Fibroblast growth factor receptor 3 inhibition by short hairpin RNAs leads to apoptosis in multiple myeloma

Protein tyrosine phosphatases in multiple myeloma

Many cell signaling pathways are activated or deactivated by protein tyrosine phosphorylation and dephosphorylation, catalyzed by protein tyrosine kinases (PTKs) and protein tyrosine phosphatases (PTPs), respectively. Even though PTPs are as important as PTKs in this process, their role has been neglected for a long time. Multiple myeloma (MM) is a cancer of plasma cells, which is characterized by production of monoclonal immunoglobulin, anemia and destruction of bone. MM is still incurable with high relapse frequency after treatment. In this review, we highlight the PTPs that were previously described in MM or have a role that can be relevant in a myeloma context. Our purpose is to show that despite the importance of PTPs in MM pathogenesis, many unanswered questions in this field need to be addressed. This might help to detect novel treatment strategies for MM patients.

FGFR3△7-9 promotes tumor progression via the phosphorylation and destabilization of ten-eleven translocation-2 in human hepatocellular carcinoma

Overexpression of fibroblast growth factor receptor 3 (FGFR3) correlates with more severe clinical features of hepatocellular carcinoma (HCC). Our previous study has shown that FGFR3_∆7–9, a novel splicing mutation of FGFR3, contributes significantly to HCC malignant character, but the epigenetic mechanism is still elusive. In this study, through mass spectrometry and co-immunoprecipitation studies, we discover a close association between FGFR3_∆7–9 and the DNA demethylase Ten-Eleven Translocation-2 (TET2). Unlike other certain types of cancer, mutation of TET2 is rare in HCC. However, activation of FGFR3_∆7–9 by FGF1 dramatically shortens TET2 half-life. FGFR3_∆7–9, but not wild-type FGFR3, directly interacts with TET2 and phosphorylates TET2 at Y1902 site, leading to the ubiquitination and proteasome-mediated degradation of TET2. Overexpression of a phospho-deficient mutant TET2 (Y1902F) significantly reduces the oncogenic potential of FGFR3_∆7–9 in vitro and in vivo. Furthermore, FGFR3_∆7–9 significantly enhances HCC cell proliferation through the TET2-PTEN-AKT pathway. Specifically, TET2 offsets the elevation of p-AKT level induced by FGFR3_∆7–9 through directly binding to PTEN promoter and increasing 5-hmC. Therefore, through phosphorylation and inhibition of TET2, FGFR3_∆7–9 reduces PTEN expression and substantiates AKT activation to stimulate HCC proliferation. Together, this study identifies TET2 as a key regulator of the oncogenic role of FGFR3_∆7–9 in HCC carcinogenesis and sheds light on new therapeutic strategies for HCC treatment.

The pro-survival function of DLEC1 and its protection of cancer cells against 5-FU-induced apoptosis through up-regulation of BCL-XL

The tumor suppressor DLEC1 has been shown to promote cell proliferation when AP-2α2 is down-regulated in HCT116 stable clones, suggesting its pro-survival nature. However, the pro-survival function of DLEC1 has not been confirmed in other cells and its underlying mechanisms remain elusive. Therefore, we knocked down DLEC1 in a panel of cell lines and found that DLEC1 depletion caused various extents of cell death through intrinsic pathway. DLEC1 overexpression promoted cell survival and reduced cell death in cancer cells after 5-FU treatment, while DLEC1 down-regulation sensitized cancer cells to 5-FU. Further studies demonstrated that DLEC1 attenuated the increase in cleaved PARP, caspase-3 and caspase-7, the activity of caspase-9 and the diffusion of cytosolic cytochrome c from mitochondria. Our data also showed that BCL-XL was up-regulated by DLEC1 in stable clones after 5-FU treatment. Altogether, these results indicated that DLEC1 protects cells against cell death induced by 5-FU through the attenuation of active proteins in caspase cascade and the up-regulation of BCL-XL. Therefore, DLEC1 can be a pro-survival protein under certain circumstances and a potential therapeutic target for increasing sensitivity of cancer cells to 5-FU.

Phenotypic and Signaling Consequences of a Novel Aberrantly Spliced Transcript FGF Receptor-3 in Hepatocellular Carcinoma

Fibroblast growth factor receptor 3 (FGFR3) plays important roles in cell proliferation, differentiation, and angiogenesis. FGFR3 is abnormally upregulated in hepatocellular carcinoma (HCC), where it correlates positively with clinicopathologic index, HCC differentiation, and advanced nuclear grade. In this study, we describe an aberrantly spliced transcript of FGFR3, termed FGFR3Δ7-9, was identified as a high frequency even in HCC. FGFR3Δ7-9 lacks exons encoding the immunoglobulin-like III domain and promoted the proliferation, migration, and metastasis of HCC cells both in vitro and in vivo Coimmunoprecipation and surface plasmon resonance assays demonstrated that the binding affinity of the aberrant FGFR3Δ7-9 receptor to FGFs was significantly higher than wild-type FGFR3IIIc Furthermore, FGFR3Δ7-9 could be self-activated by homodimerization and autophosphorylation even in the absence of ligand. Finally, FGFR3Δ7-9 more potently induced phosphorylation of the ERK and AKT kinases, leading to abnormal downstream signaling through the ERK and PI3K/AKT/mTOR pathways. FGFR3Δ7-9 also upregulated the metastasis-associated molecules Snail, MMP-9, and downregulated E-cadherin, which associated directly with FGFR3Δ7-9 Thus, as a ligand-dependent or -independent receptor, FGFR3Δ7-9 exerted multiple potent oncogenic functions in HCC cells, including proliferation, migration, and lung metastatic capacity. Overall, FGFR3 mRNA missplicing in HCC contributes significantly to its malignant character, with implications for therapeutic targeting. Cancer Res; 76(14); 4205-15. ©2016 AACR.

MiR-362-5p promotes the malignancy of chronic myelocytic leukaemia via down-regulation of GADD45α

Background

MicroRNAs (miR, miRNAs) play pivotal roles in numerous physiological and pathophysiological contexts. We investigated whether miR-362-5p act as an oncogene in chronic myeloid leukaemia (CML) and aimed to understand its potential underlying mechanisms.

Methods

We compared the miR-362-5p expression levels between CML and non-CML cell lines, and between fresh blood samples from CML patients and normal healthy controls using quantitative real-time PCR (qPCR). Cell counting kit-8 (CCK-8) and Annexin V-FITC/PI analyses were used to measure the effects of miR-362-5p on proliferation and apoptosis, and Transwell assays were used to evaluate migration and invasion. A xenograft model was used to examine in vivo tumourigenicity. The potential target of miR-362-5p was confirmed by a luciferase reporter assay, qPCR and western blotting. Involvement of the JNK_1/2 and P38 pathways was investigated by western blotting.

