CXCR4 hyperactivation cooperates with TCL1 in CLL development and aggressiveness

Longitudinal multi-tracer imaging of hepatocellular carcinoma identifies novel stage- and oncogene-specific changes

BACKGROUND

Hepatocellular carcinoma (HCC) is a leading cause of cancer-related deaths, globally. There is a need for novel biomarkers for early detection and novel, effective targeted therapies. Molecular imaging can faithfully visualize, characterize and quantify specific relevant biological processes.

BASIC PROCEDURE

We performed longitudinal dedicated small-animal positron emission tomography-computed tomography (PET/CT) imaging to analyze changes in glucose metabolism using [18F]fluorodeoxyglucose ([18F]FDG), amino acid turnover with [18F]fluoroethyltyrosine ([18F]FET), and chemokine receptor expression using [68Ga]pentixafor targeting CXCR4, during stages of early tumor development, overt HCC and regression. We used two conditional transgenic mouse models of HCC, driven by clinically relevant oncogenes c-MYC (LT2/MYC) or HRASV12 (LT2/RAS). Conditional doxycycline-regulated mouse models, enable liver-specific oncogene activation or inhibition, leading to liver tumor development and regression, respectively. Correlation of our PET/CT findings with our gene expression and metabolomics data and with histological analyses followed.

MAIN FINDINGS

We show PET/CT identifies HCC stage-specific and oncogene-specific molecular changes that may serve as potential novel biomarkers and therapeutic targets. Glucose metabolism and CXCR4 chemokine expression are differentially deregulated during HCC development in an oncogene-specific manner. Our [18F]FDG results correlated with glucose transporter GLUT1 gene expression and with our metabolomics data. Increased expression of CXCR4 and CD68 inflammatory markers mirrored [68Ga]pentixafor results in LT2/MYC mice. FET-based measurement of amino acid turnover are insensitive to stages of HCC-development, in our studies. Concurrently, no significant changes in expression of tyrosine metabolism genes were observed.

PRINCIPAL CONCLUSIONS

Our study highlights that identified changes in targeted molecular imaging can facilitate a better understanding of underlying biological processes and may help guide novel oncogene-specific targeted anti-tumor therapies in HCC, with promising translational potential.

Tumor Cell Survival Factors and Angiogenesis in Chronic Lymphocytic Leukemia: How Hot Is the Link?

Chronic lymphocytic leukemia (CLL) is characterized by the accumulation of neoplastic CD5+/CD19+ B lymphocytes in the blood. These cells migrate to and proliferate in the bone marrow and lymphoid tissues. Despite the development of new therapies for CLL, drug resistance and disease relapse still occur; novel treatment approaches are therefore still needed. Inhibition of the angiogenesis involved in the progression of CLL might be a relevant therapeutic strategy. The literature data indicate that vascular endothelial growth factor, angiopoietin-2, and matrix metalloproteinase-9 are pro-angiogenic factors in CLL. A number of other CLL factors might have pro-angiogenic activity: fibroblast growth factor-2, certain chemokines (such as CXCL-12 and CXCL-2), tumor necrosis factor-α, insulin-like growth factor-1, neutrophil gelatinase-associated lipocalin, and progranulin. All these molecules contribute to the survival, proliferation, and migration of CLL cells. Here, we review the literature on these factors' respective expression profiles and roles in CLL. We also summarize the main results of preclinical and clinical trials of novel agents targeting most of these molecules in a CLL setting. Through the eradication of leukemic cells and the inhibition of angiogenesis, these therapeutic approaches might alter the course of CLL.

Proliferating CLL cells express high levels of CXCR4 and CD5

Chronic lymphocytic leukemia (CLL) is an incurable progressive malignancy of CD5+ B cells with a birth rate between 0.1% and 1% of the entire clone per day. However, the phenotype and functional characteristics of proliferating CLL cells remain incompletely understood. Here, we stained peripheral blood CLL cells for ki67 and DNA content and found that CLL cells in G1-phase have a CXCR4loCD5hi phenotype, while CLL cells in S/G2/M-phase express high levels of both CXCR4 and CD5. Induction of proliferation in vitro using CD40L stimulation results in high ki67 levels in CXCR4loCD5hi cells with CXCR4 expression increasing as CLL cells progress through S and G2/M-phases, while CXCR4hiCD5lo CLL cells remained quiescent. Dye dilution experiments revealed an accumulation of Ki67hi-divided cells in the CXCR4hiCD5hi fraction. In Eµ-TCL1 transgenic mice, the CXCR4hiCD5hi fraction expressed high levels of ki67 and was expanded in enlarged spleens of diseased animals. Human peripheral blood CXCR4hiCD5hi CLL cells express increased levels of IgM and the chemokine receptors CCR7 and CXCR5 and migrate efficiently toward CCL21. We found higher levels of CXCR4 in patients with progressive disease and the CXCR4hiCD5hi fraction was expanded upon clinical relapse. Thus, this study defines the phenotype and functional characteristics of dividing CLL cells identifying a novel subclonal population that underlies CLL pathogenesis and may drive clinical outcomes.

