Expression of Spy1 protein in human non-Hodgkin's lymphomas is correlated with phosphorylation of p27 Kip1 on Thr187 and cell proliferation

Molecular Evolution of Classic Hodgkin Lymphoma Revealed Through Whole-Genome Sequencing of Hodgkin and Reed Sternberg Cells

The rarity of malignant Hodgkin and Reed Sternberg (HRS) cells in classic Hodgkin lymphoma (cHL) limits the ability to study the genomics of cHL. To circumvent this, our group has previously optimized fluorescence-activated cell sorting to purify HRS cells. Using this approach, we now report the whole-genome sequencing landscape of HRS cells and reconstruct the chronology and likely etiology of pathogenic events leading to cHL. We identified alterations in driver genes not previously described in cHL, APOBEC mutational activity, and the presence of complex structural variants including chromothripsis. We found that high ploidy in cHL is often acquired through multiple, independent chromosomal gains events including whole-genome duplication. Evolutionary timing analyses revealed that structural variants enriched for RAG motifs, driver mutations in B2M, BCL7A, GNA13, and PTPN1, and the onset of AID-driven mutagenesis usually preceded large chromosomal gains. This study provides a temporal reconstruction of cHL pathogenesis.

SIGNIFICANCE

Previous studies in cHL were limited to coding sequences and therefore not able to comprehensively decipher the tumor complexity. Here, leveraging cHL whole-genome characterization, we identify driver events and reconstruct the tumor evolution, finding that structural variants, driver mutations, and AID mutagenesis precede chromosomal gains. This article is highlighted in the In This Issue feature, p. 171.

Stabilization of c-Myc by the atypical cell cycle regulator, Spy1, decreases efficacy of breast cancer treatments

PURPOSE

c-Myc is frequently upregulated in breast cancers, however, targeting c-Myc has proven to be a challenge. Targeting of downstream mediators of c-Myc, such as the 'cyclin-like' cell cycle regulator Spy1, may be a viable therapeutic option in a subset of breast cancer subtypes.

METHODS

Mouse mammary tumor cells isolated from MMTV-Myc mice and human breast cancer cell lines were used to manipulate Spy1 levels followed by tamoxifen or chemotherapeutic treatment with a variety of endpoints. Patient samples from TNBC patients were obtained and constructed into a TMA and stained for c-Myc and Spy1 protein levels.

RESULTS

Over time, MMTV-Myc cells show a decreased response to tamoxifen treatment with increasing levels of Spy1 in the tamoxifen-resistant cells. shRNA against Spy1 re-establishes tamoxifen sensitivity. Spy1 was found to be highly elevated in human TNBC cell and patient samples, correlating to c-Myc protein levels. c-Myc was found to be stabilized by Spy1 and knocking down Spy1 in TNBC cells shows a significant increase in response to chemotherapy treatments.

CONCLUSION

Understanding the interplay between protein expression level and response to treatment is a critical factor in developing novel treatment options for breast cancer patients. These data have shown a connection between Spy1 and c-Myc protein levels in more aggressive breast cancer cells and patient samples. Furthermore, targeting c-Myc has proven difficult, these data suggest targeting Spy1 even when c-Myc is elevated can confer an advantage to current chemotherapies.

The expression of heat shock protein A12B (HSPA12B) in non-Hodgkin's lymphomas

Background

Heat shock protein A12B (HSPA12B) plays a considerable protective role for cells, tissues, and organs against various noxious conditions. However, the expression of HSPA12B in cancer biology remains controversial. This study aimed to investigate the expression of HSPA12B and its role in cell adhesion mediated drug resistance (CAM-DR) of non-Hodgkin’s lymphoma (NHL).

Methods

In this study, the expression of HSPA12B in NHL was determined by immunohistochemical, and the effect of HSPA12B expression on the prognosis of NHL was analyzed by Kaplan–Meier curves. Then, the transfection technique was used to research the effect of HSPA12B in cell apoptosis. The most important was to study the expression changes of HSPA12B in the adhesion model and the effect of overexpression of HSPA12B on CAM-DR.