Results

miR-362-5p was up-regulated in CML cell lines and fresh blood samples from CML patients, and was associated with Growth arrest and DNA damage-inducible (GADD)45α down-regulation. Inhibition of miR-362-5p simultaneously repressed tumour growth and up-regulated GADD45α expression in a xenograft model. Consistently, the knockdown of GADD45α expression partially neutralized the effects of miR-362-5p inhibition. Furthermore study suggested that GADD45α mediated downstream the effects of miR-362-5p, which might indirectly regulates the activation of the JNK_1/2 and P38 signalling pathways.

Conclusion

miR-362-5p acts as an oncomiR that down-regulates GADD45α, which consequently activates the JNK_1/2 and P38 signalling. This finding provides novel insights into CML leukaemogenesis and may help identify new diagnostic and therapeutic targets.

Electronic supplementary material

The online version of this article (doi:10.1186/s12943-015-0465-3) contains supplementary material, which is available to authorized users.

Bcl-2 stabilization by paxillin confers 5-fluorouracil resistance in colorectal cancer

5-Fluorouracil (5-FU) is chemotherapeutic agent widely used for the treatment of colorectal cancer. Unfortunately, advanced colorectal cancer is often resistance to such chemotherapy and poor outcome. An adaptor protein paxillin (PXN) is phosphorylated at Y31/Y118 (pPXN-Y31/Y118) by Src contributes to cell mobility and Ser (S)272 of PXN in LD4 domain is important to the interaction between PXN and Bcl-2. We thus hypothesized that pPXN-Y31/Y118 may be required for Bcl-2 protein stability via PXN interacting with Bcl-2 to confer 5-FU resistance in colorectal cancer. Mechanistically, pPXN-S272 is phosphorylated through pPXN-Y31/Y118-mediated p21 protein-activated kinase 1 (PAK1) activation and pPXN-S272 is required for PXN to interact with Bcl-2. The interaction between PXN and Bcl-2 is essential for Bcl-2 protein stability through phosphorylation of Bcl-2 at S87 (pBcl-2-S87) by pPXN-Y31/Y118-mediated ERK activation. An increase in Bcl-2 expression by PXN is responsible for resistance to 5-FU. The resistance to 5-FU can be abolished by inhibitor of Src and PAK1 or Bcl-2 antagonist in cell and animal models. Among patients, Bcl-2 expression is positively correlated with expression of PXN and pPXN-S272, respectively. Patients with high PXN/high Bcl-2 or high pPXN-S272/high Bcl-2 tumors are commonly to have an unfavorable response to 5-FU-based chemotherapy, compared with patients who have high PXN, high pPXN-S272 or high Bcl-2 tumors alone. Therefore, we suggest that Src, PAK1 or Bcl-2 inhibitor may potentially overcome the resistance of 5-FU-based chemotherapy and consequently to improve outcomes in patients with PXN/Bcl-2 and pPXN-S272/Bcl-2-positive tumors.

Synthetic lethal screening reveals FGFR as one of the combinatorial targets to overcome resistance to Met-targeted therapy

Met is a receptor tyrosine kinase that promotes cancer progression. In addition, Met has been implicated in resistance of tumors to various targeted therapies such as epidermal growth factor receptor inhibitors in lung cancers, and has been prioritized as a key molecular target for cancer therapy. However, the underlying mechanism of resistance to Met-targeting drugs is poorly understood. Here, we describe screening of 1310 genes to search for key regulators related to drug resistance to an anti-Met therapeutic antibody (SAIT301) by using a small interfering RNA-based synthetic lethal screening method. We found that knockdown of 69 genes in Met-amplified MKN45 cells sensitized the antitumor activity of SAIT301. Pathway analysis of these 69 genes implicated fibroblast growth factor receptor (FGFR) as a key regulator for antiproliferative effects of Met-targeting drugs. Inhibition of FGFR3 increased target cell apoptosis through the suppression of Bcl-xL expression, followed by reduced cancer cell growth in the presence of Met-targeting drugs. Treatment of cells with the FGFR inhibitors substantially restored the efficacy of SAIT301 in SAIT301-resistant cells and enhanced the efficacy in SAIT301-sensitive cells. In addition to FGFR3, integrin β3 is another potential target for combination treatment with SAIT301. Suppression of integrin β3 decreased AKT phosphorylation in SAIT301-resistant cells and restored SAIT301 responsiveness in HCC1954 cells, which are resistant to SAIT301. Gene expression analysis using CCLE database shows that cancer cells with high levels of FGFR and integrin β3 are resistant to crizotinib treatment, suggesting that FGFR and integrin β3 could be used as predictive markers for Met-targeted therapy and provide a potential therapeutic option to overcome acquired and innate resistance for the Met-targeting drugs.

Nestin expression throughout multistep pathogenesis of multiple myeloma

The stem cell marker nestin (NES) is found in dividing cells of developing and regenerating tissues. Upon terminal differentiation, NES expression is diminished but may be re-expressed following injury or in cancer. Surprisingly, we recently confirmed NES as a tumour-specific marker for mature CD138(+) 38(+) plasma cells (PC) in multiple myeloma (MM). The present study analysed NES expression throughout the spectrum of MM developmental stages, starting with individuals with no haematological malignancy, through monoclonal gammopathy of undetermined significance (MGUS) and MM to plasma cell leukaemia (PCL) and MM cell lines. NES was analysed in bone marrow PC of 163 MM, four PCL and nine MGUS patients, 10 individuals with no haematological malignancy and 6 myeloma cell lines (OPM-2, RPMI-8226, MOLP-8, U-266, EJM, NCI-H929) by flow cytometry and/or real-time polymerase chain reaction or immunochemistry. We observed a tendency of increased NES expression in parallel with disease progression. NES was evaluated as a reliable marker for accurate discrimination between MM patients and the control group. High NES levels were strongly associated with the presence of 1q21 gain. For the first time, NES was demonstrated to predict worse response to conventional therapy/novel agents. These results suggest that NES might become a useful clinical parameter with an important role in MM pathogenesis.

Evaluation of the Abelson gene as a control gene for real-time quantitative PCR in multiple myeloma

The Abelson (ABL) gene was the best control gene for quantitative PCR (qPCR)-based diagnosis and minimal residual disease detection in leukemic patients. However, there is still no concerted effort focused on the optimization of control genes in multiple myeloma (MM). The results of this study will provide a basis for the use of ABL as a control gene for the quantification of aberrantly expressed genes in MM. We analyzed ABL, glyceraldehyde-3-phosphate dehydrogenase (GAPDH), beta-glucuronidase, and β2-microglobulin genes expression in bone marrow samples of 62 MM patients and 31 healthy donors. MAGE-C1, the most commonly expressed cancer-testis antigen gene in MM, which is to be a potential clinical indicator for auxiliary diagnosis and prognostic evaluation in MM, was also detected. Our experimental results show that the copy numbers of the four control genes were well correlated in all samples detected. The quantitative data for MAGE-C1 using the four control genes also had high correlations. ABL and GAPDH genes were stably expressed in healthy donors and MM patients during therapy and did not vary with disease state. ABL is stable in the MM bone marrow mononuclear fraction, and it could be used as a reliable control gene for the normalization of qPCR studies in MM.

