Treatment patterns, clinical outcomes and gene mutation characteristics of hepatitis B virus-associated mantle cell lymphoma.

Mantle cell lymphoma (MCL) is an uncommon and incurable B-cell lymphoma subtype that has an aggressive course. Hepatitis B virus (HBV) infection has been associated with an increased risk for B-cell lymphomas, and is characterized by distinct clinical and genetic features. Here, we showed that 9.5% of MCL Chinese patients were hepatitis B surface antigen positive (HBsAg+). Compared to HBsAg-negative (HBsAg-) patients, HBsAg+ MCL patients had a greater incidence of elevated lactate dehydrogenase (LDH), but no difference was observed in the other clinical characteristics, including sex, age, ECOG ps, Ann Arbor stage, MIPI, extranodal involvement and Ki-67. The HD-AraC (high-dose cytarabine) regimen was the main first-line induction regimen for younger HBsAg+ patients, and cyclophosphamide, doxorubicin, vincristine and prednisone (CHOP) were used for elderly patients. HBsAg seropositivity was associated with a significantly shorter PFS than HBsAg seronegativity when patients were treated with rituximab or CHOP-based regimens. Compared with CHOP, the HD-AraC regimen was associated with longer PFS in HBsAg+ patients. Treatment with a Bruton tyrosine kinase inhibitor (BTKi) alone can also cause HBV reactivation. Among the 74 patients who underwent targeted deep sequencing (TDS), the nonsynonymous mutation load of HBsAg+ MCL patients was greater than that of HBsAg- MCL patients. HDAC1, TRAF5, FGFR4, SMAD2, JAK3, SMC1A, ZAP70, BLM, CDK12, PLCG2, SMO, TP63, NF1, PTPR, EPHA2, RPTOR and FIP1L1 were significantly enriched in HBsAg+ MCL patients.

IgG antibody response to SARS-CoV-2 infection and its influencing factors in lymphoma patients.

BACKGROUND: The ability of generating effective humoral immune responses to SARS-CoV-2 infection has not been clarified in lymphoma patients. The study aimed to investigate the antibody (Ab) production after SARS-Cov-2 infection and clarify the factors affecting the Ab generation in these patients. PATIENTS & METHODS: 80 lymphoma patients and 51 healthy controls were included in this prospective observational study. Clinical factors and treatment regimens affecting Ab positive rate (APR) and Ab levels were analyzed by univariate and multivariate methods. RESULTS: The anti-SARS-CoV-2 IgG APR and Ab levels in lymphoma patients were significantly lower than those in healthy controls. Lymphoma patients with COVID-19 vaccination had significantly higher APR and Ab levels compared with those without vaccination. Additionally, the use of dexamethasone for COVID-19 treatment had a negative impact on Ab levels. For the impact of treatment regimens on the APR and Ab levels, the results showed that patients treated with ≥ 6 times CD20 monoclonal Ab (mAb) and patients treated with autologous hematopoietic stem cell transplantation (ASCT) prior to infection produced a statistically lower APR and Ab levels compared with those treated with 1-5 times CD20 mAb and those treated without ASCT, respectively. Furthermore, multiple regression analysis indicated that the number of anti-CD20 treatment was an independent predictor for both APR and Ab levels. CONCLUSIONS: Humoral immune response to SARS-CoV-2 infection was impaired in lymphoma patients partly due to anti-CD20 and ASCT treatment. COVID-19 vaccination may be more needed for these patients.

ARHGAP4 promotes leukemogenesis in acute myeloid leukemia by inhibiting DRAM1 signaling.

Rho GTPase-activating protein 4 (ARHGAP4) is an important Rho family GTPase-activating protein that is strongly associated with the onset and progression of some tumors. We found that ARHGAP4 mRNA and protein are overexpressed in human acute myeloid leukemia (AML) patients and are associated with a poor prognosis. ARHGAP4 knockdown significantly impairs viability and colony formation capacity and induces apoptosis in AML cells. Further results demonstrate that ARHGAP4 deletion impairs AML progression in vivo. Interestingly, DRAM1 signaling is significantly activated in AML cells with ARHGAP4 knockdown. Our results also indicated that ARHGAP4 might function in AML cells by binding with p53 to inhibit DRAM1. Moreover, knockdown of DRAM1 rescues the defects of ARHGAP4 in AML cells. This newly described role of the ARHGAP4/DRAM1 axis in regulating AML progression may have important therapeutic implications.

