High p27 protein levels in chronic lymphocytic leukemia are associated to low Myc and Skp2 expression, confer resistance to apoptosis and antagonize Myc effects on cell cycle

Myc (c-Myc) counteracts p27 effects, and low p27 usually correlates with high Myc expression in human cancer. However there is no information on the co-expression of both genes in chronic lymphocytic leukemia (CLL). We found a lack of correlation between RNA and protein levels of p27 and Myc in CLL cells, so we determined the protein levels by immunoblot in 107 cases of CLL. We observed a high p27 protein expression in CLL compared to normal B cells. Ectopic p27 expression in a CLL-derived cell line resulted in cell death resistance. Surprisingly, Myc expression was very low or undetectable in most CLL cases analyzed, with a clear correlation between high p27 and low Myc protein levels. This was associated with low Skp2 expression, which is consistent with the Skp2 role in p27 degradation and with SKP2 being a Myc target gene. High Myc expression did not correlate with leukemia progression, despite that cell cycle-related Myc target genes were upregulated. However, biochemical analysis showed that the high p27 levels inhibited cyclin-Cdk complexes even in Myc expressing CLL cells. Our data suggest that the combination of high p27 and low Myc is a marker of CLL cells which is mediated by Skp2

Expresión e interacciones Myc-p27 en leucemia linfocítica crónica y en diferenciación de células mieloides

ABSTRACT: We studied expression levels of cell cycle inhibitor p27 and Myc (an oncogenic transcription factor) in more than 100 chronic lymphocytic leukemia (CLL) patients. p27 and Myc levels were inversely correlated. Thus, the ratio between p27 (overexpressed) and Myc (downregulated) appears inverted in CLL with respect to the other tumors so far known. Moreover, low p27 and high Myc expression correlated with the expression of Skp2, which is the main responsible for p27 degradation, suggesting a pathway Myc-Skp2-p27 in CLL. To investigate why p27 is expressed in CLL we overexpressed it in a CLL-derived cell line (MEC1) and observed that high levels of p27 provide resistance to fludarabine treatment. Also, we studied the erythroid differentiation in human K562 cells induced by two different p27 mutants (p27CK- and p27 Nt). p27 Nt transfection resulted in erythroid differentiation, but p27CK- only induced differentiation when Myc expression was low. Thus, we studied the correlation between both Myc and p27 in this process and we found that p27 induced erythroid differentiation through Myc downregulation.RESUMEN: Estudiamos los niveles de expresión del inhibidor de ciclo celular p27 y del factor de transcripción oncogénico Myc en más de 100 pacientes de leucemia linfocítica crónica (LLC). Los niveles de Myc y p27 fueron inversamente correlacionados. Así, el ratio entre p27 (altos niveles) y Myc (bajos niveles) aparece invertido en LLC con respecto al resto de tumores conocidos. Además, bajos niveles de p27 y alta expresión de Myc fue correlacionada con la expresión de Skp2, el cual es el principal responsable de la degradación de p27, sugiriendo una red Myc-Skp2-p27 en LLC. Para averiguar la razón por la cual p27 está sobre-expresado en LLC, utilizamos una línea derivada de un paciente de LLC (MEC1) y observamos que las células que presentaban altos niveles de p27 eran más resistentes a los tratamientos de fludarabina. Por otro lado, también estudiamos la diferenciación eritroide inducida por dos mutantes diferentes de p27 (CK- y Nt) en la línea celular K562. Mientras que el mutante Nt resultó en diferenciación eritroide, el CK- sólo fue capaz de inducirla cuando los niveles de Myc fueron bajos. Así, nosotros estudiamos la correlación entre Myc y p27 en este proceso y averiguamos que p27 induce diferenciación eritroide a través de la inhibición de Myc

Clinical Presentation and Short- and Long-term Outcomes in Patients With Isolated Distal Deep Vein Thrombosis vs Proximal Deep Vein Thrombosis in the RIETE Registry

International audienceImportance: Insufficient data exist about the clinical presentation, short-term, and long-term outcomes of patients with isolated distal deep vein thrombosis (IDDVT), that is, thrombosis in infrapopliteal veins without proximal extension or pulmonary embolism (PE).Objective: To determine the clinical characteristics, short-term, and 1-year outcomes in patients with IDDVT and to compare the outcomes in unadjusted and multivariable adjusted analyses with patients who had proximal DVT.Design, setting, and participants: This was a multicenter, international cohort study in participating sites of the Registro Informatizado Enfermedad Tromboembólica (RIETE) registry conducted from March 1, 2001, through February 28, 2021. Patients included in this study had IDDVT. Patients with proximal DVT were identified for comparison. Patients were excluded if they had a history of asymptomatic DVT, upper-extremity DVT, coexisting PE, or COVID-19 infection.Main outcomes and measures: Primary outcomes were 90-day and 1-year mortality, 1-year major bleeding, and 1-year venous thromboembolism (VTE) deterioration, which was defined as subsequent development of proximal DVT or PE.Results: A total of 33 897 patients were identified with isolated DVT (without concomitant PE); 5938 (17.5%) had IDDVT (mean [SD] age, 61 [17] years; 2975 male patients [50.1%]), and 27 959 (82.5%) had proximal DVT (mean [SD] age, 65 [18] years; 14 315 male patients [51.2%]). Compared with individuals with proximal DVT, those with IDDVT had a lower comorbidity burden but were more likely to have had recent surgery or to have received hormonal therapy. Patients with IDDVT had lower risk of 90-day mortality compared with those with proximal DVT (odds ratio [OR], 0.47; 95% CI, 0.40-0.55). Findings were similar in 1-year unadjusted analyses (hazard ratio [HR], 0.52; 95% CI, 0.46-0.59) and adjusted analyses (HR, 0.72; 95% CI, 0.64-0.82). Patients with IDDVT had a lower 1-year hazard of VTE deterioration (HR, 0.83; 95% CI, 0.69-0.99). In 1-year adjusted analyses of patients without an adverse event within the first 3 months, IDDVT was associated with lower risk of VTE deterioration (adjusted HR, 0.48; 95% CI, 0.24-0.97). By 1-year follow-up, symptoms or signs of postthrombotic syndrome were less common in patients with IDDVT (47.6% vs 60.5%).Conclusions and relevance: Results of this cohort study suggest that patients with IDDVT had a less ominous prognosis compared with patients with proximal DVT. Such differences were likely multifactorial, including the differences in demographics, risk factors, comorbidities, particularly for all-cause mortality, and a potential association of thrombus location with VTE deterioration and postthrombotic syndrome. Randomized clinical trials are needed to assess the optimal long-term management of IDDVT