Inter- and intratumoral heterogeneity of BCL2 correlates with IgH expression and prognosis in follicular lymphoma

Genomic landscape of mature B-cell non-Hodgkin lymphomas - an appraisal from lymphomagenesis to drug resistance

BACKGROUND

Mature B-cell non-Hodgkin lymphomas are one of the most common hematological malignancies with a divergent clinical presentation, phenotype, and course of disease regulated by underlying genetic mechanism.

MAIN BODY

Genetic and molecular alterations are not only critical for lymphomagenesis but also largely responsible for differing therapeutic response in these neoplasms. In recent years, advanced molecular tools have provided a deeper understanding regarding these oncogenic drives for predicting progression as well as refractory behavior in these diseases. The prognostic models based on gene expression profiling have also been proved effective in various clinical scenarios. However, considerable overlap does exist between the genotypes of individual lymphomas and at the same time where additional molecular lesions may be associated with each entity apart from the key genetic event. Therefore, genomics is one of the cornerstones in the multimodality approach essential for classification and risk stratification of B-cell non-Hodgkin lymphomas.

CONCLUSION

We hereby in this review discuss the wide range of genetic aberrancies associated with tumorigenesis, immune escape, and chemoresistance in major B-cell non-Hodgkin lymphomas.

Unraveling Tumor Heterogeneity in an Apparently Monolithic Disease: BCL2 and Other Players in the Genetic Landscape of Nodal Follicular Lymphoma

Follicular lymphoma (FL) is the most common form of non-Hodgkin lymphoma in Western countries. Although traditionally considered a well-defined, easy to diagnose lymphoproliferative disorder, in the last few years it has become clear that it is in fact composed of many different clinicopathological entities, encompassing a variegated and complex genetic background. This has led to the inclusion of specific FL variants and separate entities in the latest update of the WHO classification. However, even in the context of classical FL, many aspects of intra- and inter-tumoral heterogeneity have been recognized, with a major influence on diagnosis and clinical practice at different time points during the course of the disease. This review focuses on the molecular cytogenetic heterogeneity in classical FL from precursors and early development to progression and transformation, in terms of both clonal heterogeneity and unusual genetic features. Several factors have been investigated and suggested to contribute to the broad spectrum of clinicopathological, phenotypic, and genetic features observed in otherwise morphologically classical cases. Among them, deregulation of the epigenetic machinery and interactions with tumor microenvironment seem to play a pivotal role, together with genetic aberrations involving well-known molecular pathways and mechanisms physiologically operating in the germinal center. In the era of personalized medicine, precision diagnostics based both on understanding of the complex interplay among all these factors and on novel developments will become crucial to predict the outcome and guide the treatment of FL patients.

Hematologic Tumor Cell Resistance to the BCL-2 Inhibitor Venetoclax: A Product of Its Microenvironment?

BCL-2 family proteins regulate the intrinsic pathway of programmed cell death (apoptosis) and play a key role in the development and health of multicellular organisms. The dynamics of these proteins' expression and interactions determine the survival of all cells in an organism, whether the healthy cells of a fully competent immune system or the diseased cells of an individual with cancer. Anti-apoptotic proteins like BCL-2, BCL-XL, and MCL-1 are well-known for maintaining tumor cell survival and are therefore attractive drug targets. The BCL-2-selective inhibitor venetoclax has been approved for use in chronic lymphocytic leukemia and is now being studied in a number of other hematologic malignancies. As clinical data mature, hypotheses have begun to emerge regarding potential mechanisms of venetoclax resistance. Here, we review accumulating evidence that lymphoid microenvironments play a key role in determining hematologic tumor cell sensitivity to venetoclax.