Treatment patterns and clinical outcomes of mantle cell lymphoma: A retrospective cohort study by CHOICE.

Regimens based on Bruton's tyrosine kinase inhibitors (BTKi) have been increasingly used to treat mantle cell lymphoma (MCL). A real-world multicenter study was conducted to characterize treatment patterns and outcomes in patients with newly diagnosed MCL by Chinese Hematologist and Oncologist Innovation Cooperation of the Excellent (CHOICE). The final analysis included 1261 patients. Immunochemotherapy was the most common first-line treatment, including R-CHOP in 34%, cytarabine-containing regimens in 21% and BR in 3% of the patients. Eleven percent (n = 145) of the patients received BTKi-based frontline therapy. Seventeen percent of the patients received maintenance rituximab. Autologous hematopoietic stem cell transplantation (AHCT) was conducted in 12% of the younger (<65 years) patients. In younger patients, propensity score matching analysis did not show significant difference in 2-year progression-free survival and 5-year overall survival rate in patients receiving standard high-dose immunochemotherapy followed by AHCT than induction therapy with BTKi-based regimens without subsequent AHCT (72% vs 70%, P = .476 and 91% vs 84%, P = .255). In older patients, BTKi combined with bendamustine plus rituximab (BR) was associated with the lowest POD24 rate (17%) compared with BR and other BTKi-containing regimens. In patients with resolved hepatitis B at the baseline, HBV reactivation rate was 2.3% vs 5.3% in those receiving anti-HBV prophylaxis vs not; BTKi treatment was not associated with higher risk of HBV reactivation. In conclusion, non-HD-AraC chemotherapy combined with BTKi may be a viable therapeutic strategy for younger patients. Anti-HBV prophylaxis should be implemented in patients with resolved hepatitis B.

Long noncoding RNA SENCR facilitates the progression of acute myeloid leukemia through the miR-4731-5p/IRF2 pathway.

BACKGROUND: Acute myeloid leukemia (AML) is a type of hematological tumor caused by malignant clone hematopoietic stem cells. The relationship between lncRNAs and tumor occurrence and progression has been gaining attention. Research has shown that Smooth muscle and endothelial cell-enriched migration/differentiation-associated lncRNA (SENCR) is abnormally expressed in various diseases, whereas its role in AML is still poorly understood. METHODS: The expression of SENCR, microRNA-4731-5p (miR-4731-5p) and Interferon regulatory factor 2 (IRF2) were measured using qRT-PCR. The proliferation, cycle and apoptosis of AML cells with or without knockdown of SENCR were detected by CCK-8 assay, EdU assay, flow cytometry, western blotting and TUNEL assay, respectively. Consistently, SENCR knockdown was impaired the AML progression in immunodeficient mice. In addition, the binding of miR-4731-5p to SENCR or IRF2 was confirmed by luciferase reporter genes assay. Finally, rescue experiments were conducted to confirm the role of SENCR/miR-4731-5p/IRF2 axis in AML. RESULTS: SENCR is highly expressed in AML patients and cell lines. The patients with high SENCR expression had poorer prognosis compared with those with low SENCR expression. Interestingly, knockdown of SENCR inhibits the growth of AML cells. Further results demonstrated that the reduction of SENCR slows the progression of AML in vivo. SENCR could function as a competing endogenous RNA (ceRNA) to negatively regulate miR-4731-5p in AML cells. Furthermore, IRF2 was validated as a direct target gene of miR-4731-5p in AML cells. CONCLUSIONS: Our findings underscore the important role of SENCR in regulating the malignant phenotype of AML cells by targeting the miR-4731-5p/IRF2 axis.

CD63 acts as a functional marker in maintaining hematopoietic stem cell quiescence through supporting TGFß signaling in mice.

Hematopoietic stem cell (HSC) fate is tightly controlled by various regulators, whereas the underlying mechanism has not been fully uncovered due to the high heterogeneity of these populations. In this study, we identify tetraspanin CD63 as a novel functional marker of HSCs in mice. We show that CD63 is unevenly expressed on the cell surface in HSC populations. Importantly, HSCs with high CD63 expression (CD63hi) are more quiescent and have more robust self-renewal and myeloid differentiation abilities than those with negative/low CD63 expression (CD63-/lo). On the other hand, using CD63 knockout mice, we find that loss of CD63 leads to reduced HSC numbers in the bone marrow. In addition, CD63-deficient HSCs exhibit impaired quiescence and long-term repopulating capacity, accompanied by increased sensitivity to irradiation and 5-fluorouracil treatment. Further investigations demonstrate that CD63 is required to sustain TGFß signaling activity through its interaction with TGFß receptors I and II, thereby playing an important role in regulating the quiescence of HSCs. Collectively, our data not only reveal a previously unrecognized role of CD63 but also provide us with new insights into HSC heterogeneity.