PET imaging of CXCR4 expression using [18F]AlF-NOTA-QHY-04 for hematologic malignancy and solid tumors

C-X-C motif chemokine receptor 4 (CXCR4) is an attractive target for the diagnosis and treatment of cancers. Here, we aimed to develop a new CXCR4-targeted PET tracer, and to investigate the translational potential for noninvasive imaging of CXCR4 expression in various cancer entities through preclinical and pilot clinical studies. Methods [18F]AlF-NOTA-QHY-04 was synthesized and evaluated by cellular uptake, blocking and biolayer interferometry studies in vitro. The pharmacokinetics, biodistribution, and imaging specificity were researched in tumor-bearing mice. [18F]AlF-NOTA-QHY-04 PET/CT imaging was performed on 55 patients with different types of cancers. Correlations between ex vivo CXCR4 expression and PET parameters, and CXCR4 expression characteristics in different tumors were analyzed by histopathological staining in patients. Results [18F]AlF-NOTA-QHY-04 was prepared with high radiolabeling yield and radiochemical purity, exhibiting good stability, high binding affinity and specificity for CXCR4. NCI-H69 (small cell lung cancer, SCLC) tumor-bearing mice showed the highest tumor uptake (4.98 ± 0.98%ID/mL, P < 0.0001) on PET imaging except for Daudi lymphoma xenograft model, which was consistent with the results of cellular and histological analyses. Patients with diffuse large B-cell lymphoma showed the highest tumor uptake (SUVmax, 11.10 ± 4.79) followed by SCLC patients (SUVmax, 7.51 ± 3.01), which were both significantly higher than other solid tumors (P < 0.05). The radiotracer uptake of high-grade gliomas is significantly higher than that of low-grade gliomas (3.13 ± 0.58 vs. 1.18 ± 0.51, P = 0.005). Significant higher tumor-to-normal brain ratio of [18F]AlF-NOTA-QHY-04 than [18F]FDG was found in primary brain tumors (62.55 ± 43.24 vs 1.70 ± 0.25, P = 0.027). Positive correlations between ex vivo CXCR4 expression and [18F]AlF-NOTA-QHY-04 uptake (all P < 0.01) were recorded. Multicolor immunofluorescence staining indicated the high tracer uptake in certain patients was mainly due to the high expression of CXCR4 in tumor cells, followed by macrophages. Conclusion The CXCR4-targeted radiotracer [18F]AlF-NOTA-QHY-04 was successfully prepared with favorable yield, high specificity and binding affinity to CXCR4. Preclinical and pilot clinical studies demonstrated its feasibility and potential application in precise diagnosis for not only lymphoma but also SCLC and glioma. [18F]AlF-NOTA-QHY-04 PET/CT can also provide a complementary mapping for brain tumors to [18F]FDG PET/CT.

CXCR4 promotes migration, invasion, and epithelial-mesenchymal transition of papillary thyroid carcinoma by activating STAT3 signaling pathway

AIMS

Papillary thyroid cancer (PTC) is a serious threat to human health worldwide, while metastasis in the early phase limits therapeutic success and leads to poor survival outcomes. The CXC chemokine receptor type 4 (CXCR4) plays an important role in many cellular movements such as transcriptional modulation, cell skeleton rearrangement, and cell migration, and the change in CXCR4 levels are crucial in various diseases including cancer. In this study, we explored the role of CXCR4 in the migration and invasion of PTC and investigated the potential mechanisms underlying its effects.

SUBJECTS AND METHODS

We analyzed the expression levels of CXCR4 in PTC tissues and cell lines. Would healing migration, Transwell invasion assay in vitro, and tail-vein lung metastasis assay In vivo were performed to evaluated the migration and invasion abilities of PTC cells with stable CXCR4 knockdown or overexpression. Signal transducers and activators of transcription (STAT3) signaling pathway-related protein expressions were examined by Western blotting assays.

RESULTS

The results showed that CXCR4 was highly expressed in PTC cell lines and PTC tissues. CXCR4 knockdown in PTC cells dampened the migration, invasion, and epithelial-mesenchymal transition (EMT), whereas CXCR4 overexpression enhanced these properties. In vivo, we also found that CXCR4 promoted the metastasis of PTC. Mechanistic studies showed that CXCR4 played these vital roles through the STAT3 signaling pathway. Furthermore, PTC patients with high CXCR4 or p-STAT3 expression correlated with aggressive clinical characteristics such as extrathyroidal extension (ETE), and lymph node metastasis (LNM).