Drug-based perturbation screen uncovers synergistic drug combinations in Burkitt lymphoma

Burkitt lymphoma (BL) is a highly aggressive B-cell lymphoma associated with MYC translocation. Here, we describe drug response profiling of 42 blood cancer cell lines including 17 BL to 32 drugs targeting key cancer pathways and provide a systematic study of drug combinations in BL cell lines. Based on drug response, we identified cell line specific sensitivities, i.e. to venetoclax driven by BCL2 overexpression and partitioned subsets of BL driven by response to kinase inhibitors. In the combination screen, including BET, BTK and PI3K inhibitors, we identified synergistic combinations of PI3K and BTK inhibition with drugs targeting Akt, mTOR, BET and doxorubicin. A detailed comparison of PI3K and BTKi combinations identified subtle differences, in line with convergent pathway activity. Most synergistic combinations were identified for the BET inhibitor OTX015, which showed synergistic effects for 41% of combinations including inhibitors of PI3K/AKT/mTOR signalling. The strongest synergy was observed for the combination of the CDK 2/7/9 inhibitor SNS032 and OTX015. Our data provide a landscape of drug combination effects in BL and suggest that targeting CDK and BET could provide a novel vulnerability of BL.

Correlation between glycolytic activity on [18F]-FDG-PET and cell density on diffusion-weighted MRI in lymphoma at staging

BACKGROUND

[18F]-FDG-PET/MR carries a high diagnostic value in whole-body oncologic imaging and allows simultaneous quantitative measurements of glucose metabolism (SUV) and cell density (ADC).

PURPOSE

To determine the relationship between SUV and ADC values extracted from simultaneously acquired [18F]-FDG-PET/MR data of patients with FDG-avid lymphomas at staging.

STUDY TYPE

Prospective.

POPULATION

Patients with histologically proven lymphoma referred for staging.

FIELD STRENGTH/SEQUENCES

Hybrid PET/MR device (3T); axial, two-point Dixon, 3D, volume-interpolated, T₁ -weighted breath-hold sequence; coronal T₂ -weighted half-Fourier acquisition single-shot turbo spin-echo. Single-shot, echo-planar imaging-based, spectral adiabatic inversion recovery diffusion-weighted imaging.

ASSESSMENT

Staging was performed according to the modified Ann Arbor system by a board-certified radiologist and a board-certified nuclear medicine physician, blinded to the clinical and histological information, in consensus. SUVs and ADCs values were collected, for each positive nodal and extranodal region, from the lesion demonstrating the largest diameter.

STATISTICAL TESTS

Descriptive data included absolute frequencies and percentages for categorical data, and arithmetic means and 95% confidence intervals for scale-type data. The Pearson correlation coefficient was used to assess the relationship between SUVs and ADCs (P ≤ 0.05). Additional separate analyses were performed according to histological lymphoma subtype, for nodal and extranodal lesions and excluding bone lesions.

RESULTS

Overall, 100 patients were examined (55 males, 45 females; age ± SD in years, 51.6 ± 19.5). Histology revealed Hodgkin-lymphoma and non-Hodgkin-lymphoma in 26 and 74 patients, respectively. Twenty patients were stage I, 21 stage II, 24 stage III, and 31 stage IV on [18F]-FDG-PET/MR (ie, four patients negative at imaging). Based on 391 lesions (ie, 367 excluding bone lesions) no significant correlations between SUVmax and ADCmin, or between SUVmean and ADCmean, emerged (respectively, r = 0.091, P = 0.073, 95% CI [-0.01, 0.19] and r = -0.032, P = 0.527, 95% CI [-0.13, 0.07] including bone lesions; r = 0.06, P = 0.21, 95% CI [-0.04, 0.17] and r = -0.05, P = 0.32, 95% CI [-0.15, 0.05] excluding bone lesions). A significant correlation was observed only between ADCmean and SUVmean for follicular lymphoma (r = -0.33, P = 0.001).

DATA CONCLUSION

SUVs and ADCs were demonstrated to be independent biomarkers in lymphomas. A moderate correlation between SUVs and ADCs likely is present in follicular lymphoma.