AZD4547: an orally bioavailable, potent, and selective inhibitor of the fibroblast growth factor receptor tyrosine kinase family

The fibroblast growth factor (FGF) signaling axis is increasingly implicated in tumorigenesis and chemoresistance. Several small-molecule FGF receptor (FGFR) kinase inhibitors are currently in clinical development; however, the predominant activity of the most advanced of these agents is against the kinase insert domain receptor (KDR), which compromises the FGFR selectivity. Here, we report the pharmacologic profile of AZD4547, a novel and selective inhibitor of the FGFR1, 2, and 3 tyrosine kinases. AZD4547 inhibited recombinant FGFR kinase activity in vitro and suppressed FGFR signaling and growth in tumor cell lines with deregulated FGFR expression. In a representative FGFR-driven human tumor xenograft model, oral administration of AZD4547 was well tolerated and resulted in potent dose-dependent antitumor activity, consistent with plasma exposure and pharmacodynamic modulation of tumor FGFR. Importantly, at efficacious doses, no evidence of anti-KDR-related effects were observed, confirming the in vivo FGFR selectivity of AZD4547. Taken together, our findings show that AZD4547 is a novel selective small-molecule inhibitor of FGFR with potent antitumor activity against FGFR-deregulated tumors in preclinical models. AZD4547 is under clinical investigation for the treatment of FGFR-dependent tumors.

Sixteen years and counting: the current understanding of fibroblast growth factor receptor 3 (FGFR3) signaling in skeletal dysplasias

In 1994, the field of bone biology was significantly advanced by the discovery that activating mutations in the fibroblast growth factor receptor 3 (FGFR3) receptor tyrosine kinase (TK) account for the common genetic form of dwarfism in humans, achondroplasia (ACH). Other conditions soon followed, with the list of human disorders caused by FGFR3 mutations now reaching at least 10. An array of vastly different diagnoses is caused by similar mutations in FGFR3, including syndromes affecting skeletal development (hypochondroplasia [HCH], ACH, thanatophoric dysplasia [TD]), skin (epidermal nevi, seborrhaeic keratosis, acanthosis nigricans), and cancer (multiple myeloma [MM], prostate and bladder carcinoma, seminoma). Despite many years of research, several aspects of FGFR3 function in disease remain obscure or controversial. As FGFR3-related skeletal dysplasias are caused by growth attenuation of the cartilage, chondrocytes appear to be unique in their response to FGFR3 activation. However, the reasons why FGFR3 inhibits chondrocyte growth while causing excessive cellular proliferation in cancer are not clear. Likewise, the full spectrum of molecular events by which FGFR3 mediates its signaling is just beginning to emerge. This article describes the challenging journey to unravel the mechanisms of FGFR3 function in skeletal dysplasias, the extraordinary cellular manifestations of FGFR3 signaling in chondrocytes, and finally, the progress toward therapy for ACH and cancer.

Adenovirus-mediated siRNA targeting Bcl-xL inhibits proliferation, reduces invasion and enhances radiosensitivity of human colorectal cancer cells

Introduction

Bcl-xL, an important member of anti-apoptotic Bcl-2 family, plays critical roles in tumor progression and development. Previously, we have reported that overexpression of Bcl-xL was correlated with prognosis of colorectal cancer (CRC) patients. The aim of this study was to investigate the association of Bcl-xL expression with invasion and radiosensitivity of human CRC cells.

Methods

RT-PCR and Western blot assays were performed to determine the expression of Bcl-xL mRNA and protein in CRC cells and normal human intestinal epithelial cell line. Then, adenovirus-mediated RNA interference technique was employed to inhibit the expression of Bcl-xL gene in CRC cells. The proliferation of CRC cells was analyzed by MTT and colony formation assay. The migration and invasion of CRC cells was determined by wound-healing and tranwell invasion assays. Additionally, the in vitro and in vivo radiosensitivity of CRC cells was determined by clonogenic cell survival assay and murine xnograft model, respectively.

Results

The levels of Bcl-xL mRNA and protein expression were significantly higher in human CRC cells than in normal human intestinal epithelial cell line. Ad/shBcl-xL could significantly reduce the expression of Bcl-xL protein in CRC cells. Also, we showed that adenovirus-mediated siRNA targeting Bcl-xL could significantly inhibit proliferation and colony formation of CRC cells. Ad/shBcl-xL could significantly suppress migration and invasion of CRC cells. Moreover, Ad/shBcl-xL could enhance in vitro and in vivo radiosensitivity of CRC cells by increasing caspase-dependent apoptosis.

Conclusions

Targeting Bcl-xL will be a promising strategy to inhibit the metastatic potential and reverse the radioresistance of human CRC.

Ribosomal protein metallopanstimulin-1 impairs multiple myeloma CAG cells growth and inhibits fibroblast growth factor receptor 3

INTRODUCTION

It was demonstrated that metallopanstimulin-1 (MPS-1, RPS27) inhibited the growth of tumors formed by head and neck squamous cell carcinoma cells and reduced paxillin gene expression.

METHODS

The present study examined whether and how MPS-1 affects another type of cancer, multiple myeloma (CAG). Enhanced expression of MPS-1 dramatically inhibited CAG in vitro and in vivo.

RESULTS

Overexpression of MPS-1 resulted in decreased fibroblast growth factor (FGF2) receptor 3 and impaired endogenous MAPK/ErK signaling. MAPK/ErK signaling was not stimulated by adding recombinant FGF2 to myeloma cells overexpressing MPS-1.

CONCLUSIONS

These data suggest that MPS-1 suppresses CAG growth and that weakened FGF2 signaling may contribute to this effect.

Oncolytic-adenovirus-expressed RNA interference for cancer therapy

IMPORTANCE OF THE FIELD

RNA interference (RNAi) has generated considerable excitement for its potential cancer therapeutic applications. Because of the difficulties in delivering a large amount of siRNA to cancer cells and the short half-life of siRNA, it is important to choose an efficient delivery system for transduction of siRNA into target cells. Oncolytic adenovirus offers a better platform by virtue of its high transfection efficiency and selective replication in cancer cells.

AREAS COVERED IN THIS REVIEW

This review focuses on the synergism between oncolytic adenovirus and siRNA antitumor responses, and discusses recent progresses in oncolytic-adenovirus-expressed siRNA.

WHAT THE READER WILL GAIN

siRNA-expressing oncolytic adenovirus can generate a significantly enhanced antitumor effect through gene knockdown and viral oncolysis.

TAKE HOME MESSAGE

Due to its potency and target specificity, using siRNA delivery by oncolytic adenovirus has generated much excitement and will open new avenues for treatment of human cancer.

