Key Points• BCR signals induce resistance in CLL cells by upregulating Mcl-1.• SYK inhibitors prevent BCRmediated Mcl-1 induction more effectively than BTK or PI3Kd inhibitors.The Bcl-2 antagonist has demonstrated promising clinical activity in patients with chronic lymphocytic leukemia (CLL). ABT-199 is strongly cytotoxic against unstimulated peripheral blood CLL cells in vitro but is much less effective against CLL cells that have received survival signals from the microenvironment. In particular, stimulation of CLL cells with CD40L results in substantial resistance mediated by induction of the antiapoptotic Bcl-2 family proteins Bcl-xL and Bfl-1. In this study, we investigated whether resistance to ABT-199 can be conferred by B-cell receptor (BCR) stimulation, which is another important survival signal from the leukemic microenvironment. We show that sustained BCR stimulation results in significant ABT-199 resistance, which correlates with induction of the antiapoptotic protein Mcl-1 and less consistently with downregulation of proapoptotic Bmf, Hrk, and Bim EL . A major role for Mcl-1 in conferring ABT-199 resistance is additionally supported by knockdown and enforced expression experiments with primary CLL cells. We further show that SYK, BTK, and phosphatidylinositol 3-kinase d (PI3Kd) inhibitors significantly downregulate Mcl-1, but with different efficacy. Complete Mcl-1 downregulation was consistently achieved only with SYK inhibitors R406 and GS-9973 (entospletinib), whereas the BTK inhibitor ibrutinib and the PI3Kd inhibitor idelalisib in more than half of the cases had only a partial effect. The greater ability of SYK inhibitors to downregulate Mcl-1 correlated with their greater capacity to block BCR-mediated inactivation of GSK-3, a major negative regulator of Mcl-1. The finding that BCR signaling inhibitors differ in their ability to target Mcl-1 is relevant for the design of clinical trials combining these agents with ABT-199. (Blood. 2016;127(25):3192-3201)

Patients with chronic lymphocytic leukemia (CLL) may be more susceptible to Coronavirus disease 2019 (COVID-19) due to age, disease, and treatment-related immunosuppression. We aimed to assess risk factors of outcome and elucidate the impact of CLL-directed treatments on the course of COVID-19. We conducted a retrospective, international study, collectively including 941 patients with CLL and confirmed COVID-19. Data from the beginning of the pandemic until March 16, 2021, were collected from 91 centers. The risk factors of case fatality rate (CFR), disease severity, and overall survival (OS) were investigated. OS analysis was restricted to patients with severe COVID-19 (definition: hospitalization with need of oxygen or admission into an intensive care unit). CFR in patients with severe COVID-19 was 38.4%. OS was inferior for patients in all treatment categories compared to untreated (p < 0.001). Untreated patients had a lower risk of death (HR = 0.54, 95% CI:0.41–0.72). The risk of death was higher for older patients and those suffering from cardiac failure (HR = 1.03, 95% CI:1.02–1.04; HR = 1.79, 95% CI:1.04–3.07, respectively). Age, CLL-directed treatment, and cardiac failure were significant risk factors of OS. Untreated patients had a better chance of survival than those on treatment or recently treated.

We hereby report the clinical and biologic features of 33 of 4680 (0.7%) patients with chronic lymphocytic leukemia (CLL), managed at 10 Italian centers, who developed Hodgkin lymphoma (HL), a rare variant of Richter syndrome. The median age at CLL and at HL diagnosis were 61 years (range 41-80) and 70 years (range 46-82), respectively, with a median interval from CLL to the diagnosis of HL of 90 months (range 0-258). In 3 cases, CLL and HL were diagnosed simultaneously. Hl was characterized by advanced stage in 79% of cases, International Prognostic Score (IPS) ≥4 in 50%, extranodal involvement in 39%, B symptoms in 70%. Prior treatment for CLL had been received by 82% of patients and included fludarabine in 67%. Coexistence of CLL and HL was detected in the same bioptic tissue in 87% of cases. The most common administered treatment was the ABVD regimen given to 22 patients (66.6%). The complete response (CR) rate after ABVD was 68%, and was influenced by the IPS (P = .03) and interval from the last CLL treatment (P = .057). Survival from HL was also influenced by the IPS (P = .006) and time from the last CLL treatment (P = .047). The achievement of CR with ABVD was the only significant and independent factor predicting survival (P = .037). Taken together, our results show that the IPS and the interval from the prior CLL treatment influence the likelihood of achieving CR after ABVD, which is the most important factor predicting survival of patients with CLL developing HL.

CD49d is a remarkable prognostic biomarker of chronic lymphocytic leukemia (CLL). The cutoff value for the extensively validated 30% of positive CLL cells is able to separate CLL patients into 2 subgroups with different prognoses, but it does not consider the pattern of CD49d expression. In the present study, we analyzed a cohort of 1630 CLL samples and identified the presence of ∼20% of CLL cases (n = 313) characterized by a bimodal expression of CD49d, that is, concomitant presence of a CD49d+ subpopulation and a CD49d− subpopulation. At variance with the highly stable CD49d expression observed in CLL patients with a homogeneous pattern of CD49d expression, CD49d bimodal CLL showed a higher level of variability in sequential samples, and an increase in the CD49d+ subpopulation over time after therapy. The CD49d+ subpopulation from CD49d bimodal CLL displayed higher levels of proliferation compared with the CD49d− cells; and was more highly represented in the bone marrow compared with peripheral blood (PB), and in PB CLL subsets expressing the CXCR4dim/CD5bright phenotype, known to be enriched in proliferative cells. From a clinical standpoint, CLL patients with CD49d bimodal expression, regardless of whether the CD49d+ subpopulation exceeded the 30% cutoff or not, experienced clinical behavior similar to CD49d+ CLL, both in chemoimmunotherapy (n = 1522) and in ibrutinib (n = 158) settings. Altogether, these results suggest that CD49d can drive disease progression in CLL, and that the pattern of CD49d expression should also be considered to improve the prognostic impact of this biomarker in CLL.

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Microvescicles (MV) are shedding particles released by normal and neoplastic cells, whose levels in biological fluids highlight their potential role as disease biomarkers and therapeutic targets. By analyzing 131 newly diagnosed chronic lymphocytic leukemia (CLL), we found that the absolute number of serum CLL MV was significantly higher than in controls, in particular in advanced stages of disease. In addition, CD19 + and CD37+, B-cell derived MV, significantly correlated with high tumor burden. Absolute MV number cutoff selected by ROC analysis distinguished Rai stage 0 patients with shorter time to treatment (TTT) from those with more stable disease. Likewise, in the entire cohort, two groups of patients with different overall survival (OS) and different TTT were identified. At multivariate analysis, serum MV independently predicted for OS (along with Rai stage) and TTT (along with Rai stage, lymphocytes and CD38). In conclusion, circulating MV represent a new potential prognostic biomarker in CLL.

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