Serum Inflammatory Factor Profiles in the Pathogenesis of High-Altitude Polycythemia and Mechanisms of Acclimation to High Altitudes.

High-altitude polycythemia (HAPC) is a common aspect of chronic mountain sickness (CMS) caused by hypoxia and is the main cause of other symptoms associated with CMS. However, its pathogenesis and the mechanisms of high-altitude acclimation have not been fully elucidated. Exposure to high altitude is associated with elevated inflammatory mediators. In this study, the subjects were recruited and placed into a plain control (PC) group, plateau control (PUC) group, early HAPC (eHAPC) group, or a confirmed HAPC (cHAPC) group. Serum samples were collected, and inflammatory factors were measured by a novel antibody array methodology. The serum levels of interleukin-2 (IL-2), interleukin-3 (IL-3), and macrophage chemoattractant protein-1 (MCP-1) in the eHAPC group and the levels of interleukin-1 beta (IL-1 beta), IL-2, IL-3, tumor necrosis factor-alpha (TNF-alpha), MCP-1, and interleukin-16 (IL-16) in the cHAPC group were higher than those in the PUC group. More interestingly, the expression of IL-1 beta, IL-2, IL-3, TNF-alpha, MCP-1, and IL-16 in the PUC group showed a remarkable lower value than that in the PC group. These results suggest that these six factors might be involved in the pathogenesis of HAPC as well as acclimation to high altitudes. Altered inflammatory factors might be new biomarkers for HAPC and for high-altitude acclimation.

Megakaryocytes promote bone formation through coupling osteogenesis with angiogenesis by secreting TGF-ß1.

Rationale: The hematopoietic system and skeletal system have a close relationship, and megakaryocytes (MKs) may be involved in maintaining bone homeostasis. However, the exact role and underlying mechanism of MKs in bone formation during steady-state and stress conditions are still unclear. Methods: We first evaluated the bone phenotype with MKs deficiency in bone marrow by using c-Mpl-deficient mice and MKs-conditionally deleted mice. Then, osteoblasts (OBs) proliferation and differentiation and CD31hiEmcnhi tube formation were assessed. The expression of growth factors related to bone formation in MKs was detected by RNA-sequencing and enzyme-linked immunosorbent assays (ELISAs). Mice with specific depletion of TGF-ß1 in MKs were used to further verify the effect of MKs on osteogenesis and angiogenesis. Finally, MKs treatment of irradiation-induced bone injury was tested in a mouse model. Results: We found that MKs deficiency significantly impaired bone formation. Further investigations revealed that MKs could promote OBs proliferation and differentiation, as well as CD31hiEmcnhi vessels formation, by secreting high levels of TGF-ß1. Consistent with these findings, mice with specific depletion of TGF-ß1 in MKs displayed significantly decreased bone mass and strength. Importantly, treatment with MKs or thrombopoietin (TPO) substantially attenuated radioactive bone injury in mice by directly or indirectly increasing the level of TGF-ß1 in bone marrow. MKs-derived TGF-ß1 was also involved in suppressing apoptosis and promoting DNA damage repair in OBs after irradiation exposure. Conclusions: Our findings demonstrate that MKs contribute to bone formation through coupling osteogenesis with angiogenesis by secreting TGF-ß1, which may offer a potential therapeutic strategy for the treatment of irradiation-induced osteoporosis.

Immunosuppressive Siglec-E ligands on mouse aorta are up-regulated by LPS via NF-κB pathway.