Results

We analyzed the relationship between the expression levels of HSPA12B and clinical parameters in NHL. The expression of HSPA12B was directly related to the different NHL variants. We overexpressed HSPA12B in 2 NHL cell lines and found a subsequent reduction in apoptosis. More specifically, we used an adhesion assay to demonstrate that HSPA12B expression was induced in NHL cells when they adhered to fibronectin (FN) or bone marrow stroma cells (BMSCs). Finally, it was revealed that HSPA12B overexpression enhances CAM-DR.

Conclusions

Our data suggest that HSPA12B may play a functional role in CAM-DR and is thus a potential novel target for NHL treatment.

The cyclin-like protein SPY1 overrides reprogramming induced senescence through EZH2 mediated H3K27me3

Fully differentiated cells can be reprogrammed through ectopic expression of key transcription factors to create induced pluripotent stem cells. These cells share many characteristics of normal embryonic stem cells and have great promise in disease modeling and regenerative medicine. The process of remodeling has its limitations, including a very low efficiency due to the upregulation of many antiproliferative genes, including cyclin dependent kinase inhibitors CDKN1A and CDKN2A, which serve to protect the cell by inducing apoptotic and senescent programs. Our data reveals a unique cell cycle mechanism enabling mouse fibroblasts to repress cyclin dependent kinase inhibitors through the activation of the epigenetic regulator EZH2 by a cyclin-like protein SPY1. This data reveals that the SPY1 protein is required for reprogramming to a pluripotent state and is capable of increasing reprogramming efficiency.

RINGO/Speedy proteins, a family of non-canonical activators of CDK1 and CDK2

Cyclin-dependent kinases (CDKs) require the binding to a regulatory subunit to acquire enzymatic activity, and cyclins are the canonical CDK activators. However, there are specific situations in which CDKs can be activated by non-cyclin proteins that are less characterized. This review focuses on the family of RINGO/Speedy proteins, which have no sequence amino acid homology to cyclins but can bind to and activate CDK1 and CDK2. Interestingly, RINGO/Speedy proteins can activate CDKs under conditions in which CDK-cyclin complexes would not be active, and there is evidence that RINGO/Speedy-activated CDKs can phosphorylate different sites than the cyclin-activated CDKs. RINGO/Speedy proteins were originally described in Xenopus oocytes, but their roles in mammalian cells have also been addressed. We will summarize the properties of RINGO/Speedy proteins and how they trigger CDK activation, and discuss recent studies that characterized their physiological functions. In particular, studies using genetically modified mice have shown that RingoA, also known as Spy1, plays a key role in meiosis regulation. Emerging evidence also suggests a potential role for RingoA/Spy1 in cancer.

The atypical cyclin-like protein Spy1 overrides p53-mediated tumour suppression and promotes susceptibility to breast tumourigenesis

Background

Breast cancer is the most common cancer to affect women and one of the leading causes of cancer-related deaths. Proper regulation of cell cycle checkpoints plays a critical role in preventing the accumulation of deleterious mutations. Perturbations in the expression or activity of mediators of cell cycle progression or checkpoint activation represent important events that may increase susceptibility to the onset of carcinogenesis. The atypical cyclin-like protein Spy1 was isolated in a screen for novel genes that could bypass the DNA damage response. Clinical data demonstrates that protein levels of Spy1 are significantly elevated in ductal and lobular carcinoma of the breast. We hypothesized that elevated Spy1 would override protective cell cycle checkpoints and support the onset of mammary tumourigenesis.

Methods

We generated a transgenic mouse model driving expression of Spy1 in the mammary epithelium. Mammary development, growth characteristics and susceptibility to tumourigenesis were studied. In vitro studies were conducted to investigate the relationship between Spy1 and p53.

Results

We found that in the presence of wild-type p53, Spy1 protein is held ‘in check’ via protein degradation, representing a novel endogenous mechanism to ensure protected checkpoint control. Regulation of Spy1 by p53 is at the protein level and is mediated in part by Nedd4. Mutation or abrogation of p53 is sufficient to allow for accumulation of Spy1 levels resulting in mammary hyperplasia. Sustained elevation of Spy1 results in elevated proliferation of the mammary gland and susceptibility to tumourigenesis.

