Tumor-infiltrating lymphocytes predict efficacy of immunotherapy in advanced non-small cell lung cancer: a single-center retrospective cohort study.

BACKGROUND/PURPOSE: The current study aimed to investigate the correlation between tumor-infiltrating lymphocytes (TILs) and immunotherapy efficacy in patients with advanced non-small cell lung cancer (NSCLC). MATERIALS AND METHODS: Eighty-nine patients with advanced NSCLC who received immune checkpoint inhibitors (ICIs) monotherapy were retrospectively enrolled in this study. The density of TILs in paraffin-embedded pathological tissues taken before receiving ICIs was quantitatively analyzed by immunohistochemical staining. The density of TILs was treated as a dichotomous variable using the median as the cutoff value. The Kaplan-Meier analysis was used to assess survival differences between groups. Univariate and multivariate Cox analyses were applied to screen out independent prognostic factors and further construct a nomogram prediction model to predict survival. RESULTS: Survival analysis showed that CD8+ TILs, CD4+ TILs, and IFN-γ+ Th1 were significant positive indicators for predicting progression-free survival (PFS) and overall survival (OS) (p < 0.05), whereas Foxp3+ Treg were a significant negative predictor (p < 0.05). The predictive role of IL-4+ Th2 was not apparent in this study and requires further investigation and exploration (p > 0.05). The nomogram prediction model exhibited good discriminative ability, with C-index values of 0.723 (95% CI 0.682-0.764) and 0.793 (95% CI, 0.738-0.848) in the training cohort and validation cohort, respectively. The AUC values indicated that the nomogram prediction model had high predictive value and the calibration curve presented good prediction accuracy. CONCLUSIONS: TILs could predict the efficacy of immunotherapy and may become a promising predictor.

Modulating proteasome inhibitor tolerance in multiple myeloma: an alternative strategy to reverse inevitable resistance.

BACKGROUND: Resistance to proteasome inhibitors (PIs) is a major obstacle to the successful treatment of multiple myeloma (MM). Many mechanisms have been proposed for PI resistance; however, our mechanistic understanding of how PI resistance is inevitably acquired and reversed remains incomplete. METHODS: MM patients after bortezomib relapse, MM cell lines and mouse models were used to generate matched resistant and reversed cells. RNA sequencing and bioinformatics analyses were employed to assess dysregulated epigenetic regulators. In vitro and in vivo procedures were used to characterise PI-tolerant cells and therapeutic efficacy. RESULTS: Upon PI treatment, MM cells enter a slow-cycling and reversible drug-tolerant state. This reversible phenotype is associated with epigenetic plasticity, which involves tolerance rather than persistence in patients with relapsed MM. Combination treatment with histone deacetylase inhibitors and high-dosage intermittent therapy, as opposed to sustained PI monotherapy, can be more effective in treating MM by preventing the emergence of PI-tolerant cells. The therapeutic basis is the reversal of dysregulated epigenetic regulators in MM patients. CONCLUSIONS: We propose an alternative non-mutational PI resistance mechanism that explains why PI relapse is inevitable and why patients regain sensitivity after a 'drug holiday'. Our study also suggests strategies for epigenetic elimination of drug-tolerant cells.

Novel CAR T-cell therapies for relapsed/refractory B-cell malignancies: latest updates from 2023 ASH annual meeting.

Chimeric antigen receptors (CAR) are engineered fusion proteins that target T-cells to specific surface antigens of tumor cells to generate effective anti-tumor responses. CAR T-cell therapy is playing an increasingly important role in the treatment of relapsed/refractory B-cell malignancies (R/R BCM). Attempting to make CAR T-cells safer and more effective in treating R/R BCM, various novel engineered CAR T-cell agents are currently in the research and development or clinical trial stages. We have summarized here the latest reports on the novel CAR T-cell therapies for R/R BCM presented at the 2023 ASH Annual Meeting as well as the latest updates in related clinical trials.

[Immune Reconstitution after BTKi Treatment in Chronic Lymphocytic Leukemia].

