WITHDRAWN: TRIM44 promotes autophagy through SQSTM1 oligomerization in the response to oxidative stress induced by Arsenic Trioxide in cancer cells.

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Comprehensive Analysis of the Prognostic Significance of the TRIM Family in the Context of TP53 Mutations in Cancers.

The p53 protein is an important tumor suppressor, and TP53 mutations are frequently associated with poor prognosis in various cancers. Mutations in TP53 result in a loss of p53 function and enhanced expression of cell cycle genes, contributing to the development and progression of cancer. Meanwhile, several tripartite motif (TRIM) proteins are known to regulate cell growth and cell cycle transition. However, the prognostic values between TP53 and TRIM family genes in cancer are unknown. In this study, we analyzed the relationship between the TP53 mutations and TRIM family proteins and evaluated the prognostic significance of TRIM family proteins in cancer patients with P53 mutations. Our findings identified specific TRIM family members that are upregulated in TP53 mutant tumors and are associated with the activation of genes related to a cell-cycle progression in the context of TP53 mutations.

TRIM44 links the UPS to SQSTM1/p62-dependent aggrephagy and removing misfolded proteins.

Until recently, the ubiquitin-proteasome system (UPS) and macroautophagy/autophagy were considered to be two independent systems that target proteins for degradation by proteasomes or via lysosomes, respectively. Here, we report that TRIM44 (tripartite motif containing 44) is a novel link that connects the UPS system with the autophagy degradation pathway. Suppressing the UPS degradation pathway leads to TRIM44 upregulation, which further promotes aggregated protein clearance through the binding of K48 ubiquitin chains on proteins. TRIM44 expression activates autophagy via promoting SQSTM1/p62 oligomerization, which rapidly increases the rate of aggregate protein removal. Overall, our data reveal that TRIM44 is a newly identified link between the UPS system and the autophagy pathway. Delineating the cross-talk between these two degradation pathways may reveal new mechanisms of targeting aggregate-prone diseases, such as cancer and neurodegenerative disease.Abbreviations: 3-MA: 3-methyladenine; ACTB: actin beta; ATG5: autophagy related 5; BB: B-box domain; BECN1: beclin1; BM: bone marrow; CC: coiled-coil domain; CFTR: cystic fibrosis transmembrane conductance regulator; CON: control; CQ: chloroquine; DOX: doxycycline; DSP: dithiobis(succinimidly propionate); ER: endoplasmic reticulum; FI: fluorescence intensity; FL: full length; HIF1A/HIF-1#x3B1;: hypoxia inducible factor 1 subunit alpha; HSC: hematopoietic stem cells; HTT: huntingtin; KD: knockdown; KD-CON: knockdown construct control; MM: multiple myeloma; MTOR: mechanistic target of rapamycin kinase; NP-40: nonidet P-40; NFE2L2/NRF2: nuclear factor, erythroid 2 like 2; OE: overexpression; OE-CON: overexpression construct control; PARP: poly (ADP-ribose) polymerase; SDS: sodium dodecyl sulfate; SQSTM1/p62: sequestosome 1; Tet-on: tetracycline; TRIM44: tripartite motif containing 44; UPS: ubiquitin-proteasome system; ZF: zinc-finger.

TRIM44 mediated p62 deubiquitination enhances DNA damage repair by increasing nuclear FLNA and 53BP1 expression.

Cancer cells show increases in protein degradation pathways, including autophagy, during progression to meet the increased protein degradation demand and support cell survival. On the other hand, reduced autophagy activity during aging is associated with a reduced DNA damage response and increased genomic instability. Therefore, it is a puzzling how DNA repair can be increased in cancer cells that are resistant to chemotherapies or during progression when autophagy activity is intact or increased. We discovered that tripartite motif containing 44 (TRIM44) is a pivotal element regulating the DNA damage response in cancer cells with intact autophagy. TRIM44 deubiquitinates p62, an autophagy substrate, which leads to its oligomerization. This prevents p62 localization to the nucleus upon irradiation. Increased cytoplasmic retention of p62 by TRIM44 prevents the degradation of FLNA and 53BP1, which increases DNA damage repair. Together, our data support TRIM44 a potential therapeutic target for therapy-resistant tumor cells with intact autophagy.

TRIM44 promotes quiescent multiple myeloma cell occupancy and survival in the osteoblastic niche via HIF-1α stabilization.