KLF4 is a tumor suppressor in B-cell non-Hodgkin lymphoma and in classic Hodgkin lymphoma

The transcription factor KLF4 may act both as an oncogene and a tumor suppressor in a tissue-depending manner. In T- and pre-B-cell lymphoma, KLF4 was found to act as tumor suppressor. We found the KLF4 promoter methylated in B-cell lymphoma cell lines and in primary cases of B-cell lymphomas, namely, follicular lymphoma, diffuse large B-cell lymphoma, Burkitt lymphoma, and in classic Hodgkin lymphoma (cHL) cases. Promoter hypermethylation was associated with silencing of KLF4 expression. Conditional overexpression of KLF4 in Burkitt lymphoma cell lines moderately retarded proliferation, via cell-cycle arrest in G(0)/G(1). In the cHL cell lines, KLF4 induced massive cell death that could partially be inhibited with Z-VAD.fmk. A quantitative reverse-transcribed polymerase chain reaction array revealed KLF4 target genes, including the proapoptotic gene BAK1. Using an shRNA-mediated knock-down approach, we found that BAK1 is largely responsible for KLF4-induced apoptosis. In addition, we found that KLF4 negatively regulates CXCL10, CD86, and MSC/ABF-1 genes. These genes are specifically up-regulated in HRS cells of cHL and known to be involved in establishing the cHL phenotype. We conclude that epigenetic silencing of KLF4 in B-cell lymphomas and particularly in cHL may favor lymphoma survival by loosening cell-cycle control and protecting from apoptosis.

Targeted therapies in non-muscle-invasive bladder cancer according to the signaling pathways

With 300,000 annually new cases worldwide, urothelial-cell carcinoma of the bladder (UCCB) is the second most common urologic neoplasm after prostate carcinoma. Non-muscle-invasive bladder cancer (NMIBC), which is not immediately life-threatening, represents 70% to 80% of these initial cases. Despite optimal treatment (transurethral resection with intravesical chemo- or immunotherapy), 70% of these NMIBC will recur, and 10% to 20% will progress, highlighting the need for a new therapeutic approach. Indeed, the identification of patients at high risk of disease recurrence and progression would be beneficial in predicting which patients with NMIBC would benefit from strict follow-up and which would benefit from a more aggressive therapy. To date, conventional treatment remains disappointing in terms of oncologic results and morbidity. The growing understanding in tumor biology has enabled the signaling pathways involved in bladder tumorigenesis and progression to be identified, but few molecular targets have been available until now. The encouraging results seen in various human carcinomas suggests that these new agents should become part of the arsenal of drugs available in the treatment of NMIBC, alone or in combination with already known agents. In this article, we have tried to highlight the main molecular signaling pathways involved in NMIBC tumorigenesis and progression, and the potential targets useful for improving the treatment of NMIBC.

Vitamin K2 downregulates the expression of fibroblast growth factor receptor 3 in human hepatocellular carcinoma cells

AIM

Vitamin K2 exerts an antitumor activity on human hepatocellular carcinoma (HCC), however, its inhibitory mechanism has not yet been clarified. This study was designed to identify the attractive target molecule of vitamin K2 and shed some light on its effects on fibroblast growth factor receptor (FGFR)3 in HCC cells.

METHODS

The changes in the gene expression of HuH-7 after vitamin K2 treatment were evaluated by a DNA chip analysis. The mRNA and protein levels of FGFR were evaluated by semiquantitative reverse transcription polymerase chain reaction (RT-PCR), real-time PCR and western blot analysis. The promoter activity of the FGFR3 gene was measured by a dual-luciferase assay.

RESULTS

The DNA chip analysis revealed different inhibitory rates of gene expression of FGFR3 (60.6%) and FGFR1 (19.4%) after vitamin K2 treatment. Vitamin K2 suppresses the proliferation of HuH-7 in a dose-dependent manner and its inhibitory rate reached approximately 61.8% at the dose of 30 microM. FGFR3 mRNA was significantly reduced based on semiquantitative RT-PCR and decreased 61.5% by a real-time PCR method after vitamin K2 treatment, but FGFR1 mRNA was not. The level of FGFR3 protein was also reduced by vitamin K2 treatment. The luciferase assay demonstrated that vitamin K2 significantly suppressed the promoter activity of FGFR3. Furthermore, the FGFR3-ERK1/2 signaling pathway was suppressed by vitamin K2 treatment.

CONCLUSION

These findings suggest that vitamin K2 may suppress the proliferation of HCC cells through the downregulation of the FGFR3 expression. The transcriptional suppression of FGFR3 may be a novel mechanism of the vitamin K2 action for HCC cells.

Alternative splicing as a therapeutic target for human diseases

The majority of eukaryotic genes undergo alternative splicing, an evolutionarily conserved phenomenon, to generate functionally diverse protein isoforms from a single transcript. The fact that defective pre-mRNA splicing can generate non-functional and often toxic proteins with catastrophic effects, accurate removal of introns and joining of exons is vital for cell homeostasis. Thus, molecular tools that could either silence a disease-causing gene or regulate its expression in trans will find many therapeutic applications. Here we present two RNA-based approaches, namely RNAi and theophylline-responsive riboswitch that can regulate gene expression by loss-of-function and modulation of splicing, respectively. These strategies are likely to continue to play an integral role in studying gene function and drug discovery.

Death receptor 5 promoter-enhancing compounds isolated from Catimbium speciosum and their enhancement effect on TRAIL-induced apoptosis

The TRAIL/death-receptor signaling pathway has been considered a promising target for selective cancer therapy, although some malignant tumors exhibit TRAIL resistance. We previously found that isoflavonoid enhanced TRAIL-induced apoptosis in TRAIL-resistant cells, which is achieved through up-regulation of death receptor 5 (DR5). In our screening program targeting DR5 promoter enhancement activity, activity-guided fractionations of the extract of Catimbium speciosum led to the isolation of six compounds. Of the isolates, cardamomin (6), the most potent compound, enhanced the expressions of DR5 and DR4 and decreased the Bcl-xL level in TRAIL-resistant DLD1 cells. The combination of 6 and TRAIL synergistically enhanced TRAIL-induced apoptosis against TRAIL-resistant cells upon the activation of caspase-8, 9, and 3. In addition, enhancement of apoptosis by 6 was inhibited by human recombinant DR5/Fc and DR4/Fc chimera proteins, TRAIL-neutralizing fusion proteins, indicating that 6 sensitize TRAIL-resistant cells to TRAIL through the induction of DR5 and DR4. Also, up-regulation of DR5 by 6 paralleled that of CCAAT/enhancer-binding protein-homologous protein (CHOP).

