Preclinical activity of CPI-0610, a novel small-molecule bromodomain and extra-terminal protein inhibitor in the therapy of multiple myeloma.

Inhibition of the bromodomain and extra-terminal (BET) proteins is a promising therapeutic strategy for various hematologic cancers. Previous studies suggest that BET inhibitors constrain tumor cell proliferation and survival mainly through the suppression of MYC transcription and activity. However, suppression of the transcription of additional genes also contributes to the antitumor activity of BET inhibitors but is less well understood. Here we examined the therapeutic potential of CPI-0610, a potent BET inhibitor currently undergoing phase I clinical testing, in multiple myeloma (MM). CPI-0610 displays potent cytotoxicity against MM cell lines and patient-derived MM cells through G1 cell cycle arrest and caspase-dependent apoptosis. CPI-0610-mediated BET inhibition overcomes the protective effects conferred by cytokines and bone marrow stromal cells. We also confirmed the in vivo efficacy of CPI-0610 in a MM xenograft mouse model. Our study found IKZF1 and IRF4 to be among the primary targets of CPI-0610, along with MYC. Given that immunomodulatory drugs (IMiDs) stabilize cereblon and facilitate Ikaros degradation in MM cells, we combined it with CPI-0610. Combination studies of CPI-0610 with IMiDs show in vitro synergism, in part due to concomitant suppression of IKZF1, IRF4 and MYC, providing a rationale for clinical testing of this drug combination in MM patients.

A novel Bruton's tyrosine kinase inhibitor CC-292 in combination with the proteasome inhibitor carfilzomib impacts the bone microenvironment in a multiple myeloma model with resultant antimyeloma activity.

Bruton's tyrosine kinase (Btk) modulates B-cell development and activation and has an important role in antibody production. Interestingly, Btk may also affect human osteoclast (OC) function; however, the mechanism was unknown. Here we studied a potent and specific Btk inhibitor, CC-292, in multiple myeloma (MM). In this report, we demonstrate that, although CC-292 increased OC differentiation, it inhibited OC function via inhibition of c-Src, Pyk2 and cortactin, all involved in OC-sealing zone formation. As CC-292 did not show potent in vitro anti-MM activity, we next evaluated it in combination with the proteasome inhibitor, carfilzomib. We first studied the effect of carfilzomib on OC. Carfilzomib did not have an impact on OC-sealing zone formation but significantly inhibited OC differentiation. CC-292 combined with carfilzomib inhibited both sealing zone formation and OC differentiation, resulting in more profound inhibition of OC function than carfilzomib alone. Moreover, the combination treatment in an in vivo MM mouse model inhibited tumor burden compared with CC-292 alone; it also increased bone volume compared with carfilzomib alone. These results suggest that CC-292 combined with carfilzomib augments the inhibitory effects against OC within the bone microenvironment and has promising therapeutic potential for the treatment of MM and related bone disease.

Small-molecule multi-targeted kinase inhibitor RGB-286638 triggers P53-dependent and -independent anti-multiple myeloma activity through inhibition of transcriptional CDKs.

Small-molecule multi-targeted cyclin-dependent kinase (CDK) inhibitors (CDKIs) are of particular interest due to their potent antitumor activity independent of p53 gene alterations. P53 deletion is associated with a very poor prognosis in multiple myeloma (MM). In this regard, we tested the anti-MM activity of RGB-286638, an indenopyrazole-derived CDKI with Ki-nanomolar activity against transcriptional CDKs. We examined RGB-286638's mode-of-action in MM cell lines with wild-type (wt)-p53 and those expressing mutant p53. RGB-286638 treatment resulted in MM cytotoxicity in vitro associated with inhibition of MM tumor growth and prolonged survival in vivo. RGB-286638 displayed caspase-dependent apoptosis in both wt-p53 and mutant-p53 cells that was closely associated with the downregulation of RNA polymerase II phosphorylation and inhibition of transcription. RGB-286638 triggered p53 accumulation via nucleolar stress and loss of Mdm2, accompanied by induction of p53 DNA-binding activity. In addition, RGB-286638 mediated p53-independent activity, which was confirmed by cytotoxicity in p53-knockdown and p53-mutant cells. We also demonstrated downregulation of oncogenic miR-19, miR-92a-1 and miR-21. Our data provide the rationale for the development of transcriptional CDKIs as therapeutic agents, which activate p53 in competent cells, while circumventing p53 deficiency through alternative p53-independent cell death mechanisms in p53-mutant/deleted cells.

Lenalidomide in combination with an activin A-neutralizing antibody: preclinical rationale for a novel anti-myeloma strategy.

