enforcing telomerase-dependent telomere maintenance to restrict the formation of telomeric substrates conductive to ALT. Our work introduces a targetable pathway of telomere maintenance that holds relevance for telomere-related diseases such as cancer and aging

Response to fludarabine in B-cell chronic lymphocytic leukemia patients previously treated with chlorambucil as up-front therapy and a CHOP-like regimen as second line therapy

BACKGROUND AND OBJECTIVES: Fludarabine (FAMP) is the most active single agent in relapsed and refractory patients with B-cell chronic lymphocytic leukemia (B-CLL). However, it is not clear whether it should be used immediatly after failure of chlorambucil (CLB). We addressed such an issue retrospectively analyzing a series of patients in whom FAMP was used as third-line therapy after a sequential use of CLB and CHOP (cyclophosphamide, doxorubicin, vincristine, prednisone) or CHOP-like regimen, respectively. DESIGN AND METHODS: On a retrospective basis, 57 B-CLL patients fulfilling the above mentioned criteria and followed-up in seven different hematologic institutions, were evaluated. RESULTS: Of 57 patients who were evaluated for response, 3 (5.2%) achieved a complete response (CR), 30 (52.6%) had a partial response (PR) and the remaining 24 (42.1%) failed to respond to FAMP. Overall median survival from the start of FAMP therapy was 30 months. Survival by tumor response did not show any difference between responders and non-responders (p = 0.536). The survival was significantly shorter in the group of patients with progressive disease than in all other patients included in our study (p = 0.05). Using each patient as his own control (McNemar test) we attempted to evaluate the value of FAMP in inducing a therapeutic response after failure of previous therapies. Among the 37 patients resistant to CLB the response rate was 40.3% with FAMP (p = 0.037) and only 17.5% with CHOP (p = 1.0). Among 35 patients resistant to a CHOP-like regimen, the response rate was 29.8% (p = 0.066) after FAMP therapy. INTERPRETATION AND CONCLUSIONS: From our results, it seems that FAMP works better than a CHOP-like regimen in patients resistant to CLB although results do not translate into a survival advantage for responders

Molecular remission in PML/RAR alpha-positive acute promyelocytic leukemia by combined all-trans retinoic acid and Idarubicin (AIDA) therapy

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Validation of a simulation algorithm for safety-critical human multitasking.

Multitasking has become surprisingly present in our life. This is mostly due to the fact that nowadays most of our activities involve the interaction with one or more devices. In such a context the brain mechanism of selective attention plays a key role in determining the success of a human’s interaction with a device. Indeed, it is a resource to be shared among the concurrent tasks to be performed, and the sharing of attention turns out to be a process similar to process scheduling in operating systems. In order to study human multitasking situations in which a user interacts with more than one device at the same time, we proposed in a previous work an algorithm for simulating human selective attention. Our algorithm focuses, in particular, on safety-critical human multitasking, namely situations in which some of the tasks the user is involved in may lead to dangerous consequences if not executed properly. In this paper, we present the validation of such an algorithm against data gathered from an experimental study performed with real users involved concurrently in a “main” task perceived as safety-critical and in a series of “distractor” tasks having different levels of cognitive load