CONCLUSIONS

We provided evidence that CXCR4 might activate the STAT3 signaling pathway and further promote PTC development. Thus, CXCR4 might be a novel therapeutic target for PTC.

Role of the tumor microenvironment in CLL pathogenesis

Chronic lymphocytic leukemia (CLL) cells extensively interact with and depend on their surrounding tumor microenvironment (TME). The TME encompasses a heterogeneous array of cell types, soluble signals, and extracellular vesicles, which contribute significantly to CLL pathogenesis. CLL cells and the TME cooperatively generate a chronic inflammatory milieu, which reciprocally reprograms the TME and activates a signaling network within CLL cells, promoting their survival and proliferation. Additionally, the inflammatory milieu exerts chemotactic effects, attracting CLL cells and other immune cells to the lymphoid tissues. The intricate CLL-TME interactions also facilitate immune evasion and compromise leukemic cell surveillance. We also review recent advances that have shed light on additional aspects that are substantially influenced by the CLL-TME interplay.

CXCR4 overexpression in chronic lymphocytic leukemia associates with poorer prognosis: A prospective, single-center, observational study

Controversial data have been reported on the prognostic value of C-X-C motif chemokine receptor 4 (CXCR4) in chronic lymphocytic leukemia (CLL). This prospective, single-center, observational study aimed to evaluate the role of CXCR4 in the pathophysiology of CLL and its prognostic role. A total of 158 patients of CLL were enrolled, and CXCR4 expression on CLL cells was detected by flow cytometry (FCM) at initial diagnosis. The patients were divided into 2 groups according to the CXCR4 mean fluorescence intensity (MFI) median. Also, four patient specimens from the CXCR4low and CXCR4high groups were selected for RNASeq analysis. The progression-free survival (PFS) of CLL patients in the CXCR4high group was significantly shorter than the CXCR4low group, with a median follow-up time of 27 months (log-rank P < 0.001). Moreover, CXCR4 overexpression (MFI > 3376) was an independent marker of poor PFS in CLL patients (P < 0.001). Analysis of RNASeq results revealed that CXCR4 plays an important role in the migration of CLL. Collectively, CXCR4 expression levels on leukemia cells can be detected rapidly by FCM. CXCR4 overexpression was significantly associated with poorer prognosis in CLL patients within a shorter follow-up time.

B cell receptor signaling and associated pathways in the pathogenesis of chronic lymphocytic leukemia

B cell antigen receptor (BCR) signaling is a key driver of growth and survival in both normal and malignant B cells. Several lines of evidence support an important pathogenic role of the BCR in chronic lymphocytic leukemia (CLL). The significant improvement of CLL patients' survival with the use of various BCR pathway targeting inhibitors, supports a crucial involvement of BCR signaling in the pathogenesis of CLL. Although the treatment landscape of CLL has significantly evolved in recent years, no agent has clearly demonstrated efficacy in patients with treatment-refractory CLL in the long run. To identify new drug targets and mechanisms of drug action in neoplastic B cells, a detailed understanding of the molecular mechanisms of leukemic transformation as well as CLL cell survival is required. In the last decades, studies of genetically modified CLL mouse models in line with CLL patient studies provided a variety of exciting data about BCR and BCR-associated kinases in their role in CLL pathogenesis as well as disease progression. BCR surface expression was identified as a particularly important factor regulating CLL cell survival. Also, BCR-associated kinases were shown to provide a crosstalk of the CLL cells with their tumor microenvironment, which highlights the significance of the cells' milieu in the assessment of disease progression and treatment. In this review, we summarize the major findings of recent CLL mouse as well as patient studies in regard to the BCR signalosome and discuss its relevance in the clinics.

Human and mouse early B cell development: So similar but so different

Early B cell development in the bone marrow ensures the replenishment of the peripheral B cell pool. Immature B cells continuously develop from hematopoietic stem cells, in a process guided by an intricate network of transcription factors as well as chemokine and cytokine signals. Humans and mice possess somewhat similar regulatory mechanisms of B lymphopoiesis. The continuous discovery of monogenetic defects that impact early B cell development in humans substantiates the similarities and differences with B cell development in mice. These differences become relevant when targeted therapeutic approaches are used in patients; therefore, predicting potential immunological adverse events is crucial. In this review, we have provided a phenotypical classification of human and murine early progenitors and B cell stages, based on surface and intracellular protein expression. Further, we have critically compared the role of key transcription factors (Ikaros, E2A, EBF1, PAX5, and Aiolos) and chemo- or cytokine signals (FLT3, c-kit, IL-7R, and CXCR4) during homeostatic and aberrant B lymphopoiesis in both humans and mice.