Therapeutic potential of RNA interference in drug-resistant cancers

Resistance including multidrug resistance to chemotherapy is a common clinical problem in patients suffering from cancer. Multidrug resistance is often mediated by overexpression of transmembrane xenobiotic transport molecules belonging to the superfamily of ATP-binding cassette (ABC)-transporters. Inhibition of ABC-transporters by low-molecular weight compounds in cancer patients has been extensively investigated in clinical trials, but the results have been disappointing. Thus, alternative experimental therapeutic strategies for overcoming multidrug resistance are under investigation. These include the application of RNA interference (RNAi) technology. Various RNAi strategies were applied to reverse multidrug resistance in different tumor models in vitro and in vivo. Results and conclusions of these RNAi studies as well as their potential impact for the development of potential RNAi therapeutics will be discussed.

Resistance to chemotherapy is associated with fibroblast growth factor receptor 4 up-regulation

PURPOSE

Establishment of antiapoptotic signaling pathways in tumor cells is a major cause for the failure of chemotherapy against cancer. To investigate the underlying mechanisms, we developed an experimental approach that is based on the genetic plasticity of cancer cells and the selection for cell survival on treatment with chemotherapeutic agents.

EXPERIMENTAL DESIGN

Gene expression changes of surviving cell clones were analyzed by macroarrays. Involvement of fibroblast growth factor receptor 4 (FGFR4) in antiapoptotic pathways was elucidated by apoptosis assays, small interfering RNA experiments, and an antagonistic antibody.

RESULTS

We show that FGFR4 gene expression is up-regulated in doxorubicin-treated, apoptosis-resistant cancer cell clones. Ectopic expression of FGFR4 in cancer cells led to reduced apoptosis sensitivity on treatment with doxorubicin or cyclophosphamide, whereas knockdown of endogenous FGFR4 expression in breast cancer cell lines had the opposite effect. FGFR4 overexpression resulted in Bcl-xl up-regulation at both mRNA and protein levels. Knockdown of FGFR4 expression by small interfering RNA caused a decrease in phospho-extracellular signal-regulated kinase 1/2 levels and reduced Bcl-xl expression. Moreover, an antagonistic FGFR4 antibody suppressed the resistance of cancer cells with endogenous FGFR4 expression against apoptosis-inducing chemotherapeutic agents.

CONCLUSION

Based on these findings, we propose an antiapoptotic signaling pathway that is initiated by FGFR4 and regulating the expression of Bcl-xl through the mitogen-activated protein kinase cascade. Our findings are exemplary for a novel strategy toward the elucidation of diverse signaling pathways that define antiapoptotic potential in cancer cells. These observations open new avenues toward the diagnosis of chemoresistant tumors and therapies targeting FGFR4-overexpressing cancers.

Identification of primary MAFB target genes in multiple myeloma

OBJECTIVE

In multiple myeloma (MM), seven primary recurrent translocations involving the immunoglobulin heavy chain locus have been identified. One of the partner loci maps to 20q12 and involves the MAFB gene resulting in its ectopic expression. We attempt here to identify MAFB target genes in MM.

MATERIALS AND METHODS

We used an inducible system to upregulate MAFB in MM cell lines not carrying the t(14;20). Microarray expression analysis was used to detect gene expression changes upon MAFB expression. These genes were further evaluated comparatively with gene expression profiles obtained from MM or plasma cell leukemia tumors carrying an activated MAFB gene. Functional implications of these upregulated genes were studied by testing their promoter activity in reporter assays. C-MAF was included comparatively as well.

RESULTS

The inducible cell lines identified a total of 284 modulated transcripts. After further evaluation using ex vivo data 14 common upregulated genes were found, common to the C-MAF pathway as well. The promoter activity of some of these secondary genes proved a functional relationship with MAFB. In connection with one of these secondary genes (NOTCH2), even tertiary upregulated genes were found. Functional studies indicated that inducible MAFB expression conferred antiapoptotic effects.

CONCLUSION

We identified 14 upregulated genes, and their downstream consequences in the combined MAFB/C-MAF pathway. Eleven of these genes are novel in the C-MAF pathway as well. These direct target genes may be responsible for the oncogenic transformation of MAF expressing myeloma cells.

Bcl-xL antisense oligonucleotide and cisplatin combination therapy extends survival in SCID mice with established mesothelioma xenografts

Bcl-xL functions as a dominant regulator of apoptotic cell death and is implicated in chemotherapeutic resistance of malignant pleural mesothelioma (MPM). Mesothelioma cell lines demonstrate increasing levels of Bcl-xL as resistant clones are selected in vitro. Moreover, upon introduction of antisense oligonucleotides specific to Bcl-xL mRNA, MPM cells are sensitized to chemotherapeutic agents. Here we describe the therapeutic effects of a novel combination therapy, Bcl-xL antisense oligonucleotide (ASO 15999) and cisplatin, on mesothelioma cell lines in vitro and in vivo; in addition, efficacy of ASO 15999 in decreasing tumor load as well as its effect on survival in an animal model. Finally, we initiated preliminary toxicity studies involved with intraperitoneal (IP) injections of ASO 15999 into mice. This novel combination, with doses of cisplatin four times below established IC(50) levels, significantly decreased viability of MPM cell lines after 48 hr. The growth of established mouse flank human tumor xenografts was reduced with intra-tumor administration of ASO 15999. Local spread and development of IP xenografts was reduced with treatments of ASO alone, and survival of mice afflicted with these xenografts was prolonged after administration of ASO alone and ASO 15999 + cisplatin combination therapy. These findings suggest that ASO 15999 sensitizes MPM cell lines to the toxic effects of cisplatin. ASO 15999 induced reduction of Bcl-xL is effective in slowing the progression of human mesothelioma cell lines both in vitro and in vivo. More notably, the combination of Bcl-xL ASO and cisplatin extends survival in an orthotopic tumor xenograft model.

Streptolysin-O reversible permeabilisation is an effective method to transfect siRNAs into myeloma cells

RNA interference (RNAi) has been shown to be a valuable tool to specifically target gene expression in a number of organisms becoming an indispensable weapon in the arsenal in functional genomics. In this study, we demonstrate that streptolysin-O (SLO) reversible permeabilisation is an efficient method to deliver small interfering RNAs (siRNAs) to hard-to-transfect human myeloma cell lines. We used published, pre-validated siRNAs for ERK2 and non-silencing siRNA control. We transfected siRNAs into human myeloma cell lines using SLO reversible permeabilisation method. Flow cytometry and western blot analysis were performed to assess the effect of SLO on transfection efficiency and ERK2 knockdown. These experiments demonstrate that SLO reversible permeabilisation method is an efficient and easy-to-use method to deliver siRNAs into human myeloma cell lines. Optimised SLO permeabilisation method showed to transfect >80% of JIM-3, H929, RPMI8226 and U266 cells, with minimal effect on cell viability (<10%) and cell cycle. Equally important, SLO permeabilisation induced a substantial knockdown of ERK2 at the protein level. These studies demonstrate that reversible SLO permeabilisation can successfully be applied to hard-to-transfect human myeloma cell lines to effectively silence genes.

