Hongtao Gu

Caspase-2 functions upstream of mitochondria in endoplasmic reticulum stress-induced apoptosis by bortezomib in human myeloma cells

Multiple myeloma is an incurable plasma cell malignancy. The 26S proteasome inhibitor, bortezomib, selectively induces apoptosis in multiple myeloma cells; however, the mechanism by which this compound acts remains unknown. Here, we, using immunoblotting analysis, observed that the expression of BiP, CHOP, and XBP-1 is up-regulated in bortezomib-induced apoptosis in human multiple myeloma cell lines NCI-H929 and RPMI-8226/S, strongly suggesting that endoplasmic reticulum (ER) stress response or the unfolded protein response (UPR), a signaling pathway activated by the accumulation of unfolded proteins within ER, is initiated. In the meantime, we also showed that bortezomib inhibited classic ER stressor brefeldin A–induced up-regulation of prosurvival UPR components BiP and XBP-1, resulting in increased induction of apoptosis in multiple myeloma cell lines, raising the possibility that bortezomib induces apoptosis of multiple myeloma cells by means of evoking the severe ER stress but disrupting the prosurvival UPR required. Using caspase inhibitors and a RNA interference approach, we finally confirmed that bortezomib-triggered apoptosis in multiple myeloma cells is dependent on caspase-2 activation, which is associated with ER stress and required for release of cytochrome c, breakdown of mitochondrial transmembrane potential, and its downstream caspase-9 activation. Taken together, these data strongly suggest that caspase-2 can serve as a proximal caspase that functions upstream of mitochondrial signaling during ER stress-induced apoptosis by bortezomib in multiple myeloma cells. [Mol Cancer Ther 2008;7(8):2298–307]

Dysregulation of unfolded protein response partially underlies proapoptotic activity of bortezomib in multiple myeloma cells.

The 26S proteasome inhibitor, bortezomib, has shown remarkable therapeutic efficacy in multiple myeloma (MM), however, the mechanism by which this compound acts remains unknown. Here, we have demonstrated that bortezomib targets the prototypical expression of unfolded protein response (UPR) genes BiP, CHOP and XBP-1 at the mRNA and protein levels, resulting in induction of proapoptotic UPR outputs and suppression of cytoprotective UPR components, leading to caspase-dependent apoptosis in human MM H929 and 8226/S cell lines. Moreover, knockdown of XPB-1s, via lentivirus-mediated RNA interference approach, sensitises MM cells to apoptosis induction by bortezomib. Together, these data strongly suggest that dysregulated or disruptive UPR may, at least partly, underlie the antimyeloma activity of bortezomib.

Risk factors for multiple myeloma: A hospital-based case–control study in Northwest China

BACKGROUND The distinctive racial/ethnic and geographic distribution of multiple myeloma (MM) suggests that both family history and environmental factors may contribute to its development. METHODS A hospital-based case-control study consisting of 220 confirmed MM cases and 220 individually matched patient controls, by sex, age and hospital was carried out at 5 major hospitals in Northwest China. A questionnaire was used to obtain information on demographics, family history, and the frequency of food items consumed. RESULTS Based on multivariate analysis, a significant association between the risk of MM and family history of cancers in first degree relatives was observed (OR=4.03, 95% CI: 2.50-6.52). Fried food, cured/smoked food, black tea, and fish were not significantly associated with the risk of MM. Intake of shallot and garlic (OR=0.60, 95% CI: 0.43-0.85), soy food (OR=0.52, 95% CI: 0.36-0.75) and green tea (OR=0.38, 95% CI: 0.27-0.53) was significantly associated with a reduced risk of MM. In contrast, intake of brined vegetables and pickle was significantly associated with an increased risk (OR=2.03, 95% CI: 1.41-2.93). A more than multiplicative interaction on the decreased risk of MM was found between shallot/garlic and soy food. CONCLUSION Our study in Northwest China found an increased risk of MM with a family history of cancer, a diet characterized by low consumption of garlic, green tea and soy foods, and high consumption of pickled vegetables. The effect of green tea in reducing the risk of MM is an interesting new finding which should be further confirmed.

Increased expression of TIGIT on CD4+ T cells ameliorates immune-mediated bone marrow failure of aplastic anemia.