Despite progress in the treatment of MM, including the use of high-dose chemotherapy and autologous stem cell transplantation, a considerable proportion of patients are refractory to all therapies. This resistance is related to the molecular genetic heterogeneity in MM cells as well as to the contributions from the BM, which is one of the key determinants of treatment outcome. Our previous studies using fluorescent tracers revealed that MM heterogeneity is correlated with the presence of quiescent stem-like cancer cells, which prefer to reside within the osteoblastic niche of the BM. In this report, we identified a novel protein, tripartite motif containing 44 (TRIM44), which is overexpressed in the osteoblastic niche of the BM, enabling MM cells to compete with HSCs for niche support. TRIM44 expression in MM cells promoted cell quiescence but increased bone destruction in xenograft mice, similar to what is observed in MM patients. TRIM44 functions as a deubiquitinase for hypoxia inducible factor-1α (HIF-1α), which stabilizes HIF-1α expression during hypoxia and normoxia. Stabilized HIF-1α stimulates MM cell growth and survival during hypoxia. Our work is the first report to reveal signaling in quiescent MM cells and the functions of TRIM44.

Bifurcated BACH2 control coordinates mantle cell lymphoma survival and dispersal during hypoxia.

BACH2, a B-cell-specific transcription factor, plays a critical role in oxidative stress-mediated drug resistance in mantle cell lymphoma (MCL); however, the biological functions of BACH2 and its regulation of B-cell malignancies in chronic hypoxic microenvironment have not been studied. Here, we found that silencing BACH2 led to not only increased tumor formation and colony formation but also increased tumor dispersal to spleen and bone marrow. Decreased BACH2 levels in patients were also correlated with bone marrow and gastrointestinal dispersal of MCL and blastoid subtypes of MCL. Unexpectedly, decreased BACH2 levels in dispersed MCL cells were due to direct transcriptional repression by hypoxia-induced factor 1α (HIF-1α) and increased heme-mediated protein degradation. In normoxic conditions, BACH2 was able to modulate HIF-1α degradation by suppressing prolyl hydroxylase 3 expression. Bifurcated BACH2 controls during hypoxia and normoxia coordinate not only MCL tumor dispersal but also drug resistance, including bortezomib resistance, via plasmacytic differentiation. Our data highlight an interactive relationship between tumor cells and local microenvironment and the mechanisms of B-cell transcription factor in the regulation of MCL dispersal.

CRISPR Editing in Biological and Biomedical Investigation.

The revolutionary technology for genome editing known as the clustered regularly interspaced short palindromic repeat (CRISPR)-CRISPR-associated protein 9 (Cas9) system has sparked advancements in biological and biomedical research. The scientific breakthrough of the development of CRISPR-Cas9 technology has allowed us to recapitulate human diseases by generating animal models of interest ranging from zebrafish to non-human primates. The CRISPR-Cas9 system can also be used to delineate the mechanisms underlying the development of human disorders and to precisely correct disease-causing mutations. Repurposing this technology enables wider applications in transcriptome and epigenome manipulation and holds promise to reach the clinic. In this review, we highlight the latest advances of the CRISPR-Cas9 system in different platforms and discuss the hurdles and challenges this technology is facing. J. Cell. Biochem. 118: 4152-4162, 2017. © 2017 Wiley Periodicals, Inc.

Tampering with cancer chemoresistance by targeting the TGM2-IL6-autophagy regulatory network.

Macroautophagy/autophagy is a well-established process involved in maintaining cellular homeostasis, but its role in cancer is complex and even controversial. Many studies have reported a correlative relationship between increased autophagy and evolving cancer cells under stress conditions such as nutrient or oxygen deprivation; however, there has been a lack of a plausible mechanistic link to properly target the autophagy process in the context of this microenvironment. We recently unveiled a positive regulatory loop involving TGM2 (transglutaminase 2)-NFKB/NF-κB signaling, IL6 and autophagy in cancer using mantle cell lymphoma (MCL) as a model system. These pathways are functionally connected to each other, thereby promoting malignant B cell survival and leading to enhanced lymphoma progression both in mice and in patients. Disruption of this network could provide an opportunity to increase the efficacies of current therapies and to reduce MCL drug resistance.

CRISPR-Cas9 technology and its application in haematological disorders.