OBJECTIVE: To analyze the immune reconstitution after BTKi treatment in patients with chronic lymphocytic leukemia (CLL). METHODS: The clinical and laboratorial data of 59 CLL patients admitted from January 2017 to March 2022 in Fujian Medical University Union Hospital were collected and analyzed retrospectively. RESULTS: The median age of 59 CLL patients was 60.5(36-78). After one year of BTKi treatment, the CLL clones (CD5 +/CD19 +) of 51 cases (86.4%) were significantly reduced, in which the number of cloned-B cells decreased significantly from (46±6.1)×109/L to (2.3±0.4)×109/L (P =0.0013). But there was no significant change in the number of non-cloned B cells (CD19 + minus CD5 +/CD19 +). After BTKi treatment, IgA increased significantly from (0.75±0.09)g/L to (1.31±0.1)g/L (P <0.001), while IgG and IgM decreased from (8.1±0.2)g/L and (0.52±0.6)g/L to (7.1±0.1)g/L and (0.47±0.1)g/L, respectively (P <0.001, P =0.002). BTKi treatment resulted in a significant change in T cell subpopulation of CLL patients, which manifested as both a decrease in total number of T cells from (2.1±0.1)×109/L to (1.6±0.4)×109/L and NK/T cells from (0.11±0.1)×109/L to (0.07±0.01)×109/L (P =0.042, P =0.038), both an increase in number of CD4 + cells from (0.15±6.1)×109/L to (0.19±0.4)×109/L and CD8 + cells from (0.27±0.01)×109/L to (0.41±0.08)×109/L (both P <0.001). BTKi treatment also up-regulated the expression of interleukin (IL)-2 while down-regulated IL-4 and interferon (IFN)-γ. However, the expression of IL-6, IL-10, and tumor necrosis factor (TNF)-α did not change significantly. BTKi treatment could also restored the diversity of TCR and BCR in CLL patients, especially obviously in those patients with complete remission (CR) than those with partial remission (PR). Before and after BTKi treatment, Shannon index of TCR in patients with CR was 0.02±0.008 and 0.14±0.001 (P <0.001), while in patients with PR was 0.01±0.03 and 0.05±0.02 (P >0.05), respectively. Shannon index of BCR in patients with CR was 0.19±0.003 and 0.33±0.15 (P <0.001), while in patients with PR was 0.15±0.009 and 0.23±0.18 (P <0.05), respectively. CONCLUSIONS: BTKi treatment can shrink the clone size in CLL patients, promote the expression of IgA, increase the number of functional T cells, and regulate the secretion of cytokines such as IL-2, IL-4, and IFN-γ. BTKi also promote the recovery of diversity of TCR and BCR. BTKi treatment contributes to the reconstitution of immune function in CLL patients.

CRIP1 involves the pathogenesis of multiple myeloma via dual-regulation of proteasome and autophagy.

BACKGROUND: Multiple myeloma (MM) is an incurable hematological malignancy of the plasma cells. The maintenance of protein homeostasis is critical for MM cell survival. Elevated levels of paraproteins in MM cells are cleared by proteasomes or lysosomes, which are independent but inter-connected with each other. Proteasome inhibitors (PIs) work as a backbone agent and successfully improved the outcome of patients; however, the increasing activity of autophagy suppresses the sensitivity to PIs treatment. METHODS: The transcription levels of CRIP1 were explored in plasma cells obtained from healthy donors, patients with newly diagnosed multiple myeloma (NDMM), and relapsed/refractory multiple myeloma (RRMM) using Gene expression omnibus datasets. Doxycycline-inducible CRIP1-shRNA and CRIP1 overexpressed MM cell lines were constructed to explore the role of CRIP1 in MM pathogenesis. Proliferation, invasion, migration, proteasome activity and autophagy were examined in MM cells with different CRIP1 levels. Co-immunoprecipitation (Co-IP) with Tandem affinity purification/Mass spectrum (TAP/MS) was performed to identify the binding proteins of CRIP1. The mouse xenograft model was used to determine the role of CRIP1 in the proliferation and drug-resistance of MM cells. FINDINGS: High CRIP1 expression was associated with unfavorable clinical outcomes in patients with MM and served as a biomarker for RRMM with shorter overall survival. In vitro and in vivo studies showed that CRIP1 plays a critical role in protein homeostasis via the dual regulation of the activities of proteasome and autophagy in MM cells. A combined analysis of RNA-seq, Co-IP and TAP/MS demonstrated that CRIP1 promotes proteasome inhibitors resistance in MM cells by simultaneously binding to de-ubiquitinase USP7 and proteasome coactivator PA200. CRIP1 promoted proteasome activity and autophagosome maturation by facilitating the dequbiquitination and stabilization of PA200. INTERPRETATION: Our findings clarified the pivotal roles of the CRIP1/USP7/PA200 complex in ubiquitin-dependent proteasome degradation and autophagy maturation involved in the pathogenesis of MM. FUNDING: A full list of funding sources can be found in the acknowledgements section.