Conclusions

This mouse model demonstrates for the first time that degradation of the cyclin-like protein Spy1 is an essential component of p53-mediated tumour suppression. Targeting cyclin-like protein activity may therefore represent a mechanism of re-sensitizing cells to important cell cycle checkpoints in a therapeutic setting.

Silencing of LIMD1 promotes proliferation and reverses cell adhesion-mediated drug resistance in non-Hodgkin's lymphoma

LIM domains-containing protein 1 (LIMD1) is a tumor suppressor protein downregulated in numerous solid malignancies. However, the functional role of LIMD1 in non-Hodgkin's lymphoma (NHL) remains unclear. In the present study, it was demonstrated that LIMD1 is associated with the proliferation of NHL and cell adhesion mediated-drug resistance (CAM-DR). It was indicated by western blot analysis that LIMD1expression is lower in progressive lymphoma compared with indolent lymphoma. Furthermore, it was indicated that the role of LIMD1 in cell viability and proliferation remains unclear. Finally, the present study demonstrated that LIMD1 serves an important role in CAM-DR by regulating cell cycle progression. Silencing of LIMD1 may reverse CAM-DR in NHL. Therefore, the findings of the present study suggested that LIMD1 may be a potential therapeutic target for patients with NHL.

Structural basis of divergent cyclin-dependent kinase activation by Spy1/RINGO proteins

Cyclin-dependent kinases (Cdks) are principal drivers of cell division and are an important therapeutic target to inhibit aberrant proliferation. Cdk enzymatic activity is tightly controlled through cyclin interactions, posttranslational modifications, and binding of inhibitors such as the p27 tumor suppressor protein. Spy1/RINGO (Spy1) proteins bind and activate Cdk but are resistant to canonical regulatory mechanisms that establish cell-cycle checkpoints. Cancer cells exploit Spy1 to stimulate proliferation through inappropriate activation of Cdks, yet the mechanism is unknown. We have determined crystal structures of the Cdk2-Spy1 and p27-Cdk2-Spy1 complexes that reveal how Spy1 activates Cdk. We find that Spy1 confers structural changes to Cdk2 that obviate the requirement of Cdk activation loop phosphorylation. Spy1 lacks the cyclin-binding site that mediates p27 and substrate affinity, explaining why Cdk-Spy1 is poorly inhibited by p27 and lacks specificity for substrates with cyclin-docking sites. We identify mutations in Spy1 that ablate its ability to activate Cdk2 and to proliferate cells. Our structural description of Spy1 provides important mechanistic insights that may be utilized for targeting upregulated Spy1 in cancer.

Upregulation of ADAM12 contributes to accelerated cell proliferation and cell adhesion-mediated drug resistance (CAM-DR) in Non-Hodgkin's Lymphoma

OBJECTIVE

ADAM12 is a member of a disintegrin and metalloproteinase family and has been reported to participate in the development of variety of tumors. However, the role of ADAM12 in Non-Hodgkin Lymphoma (NHL) has not been investigated. The present study was undertaken to determine the expression and biologic function of ADAM12 in human NHL.

METHODS

First, we constructed a model of cell adhesion in NHL, the mRNA, and protein level of ADAM12 in suspension and the adhesion model was analyzed by RT-PCR and western blot. Then, flow cytometry assay and western blot were used to investigate the mechanism of ADAM12 in the proliferation of NHL cells. In vitro, after using siRNA interfering ADAM12 expression, we performed adhesion assay and cell viability assay to determine the effect of ADAM12 on adhesive rate and drug sensitivity.

RESULTS

ADAM12 was lowly expressed in suspended cells and highly expressed in adherent NHL cells. In addition, ADAM12 was positively correlated with the proliferation and apoptosis of NHL cells by regulating the expression of p-AKT and p-GSK-3β. Furthermore, ADAM12 promoted cell adhesion-mediated drug resistance (CAM-DR) in DLBCL via AKT signaling pathway.