Given the prevalence of osteolytic bone disease in multiple myeloma (MM), novel therapies targeting bone microenvironment are essential. Previous studies have identified activin A to be of critical importance in MM-induced osteolysis. Lenalidomide is a known and approved treatment strategy for relapsed MM. Our findings demonstrate that lenalidomide acts directly on bone marrow stromal cells via an Akt-mediated increase in Jun N-terminal kinase-dependent signaling resulting in activin A secretion, with consequent inhibition of osteoblastogenesis. Here, we attempted to augment the antitumor benefits of lenalidomide while overcoming its effects on osteoblastogenesis by combining it with a neutralizing antibody to activin A. Increased activin A secretion induced by lenalidomide was abrogated by the addition of activin A-neutralizing antibody, which effectively restored osteoblast function and inhibited MM-induced osteolysis without negating the cytotoxic effects of lenalidomide on malignant cells. This provides the rationale for an ongoing clinical trial (NCT01562405) combining lenalidomide with an anti-activin A strategy.

Elevated immunoglobulin G antibodies to the proline-rich amino-terminal region of Epstein-Barr virus nuclear antigen-2 in sera from patients with systemic connective tissue diseases and from a subgroup of Sjögren's syndrome patients with pulmonary involvements.

Associations of Epstein-Barr virus (EBV) and autoimmune diseases have been hypothesized. We have analysed IgG antibodies to EBV nuclear antigen (EBNA)-2 in sera from Japanese patients with autoimmune systemic connective tissue diseases (CTD), exemplified by systemic lupus erythematosus (SLE), primary Sjogren's syndrome (SS), rheumatoid arthritis (RA), systemic sclerosis (SSc) and secondary SS (classical CTDs complicated with SS). An enzyme-linked immunosorbent assay (ELISA) which uses glutathione-S-transferase polypeptides fused to EBV nuclear antigen (EBNA)-2 and EBNA-1 was developed. Ratios of IgG antibody reactivity to whole IgG concentrations of sera were calculated to normalize EBNA-2 and EBNA-1 antibody levels to the hypergammaglobulinaemia that occurs in CTD. The ELISA optical density OD(450) readings of IgG antibodies to both the amino-terminal aa 1-116 of EBNA-2 and carboxyl-terminal aa 451-641 of EBNA-1 were elevated significantly in patients with SLE, primary SS, RA, SSc and secondary SS when compared to EBNA-1. The OD readings were divided by serum IgG concentrations to normalize for the hypergammaglobulinaemia. The specific levels of IgG antibodies to the amino-terminal region of EBNA-2 were elevated in patients with SLE, primary SS or RA, as well as those with secondary SS complicated with SLE or RA. The EBNA-2 amino-terminal region contains a polyproline tract and a proline-rich sequence and has considerable amino acid sequence homology with many cellular proline-rich proteins. High ratios of EBNA-2 aa 1-116 to EBNA-1 aa 451-641 IgG antibody levels which probably suggest reactivation of EBV latent infection were associated significantly with pulmonary involvement in SS patients. These results are consistent with the hypothesis that the sequence similarity between the amino-terminal region of EBNA-2 and proline-rich cellular proteins is associated with pathogenesis in a subpopulation of CTD patients, possibly by the molecular mimicry-epitope shift mechanism.

A monoclonal antibody that recognizes Epstein-Barr virus nuclear antigen 2 (EBNA 2) amino acids 1-58 does not react with EBNA 2 in native form, consistent with the self-association of EBNA 2 through the amino-terminus.

We have generated a mouse IgG1 monoclonal antibody (mAb) that recognizes amino acids 1-58 of Epstein-Barr virus (EBV) nuclear antigen 2 (EBNA 2) of type 1 EBV strain B95-8. mAb Y101 also reacted with EBNA 2 of EBV type 2 strains MISP and Jijoye in immunoblots, whereas Jijoye EBNA 2 was not detected by the widely used mAb PE2. mAb Y101, in contrast to mAb PE2, reacted with faster migrated, hypophosphorylated proteins of type 1 EBNA 2 as intensely as slower migrated, hyperphosphorylated ones. mAb Y101 did not react in fixed-cell immunostaining or cell extract immunoprecipitation. The results implicate that the amino-terminal epitope is not exposed in a native form, consistent with the previously reported idea of self-association of EBNA 2 through the amino-terminus. mAb Y101 is the first mAb to the EBNA 2 amino-terminus and will be useful for further analyses of the structure and function of EBNA 2.

Epstein-Barr virus nuclear antigen-1 colocalizes with lamin B1 in the nucleoplasm and along the nuclear rim.