Arsenic trioxide and p97 inhibitor synergize against acute myeloid leukemia by targeting nascent polypeptides and activating the ZAKα-JNK pathway.

Arsenic trioxide (ATO) has exhibited remarkable efficacy in treating acute promyelocytic leukemia (APL), primarily through promoting the degradation of the PML-RARα fusion protein. However, ATO alone fails to confer any survival benefit to non-APL acute myeloid leukemia (AML) patients and exhibits limited efficacy when used in combination with other agents. Here, we explored the general toxicity mechanisms of ATO in APL and potential drugs that could be combined with ATO to exhibit synergistic lethal effects on other AML. We demonstrated that PML-RARα degradation and ROS upregulation were insufficient to cause APL cell death. Based on the protein synthesis of different AML cells and their sensitivity to ATO, we established a correlation between ATO-induced cell death and protein synthesis. Our findings indicated that ATO induced cell death by damaging nascent polypeptides and causing ribosome stalling, accompanied by the activation of the ZAKα-JNK pathway. Furthermore, ATO-induced stress activated the GCN2-ATF4 pathway, and ribosome-associated quality control cleared damaged proteins with the assistance of p97. Importantly, our data revealed that inhibiting p97 enhanced the effectiveness of ATO in killing AML cells. These explorations paved the way for identifying optimal synthetic lethal drugs to enhance ATO treatment on non-APL AML.

Myeloid-derived suppressor cells: key immunosuppressive regulators and therapeutic targets in hematological malignancies.

The immunosuppressive tumor microenvironment (TME) supports the development of tumors and limits tumor immunotherapy, including hematological malignancies. Hematological malignancies remain a major public health issue with high morbidity and mortality worldwide. As an important component of immunosuppressive regulators, the phenotypic characteristics and prognostic value of myeloid-derived suppressor cells (MDSCs) have received much attention. A variety of MDSC-targeting therapeutic approaches have produced encouraging outcomes. However, the use of various MDSC-targeted treatment strategies in hematologic malignancies is still difficult due to the heterogeneity of hematologic malignancies and the complexity of the immune system. In this review, we summarize the biological functions of MDSCs and further provide a summary of the phenotypes and suppressive mechanisms of MDSC populations expanded in various types of hematological malignancy contexts. Moreover, we discussed the clinical correlation between MDSCs and the diagnosis of malignant hematological disease, as well as the drugs targeting MDSCs, and focused on summarizing the therapeutic strategies in combination with other immunotherapies, such as various immune checkpoint inhibitors (ICIs), that are under active investigation. We highlight the new direction of targeting MDSCs to improve the therapeutic efficacy of tumors.

The novel HLA-DQB1*04:93 allele, identified by Sanger dideoxy nucleotide sequencing in a Chinese individual.

HLA-DQB1*04:93 differs from HLA-DQB1*04:01:01:01 by one nucleotide in exon 2.

SYT7 regulates the progression of chronic lymphocytic leukemia through interacting and regulating KNTC1.

BACKGROUND: Chronic lymphocytic leukemia (CLL) is one of the most frequent occurring types of leukemia. It typically occurs in elderly patients and has a highly variable clinical course. At present, the molecular mechanism driving the pathogenesis and progression of CLL is not fully understood. The protein Synaptotagmin 7 (SYT7) encoded by the SYT7 gene has been found to be closely related to the development of various solid tumors, but its role in CLL is unclear. In this study, we investigated the function and molecular mechanism of SYT7 in CLL. METHODS: The expression level of SYT7 in CLL was determined by immunohistochemical staining and qPCR. The role of SYT7 in promoting CLL development was verified by in vivo and in vitro experiments. The molecular mechanism of SYT7 in CLL was elucidated by methods such as GeneChip analysis and Co-immunoprecipitation assay. RESULTS: Malignant behaviors such as proliferation, migration, and anti-apoptosis of CLL cells were significantly inhibited after SYT7 gene knockdown. In contrast, SYT7 overexpression promoted CLL development in vitro. Consistently, the knockdown of SYT7 also inhibited xenograft tumor growth of CLL cells. Mechanistically, SYT7 promoted CLL development by inhibiting SYVN1-mediated KNTC1 ubiquitination. The KNTC1 knockdown also attenuated the effects of SYT7 overexpression on development of CLL. CONCLUSIONS: SYT7 regulates the progression of CLL through SYVN1-mediated KNTC1 ubiquitination, which has potential value for molecular targeted therapy of CLL.