CONCLUSION AND DISCUSSION

Our data support a role for ADAM12 in NHL cell proliferation, adhesion, and drug resistance, and it may pave the way for a novel therapeutic approach for CAM-DR in NHL.

High expression of TRIM44 is associated with enhanced cell proliferation, migration, invasion, and resistance to doxorubicin in hepatocellular carcinoma

Dysregulation of TRIM44 has been reported to be involved in tumorigenesis, but its role in hepatocellular carcinoma (HCC) remains unclear. In the present study, we investigated the clinicopathological and biological significance of TRIM44 in HCC. We found that TRIM44 mRNA and protein expression was upregulated in HCC compared with matched normal tissues. Intriguingly, we also found that TRIM44 expression was significantly correlated with tumor size (P < 0.001), vascular invasion (P < 0.001), intrahepatic metastasis (P < 0.001), distant metastasis (P < 0.001), and Ki-67 expression (P < 0.001). Kaplan-Meier analysis showed that high TRIM44 staining was significantly correlated with shorter overall survival (P < 0.001). TRIM44 was an independent predictor of overall survival in patients with HCC. Furthermore, we found that ectopic expression of TRIM44 could promote cell proliferation via accelerating the G1/S-phase transition in HCC. Moreover, overexpression of TRIM44 could enhance the invasive and migratory capacity of HCC cells. Meanwhile, we found that high expression of TRIM44 could enhance resistance of HCC cells to doxorubicin via accelerating NF-κB activation. In conclusion, our results suggest that TRIM44 may be a novel prognostic indicator and potential therapeutic target of HCC.

Expression of far upstream element binding protein 1 in B‑cell non‑Hodgkin lymphoma is correlated with tumor growth and cell‑adhesion mediated drug resistance

Cell adhesion‑mediated drug resistance (CAM‑DR) remains a major obstacle to the effectiveness of chemotherapeutic treatment of lymphoma. Far upstream element binding protein 1 (FBP1) is a multifunctional protein that is highly expressed in proliferating cells of several solid neoplasms; however, its expression and biological function in B‑cell lymphoma is largely unknown. FBP1 expression in both reactive lymphoid tissues and several B‑cell lymphomas, including follicular lymphoma and diffuse large B‑cell lymphoma were detected by immunohistochemistry analysis. FBP1 expression in B‑cell lymphoma was also associated with poor survival outcomes. Functionally, small interfering RNA‑mediated silencing of FBP1 was able to inhibit the proliferation of B‑cell lymphoma cells, resulting in G0/G1 phase cell cycle arrest. Furthermore, results of a cell adhesion assay demonstrated that adhesion to fibronectin or bone marrow stromal cells induced FBP1 expression, which in turn facilitated cell adhesion. Finally, FBP1 knockdown reversed CAM‑DR. These findings support a role for FBP1 in non‑Hodgkin lymphoma cell proliferation, adhesion and drug resistance, and may lead to the generation of a novel therapeutic approach targeting this molecule.

Direct interactions with both p27 and Cdk2 regulate Spy1-mediated proliferation in vivo and in vitro

Families of cyclin-like proteins have emerged that bind and activate cyclin dependent kinases (Cdk)s, directing the phosphorylation of noncanonical Cdk substrates. One of these proteins, Spy1, has demonstrated the unique ability to directly bind and activate both Cdk1 and Cdk2, as well as binding and promoting the degradation of at least one Cdk inhibitor, p27(Kip1). Spy1 accelerates somatic cell growth and proliferation and is implicated in a number of human cancers including the breast, brain and liver. Herein we isolate key residues mediating the direct interaction with p27. We use mutants of Spy1 to determine the physiological role of direct interactions with distinct binding partners Cdk2 and p27. We demonstrate that disrupting the direct interaction with either Spy1 binding partner decreased endogenous activity of Cdk2, as well as Spy1-mediated proliferation. However, only the direct interaction with p27 was essential for Spy1-mediated effects on p27 stability. In vivo neither mutation completely prevented tumorigenesis, although each mutation slowed the rate of Spy1-mediated tumorigenesis and decreased overall tumor volumes. This work supports the conclusion that direct interaction with both p27 and Cdk2 contribute to Spy1-mediated effects on cell growth. It is important to elucidate the dynamics of these interactions and to consider these data when assessing functional outcomes.

