Promyelocytic leukemia (PML) has been implicated in a variety of functions, including control of TP53 function and modulation of cellular senescence. Sumolated PML is the organizer of mature PML bodies, recruiting a variety of proteins onto these nuclear domains. The PML gene is predicted to encode a variety of protein isoforms. Overexpression of only one of them, PML-IV, promotes senescence in human diploid fibroblasts, whereas PML-III was proposed to specifically interact with the centrosome. We show that all PML isoform proteins are expressed in cell lines or primary cells. Unexpectedly, we found that PML-III, PML-IV, and PML-V are quantitatively minor isoforms compared with PML-I/II and could not confirm the centrosomal targeting of PML-III. Stable expression of each isoform, in a pml-null background, yields distinct subcellular localization patterns, suggesting that, like in other RBCC/TRIM proteins, the COOHterminal domains of PML are involved in interactions with specific cellular components. Only the isoform-specific sequences of PML-I and PML-V are highly conserved between man and mouse. That PML-I contains all conserved exons and is more abundantly expressed than PML-IV suggests that it is a critical contributor to PML function(s). (Cancer Res 2006; 66(12): 6192-8)
PURPOSE To evaluate first-line pembrolizumab monotherapy efficacy and safety in patients with unresectable cutaneous squamous cell carcinomas (CSCCs). PATIENTS AND METHODS Patients, predominantly men, with their CSSCs’ immunohistochemically determined programmed cell death-ligand 1 (PD-L1) status determined (tumor proportion score threshold, 1%), received pembrolizumab (200 mg every 3 weeks). The primary endpoint was the 39-patient primary cohort’s objective response rate at week 15 (ORRW15). Secondary objectives were best ORR, overall survival (OS), progression-free survival (PFS), duration of response (DOR), safety, ORR according to PD-L1 status and health-related quality of life using Functional Assessment of Cancer Therapy–General (FACT-G) score. An 18-patient expansion cohort, recruited to power the study to evaluate the ORRW15 difference between PD-L1+ and PD-L1– patients, was assessed for ORR, disease control rate, and safety, but not survival. RESULTS Median age of all patients was 79 years. The primary cohort’s ORRW15 was 41% (95% CI, 26% to 58%), including 13 partial and 3 complete responses. Best responses were 8 partial and 8 complete responses. At a median follow-up of 22.4 months, respective median PFS, DOR, and OS were 6.7 months, not reached, and 25.3 months, respectively. Pembrolizumab-related adverse events affected 71% of the patients, and 4 (7%) were grade ≥ 3. One death was related to rapid CSCC progression; another resulted from a fatal second aggressive head and neck squamous cell carcinoma diagnosed 15 weeks postinclusion. ORRW15 for the entire population was 42%; it was significantly higher for PD-L1+ patients (55%) versus PD-L1– patients (17%; P = .02). Responders’ W15 total FACT-G score had improved ( P = .025) compared with nonresponders. CONCLUSION First-line pembrolizumab monotherapy exhibited promising anti-CSCC activity, with durable responses and manageable safety. PD-L1 positivity appears to be predictive of pembrolizumab efficacy.
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