Epstein-Barr virus nuclear antigen 1 (EBNA-1) is essential for the maintenance of latent EBV plasmids, and is also a transcriptional regulator. Nuclear lamins, components of the nuclear lamina, have also been found in the nucleoplasm. We report here that EBNA-1 coincided with lamin B1 in the nucleoplasm and around the nuclear rim during S-phase by confocal microscopy of cells transfected with EBNA-1 in the absence of EBV plasmids. Lamin B1, which is rarely detected in nuclear soluble fractions, was detected in chromatin and nuclear matrix fractions of the EBNA-1-expressing cells. These observations suggest that EBNA-1 colocalizes with lamin B1 in the subnuclear sites.

Interaction between hydroxyapatite and proteins by liquid chromatography using simulated body fluids as eluents.

Hydroxyapatite (HAp) column chromatography for proteins using simulated body fluids (SBFs) as eluents was investigated in order to mimic the flow environment of human body fluid on the HAp surface in vivo. Acidic plasma proteins such as albumin, gamma-globulin, and fibrinogen having carboxyl groups with a negative charge were suggested to adsorb at positively charged sites (Ca sites) on the HAp surface. These acidic plasma proteins were not even eluted at higher inorganic ion molarities of human body fluid. Whereas basic proteins such as papin, cytochrome c, and lysozyme were easily eluted at lower inorganic ion molarities of human body fluid due to existing Na(+), Ca(2 +), Mg(2 +) and (CH(2)OH)(3)CNH(4)(+) ions in the eluents. The elution behavior of proteins using SBF in the presence or absence of glucose did not change. From these considerations, bone matrix proteins as acidic and neutral proteins would be considered an advantageous condition in order to adsorb on HAp in vivo.

Cortical mapping of gait in humans: a near-infrared spectroscopic topography study.

While we have a fair understanding of how and where forelimb-hand manipulative movements are controlled by the neocortex, due to functional imaging studies, we know little about the control of bipedal movements such as walking because of technical difficulties. We succeeded in visualizing cortical activation patterns of human gait by measuring relative changes in local hemoglobin oxygenation using a recently developed near-infrared spectroscopic (NIRS) topography technique. Walking activities were bilaterally associated with increased levels of oxygenated and total hemoglobin in the medial primary sensorimotor cortices and the supplementary motor areas. Alternating foot movements activated similar but less broad regions. Gait imagery increased activities caudally located in the supplementary motor areas. These findings provide new insight into cortical control of human locomotion. NIRS topography might be also useful for evaluating cerebral activation patterns during pathological gait and rehabilitative intervention.

Establishment and characterization of a new HPV-negative squamous cell carcinoma cell line (Yumoto) from the human uterine cervix.

A new cell line, Yumoto, derived from a squamous cell carcinoma of the uterine cervix, was established from serially transplanted tumor tissues in nude mice. Monolayer cultured cells were polygonal and formed pavement-like sheet. They showed a piling-up tendency and were devoid of contact inhibition. Electron micrographs demonstrated the presence of microvilli on the cell surface, abundant tonofilaments in the cytoplasm, and the connection with desmosomes. These electron micrographical characteristics of Yumoto cells were consistent with those of squamous cell origin. Yumoto cells were highly tumorigenic in BALB/c nude mice and produced a well-differentiated squamous cell carcinoma of keratinizing type which closely resembled to the original tumor tissues in nude mice. The presence of HPV DNA was examined using polymerase chain reaction and Southern blot analysis, but no known types of HPV DNA could be detected. Exons 2 through 11 of the p53 gene were analyzed by direct DNA sequencing, revealing a homozygous mutation at codon 281 in exon 8, GAC to CAC (Asp-->His). Furthermore, physical p53-gene deletion was demonstrated by dual-color fluorescence in situ hybridization. This cell line is useful for studying the carcinogenesis of cervical carcinoma and for investigating the biological characteristics of a HPV-negative and mutated p53 squamous cell carcinoma of the uterine cervix.

High susceptibility of human cancer xenografts with higher levels of cytidine deaminase to a 2'-deoxycytidine antimetabolite, 2'-deoxy-2'-methylidenecytidine.