Upregulation of nuclear transporter, Kpnβ1, contributes to accelerated cell proliferation- and cell adhesion-mediated drug resistance (CAM-DR) in diffuse large B-cell lymphoma

BACKGROUND

The Karyopherin proteins are involved in the shuttling of cargo proteins, and certain RNAs, across the nuclear pore complex into and out of the cell nucleus. Karyopherin β1 (Kpnβ1) is a member of the Karyopherin β superfamily of nuclear transport proteins. In addition to the nuclear import function, Kpnβ1 is associated with the occurrence of tumors. This study investigated the expression and biologic function of Kpnβ1 in diffuse large B-cell lymphoma (DLBCL).

METHODS

The prognostic value of Kpnβ1 expression was evaluated using immunohistochemical staining. The role of Kpnβ1 on cell proliferation- and cell adhesion-mediated drug resistance (CAM-DR) was also determined.

RESULTS

We demonstrated that Kpnβ1 mRNA and protein expression levels were significantly higher in DLBCL B-cells and DLBCL cell lines than in normal CD19 purified B-cells. Immunohistochemical analysis suggested that the expression of Kpnβ1 was correlated with Ki-67 (P < 0.001). Kaplan-Meier curve showed that high expression of Kpnβ1 was significantly associated with shorter overall survival. In addition, Kpnβ1 was associated with the proliferation of DLBCL cells. Importantly, we found that Kpnβ1 could interact with p65 and promote CAM-DR via accelerating NF-κB activation in DLBCL.

CONCLUSIONS

Patients with tumors highly expressing Kpnβ1 have poorer overall survivals. Kpnβ1 interacts with p65 and enhances CAM-DR.

Overexpression of TRIP6 promotes tumor proliferation and reverses cell adhesion-mediated drug resistance (CAM-DR) via regulating nuclear p27(Kip1) expression in non-Hodgkin's lymphoma

Recent studies have identified that thyroid hormone receptor-interacting protein 6 (TRIP6) is implicated in tumorigenesis. However, the functional role of TRIP6 in non-Hodgkin's lymphoma (NHL) has never been elucidated. In this study, we demonstrated that TRIP6 is reversely correlated with the clinical outcomes of NHL patients. Western blot and immunohistochemical analysis revealed that TRIP6 expression is lower in indolent lymphoma than in progressive lymphoma. Kaplan-Meier survival curves indicated that the upregulation of TRIP6 is significantly associated with poor overall survival. Moreover, patients with higher expression of TRIP6 are prone to shorter time to recurrence. Furthermore, we also found that TRIP6 can promote the proliferation of NHL cells via regulating cell cycle progression. In addition, adhesion of lymphoma cells to fibronectin (FN) decreased TRIP6 expression, which led to the upregulation of nuclear p27(Kip1) expression by decreasing phosphorylation of p27(Kip1) at T157. Importantly, overexpression of TRIP6 can reverse cell adhesion-mediated drug resistance (CAM-DR) phenotype in NHL. In summary, these results suggest that TRIP6 is a novel prognostic indicator for NHL patients and may shed new insights into the important role of TRIP6 in cancer development.

Histamine-releasing factor/translationally controlled tumor protein plays a role in induced cell adhesion, apoptosis resistance and chemoresistance in non-Hodgkin lymphomas

Mounting evidence has proved that cellular adhesion confers resistance to chemotherapy in multiple lymphomas. The molecular mechanism underlying cell adhesion-mediated drug resistance (CAM-DR) is, however, poorly understood. In this study, we investigated the expression and biologic function of histamine-releasing factor (HRF) in non-Hodgkin lymphomas (NHLs). Clinically, by immunohistochemistry analysis we observed obvious up-regulation of HRF in NHLs including diffuse large B-cell lymphoma (DLBCL), follicular lymphoma (FL) and natural killer (NK)/T-cell lymphoma. Functionally, overexpression and knockdown of HRF demonstrated the antiapoptotic effect of HRF in NHL cells, which may be associated with activation of the p-CREB/BCL-2 signaling pathway. Moreover, cell adhesion assay demonstrated that adhesion to fibronectin (FN) or HS-5 up-regulated HRF expression, while knockdown of HRF resulted in decreased cell adhesion, which led to reversed CAM-DR. Our finding supports the role of HRF in NHL cell apoptosis, adhesion and drug resistance, and may provide a clinical therapeutic target for CAM-DR in NHL.