Aplastic anemia (AA) is an autoimmune disease in which T cell activation is suspected to play an important role. T cell immunoglobulin and ITIM (immunoreceptor tyrosine‐based inhibition motif) domain (TIGIT) is an inhibitory receptor, which exhibits inhibitory functions on the immune response. However, its role in AA has not been clearly determined. In the current study, we showed that the frequency of TIGIT‐positive CD4+ T cells was reduced in the vast majority of AA patients (85%, 17/20). In TIGIT‐silenced human CD4+ T cells, stimulation of agonistic anti‐TIGIT monoclonal antibody significantly facilitated cell proliferation, increased production of IL‐2 and IFN‐γ, and inhibited production of IL‐10. However, in TIGIT‐overexpressed human CD4+ T cells, cell proliferation and the production of IL‐2, IFN‐γ, and TNF‐α were significantly hindered; in contrast, the secretion of IL‐10 was improved. RT‐PCR and Western blotting showed that T‐bet expression in human CD4+ T cells was significantly decreased by TIGIT overexpression, but only slightly altered by TIGIT knockdown. In mouse models, lentivirus‐mediated TIGIT‐overexpressed CD4+ T cell transfer significantly rescued the decreased red blood cell count, attenuated the increase in serum INF‐γ and TNF‐α levels, and lengthened the median survival time. The mRNA levels of CD34, stem cell factor (SCF), and granulocyte/macrophage‐colony‐stimulating factor (GM‐CSF) in bone marrow mononuclear cells were also up‐regulated. In conclusion, increased expression of TIGIT could inhibit the function of CD4+ T cells in vitro and ameliorate immune‐mediated bone marrow failure of AA in vivo providing a new potential strategy for the treatment of AA. J. Cell. Biochem. 115: 1918–1927, 2014.

RhoA effector mDia1 is required for PI 3-kinase-dependent actin remodeling and spreading by thrombin in platelets

The RhoA effector mDia1 is involved in controlling the balance between filamentous and monomeric actin, but its role in modulating thrombin-induced actin remodeling and platelet spreading on fibrinogen matrices remains unclear. In this study, mDia1 was shown to translocate to the platelet cytoskeleton following thrombin stimulation, in a phosphoinositide 3-kinase (PI 3-kinase)-dependent manner. Anti-mDia1 loading or pretreatment with PI 3-kinase inhibitors essentially abrogated thrombin-elicited actin stress fiber formation, with a corresponding decrease in the proportion of platelets exhibiting a fully spread morphology. We also investigated the mechanisms underlying the effects of mDia1 on thrombin-induced actin remodeling and platelet spreading, and found that these involved PI 3-kinase-mediated induction of mDia1 interaction with RhoA. Collectively, these results suggest that the PI 3-kinase/RhoA/mDia1 axis is a critical pathway for coupling thrombin signaling to actin cytoskeletal remodeling during platelet spreading.

A phase 2 study of methotrexate, etoposide, dexamethasone, and pegaspargase chemotherapy for newly diagnosed, relapsed, or refractory extranodal natural killer/T‐cell lymphoma, nasal type: a multicenter trial in Northwest China

The nasal type of extranodal natural killer/T‐cell lymphoma is a rare aggressive lymphoma with poor prognosis. To discover a successful treatment, we investigated the efficacy and safety of chemotherapy with methotrexate, etoposide, dexamethasone, and polyethylene glycol‐asparaginase (MESA). Three cycles of MESA were administered to 46 patients with new or relapsed/refractory natural killer/T‐cell lymphoma. Complete response after 3 treatment cycles was 43.5%, the overall response rate was 87%, and 2‐year overall survival was 83.4%. Complete response was significantly better for newly diagnosed patients than for patients with relapsed/refractory disease. Patients with newly diagnosed disease had a significantly better overall response rate after 1, but not after 2 or 3 treatment cycles. Overall survival and progression‐free survival did not differ over 2 years. Grade 1/2 toxicities were frequent, but MESA was associated with fewer grade 3/4 events or treatment‐related deaths. These results will require confirmation in larger prospective trials.

Increased 14-3-3ζ Expression in the Multidrug-Resistant Leukemia Cell Line HL-60/VCR as Compared to the Parental Line Mediates Cell Growth and Apoptosis in Part through Modification of Gene Expression

Background: Acute myeloid leukemia (AML) recurrence is largely a result of multidrug resistance (MDR). We aimed to examine the role of 14-3-3ζ in AML chemosensitivity using HL-60 and vincristine-resistant HL-60/VCR cells. Methods: The effects of 14-3-3ζ siRNA on the growth and cell cycle progression of HL-60 and HL-60/VCR cells were determined. The effect of 14-3-3ζ siRNA on topotecan (TPT)-induced apoptosis was evaluated by several assays. Results: Compared to HL-60 cells, HL-60/VCR cells had increased 14-3-3ζ mRNA and protein expression. Increased mdr-1 mRNA as well as mdr-1, Bcl-2 and Mcl-1 protein expression were observed in HL-60/VCR cells. In both HL-60 and HL-60/VCR cells, 14-3-3ζ was observed in the cytoplasm and nuclear compartments. 14-3-3ζ siRNA significantly reduced HL-60 and HL-60/VCR cell growth after 48 h and increased the proportion of cells in the G0/G1 phase. Moreover, 14-3-3ζ siRNA significantly increased the sensitivity of both HL-60 and HL-60/VCR cells to TPT, possibly through the inhibition of Bcl-2, Mcl-1 and mdr-1 protein expression. Conclusions: Silencing of 14-3-3ζ increased the sensitivity of both sensitive and resistant HL-60 cells to TPT-induced apoptosis, possibly through altering the expression of apoptosis-associated proteins, suggesting that it may be a potential target for MDR AML.