Exosome miRNAs profiling in serum and prognostic evaluation in patients with multiple myeloma.

MicroRNAs (MiRNAs) carried by exosomes play pivotal roles in the crosstalk between cell components in the tumor microenvironment. Our study aimed at identifying the expression profile of exosomal miRNAs (exo-miRNAs) in the serum of multiple myeloma (MM) patients and investigating the regulation networks and their potential functions by integrated bioinformatics analysis. Exosomes in serum from 19 newly diagnosed MM patients and 9 healthy donors were isolated and the miRNA profile was investigated by small RNA sequencing. Differential expression of exo-miRNAs was calculated and target genes of miRNAs were predicted. CytoHubba was applied to identify the hub miRNAs and core target genes. The LASSO Cox regression model was used to develop the prognostic model, and the ESTIMATE immune score was calculated to investigate the correlation between the model and immune status in MM patients. The top six hub differentially expressed serum exo-miRNAs were identified. 513 target genes of the six hub exo-miRNAs were confirmed to be differentially expressed in MM cells in the Zhan Myeloma microarray dataset. Functional enrichment analysis indicated that these target genes were mainly involved in mRNA splicing, cellular response to stress, and deubiquitination. 13 core exo-miRNA target genes were applied to create a novel prognostic signature to provide risk stratification for MM patients, which is associated with the immune microenvironment of MM patients. Our study comprehensively investigated the exo-miRNA profiles in MM patients. A novel prognostic signature was constructed to facilitate the risk stratification of MM patients with distinct outcomes.

Multidisciplinary recommendations for the management of CAR-T recipients in the post-COVID-19 pandemic era.

The outbreak of coronavirus disease 2019 (COVID-19) posed an unprecedented challenge on public health systems. Despite the measures put in place to contain it, COVID-19 is likely to continue experiencing sporadic outbreaks for some time, and individuals will remain susceptible to recurrent infections. Chimeric antigen receptor (CAR)-T recipients are characterized by durable B-cell aplasia, hypogammaglobulinemia and loss of T-cell diversity, which lead to an increased proportion of severe/critical cases and a high mortality rate after COVID-19 infection. Thus, treatment decisions have become much more complex and require greater caution when considering CAR T-cell immunotherapy. Hence, we reviewed the current understanding of COVID-19 and reported clinical experience in the management of COVID-19 and CAR-T therapy. After a panel discussion, we proposed a rational procedure pertaining to CAR-T recipients with the aim of maximizing the benefit of CAR-T therapy in the post COVID-19 pandemic era.

Rituximab and new regimens for indolent lymphoma: a brief update from 2012 ASCO Annual Meeting.

Indolent lymphoma (IL), the second most common lymphoma, remains incurable with chemotherapy alone. While R-CHOP (rituximab, cyclophosphamide, doxorubicin, vincristine, prednisone) remains the standard frontline regimen for diffuse Large B -cell lymphoma, the optimal chemotherapy regimen for frontline therapy of advanced IL remains uncertain. FCR (fludarabine, cyclophosphamide, rituximab) has been shown to be better than fludarabine alone and fludarabine plus cyclophosphamide for IL. In FOLL05 trial, R-CHOP was compared with R-CVP (cyclophosphamide, vincristine, prednisone) and R-FM (fludarabine, mitoxantrone). The study showed that R-CHOP appears to have the best risk-benefit ratio for IL. The StiL NHL1 trial showed that BR (bendamustine, rituximab) has longer progression free survival and is better tolerated than R-CHOP. Long-term complications with secondary malignancies between the two regimens appear to be comparable. In this review, new combination regimens reported at 2012 ASCO annual meeting were evaluated for frontline and salvage therapy of indolent lymphoma.

Targeting matrix metallopeptidase 2 by hydroxyurea selectively kills acute myeloid mixed-lineage leukemia.