AIMS: Siglec-E, the mouse ortholog of human Siglec-9, is an immunosuppressive cell surface receptor. Both Siglec-E and Siglec-9 are primarily found on neutrophils, macrophages, and monocytes. When Siglec-E binds to sialoglycan ligands in its extracellular environment, it halts the immune cells' inflammatory responses. In the present study, we aimed to investigate expression, mechanisms of action and regulation of Siglec-E ligands during vascular inflammation induced by E. coli lipopolysaccharides (LPS) in mouse aorta. METHODS: The distribution, molecular size and glycoprotein class of Siglec-E ligands on mouse aorta were determined, and the protein carrier of the ligands was identified. In vivo, the expression of Siglec-E ligands was detected after LPS treatment, with or without NF-κB inhibitor administration. In vitro, cultured primary mouse aortic endothelial cells (MAECs) were used to study changes in expression of Siglec-E ligands induced by LPS with or without NF-κB inhibitors. MAECs induced by LPS were co-cultured with macrophages and the effect of increased expression of Siglec-E ligands analyzed. RESULTS: Siglec-E ligands are O-linked sialoglycoproteins with molecular weights of 70-300 kDa and are distributed broadly on mouse aorta as well as on MAECs in vitro. In vivo, the expression of Siglec-E ligands was increased in mice aortas in response to LPS treatment in an NF-κB signaling pathway dependent manner. In MAECs, the expression of Siglec-E ligands was also increased by LPS via an NF-κB signaling pathway. Deleted in malignant brain tumors-1 was identified to be one of multiple protein carriers of Siglec-E ligands, and glycans of ligands involved in MAECs induced by LPS. Notably, co-incubation of macrophages with LPS-treated MAECs induced macrophage apoptosis and decreased macrophage phagocytosis, effects that were completely reversed by blocking Siglec-E binding to Siglec-E ligands. CONCLUSIONS: These data demonstrated that Siglec-E ligands were highly expressed in response to LPS-induced vascular inflammation and inhibited the immune response of macrophages, which may be a therapeutic strategy to interfere with vascular inflammation.

SRC3 expressed in bone marrow mesenchymal stem cells promotes the development of multiple myeloma.

SRC3 plays critical roles in various biological processes of diseases, including proliferation, apoptosis, migration, and cell cycle arrest. However, the effect of SRC3 expression in mesenchymal stem cells (MSCs) on multiple myeloma (MM) is not clear yet. In our study, MSCs (MSC-SRC3, MSC-SRC3-/-) and MM cells were co-cultured in a direct or indirect way. The proliferation of MM cells was studied by CCK-8 and colony formation assays. The apoptosis and cell cycle of MM cells were detected by flow cytometry. In addition, the expressions of proteins in MM cells were detected by western blot analysis and the secretions of cytokines were measured by ELISA. Our data showed that the expression of SRC3 in bone marrow mesenchymal stem cells (BM-MSCs) could promote cell proliferation and colony formation of MM cells through accelerating the transformation of the G1/S phase, no matter what kind of culture method was adopted. Meanwhile, SRC3 expressed in BM-MSCs could inhibit the apoptosis of MM cells through the caspase apoptosis pathway and mitochondrial apoptosis pathway. Moreover, SRC3 could enhance the adhesion ability of MM cells through up-regulating the expression of adhesion molecules including CXCL4, ICAM1, VLA4, and syndecan-1. SRC3 also played a regulatory role in the progress of MM through the NF-κB and PI-3K/Akt pathways. SRC3 expressed in MSCs was found to promote the growth and survival of MM cells, while SRC3 silencing in MSCs could inhibit the development of MM. These results would be useful for developing a more effective new strategy for MM treatment.

Challenges and Opportunities for High-grade B-Cell Lymphoma With MYC and BCL2 and/or BCL6 Rearrangement (Double-hit Lymphoma).

The most common subtype of non-Hodgkin lymphoma, diffuse large B-cell lymphoma, is cured in approximately two thirds of patients after initial therapy. The remaining one-third of patients who suffer relapse or become refractory have very poor survival outcomes despite salvage chemotherapy with or without stem cell transplantation. A considerable proportion of relapsed or refractory large B cells belong to the WHO subtype known as high-grade B-cell lymphoma with rearrangement of MYC and BCL2 and/or BCL6, also known as double-hit lymphoma (DHL). Most DHL patients present with Ann Arbor's stage III/IV, a comparatively higher rate of extranodal involvement including bone marrow and central nervous system infiltration, high levels of lactate dehydrogenase, and an elevated Ki67 expression in the tumor cells. Newer therapeutic approaches, including targeted therapy against BCL2, MYC, or other associated pathways, are needed. In addition, recent therapies that harness the immune system, such as checkpoint inhibitors and chimeric antigen receptor T-cell therapy, are changing the paradigm of treatment for non-Hodgkin lymphoma and could impact the outcome of DHL.