The recent advent of the Clustered Regularly Interspaced Short Palindromic Repeats (CRISPR)-CRISPR associated protein 9 (Cas9) system for precise genome editing has revolutionized methodologies in haematology and oncology studies. CRISPR-Cas9 technology can be used to remove and correct genes or mutations, and to introduce site-specific therapeutic genes in human cells. Inherited haematological disorders represent ideal targets for CRISPR-Cas9-mediated gene therapy. Correcting disease-causing mutations could alleviate disease-related symptoms in the near future. The CRISPR-Cas9 system is also a useful tool for delineating molecular mechanisms involving haematological malignancies. Prior to the use of CRISPR-Cas9-mediated gene correction in humans, appropriate delivery systems with higher efficiency and specificity must be identified, and ethical guidelines for applying the technology with controllable safety must be established. Here, the latest applications of CRISPR-Cas9 technology in haematological disorders, current challenges and future directions are reviewed and discussed.

TG2 and NF-κB Signaling Coordinates the Survival of Mantle Cell Lymphoma Cells via IL6-Mediated Autophagy.

Expression of the transglutaminase TG2 has been linked to constitutive activation of NF-κB and chemotherapy resistance in mantle cell lymphoma (MCL) cells. TG2 forms complexes with NF-κB components, but mechanistic insights that could be used to leverage therapeutic responses has been lacking. In the current study, we address this issue with the discovery of an unexpected role for TG2 in triggering autophagy in drug-resistant MCL cells through induction of IL6. CRISPR-mediated silencing of TG2 delayed apoptosis while overexpressing TG2 enhanced tumor progression. Under stress, TG2 and IL6 mediate enhanced autophagy formation to promote MCL cell survival. Interestingly, the autophagy product ATG5 involved in autophagosome elongation positively regulated TG2/NF-κB/IL6 signaling, suggesting a positive feedback loop. Our results uncover an interconnected network of TG2/NF-κB and IL6/STAT3 signaling with autophagy regulation in MCL cells, the disruption of which may offer a promising therapeutic strategy. Cancer Res; 76(21); 6410-23. ©2016 AACR.

Hedgehog inhibitors selectively target cell migration and adhesion of mantle cell lymphoma in bone marrow microenvironment.

The clinical benefits of a Hedgehog (Hh) inhibitor, LDE225 (NPV-LDE-225, Erismodegib), have been unclear in hematological cancers. Here, we report that LDE225 selectively inhibited migration and adhesion of mantle cell lymphoma (MCL) to bone marrows via very late antigen-4 (VLA-4) mediated inactivation of focal adhesion kinase (FAK) signaling. LDE225 treatment not only affected MCL cells, but also modulated stromal cells within the bone marrow microenvironment by decreasing their production of SDF-1, IL-6 and VCAM-1, the ligand for VLA-4. Surprisingly, LDE225 treatment alone did not suppress cell proliferation due to increased CXCR4 expression mediated by reactive oxygen species (ROS). The increased ROS/CXCR4 further stimulated autophagy formation. The combination of LDE225 with the autophagy inhibitors further enhanced MCL cell death. Our data, for the first time, revealed LDE225 selectively targets MCL cells migration and adhesion to bone marrows. The ineffectiveness of LDE225 in MCL is due to autophagy formation, which in turn increases cell viability. Inhibiting autophagy will be an effective adjuvant therapy for LDE225 in MCL, especially for advanced MCL patients with bone marrow involvement.

ROS-Induced CXCR4 Signaling Regulates Mantle Cell Lymphoma (MCL) Cell Survival and Drug Resistance in the Bone Marrow Microenvironment via Autophagy.

PURPOSE: Patients with advanced stages of mantle cell lymphoma (MCL) have a poor prognosis after standard therapies. MCL cells in those patients often spread into tissues other than lymph nodes, such as the bone marrow. Apart from directed migration and homing, there is little understanding of the function of the CXCR4/SDF-1 signaling axis in MCL. In this report, we aim to understand mechanisms of MCL cell survival in the bone marrow. EXPERIMENTAL DESIGN: For comprehensive analyses of MCL interactions with bone marrow stromal cells, we have generated gene knockout cells using CRISPR-CAS9 system and gene knockdown cells to reveal novel roles of the CXCR4/SDF-1 signaling. RESULTS: CXCR4 silencing in MCL cells led to a significant reduction in proliferation, cell adhesion to bone marrow stromal cells, and colony formation in PHA-LCM methylcellulose medium, which were reversed upon the addition of SDF-1-neutralizing antibodies. In addition, tracking MCL cell engraftment in vivo revealed that quiescent MCL cells are significantly reduced in the bone marrow upon CXCR4 silencing, indicating that CXCR4/SDF-1 signaling is required for the survival and maintenance of the quiescent MCL cells. Further analysis revealed novel mechanisms of ROS-induced CXCR4/SDF-1 signaling that stimulate autophagy formation in MCL cells for their survival. CONCLUSIONS: Our data, for the first time, revealed new roles of the CXCR/SDF-1 signaling axis on autophagy formation in MCL, which further promoted their survival within the bone marrow microenvironment. Targeting the CXCR4/SDF-1/autophagy signaling axis may contribute to an enhanced efficacy of current therapies.