Natural Killer/T Cell Lymphoma, Nasal Type: A Retrospective Clinical Analysis in North-Western China

Background: Extranodal natural killer (NK)/T cell lymphoma (ENKTL) is an aggressive non-Hodgkins lymphoma with high mortality and poor prognosis despite radiotherapy and chemotherapy. The current analysis aimed to assess the pathological features, clinical features, and prognostic indicators of ENKTL. Material and Methods: 120 ENKTL patients were analyzed for pathologic diagnosis and clinical disease manifestations from April 2007 to October 2012. Complete remission, 2-year overall survival, and progression-free survival were analyzed. Results: Compared with the nasal group, a greater percentage of patients in the non-nasal group intended to receive autologous stem cell transplantation had Epstein-Barr virus (EBV) DNA, Ann Arbor stage IV, Ki-67 expression ≥ 60%, and abnormal ferroprotein and β-microglobulin levels. The rate of complete remission in the non-nasal group was higher than that in the nasal group. The overall survival rate was 74.9% at 24 months. Patients receiving chemotherapy and radiotherapy were more likely to have disease progression compared with patients who received chemotherapy or radiotherapy alone. Conclusions: Further understanding the pathological and clinical features of ENKTL will be critical for moving forward. Ki-67, β-microglobulin, EBV DNA, and primary site prognostic indicators may be useful to stratify patients into different risk groups, to gain insight into patient-specific treatments, and to potentially improve survival.

Survival outcomes of primary cutaneous T-cell lymphoma in HIV-infected patients: a national population-based study

This study aimed to investigate clinical characteristics and survival outcomes of primary cutaneous T-cell lymphoma (CTCL) in HIV-infected and non-HIV-infected patients. All data were from the Surveillance, Epidemiology, and End Results program, 1973–2013, of the U.S. National Cancer Institute. Data of 318 HIV-infected patients and 1272 non-HIV-infected patients with primary CTCL were analyzed. Endpoints were overall survival and cancer-specific mortality. Independent variables included demographics, pre-existing malignancy, treatments, and environmental factors. Among 8823 patients with CTCL, 318 (3.60 per cent) were HIV-infected and 8505 (96.40 per cent) were not. 318 HIV-infected patients and 1272 non-HIV-infected patients selected by matching diagnosis dates were analyzed, including 941 (59.2 per cent) males and 649 (40.8 per cent) females with mean age 58.8 years. HIV-infected patients with CTCL had higher survival and significantly lower risk of overall mortality than non-HIV-infected patients (adjusted HR 0.37, 95 per cent CI 0.24 to 0.59, P<0.001). Non-HIV-infected, age and black race were significant risk factors for overall mortality. Age and race are independent risk factors for overall mortality in primary CTCL individuals, and HIV-infected status is an independent protective factor, suggesting that advanced antiretroviral therapy restores immunity and prolongs survival in HIV-infected patients with CTCL.

Distribution of lymphoid neoplasms in Northwest China: Analysis of 3244 cases according to WHO classification in a single institution

To explore the distribution of lymphoid neoplasms in Northwest China, the clinical and pathological data of lymphoma patients from 2006 to 2014 were analyzed according to the WHO classification in Xijing Hospital. Of the 3244 cases, mature B-cell neoplasms occupied 60.7%, while mature T/NK-cell neoplasms and Hodgkins lymphomas (HL) occupied 26.2% and 8.1%, respectively. The most common subtype of lymphoma was diffuse large B-cell lymphoma (35.0%), followed by extranodal NK/T-cell lymphoma, nasal type (ENKTCL) (12.9%) and marginal zone B-cell lymphoma (7.8%). Mixed cellularity (34.0%) was the most common subtype of HL. The especially high proportion of ENKTCL was the most outstanding feature of our study in comparison to previous reports. The mean age of all lymphoid neoplasms cases was 51years and most subtypes showed male predominance, with an average male-female ratio of 1.6. Extranodal lymphomas took up about 60% of all cases and gastrointestinal tract was the most frequently involved site. In conclusion, the distribution of lymphoid neoplasms of Northwest China showed some features similar to previous reports of China and other countries, but some subtypes presented distinct features.