Dual inhibition of PI3K signaling and histone deacetylation halts proliferation and induces lethality in mantle cell lymphoma.

The dysregulation of PI3K signaling has been implicated as an underlying mechanism associated with resistance to Bruton's tyrosine kinase inhibition by ibrutinib in both chronic lymphocytic leukemia and mantle cell lymphoma (MCL). Ibrutinib resistance has become a major unmet clinical need, and the development of therapeutics to overcome ibrutinib resistance will greatly improve the poor outcomes of ibrutinib-exposed MCL patients. CUDC-907 inhibits both PI3K and HDAC functionality to exert synergistic or additive effects. Therefore, the activity of CUDC-907 was examined in MCL cell lines and patient primary cells, including ibrutinib-resistant MCL cells. The efficacy of CUDC-907 was further examined in an ibrutinib-resistant MCL patient-derived xenograft (PDX) mouse model. The molecular mechanisms by which CUDC-907 dually inhibits PI3K and histone deacetylation were assessed using reverse protein array, immunoblotting, and chromatin immunoprecipitation (ChIP) coupled with sequencing. We showed evidence that CUDC-907 treatment increased histone acetylation in MCL cells. We found that CUDC-907 caused decreased proliferation and increased apoptosis in MCL in vitro and in vivo MCL models. In addition, CUDC-907 was effective in inducing lethality in ibrutinib-resistant MCL cells. Lastly, CUDC-907 treatment increased histone acetylation in MCL cells. Overall, these studies suggest that CUDC-907 may be a promising therapeutic option for relapsed or resistant MCL.

Long-term outcomes and mutation profiling of patients with mantle cell lymphoma (MCL) who discontinued ibrutinib.

Long term outcomes and mutations in patients with mantle cell lymphoma (MCL) who discontinued ibrutinib have not been described. Using deep targeted next generation sequencing, we performed somatic mutation profiling from 15 MCL patients (including 5 patients with paired samples; before and after progression on ibrutinib). We identified 80 patients with MCL who discontinued ibrutinib therapy for various reasons. Median follow-up after ibrutinib discontinuation was 38 months. The median duration on ibrutinib was 7·6 months. Forty-one (51%) patients discontinued ibrutinib due to disease progression/transformation, 20 (25%) for intolerance, 7 (9%) due to patient choice, 5 (6%) for stem cell transplant, 4 (5%) due to second cancers and 3 (4%) other causes. The median survival after ibrutinib was 10 and 6 months for disease progression and transformation, respectively, and 25 months for patients with ibrutinib intolerance. Overall, BTK mutations were observed in 17% patients after progression on ibrutinib. Notably, TP53 alterations were observed after progression in 75% patients. Among the 4 patients with blastoid transformation, 3 (75%) had NSD2 mutations (co-existing with TP53). Ibrutinib-refractory MCL patients had a short survival. Demonstration of TP53 and NSD2 mutations in patients who developed blastoid transformation and ATM and TP53 mutations in patients who progressed, opens the door for future investigations in ibrutinib-refractory MCL.

Tannic acid attenuated irradiation-induced apoptosis in megakaryocytes.

Ionizing radiation (IR) triggers the generation of reactive oxygen species (ROS), which shows potential roles in damaging the DNA and proteins at the nucleus, and eventually results in apoptosis and even cell death. Antioxidant agents can inhibit the generation of ROS after IR exposure. Tannic acid (TA), has an antioxidant activity involving in preventing cardiovascular and cerebrovascular diseases. However, little is known about the effects of TA on irradiation-induced apoptosis in megakaryocytes. Here, we evaluated the anti-radiation activity of TA in megakaryocytes. Our results showed that TA protected megakaryocytes from apoptosis induced by IR, attenuated IR-induced increases in the production of ROS, and inhibited the changes of mitochondrial membrane potential (MMP). Moreover, TA down-regulated NAPDH oxidase 1 (Nox1) expression, and decreased the phosphorylated levels of JNK and p38. Furthermore, JNK inhibitor could reduce apoptosis induced by X-irradiation in M07e cells. In vivo experiments confirmed that TA could promote the platelet recovery, reduce the percentage of apoptosis CD41+ megakaryocytes in bone marrow and raise survival during 30 days in mice by total body irradiation. In conclusion, TA can protecte the megakaryocytes from apoptosis caused by IR through inhibiting Nox1 expression to reduce ROS generation and repressing JNK/p38 MAPK pathway activation.