Osteoblastic niche supports the growth of quiescent multiple myeloma cells.

The heterogeneity of multiple myeloma (MM) contributes to variable responses to therapy. In this study, we aim to correlate the heterogeneity of MM to the presence of quiescent cells using the PKH26 dye. We tracked the rare quiescent cells in different niches of the bone marrow by allowing the cells to cycle in vivo. Surprisingly, quiescent PKH(+) MM cells prefer to reside within the osteoblastic niches of the bone marrow (PKH(+)/OS) rather than the vascular (VS) niches or the spleen. These cells (PKH(+)/OS) displayed enhanced stemlike properties by forming colonies in semisolid medium. PKH(+) cells were highly tumorigenic compared with PKH(-) cells and were resistant to a variety of drugs. However, the levels of drug resistance were somewhat similar regardless of where the PKH(+) cells were isolated. Our data indicate that osteoblastic niches support the growth of quiescent PKH(+) cells and allow them to have stemlike functions.

Nuclear translocation of B-cell-specific transcription factor, BACH2, modulates ROS mediated cytotoxic responses in mantle cell lymphoma.

BACH2, a B-cell specific transcription factor, plays a critical role in oxidative stress-mediated apoptosis. Bortezomib (Velcade(TM)) is widely used to treat relapsed mantle cell lymphoma (MCL) patients despite varying clinical outcomes. As one of the potential mechanisms of action, bortezomib was reported to elicit endoplasmic reticulum (ER) stress which triggers reactive oxygen species (ROS). In the present study, we investigated the redox-sensitive intracellular mechanism that might play a critical role in bortezomib response in MCL cells. We demonstrated that in MCL cells that are sensitive to bortezomib treatments, BACH2 was translocated to the nucleus in response to bortezomib and induced apoptotic responses through the modulation of anti-oxidative and anti-apoptotic genes. On the other hand, in bortezomib resistant cells, BACH2 expression was confined in the cytoplasm and no suppression of antiapoptotic or antioxidative genes, Nrf2, Gss, CAT, HO-1 and MCL1, was detected. Importantly, levels of BACH2 were significantly higher in bortezomib sensitive MCL patient cells, indicating that BACH2 levels could be an indicator for clinical bortezomib responses. BACH2 translocation to the cytoplasm after phosphorylation was inhibited by PI3K inhibitors and combinatory regimens of bortezomib and PI3K inhibitors sensitized MCL cells to bortezomib. These data suggest that cellular distribution of BACH2 in response to ROS determines the threshold for the induction of apoptosis. Therapies that inhibit BACH2 phosphorylation could be the key for increasing bortezomib cytotoxic response in patients.

Synergistic anticancer effects of arsenic trioxide with bortezomib in mantle cell lymphoma.

Mantle cell lymphoma (MCL) is a subtype of B-cell Non-Hodgkin's Lymphoma (NHL) and accounts for ~6% of all lymphomas. MCL is highly refractory to most chemotherapy including newer antibody-based therapeutic approaches, and high-grade MCL has one of the worst survival rates among NHLs. Therefore, the development of new therapeutic strategies to overcome drug resistance of MCL is important. In this article, we tested the effects of arsenic trioxide (As(2) O(3) , ATO) in bortezomib-resistant MCL. ATO is reported to induce complete remission in the patients with relapsed or refractory acute promyelocytic leukemia. Their effects in MCL, however, have not been explored. In this report, we show that ATO effectively inhibited the growth of MCL cells in vitro. ATO treatment also reduced cyclin D1 expression which is a genetic hallmark of MCL and NF-kB expression which was reported to have a prosurvival role in some MCL cells. The induction of apoptosis in MCL was partially due to reduced levels of cyclin D1 and increased levels of apoptosis-related molecules. The antiproliferative effects of bortezomib on MCL greatly increased when the cells were also treated with ATO, indicating ATO can sensitize MCL to bortezomib. Similar results were noted in bortezomib-resistant cell lines. In conclusion, ATO may be an alternative drug for use in combined adjuvant therapies for MCL, and further clinical testing should be performed.