The role of the bone marrow microenvironment in the pathophysiology of myeloma and its significance in the development of more effective therapies

Multiple myeloma (MM) is viewed as a prototypic disease state for the study of how neoplastic cells interact with their local bone marrow (BM) microenvironment. This interaction reflects not only the osteo-tropic clinical behavior of MM and the clinical impact of the lytic bone lesions caused by its tumor cells but also underlines the broadly accepted notion that nonneoplastic cells of the BM can attenuate the activity of cytotoxic chemotherapy and glucocorticoids. This article summarizes the recent progress in characterization, at the molecular and cellular levels, of how the BM milieu interacts with MM cells and modifies their biologic behavior.

Successful application of a direct detection slide-based sequential phenotype/genotype assay using archived bone marrow smears and paraffin embedded tissue sections

Identification of genetic abnormalities in pathological samples is critical for accurate diagnosis, risk stratification, detection of minimal residual disease, and assessment of response to therapy. Interphase fluorescence in situ hybridization analysis is the standard cytogenetic assay used by many laboratories to detect specific clonal karyotypic aberrations in formalin-fixed, paraffin-embedded tissue. However, direct correlation with immunophenotype or morphology in individual cells is rarely performed because the procedural steps are labor intensive and usually require extensive troubleshooting. In this study, we present a sequential fluorescence in situ hybridization-based technique that uses the identical archived bone marrow smears or paraffin-embedded tissue sections previously evaluated by a pathologist for morphological or immunohistochemical characteristics. This approach is relatively straightforward, using uncomplicated pretreatment and hybridization conditions and basic equipment attached to an automated image analyzer with image capture software to record the location of targeted cells for genotypic/phenotype correlation. Furthermore, the method has proved reliable and reproducible on test samples regardless of specimen age, tissue type, or referring institution.

Adenovirus-mediated small hairpin RNA targeting Bcl-XL as therapy for colon cancer

Bcl-XL, an anti-apoptotic protein of Bcl-2 family, is overexpressed in colon cancers. To determine Bcl-XL's potential feasibility as a therapeutic target, we constructed a recombinant adenovirus that expressed a U6 promoter-driven small hairpin RNA (shRNA) targeting Bcl-XL (Ad/Bcl-XL shRNA) and evaluated the vector's ability to induce RNA interference in vivo and alter apoptosis induction in colon cancer cells and tumours. Ad/Bcl-XL shRNA effectively knocked down Bcl-XL expression in colon cancer cells and decreased their viability. Treatment with Ad/Bcl-XL shRNA but not control vectors led to dramatically increased cleavage of cellular apoptosis-related enzymes caspase-9, caspase-3 and poly(ADP-ribose) polymerase. Ad/Bcl-XL shRNA also significantly suppressed the growth of subcutaneous tumours derived from DLD1 cells in a nude mouse model and did so without causing any obvious damage to normal tissues or normal human fibroblasts. Together, our results support the feasibility of using adenovirus-mediated RNA interference therapy targeting Bcl-XL against colon cancers and warrant further studies of its safety and efficacy.

The multiple myeloma associated MMSET gene contributes to cellular adhesion, clonogenic growth, and tumorigenicity

Multiple myeloma (MM) is an incurable hematologic malignancy characterized by recurrent chromosomal translocations. Patients with t(4;14)(p16;q32) are the worst prognostic subgroup in MM, although the basis for this poor prognosis is unknown. The t(4;14) is unusual in that it involves 2 potential target genes: fibroblast growth factor receptor 3 (FGFR3) and multiple myeloma SET domain (MMSET). MMSET is universally overexpressed in t(4;14) MM, whereas FGFR3 expression is lost in one-third of cases. Nonetheless, the role of MMSET in t(4;14) MM has remained unclear. Here we demonstrate a role for MMSET in t(4;14) MM cells. Down-regulation of MMSET expression in MM cell lines by RNA interference and by selective disruption of the translocated MMSET allele using gene targeting dramatically reduced colony formation in methylcellulose but had only modest effects in liquid culture. In addition, MMSET knockdown led to cell-cycle arrest of adherent MM cells and reduced the ability of MM cells to adhere to extracellular matrix. Finally, MMSET knockdown and knockout reduced tumor formation by MM xenografts. These results provide the first direct evidence that MMSET plays a significant role in t(4;14) MM and suggest that therapies targeting this gene could impact this particular subset of poor-prognosis patients.

Multiple myeloma: a prototypic disease model for the characterization and therapeutic targeting of interactions between tumor cells and their local microenvironment

The interaction between tumor cells and the local milieu where are homing has recently become the focus of extensive research in a broad range of malignancies. Among them, multiple myeloma (MM) is now recognized as a prototypical tumor model for the characterization of these interactions. This is due not only to the propensity of MM cells to target the skeleton and form lytic bone lesions, but because interactions of MM cells with normal cells of the bone milieu can attenuate the anti-tumor activity of conventional therapies, such as glucocorticoids and standard cytotoxic agents, including alkylators. Herein, we highlight the recent advances in our understanding of cellular and molecular mechanisms of interactions between MM cells and their milieu. Particular emphasis is placed on the interface between MM cells and normal cell compartments of the BM, especially bone marrow stromal cells (BMSCs), and on the development of a series of new classes of therapeutic agents, including the proteasome inhibitor bortezomib, thalidomide and lenalidomide, which counteract specific aspects of those MM-BM interactions. The significant clinical activity of these novel therapies has not only led to a new era in the therapeutic management of this disease, but also underscored the importance of comprehensively characterizing the role of the local microenvironment in the pathophysiology of human neoplasias.

Knockdown by shRNA identifies S249C mutant FGFR3 as a potential therapeutic target in bladder cancer

More than 60% of low-grade non-invasive papillary urothelial cell carcinomas contain activating point mutations of fibroblast growth factor receptor 3 (FGFR3). The phenotypic consequences of constitutive activation of FGFR3 in bladder cancer have not been elucidated and further studies are required to confirm the consequences of inhibiting receptor activity in urothelial cells. We measured FGFR3 transcript levels and demonstrated that transcript levels were significantly more abundant in low-stage and grade tumours. We identified a tumour cell line, 97-7, expressing the most common FGFR3 mutation (S249C) at similar FGFR3 transcript levels to low-stage and grade tumours. In these cells, S249C FGFR3 protein formed stable homodimers and was constitutively phosphorylated. We used retrovirus-mediated delivery of shRNA to knockdown S249C FGFR3. This induced cell flattening, decreased cell proliferation and reduced clonogenicity on plastic and in soft agar. However, no effects of knockdown of wild-type FGFR3 were observed in telomerase immortalized normal human urothelial cells, indicating possible dependence of the tumour cell line on mutant FGFR3. Re-expression of S249C FGFR3 in shRNA-expressing 97-7 cells resulted in a reversal of phenotypic changes, confirming the specificity of the shRNA. These results indicate that targeted inhibition of S249C FGFR3 may represent a useful therapeutic approach in superficial bladder cancer.