Paramount therapy for young and fit patients with mantle cell lymphoma: strategies for front-line therapy.

The natural history of mantle cell lymphoma (MCL) is a continuous process with the vicious cycle of remission and recurrence. Because MCL cells are most vulnerable before their exposure to therapeutic agents, front-line therapy could eliminate MCL cells at the first strike, reduce the chance for secondary resistance, and cause long-term remissions. If optimized, it could become an alternative to cure MCL. The key is the intensity of front-line therapy. Both the Nordic 2 and the MD Anderson Cancer Center HCVAD trials, with follow-up times greater than 10 years, achieved long-term survivals exceeding 10 years. But the Achilles heel in both trials were the severe toxicities, such as secondary malignancies including myelodysplastic syndromes /leukemia. Therefore, intensive therapies can act as a double-edged sword providing long term survival at the cost of severe toxicities. In our opinion, although intensive chemotherapy can cause detrimental side effects, it is indispensable given that we run the risk of sacrificing long-term survivals in these young and fit patients. We must seek for a powerful alternative at the front-line. Furthermore, minimal residual disease negativity should be the optimal therapeutic goal to achieve before and after autologous stem cell transplantation. Some novel therapeutic strategies have shown to improve outcomes, but it is not yet clear as to how these results translate in population. Of note, MCL patients need to be stratified at diagnosis and be provided with different intensities of front-line regimen. In this review, we discuss current strategies for the treatment of young patients with newly diagnosed MCL.

Frontline Treatment for Older Patients with Mantle Cell Lymphoma.

The natural history of mantle cell lymphoma (MCL) undergoing chemotherapy is a cyclical pattern of remission followed by recurrence of disease due to acquired chemotherapy resistance. The median age of the occurrence of MCL is 65 years, so half of the newly diagnosed MCL patients are considered "elderly." The tolerance to long-term chemotherapy in elderly patients is decreased; hence, the response to frontline therapy used is of paramount importance. We hope that our review may guide clinicians in treating such populations in a more personalized and evidence-based manner.In the older patients with risk variables, frontline treatment is determined according to different body status of fit, unfit or compromised, and frail. In the fit patients, the pursuit of remission and prolongation of survival might currently justify the use of more intense and toxic therapies. For unfit or compromised older patients, disease control needs to be prioritized, maintaining a balance between the benefits and toxicities of the treatment. For frail patients, tolerance of treatment and minimizing myelotoxicity should be the primary focus. "Chemotherapy-free" regimens are likely to be considered as the first-line strategy for this population. On the other hand, in the older MCL population without risk variables, observation or "watch and wait" can prevent overtreatment. Furthermore, more clinical trials and research studies on novel agents and targeted therapies need to be translated into the general population to provide optimal treatment and to guide personalized treatment. IMPLICATIONS FOR PRACTICE: This review emphasizes the importance of frontline therapies for older MCL patients. MCL patients commonly experience a cyclical pattern of remission followed by recurrence of disease due to acquired chemotherapy resistance. As a special population, elderly patients have various comorbidities and decreased organ function, which may reduce the chances of undergoing treatment for recurrent disease. Thus, this older population of patients with MCL should be treated separately and exceptionally. So far, systematic reviews with regard to frontline treatment for older patients with MCL have not been encountered, but the hope is that this review may guide clinicians in treating such populations in a more personalized and evidence-based manner.

Spontaneous regression of mantle cell lymphoma: a report of four cases.

BACKGROUND: Spontaneous regression has been reported in some indolent forms of lymphoma. Mantle cell lymphoma (MCL) is an aggressive lymphoid neoplasm and has a poor prognosis. However, approximately 30% of MCL patients can exhibit indolent clinical behavior. To date, complete spontaneous regression of MCL has not been reported. CASE PRESENTATION: We describe four cases of spontaneous regression of MCL. At the time of presentation, these patients were asymptomatic, with lymph node enlargement and mild to moderate fluorodeoxyglucose (FDG) uptake on FDG-positron emission tomography combined with computed tomography. One of the possible mechanisms of spontaneous regression of the tumor could be due to the host immune response through humoral and cellular immunity, which may have a role in the clearance of tumor cells. CONCLUSIONS: In this report, we support the use of a "wait and watch" strategy for MCL patients with no risk factors and indolent behavior. This strategy helps spare patients from further potentially harmful chemotherapy. In addition, we describe the phenomenon of spontaneous regression in MCL patients who are asymptomatic and have low-volume disease.