The microenvironment provides a functional substratum supporting tumour growth. Hyaluronan (HA) is a major component of this structure. While the role of HA in malignancy is well-defined, the mechanisms driving its biosynthesis in cancer are poorly understood. We show that the eukaryotic translation initiation factor eIF4E, an oncoprotein, drives HA biosynthesis. eIF4E stimulates production of enzymes that synthesize the building blocks of HA, UDP-Glucuronic acid and UDP-N-Acetyl-Glucosamine, as well as hyaluronic acid synthase which forms the disaccharide chain. Strikingly, eIF4E inhibition alone repressed HA levels as effectively as directly targeting HA with hyaluronidase. Unusually, HA was retained on the surface of high-eIF4E cells, rather than being extruded into the extracellular space. Surface-associated HA was required for eIF4E’s oncogenic activities suggesting that eIF4E potentiates an oncogenic HA program. These studies provide unique insights into the mechanisms driving HA production and demonstrate that an oncoprotein can co-opt HA biosynthesis to drive malignancy.
Disease progression to accelerated/blast phase (AP/BP) in patients with chronic phase chronic myeloid leukemia (CP-CML) after treatment discontinuation (TD) has never been systematically reported in clinical trials. However, recent reports of several such cases has raised concern. To estimate the risk of AP/BP among TD-eligible patients, we conducted TFR-PRO, a cohort retro-prospective study: 870 CP-CML patients eligible for TD formed a discontinuation cohort (505 patients) and a reference one (365 patients). The primary objective was the time adjusted rate (TAR) of progression in relation to TD. Secondary endpoints included the TAR of molecular relapse, that is, loss of major molecular response (MMR). With a median follow up of 5.5 years and 5188.2 person-years available, no events occurred in the TD cohort. One event of progression was registered 55 months after the end of TD, when the patient was contributing to the reference cohort. The TAR of progression was 0.019/100 person-years (95% CI [0.003-0.138]) in the overall group; 0.0 (95% CI [0-0.163]) in the discontinuation cohort; and 0.030 (95% CI [0.004-0.215]) in the reference cohort. These differences are not statistically significant. Molecular relapses occurred in 172/505 (34.1%) patients after TD, and in 64/365 (17.5%) patients in the reference cohort, p < .0001. Similar rates were observed in TD patients in first, second or third line of treatment. CML progression in patients eligible for TD is rare and not related to TD. Fears about the risk of disease progression among patients attempting TD should be dissipated.
Diffuse large B-cell lymphoma (DLBCL) patients are typically treated with immunochemotherapy containing rituximab (rituximab, cyclophosphamide, hydroxydaunorubicin-vincristine (Oncovin), and prednisone [R-CHOP]); however, prognosis is extremely poor if R-CHOP fails. To identify genetic mechanisms contributing to primary or acquired R-CHOP resistance, we performed target-panel sequencing of 135 relapsed/refractory DLBCLs (rrDLBCLs), primarily comprising circulating tumor DNA from patients on clinical trials. Comparison with a metacohort of 1670 diagnostic DLBCLs identified 6 genes significantly enriched for mutations upon relapse. TP53 and KMT2D were mutated in the majority of rrDLBCLs, and these mutations remained clonally persistent throughout treatment in paired diagnostic-relapse samples, suggesting a role in primary treatment resistance. Nonsense and missense mutations affecting MS4A1, which encodes CD20, are exceedingly rare in diagnostic samples but show recurrent patterns of clonal expansion following rituximab-based therapy. MS4A1 missense mutations within the transmembrane domains lead to loss of CD20 in vitro, and patient tumors harboring these mutations lacked CD20 protein expression. In a time series from a patient treated with multiple rounds of therapy, tumor heterogeneity and minor MS4A1-harboring subclones contributed to rapid disease recurrence, with MS4A1 mutations as founding events for these subclones. TP53 and KMT2D mutation status, in combination with other prognostic factors, may be used to identify high-risk patients prior to R-CHOP for posttreatment monitoring. Using liquid biopsies, we show the potential to identify tumors with loss of CD20 surface expression stemming from MS4A1 mutations. Implementation of noninvasive assays to detect such features of acquired treatment resistance may allow timely transition to more effective treatment regimens.
Abstract Diffuse Large B Cell Lymhoma (DLBCL) is a highly heterogeneous disease in terms of clinical presentation, cell morphology, molecular characteristics and response to therapy. Gene expression profiling studies in patients have indicated that DLBCL can be sub-classified in relationship to the different stages of normal B cell development at which the cancer arises; germinal center B cell (GCB) and activated B cell (ABC). More recently, a similar approach distinguished three different reproducible clusters referred to as oxidative phosphorylation (OxPhos), B cell receptor/proliferation (BCR) and host response (HR). Importantly, DLBCL has also been well characterized at the genomic level. A large number of genes encoding epigenetic modifying enzymes are mutated in DLBCL, which implicates epigenetic regulation as an important factor in DLBCL pathogenesis, and a potential target for therapy. Among epigenetic therapies, histone deacetylase inhibitors (HDACi) have shown some clinical activity in DLBCL patients ranging from 5 to 25%, although responsive patients ultimately develop resistance. Aiming to understand resistance and response to HDACi in DLBCL, we developed HDACi-resistant cell lines from the GCB and BCR subtype cells SUDHL6 and SUDHL4. Gene expression array analysis was performed in parental SUDHL6 and the resistant clone SUDHL6-X. Strikingly, we found that the resistant cells have switched gene expression profile from GCB to ABC subtype and from BCR to OXPHOS. Also, we observe features of more differentiated, plasmablast-like cells in SUDHL6-X cells and in all other resistant subclones we developed, including inactivated B cell receptor signaling, increased endoplasmic reticulum stress and activation of the unfolded protein response. These characteristics are reflected in a distinctive response pattern to other targeted drugs. We observe that HDACi-resistant cells become cross-resistant to the anti-CD20 antibody rituximab, but, interestingly, they gain susceptibility to inhibitors of the proteasome bortezomib and MLN2238. Importantly, analysis of lymphoma cells isolated from de novo resistant DLBCL patients treated with the HDACi panobinostat for 15 days showed a switch in gene expression profiles from GCB to ABC, similar to SUDHL6X cells, indicating that our observations are not exclusive of in vitro systems. In conclusion, we have shown for the first time that resistance to HDACi is associated with differentiation of lymphoma cells that we predict makes them insensitive to drugs targeting the B cell receptor and anti-CD20 antibody, but sensitive to proteasome inhibition. Citation Format: Daphné Dupéré-Richer, Mena Kinal, Filippa Pettersson, Mona Hassawi, Yang ShaoNing, Torsten H. Nielsen, Kathleen Klein, Teresa Ezponda-Itoiz, Jonathan D. Licht, Nathalie Johnson, Sarit E. Assouline, Leandro Cerchietti, Wilson H. Miller, Koren K. Mann. Development of HDACi resistance in DLBCL leads to a switch in subtype towards a more differentiated B-cell and is associated with increased sensitivity to proteasome inhibition. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 5538. doi:10.1158/1538-7445.AM2014-5538