LEVEL OF EVIDENCE

1 Technical Efficacy: Stage 3 J. Magn. Reson. Imaging 2018;47:1217-1226.

Quantification of HER2 and estrogen receptor heterogeneity in breast cancer by single-molecule RNA fluorescence in situ hybridization

Intra-tumor heterogeneity is a pervasive property of human cancers that poses a major clinical challenge. Here, we describe the characterization, at the transcriptional level, of the intra-tumor topography of two prominent breast cancer biomarkers and drug targets, epidermal growth factor receptor 2 (HER2) and estrogen receptor 1 (ER) in 49 archival breast cancer samples. We developed a protocol for single-molecule RNA FISH in formalin-fixed, paraffin-embedded tissue sections (FFPE-smFISH), which enabled us to simultaneously detect and perform absolute quantification of HER2 and ER mature transcripts in single cells and multiple tumor regions. We benchmarked our method with standard diagnostic techniques, demonstrating that FFPE-smFISH is able to correctly classify breast cancers into well-established molecular subgroups. By counting transcripts in thousands of single cells, we identified different expression modes and levels of inter-cellular variability. In samples expressing both HER2 and ER, many cells co-expressed both genes, although expression levels were typically uncorrelated. Finally, we applied diversity metrics from the field of ecology to assess the intra-tumor topography of HER2 and ER gene expression, revealing that the spatial distribution of these key biomarkers can vary substantially even among breast cancers of the same subtype. Our results demonstrate that FFPE-smFISH is a reliable diagnostic assay and a powerful method for quantification of intra-tumor transcriptional heterogeneity of selected biomarkers in clinical samples.

Intratumoral genetic heterogeneity and number of cytogenetic aberrations provide additional prognostic significance in chronic lymphocytic leukemia

PURPOSE

Chronic lymphocytic leukemia (CLL) is a heterogeneous disease with cytogenetic aberrations that are still considered the gold standard of prognostic factors. However, heterogeneity remains within each cytogenetic group, especially in patients with concomitant cytogenetic aberrations.

METHODS

A panel of DNA probes was used to detect cytogenetic aberrations, including RB1/D13S25 at 13q14, ATM at 11q22, TP53 at 17p13, CEP12 and IGH translocation at 14q32, by fluorescence in situ hybridization. A comprehensive method integrating the number of cytogenetic aberrations and intratumoral genetic heterogeneity was used to analyze the prognosis for patients with concomitant aberrations.

RESULTS

Within the conventional favorable or neutral prognostic groups (i.e., with del 13q, trisomy 12, and/or t(14q32)), the coincidence of these three aberrations worsened survival in terms of time to first therapy, progression-free survival, and overall survival. However, within the conventional unfavorable prognostic group (i.e., del 11q or del 17p), patients with a minor unfavorable clone had an unexpected survival advantage compared with patients with a major unfavorable clone. A new cytogenetic prognostic system that integrates the number of cytogenetic aberrations and intratumoral genetic subclones was more precise than the conventional system.

CONCLUSION

The number of cytogenetic aberrations and the size of intratumoral genetic subclones should be comprehensively considered to determine the prognosis for CLL.Genet Med 19 2, 182-191.

Die-hard survivors: heterogeneity in apoptotic thresholds may underlie chemoresistance

The unmatched efficacy of microtubule-targeting agents (MTAs) as chemotherapeutics was once assumed to originate from their impact on mitotic processes; however, this misconception is being eroded by amassing data that MTAs instead target interphase functions in patients' tumors. What remains murky is how MTAs target malignant cells over non-malignant ones if proliferation rates do not distinguish them. In many instances, malignant cells are actually more 'primed' for apoptosis than non-malignant ones. Nevertheless, even if most cells within the tumor are more apoptosis-susceptible than those in healthy tissues, there likely exist small subpopulations of apoptosis-resistant clones that engender incomplete responses to MTAs and relapse. Therefore, intratumor heterogeneity in terms of proximity to the apoptotic threshold must be better understood to facilitate the design of chemotherapeutic regimens, which may benefit from including drugs like BH3 mimetics that help in lowering the apoptotic threshold of tumor cells within these chemoresistant subpopulations.