Interobserver Agreement Rates on C-X-C Motif Chemokine Receptor 4-Directed Molecular Imaging and Therapy

BACKGROUND

We aimed to evaluate the interobserver agreement rates in patients scanned with C-X-C motif chemokine receptor 4 (CXCR4)-directed PET/CT, including the rate of patients eligible for CXCR4-targeted radioligand therapy (RLT) based on scan results.

METHODS

Four independent observers reviewed 50 CXCR4-targeted [ 68 Ga]pentixafor PET/CT of patients with various solid cancers. On a visual level, the following items were assessed by each reader: overall scan impression, number of organ and lymph node (LN) metastases and number of affected organs and LN regions. For a quantitative investigation, readers had to choose a maximum of 3 target lesions, defined as largest in size and/or most intense uptake per organ compartment. Reference tissues were also quantified, including unaffected hepatic parenchyma and blood pool. Last, all observers had to decide whether patients were eligible for CXCR4-targeted RLT. Concordance rates were tested using intraclass correlation coefficients (ICCs). For interpretation, we applied the definition of Cicchetti (with 0.4-0.59 indicating fair; 0.6-0.74, good; 0.75-1, excellent agreement).

RESULTS

On a visual level, fair agreement was achieved for an overall scan impression (ICC, 0.58; 95% confidence interval, 0.45-0.71). Organ and LN involvement (ICC, ≥0.4) demonstrated fair, whereas CXCR4 density and number of LN and organ metastases showed good agreement rates (ICC, ≥0.65). Number of affected organs and affected LN areas, however, showed excellent concordance (ICC, ≥0.76). Quantification in LN and organ lesions also provided excellent agreement rates (ICC, ≥0.92), whereas quantified uptake in reference organs provided fair concordance (ICC, ≥0.54). Again, excellent agreement rates were observed when deciding on patients eligible for CXCR4-RLT (ICC, 0.91; 95% confidence interval, 0.85-0.95).

CONCLUSIONS

In patients scanned with CXCR4-targeted PET/CT, we observed fair to excellent agreement rates for both molecular imaging and therapy parameters, thereby favoring a more widespread adoption of [ 68 Ga]pentixafor in the clinic.

Biology and Treatment of Richter Transformation

Richter transformation (RT), defined as the development of an aggressive lymphoma on a background of chronic lymphocytic leukemia/small lymphocytic lymphoma (CLL/SLL), represents a clinical unmet need because of its dismal prognosis. An increasing body of knowledge in the field of RT is arising from the recent development of preclinical models depicting the biology underlying this aggressive disease. Consistently, new therapeutic strategies based on a genetic rationale are exploring actionable pathogenic pathways to improve the outcome of patients in this setting. In this review, we summarize the current understandings on RT biology and the available treatment options.

The Modes of Dysregulation of the Proto-Oncogene T-Cell Leukemia/Lymphoma 1A

Simple Summary

T-cell leukemia/lymphoma 1A (TCL1A) is a proto-oncogene that is mainly expressed in embryonic and fetal tissues, as well as in some lymphatic cells. It is frequently overexpressed in a variety of T- and B-cell lymphomas and in some solid tumors. In chronic lymphocytic leukemia and in T-prolymphocytic leukemia, TCL1A has been implicated in the pathogenesis of these conditions, and high-level TCL1A expression correlates with more aggressive disease characteristics and poorer patient survival. Despite the modes of TCL1A (dys)regulation still being incompletely understood, there are recent advances in understanding its (post)transcriptional regulation. This review summarizes the current concepts of TCL1A’s multi-faceted modes of regulation. Understanding how TCL1A is deregulated and how this can lead to tumor initiation and sustenance can help in future approaches to interfere in its oncogenic actions.

Abstract

Incomplete biological concepts in lymphoid neoplasms still dictate to a large extent the limited availability of efficient targeted treatments, which entertains the mostly unsatisfactory clinical outcomes. Aberrant expression of the embryonal and lymphatic TCL1 family of oncogenes, i.e., the paradigmatic TCL1A, but also TML1 or MTCP1, is causally implicated in T- and B-lymphocyte transformation. TCL1A also carries prognostic information in these particular T-cell and B-cell tumors. More recently, the TCL1A oncogene has been observed also in epithelial tumors as part of oncofetal stemness signatures. Although the concepts on the modes of TCL1A dysregulation in lymphatic neoplasms and solid tumors are still incomplete, there are recent advances in defining the mechanisms of its (de)regulation. This review presents a comprehensive overview of TCL1A expression in tumors and the current understanding of its (dys)regulation via genomic aberrations, epigenetic modifications, or deregulation of TCL1A-targeting micro RNAs. We also summarize triggers that act through such transcriptional and translational regulation, i.e., altered signals by the tumor microenvironment. A refined mechanistic understanding of these modes of dysregulations together with improved concepts of TCL1A-associated malignant transformation can benefit future approaches to specifically interfere in TCL1A-initiated or -driven tumorigenesis.