Oncogene-induced tumorigenesis results in the variation of epigenetic modifications, and in addition to promoting cell immortalization, cancer cells undergo more intense cellular stress than normal cells and depend on other support genes for survival. Chromosomal translocations of mixed-lineage leukemia (MLL) induce aggressive leukemias with an inferior prognosis. Unfortunately, most MLL-rearranged (MLL-r) leukemias are resistant to conventional chemotherapies. Here, we showed that hydroxyurea (HU) could kill MLL-r acute myeloid leukemia (AML) cells through the necroptosis process. HU target these cells by matrix metallopeptidase 2 (MMP2) deficiency rather than subordinate ribonucleotide reductase regulatory subunit M2 (RRM2) inhibition, where MLL directly regulates MMP2 expression and is decreased in most MLL-r AMLs. Moreover, iron chelation of HU is also indispensable for inducing cell stress, and MMP2 is the support factor to protect cells from death. Our preliminary study indicates that MMP2 might play a role in the nonsense-mediated mRNA decay pathway that prevents activation of unfolding protein response under innocuous endoplasmic reticulum stress. Hence, these results reveal a possible strategy of HU application in MLL-r AML treatment and shed new light upon HU repurposing.

2-Methoxyestradiol blocks cell-cycle progression at the G2/M phase and induces apoptosis in human acute T lymphoblastic leukemia CEM cells.

2-Methoxyestradiol (2-ME2) is an endogenous metabolite of 17beta-estradiol (E2) with estrogen receptor-independent anti-cancer activity. The current study sought to determine the mechanism of anti-cancer activity of 2-ME2 in human acute T lymphoblastic leukemia CEM cells. Results showed that 2-ME2 markedly suppressed proliferation of CEM cells in a time- and dose-dependent manner. 2-ME2-treated CEM cells underwent typical apoptotic changes. Exposure to 2-ME2 led to G(2)/M phase cell-cycle arrest, which preceded apoptosis characterized by the appearance of a sub-G(1) cell population. In addition, cytosolic cytochrome c release, increased procaspase-9 and -3 expressions, poly(ADP-ribose) polymerase (PARP) cleavage, and induced expression of caspase-8 were detected, suggesting that both the intrinsic apoptotic pathway and extrinsic apoptotic pathway were involved in 2-ME2-induced apoptosis. Moreover, the expression level of p21 protein was upregulated, whereas Bcl-2 and dysfunctional p53 protein were downregulated, which also contributed to 2-ME2-induced apoptosis. Our findings revealed that 2-ME2 might be a potent natural candidate for chemotherapeutic treatment of human acute T lymphoblastic leukemia when the precise effects of 2-ME2 were investigated further in other T leukemia cell lines and in primary T-cell leukemias.

Cytogenetic abnormalities in patients with newly diagnosed multiple myeloma as a secondary primary malignancy: a retrospective study.

Objectives: Multiple myeloma (MM) often develops as a secondary primary malignancy (SPM). The retinoblastoma susceptibility gene (RB1) was the first tumour suppressor gene to be identified. We pooled and analyzed available data to compare the incidence of RB1 gene deletions and other cytogenetic abnormalities in patients with MM alone or as an SPM.Methods: We conducted a retrospective study of 475 patients. The experimental group comprised 18 patients with MM as an SPM, and the control group comprised 457 MM patients. We analyzed the baseline information in both groups, and used the odds ratio (OR), 95% confidence interval (CI), and forest plot to determine the incidence of SPMs with and without cytogenetic abnormalities.Results: The incidence of RB1 gene deletion was higher in the experimental group. There was no significant difference in other cytogenetic abnormalities.Conclusions: RB1 gene deletions appear to be associated with MM that develops as an SPM.

Restoring MLL reactivates latent tumor suppression-mediated vulnerability to proteasome inhibitors.

MLL undergoes multiple distinct chromosomal translocations to yield aggressive leukemia with dismal outcomes. Besides their well-established role in leukemogenesis, MLL fusions also possess latent tumor-suppressive activity, which can be exploited as effective cancer treatment strategies using pharmacological means such as proteasome inhibitors (PIs). Here, using MLL-rearranged xenografts and MLL leukemic cells as models, we show that wild-type MLL is indispensable for the latent tumor-suppressive activity of MLL fusions. MLL dysfunction, shown as loss of the chromatin accumulation and subsequent degradation of MLL, compromises the latent tumor suppression of MLL-AF4 and is instrumental for the acquired PI resistance. Mechanistically, MLL dysfunction is caused by chronic PI treatment-induced epigenetic reprogramming through the H2Bub-ASH2L-MLL axis and can be specifically restored by histone deacetylase (HDAC) inhibitors, which induce histone acetylation and recruits MLL on chromatin to promote cell cycle gene expression. Our findings not only demonstrate the mechanism underlying the inevitable acquisition of PI resistance in MLL leukemic cells, but also illustrate that preventing the emergence of PI-resistant cells constitutes a novel rationale for combination therapy with PIs and HDAC inhibitors in MLL leukemias.