Ubiquitin-specific protease 14 (USP14) regulates cellular proliferation and apoptosis in epithelial ovarian cancer

Epithelial ovarian cancer (EOC) is the most lethal gynecologic malignancy. Thus, there is an emergent need to invest a novel therapeutic for EOC. In this study, we defined ubiquitin-specific protease 14 (USP14) as a therapeutic target for EOC. Western blot was used to evaluate the expression of USP14 in nine fresh EOC tissues and three fresh normal ovarian tissues. The protein level of USP14 was higher in the cancer samples compared with that in the normal ovary tissues. Immunohistochemistry analysis was performed on formalin-fixed paraffin-embedded section of 116 cases of EOCs and indicated that USP14 was significantly associated with clinical pathologic variables. Kaplan-Meier curve showed that high expression of USP14 was related to poor prognosis of EOC patients. Starvation and re-feeding assay was used to imitate cell cycle, suggesting that USP14 played a critical role in SKOV3 cell proliferation. CCK-8 assay showed that SKOV3 cells treated with USP14-shRNA (shUSP14) grew more slowly than control group. Flow cytometry revealed that the reduced expression of USP14 induced the apoptosis of the SKOV3 EOC cells. In summary, our findings suggest that USP14 is involved in the progression of EOC and that it may be a useful target of therapy in EOC.

Expression of small glutamine-rich TPR-containing protein A (SGTA) in Non-Hodgkin's Lymphomas promotes tumor proliferation and reverses cell adhesion-mediated drug resistance (CAM-DR)

The expression and biologic function of SGTA in Non-Hodgkin's Lymphomas (NHL) was investigated in this study. Clinically, by immunohistochemistry analysis we detected SGTA expression in both reactive lymphoid tissues and NHL tissues. In addition, we also correlated high expression of SGTA with poor prognosis. Functionally, SGTA expression was positively related with cell proliferation and negative related with cell adhesion. Finally, SGTA knockdown induced adhesion-mediated drug resistance. Our finding supports a role of SGTA in NHL cell proliferation, adhesion and drug resistance, and it may pave the way for a novel therapeutic approach for CAM-DR in NHL.

Adhesion to fibronectin induces p27(Kip1) nuclear accumulation through down-regulation of Jab1 and contributes to cell adhesion-mediated drug resistance (CAM-DR) in RPMI 8,226 cells

Mounting evidence has been shown that integrin-mediated cellular adhesion confers resistance to chemotherapy of multiple myeloma. The molecular mechanism underlying cell adhesion-mediated drug resistance (CAM-DR) is, however, poorly understood. In this report, we demonstrated that RPMI 8,226 cells accumulated p27(Kip1) in the nucleus when they were adhered to fibronectin (FN). The adhesion-mediated p27(Kip1) nuclear recruitment was regulated via the down-regulation of Jab1, a negative regulator of cell cycle. Overexpression of Jab1 reversed the elevated p27(Kip1) in the nucleus, which needed phosphorylation of p27(Kip1) on Serine 10, whereas inhibition of Jab1 by siRNA further increased the elevated p27(Kip1). Furthermore, we found overexpression of Jab1 did not affect 8,226 cells adhesion to FN, but reversed doxorubicin or mitoxantrone-induced CAM-DR phenotype. In conclusion, our data suggest that Jab1 plays an important role in CAM-DR, which depends on pSer10-p27(Kip1)-mediated subcellular localization of p27(Kip1). The understanding of this novel molecular mechanism may prove valuable in designing new therapeutic approaches for CAM-DR in Multiple myeloma.