Ten years and counting: so what do we know about t(4;14)(p16;q32) multiple myeloma

Multiple myeloma is a genetically heterogenous disease with a wide variety of characterized genetic aberrations. Until recently, the impact of these aberrations on patient outcome was not known. However, in the last 5-10 years, several genetic markers have been linked to patient outcome. One of the strongest predictors of outcome identified to date is t(4;14)(p16;q32). Although this translocation is tightly linked to chromosome 13 deletions, another poor prognosis marker, it is becoming apparent that the translocation and not the deletion of 13 is the important factor. Unfortunately, despite the known association with outcome, an understanding of the mechanism(s) whereby the translocation contributes to developing and maintaining this aggressive form of myeloma remains elusive.

MUC1 oncoprotein functions in activation of fibroblast growth factor receptor signaling

Activation of the fibroblast growth factor (FGF) receptor 3 (FGFR3) has been linked to the development of human cancers by mechanisms that are not well understood. The MUC1 oncoprotein is aberrantly overexpressed by certain hematologic malignancies and most human carcinomas. The present studies show that MUC1 associates with FGFR3. Stimulation of cells with FGF1 increased the interaction between MUC1 and FGFR3. FGF1 stimulation also induced c-Src-dependent tyrosine phosphorylation of the MUC1 cytoplasmic domain on a YEKV motif. FGF1-induced tyrosine phosphorylation of MUC1 was associated with increased binding of MUC1 to beta-catenin and targeting of MUC1 and beta-catenin to the nucleus. FGF1 also induced binding of MUC1 to the heat shock protein 90 (HSP90) chaperone by a mechanism dependent on phosphorylation of the YEKV motif. Notably, beta-catenin and HSP90 compete for binding to the MUC1 cytoplasmic domain, indicating that MUC1 forms mutually exclusive complexes with these proteins. The results also show that inhibition of HSP90 with geldanamycin or 17-(allylamino)-17-demethoxygeldanamycin attenuates FGF1-induced binding of MUC1 to HSP90 and targeting of MUC1 to the mitochondrial outer membrane. These findings indicate that FGF1 induces phosphorylation of MUC1 on YEKV and thereby activates two distinct pathways: (a) nuclear localization of MUC1 and beta-catenin and (b) delivery of MUC1 to mitochondria by HSP90.

FGFR3 is a negative regulator of the expansion of pancreatic epithelial cells

Fibroblast growth factors (FGFs) and their receptors (FGFRs) are key signaling molecules for pancreas development. Although FGFR3 is a crucial developmental gene, acting as a negative regulator of bone formation, its participation remains unexplored in pancreatic organogenesis. We found that FGFR3 was expressed in the epithelia in both mouse embryonic and adult regenerating pancreata but was absent in normal adult islets. In FGFR3 knockout mice, we observed an increase in the proliferation of epithelial cells in neonates, leading to a marked increase in islet areas in adults. In vitro studies showed that FGF9 is a very potent ligand for FGFR3 and activates extracellular signal-related kinases (ERKs) in pancreatic cell lines. Moreover, FGFR3 blockade or FGFR3 deficiency led to increased proliferation of pancreatic epithelial cells in vivo. This was accompanied by an increase in the proportion of potential islet progenitor cells. Thus, our results show that FGFR3 signaling inhibits the expansion of the immature pancreatic epithelium. Consequently, this study suggests that FGFR3 participates in regulating pancreatic growth during the emergence of mature islet cells.

Mechanism of apoptosis induced by IFN-alpha in human myeloma cells: role of Jak1 and Bim and potentiation by rapamycin

Interferon-alpha (IFN-alpha) has been used for the last 20 years in the maintenance therapy of multiple myeloma (MM), though it is only effective in some patients. Congruent with this, IFN-alpha induces apoptosis in some MM cell lines. Understanding the mechanism of IFN-alpha-induced apoptosis could be useful in establishing criteria of eligibility for therapy. Here we show that IFN-alpha-induced apoptosis in the MM cell lines U266 and H929 was completely blocked by a specific inhibitor of Jak1. The mTOR inhibitor rapamycin mitigated apoptosis in U266 but potentiated it in H929 cells. IFN-alpha induced PS exposure, DeltaPsi(m) loss and pro-apoptotic conformational changes of Bak, but not of Bax, and was fully prevented by Mcl-1 overexpression in U266 cells. IFN-alpha treatment caused the release of cytochrome c from mitochondria to cytosol and consequently, a limited proteolytic processing of caspases. Apoptosis induced by IFN-alpha was only slightly prevented by caspase inhibitors. Levels of the BH3-only proteins PUMA and Bim increased during IFN-alpha treatment. Bim increase and apoptosis was prevented by transfection with the siRNA for Bim. PUMA-siRNA transfection reduced electroporation-induced apoptosis but had no effect on apoptosis triggered by IFN-alpha. The potentiating effect of rapamycin on apoptosis in H929 cells was associated to an increase in basal and IFN-alpha-induced Bim levels. Our results indicate that IFN-alpha causes apoptosis in myeloma cells through a moderate triggering of the mitochondrial route initiated by Bim and that mTOR inhibitors may be useful in IFN-alpha maintenance therapy of certain MM patients.

Toxicogenomics of A375 human malignant melanoma cells treated with arbutin

Although arbutin is a natural product and widely used as an ingredient in skin care products, its effect on the gene expression level of human skin with malignant melanoma cells is rarely reported. We aim to investigate the genotoxic effect of arbutin on the differential gene expression profiling in A375 human malignant melanoma cells through its effect on tumorigenesis and related side-effect. The DNA microarray analysis provided the differential gene expression pattern of arbutin-treated A375 cells with the significant changes of 324 differentially expressed genes, containing 88 up-regulated genes and 236 down-regulated genes. The gene ontology of differentially expressed genes was classified as belonging to cellular component, molecular function and biological process. In addition, four down-regulated genes of AKT1, CLECSF7, FGFR3, and LRP6 served as candidate genes and correlated to suppress the biological processes in the cell cycle of cancer progression and in the downstream signaling pathways of malignancy of melanocytic tumorigenesis.

MIP-1alpha (CCL3) is a downstream target of FGFR3 and RAS-MAPK signaling in multiple myeloma

Overexpression of fibroblast growth factor receptor 3 (FGFR3) is a hallmark of t(4;14) multiple myeloma (MM). To dissect the mechanism of FGFR3 oncogenesis in MM, we used 3 FGFR selective kinase inhibitors-CHIR258, PD173074, and SU5402-and FGFR3-specific siRNA to modulate FGFR3 activity. Conversely, the ligand FGF was used to stimulate FGFR3 function in human MM cells. The transcriptional response to FGFR3 modification was recorded, and gene expression changes common to all 5 modifiers were documented. Ten genes were commonly regulated. Macrophage inflammatory protein-1 alpha (MIP-1alpha) was the single most differentially altered gene. MIP-1 alpha promoter function, gene expression, and protein secretion were each down-regulated following inhibition of FGFR3 signaling. Down-regulation of MIP-1 alpha was not, however, observed following FGFR3 inhibition in MM cells with RAS mutations implicating RAS-MAPK in MIP-1 alpha regulation. As confirmation, inhibition of ERK1 also down-regulated MIP-1 alpha in FGFR3 inhibitor-resistant cells harboring RAS mutations. MIP-1 alpha is implicated in the survival and proliferation of MM cells and the pathogenesis of MM bone disease. Our observation is the first to directly link an initiating IgH translocation not only to MM-cell growth and survival but also to the disease-associated bone disease.