Calcium blockers decrease the bortezomib resistance in mantle cell lymphoma via manipulation of tissue transglutaminase activities.

Although bortezomib is clinically approved for the treatment of mantle cell lymphoma (MCL), only limited effects of this treatment have been demonstrated. To improve survival for bortezomib-resistant patients, it is necessary to develop new therapeutic strategies. In the present study, we used biochemical and molecular methodologies to demonstrate that tissue transglutaminase (TG) activates downstream NF-κB signaling pathways. The signaling axis from TG to NF-κB could be a new therapeutic target to overcome bortezomib resistance in MCL. TG2 is a calcium-dependent protein cross-linking enzyme reported to be overexpressed in various cancer cells. We found that MCL cells expressed elevated levels of TG2 and that the modification of TG2 activities altered NF-κB expression and downstream signaling in MCL cells. When TG2 signaling was inhibited by calcium blockers, the combination of a calcium blocker (perillyl alcohol) with bortezomib suppressed NF-κB expression and improved the cytotoxicity of bortezomib in MCL cells. Our study is the first to show the expression of TG2 and the contribution of TG2 to NF-κB signaling in MCL. TG2 inhibition may be used as an alternative target anti-MCL therapy, and calcium blockers may be combined with bortezomib to overcome the bortezomib resistance in MCL.

Bortezomib-resistant nuclear factor κB expression in stem-like cells in mantle cell lymphoma.

Mantle cell lymphoma (MCL) is a subtype of B-cell Non-Hodgkin's Lymphoma (NHL) and accounts for approximately 6% of all lymphomas. Unlike small lymphocytic lymphoma and chronic lymphocytic lymphoma, which are relatively sensitive to chemotherapy, MCL is highly refractory to most chemotherapy, and has the worst survival rate among NHL patients. Stem-like cells in MCL, which we have termed mantle cell lymphoma-initiating cells (MCL-ICs), enriched in the population that are lack of prototypic B-cell marker CD19. These cells were able to self-renew upon serial transplantation and are highly tumorigenic. Importantly, these stem-like cells confer chemotherapeutic resistance to MCL. In this report, we show that stem-like MCL-ICs are resistant to bortezomib, as well as chemotherapeutic regimens containing bortezomib, despite constitutive nuclear factor-κB (NF-κB) expression. Interestingly, bortezomib treatment induced MCL-IC differentiation in plasma-like cells with upregulated expression of CD38 and CD138. This process was accompanied by expression of plasma cell differentiation transcriptional factors, BLIMP-1 and IRF4. This article is the first to show that stem-like MCL cells utilize constitutive NF-κB expression for survival. Given that the NF-κB expression in MCL-ICs is resistant to bortezomib, it will be important to find alternative therapeutic strategies to inhibit NF-κB expression.

Stem-like tumor cells confer drug resistant properties to mantle cell lymphoma.

We recently identified clonogenic malignant stem cell populations in human mantle cell lymphoma (MCL), a particularly deadly subtype of non-Hodgkin lymphoma (NHL). We discovered that CD45+CD19- MCL cells, which we termed MCL-initiating cells (MCL-ICs), are highly tumorigenic and display self-renewal capacity in vivo; in contrast, CD45+CD19+ MCL cells, which constitute the vast majority of cells within the tumors, show no self-renewal capacity and greatly reduced tumorigenicity. Given the newly appreciated role of cancer-initiating cells in the drug resistance of cancers, it is critical to investigate whether CD45+CD19- MCL-ICs play a role in the drug resistance of human MCL. We discovered that MCL-ICs were more resistant to clinically relevant chemotherapeutic agents, in combination or in a single regimen, compared to CD45+CD19+ cells, and that this drug resistance was largely due to quiescent properties with enriched ABC transporters. In conclusion, designing novel therapies to kill CD45+CD19- MCL-ICs may prevent relapse and increase patient survival.