SENP2 exerts an anti­tumor effect on chronic lymphocytic leukemia cells through the inhibition of the Notch and NF­κB signaling pathways.

Chronic lymphocytic leukemia (CLL) is one of the most often diagnosed hematological malignant tumors in the Western world and a type of inert B­cell lymphoma that commonly attacks the elderly. Small ubiquitin related modifier (SUMO)­specific protease 2 (SENP2) can act as a suppressor in various types of cancer by regulating the stability of ß­catenin to affect the Notch signaling pathway; however, it has a low expression level in CLL cells. In this study, we firstly used western blot analysis and RT­qPCR to detect the protein and mRNA expression levels of SENP2 in the peripheral blood of patients with CLL and healthy volunteers. Secondly, we overexpressed or knocked down the expression of SENP2 in CLL cells and then determined the cell invasive and chemotactic ability in a Transwell assay and chemotaxis assay. We examined the sensitivity of the cells to cytarabine and dexamethasone via a CCK­8 assay and determined the cell apoptotic condition and the expression of the Notch signaling pathway using flow cytometry and western blot analysis. The results demonstrated that the patients with CLL had relatively low expression levels of SENP2. The overexpression of SENP2 in the CLL cells decreased their invasive and proliferative ability, as well as their chemotactic response and enhanced their sensitivity to cytarabine and dexamethasone, while it promoted cell apoptosis. The silencing of SENP2 in the CLL cells generally produced the opposite results. We thus hypothesized that the overexpression of SENP2 downregulated ß­catenin expression, thus inhibiting the Notch signaling pathway in CLL cells. Moreover, the nuclear factor (NF)­κB signaling pathway was also regulated by the overexpression of SENP2. On the whole, the findings of this study indicate tha SENP2 can act as a tumor suppressor in CLL cells, and may thus prove to be a novel target for CLL treatment in clinical practice.

[Recent Research Advances on Signaling Pathway in B-cell Malignancy - Review].

B-cell malignancy, a kind of malignant tumor of blood system, is characterized by heterogeneity and complexity of the pathogenesis. In this review, the recent advances of studies on B-cell malignancy and signaling pathways are briefly summarized. This review focuses on the role of signaling pathways, especially the NF-κ B, Wnt, PI3K/Akt, Notch and JAK/STAT signaling pathway in the occurrence and development of B-cell malignancy, and discussed the influence of signaling pathways on the invasiveness and drug resistance of B-cell malignancy, and the clinical application of signaling pathway inhibitors.

Bone marrow stromal cells enhance the survival of chronic lymphocytic leukemia cells by regulating HES-1 gene expression and H3K27me3 demethylation.

The majority of patients with chronic lymphocytic leukemia (CLL) are not cured by traditional chemotherapy. One possible explanation for this is that the microenvironment protects CLL cells from both spontaneous- and cytotoxic-mediated apoptosis. The present study was designed to investigate the mechanisms accounting for these effects, since this information is crucial to understanding CLL physiopathology and identifying potential treatment targets. The CLL cell line L1210 and primary CLL cells were cultured under different conditions: With serum, cyclophosphamide (CTX), or with monolayers and conditioned medium (CM) from the stromal cell line HESS-5. Apoptosis, Hes family BHLH transcription factor 1 (HES-1) gene and protein expression, and histone H3K27me3 DNA demethylation were determined. Co-culture of L1210 cells with HESS-5 cells significantly inhibited serum deprivation- and CTX-induced apoptosis of leukemia cells, and resulted in a significant increase in short-term proliferation. Soluble factors in the CM from HESS-5 cells had a negligible effect. The HESS-5 cell-mediated inhibition of apoptosis of CLL cells was associated with increased HES-1 expression and hypomethylation of the H3K27me3 gene in the leukemia cells. These results indicate that stromal cells enhance the survival of CLL cells by regulating the HES-1 gene and protein expression, as well as H3K27me3 DNA demethylation, and suggest that specific interactions between stromal and leukemia cells may enhance the resistance of leukemia cells to chemotherapy.