The role of the bone microenvironment in the pathophysiology and therapeutic management of multiple myeloma: interplay of growth factors, their receptors and stromal interactions

The close relationship between the biological behaviour of malignant cells and the local microenvironment where they reside is a feature of diverse neoplasias. Multiple myeloma (MM) is considered a main disease model for the study of such interactions and the mechanisms that can lead to bone-related clinical complications, as well as the role of these interactions in attenuating the activity of conventional anti-MM therapeutics, such as dexamethasone and cytotoxic chemotherapeutics. This review focuses on recent progress in the study of interactions of MM cells with their local microenvironment. Major emphasis is placed on how bone marrow stromal cells (BMSCs) and other normal constituents of the bone marrow milieu promote, through cell adhesion- and cytokine-mediated mechanisms, the ability of MM cells to resist conventional anti-MM therapies. The review also addresses ongoing research into these mechanisms, which has already provided several new molecular targets and corresponding therapeutic strategies, such as the proteasome inhibitor bortezomib and thalidomide derivatives (e.g. lenalidomide), for the management of myeloma.

The inhibitory anti-FGFR3 antibody, PRO-001, is cytotoxic to t(4;14) multiple myeloma cells

The association of fibroblast growth factor receptor 3 (FGFR3) expression with t(4;14) multiple myeloma (MM) and the demonstration of the transforming potential of this receptor tyrosine kinase (RTK) make it a particularly attractive target for drug development. We report here a novel and highly specific anti-FGFR3-neutralizing antibody (PRO-001). PRO-001 binds to FGFR3 expressed on transformed cells and inhibits FGFR3 autophosphorylation and downstream signaling. The antibody inhibited the growth of FGFR3-expressing FDCP cells (IC(50) of 0.5 microg/mL) but not that of cells expressing FGFR1 or FGFR2, and potently inhibited FGFR3-dependent solid tumor growth in a mouse xenograft model. Furthermore, PRO-001 inhibited the growth of the FGFR3-expressing, human myeloma cell line, UTMC2. Inhibition of viability was still observed when cells were cocultured with stroma or in the presence of IL-6 or IGF-1. PRO-001 did not inhibit constitutive activation of K650E, G384D, and Y373C FGFR3 in myeloma cell lines and failed to inhibit the growth of these cells. Most importantly, however, PRO-001 induced cytotoxic responses in primary t(4;14)(+) MM samples with an increase in apoptotic index of 20% to 80% as determined by annexin V staining. The data demonstrate that PRO-001 is a potent and specific inhibitor of FGFR3 and deserves further study for the treatment of FGFR3-expressing myeloma.

The ribonucleotide reductase subunit M2B subcellular localization and functional importance for DNA replication in physiological growth of KB cells

Ribonucleoside diphosphate reductase (EC 1.17.4.1) (RR) is a potential target for antineoplastic agents due to its crucial role in DNA replication and repair. The expression and activity of RR subunits are highly regulated to maintain an optimal dNTP pool, which is required to maintain genetic fidelity. The human RR small subunit M2B (p53R2) is thought to contribute to DNA repair in response to DNA damage. However, it is not clear whether M2B is involved in providing dNTPs for DNA replication under physiological growth conditions. Serum starvation synchronized studies showed that a rapid increase of M2B was associated with cyclin E, which is responsible for regulation of G(1)/S-phase transition. A living cell sorting study that used KB cells in normal growth, further confirmed that M2B increased to maximum levels at the G(1)/S-phase transition, and decreased with DNA synthesis. Confocal studies revealed that M2B redistributed from the cytoplasm to the nucleus earlier than hRRM2 in response to DNA replication. Nuclear accumulation of M2B is associated with dynamic changes in dNTP at early periods of serum addition. By using M2B-shRNA expression vectors, inhibition of M2B may result in growth retardation in KB cells. We conclude that M2B may translocate from the cytoplasm into the nucleus and allow dNTPs to initiate DNA synthesis in KB cells under physiological conditions. Thus, our findings suggested that M2B might play an important role for initiating DNA replication of KB cells in normal growth.

Genomics in multiple myeloma: biology and clinical implications

The advent of new techniques, such as interphase fluorescence in situ hybridization, and, more recently, global array-based gene expression profiling, has accelerated genomic research in myeloma. Distinct biologic subtypes, characterized by unique genetic abnormalities with differing clinical outcomes, have been identified. The identification of these primary genetic defects, and the deregulated oncogenes and pathways in myeloma, has allowed for the development of more targeted therapies. This has led to the discovery of an increased number of active agents in the treatment of myeloma. Genetics also have prognostic importance in myeloma. Recent studies have elucidated a genetic prognostic hierarchy, and have enabled improved definition of the prognostic significance of their interactions. The current challenges are to: improve the dissection of the genetic heterogeneity of the disease; better define progression events; improve the risk stratification of patients; more accurately select patients who will respond well to a particular treatment; and develop more rational combinations of treatment. Genomics will have an important role to play in all of these goals.

Targeting plasma cells improves detection of cytogenetic aberrations in multiple myeloma: phenotype/genotype fluorescence in situ hybridization

Standard fluorescence in situ hybridization (FISH) easily detects nonrandom karyotypic abnormalities in multiple myeloma (MM) at disease presentation, when tumor burden is high. In contrast, the detection of residual MM using the standard 200 unselected nonmitotic nuclei FISH approach correlates poorly with residual disease detected by morphology, flow cytometry, immunohistochemistry, or reverse-transcription polymerase chain reaction (RT-PCR). We have used sequential May-Grunwald Giemsa stain to identify plasma cell populations, followed by FISH analyses (target FISH or T-FISH) to detect immunoglobulin heavy-chain gene (IGH) rearrangements, 13q or 17p deletions, or hyperdiploidy. In this study, 115 samples were collected from 100 patients with MM regardless of treatment status. In this proof-of-principle prospective study, T-FISH detected MM in 52 samples (45%), a percentage similar to that obtained by pathology. Disease detection increased from 5.6% with standard FISH to 48% with T-FISH, and cell culture experiments showed that T-FISH consistently detected a clonal abnormality at dilutions of 10(-3). In five patients, T-FISH further identified myelodysplastic-associated karyotypic changes restricted to myeloid cells. Our observations suggest that T-FISH identifies cell lineage involvement of cytogenetic abnormalities, improves detection of low-level or residual MM, and may define the coexistence of hematologic karyotypic changes in individual patients.