2'-Deoxy-2'-methylidenecytidine (DMDC) is a new 2'-deoxycytidine (dCyd) antimetabolite. The present study compared its antitumor activities with those of 2',2'-difluorodeoxy-cytidine (gemcitabine) in 15 human cancer xenograft models. DMDC was highly resistant to cytidine (Cyd) deaminase, which deaminates the dCyd analogues to inactive molecules, whereas gemcitabine was susceptible to the enzyme. Given p.o., high antitumor activity with therapeutic index of more than 10 was found with DMDC in 7 of 15 xenograft lines. In contrast, gemcitabine given i.v. or p.o. was highly effective in 4 of 15 human cancer xenograft lines. The antitumor spectrum of these compounds was quite different, although their molecular targets are reported to be similar. DMDC was highly effective in tumors with higher levels of Cyd deaminase activity, whereas it showed only slight activity in those with lower levels of Cyd deaminase. In contrast, gemcitabine appeared to be less effective in tumors with high levels of Cyd deaminase. We also investigated the correlation with the susceptibility to the two dCyd antimetabolites and dCyd kinase activity in tumors, but none was observed. Cyd deaminase activity was found to be high in tumor tissues from various types of human cancers thus far tested, such as colorectal cancer and non-small cell lung cancer. Such cancer types or individual patients who have tumors with high activity of the enzyme may be targets for DMDC therapy.

The antiproliferative activity of DMDC is modulated by inhibition of cytidine deaminase.

We showed that the efficacy of the new 2'-deoxycytidine (2'-dCyd) analogue antimetabolite 2'-deoxy-2'-methylidenecytidine (DMDC) correlates well with tumor levels of cytidine (Cyd) deaminase in human cancer xenograft models. DMDC was highly effective in tumors with higher levels of Cyd deaminase, whereas lower levels yielded only slight activity. In contrast, gemcitabine (2',2'-difluorodeoxycytidine), which has action mechanisms similar to those of DMDC, is only slightly active in tumors with higher levels of the enzyme. In the present study, we investigated the roles of Cyd deaminase in the antitumor activity of the two 2'-dCyd antimetabolites in 13 human cancer cell lines. Tetrahydrouridine, an inhibitor of Cyd deaminase, reduced the antiproliferative activity of DMDC (P = 0.0015). Furthermore, tumor cells transfected with the gene of human Cyd deaminase become more susceptible to DMDC both in vitro and in vivo. These results indicate that Cyd deaminase is indeed essential for the activity of DMDC. In contrast, the antiproliferative activity of gemcitabine was increased to some extent by tetrahydrouridine (P = 0.0277), particularly in tumor cell lines with higher levels of Cyd deaminase. This suggests that higher levels of Cyd deaminase may inactivate gemcitabine. Among nucleosides and deoxynucleosides tested, only dCyd, a natural substrate of both Cyd deaminase and dCyd kinase, suppressed the antiproliferative activity of DMDC by up to 150-fold. Because the Vmax/Km of DMDC for dCyd kinase was 8-fold lower than that for dCyd, the activation of DMDC to DMDC monophosphate (DMDCMP) by dCyd kinase might be competitively inhibited by dCyd. In addition, the dCyd concentrations in human cancer xenografts were inversely correlated with levels of Cyd deaminase activity. It is therefore suggested that higher levels of Cyd deaminase reduce the intrinsic cellular concentrations of dCyd in tumors, resulting in efficient activation of DMDC to DMDCMP by dCyd kinase. These results indicate that the efficacy of DMDC may be predicted by measuring the activity of Cyd deaminase in tumor tissues before treatment starts and that DMDC may be exploited in a new treatment modality: tumor enzyme-driven cancer chemotherapy.

Near-infrared estimation of O2 supply and consumption in forearm muscles working at varying intensity.

We estimated a blood flow index, O2 supply index, and O2 consumption index from near-infrared (NIR) signals during venous occlusion imposed at rest and immediately after handgrip exercise with loads equal to 5, 10, 15, 20, 25, and 30% of the maximum voluntary contraction. We also estimated forearm blood flow (BFfa) by strain-gauge plethysmography and forearm O2 consumption (VO2fa) by the invasive method. There was a significant correlation between the rate of increase in total hemoglobin during venous occlusion obtained from NIR signals and BFfa in each subject (r = 0.853 approximately 0.981, P < 0.001). There was also a significant correlation (r = 0.854 approximately 0.944, P < 0.001) between the O2 consumption index estimated from NIR signals and VO2fa. The mean values for O2 supply index in five subjects increased with exercise intensity, while the O2 consumption index showed no further increase about 25% of maximum voluntary contraction. We found significant positive correlations between the O2 supply index and BFfa (r = 0.986, P < 0.001) and the O2 consumption index and VO2fa (r = 0.976, P < 0.001) during exercise at 5-30% of maximum voluntary contraction. These results demonstrate that analysis of NIR signals during venous occlusion provides an advantageous method of estimation of O2 supply and consumption in working muscles during exercise of varying intensity.

Optical tomography by the temporally extrapolated absorbance method.

The concept of the temporally extrapolated absorbance method (TEAM) for optical tomography of turbid media has been verified by fundamental experiments and image reconstruction. The TEAM uses the time-resolved spectroscopic data of the reference and object to provide projection data that are processed by conventional backprojection. Optical tomography images of a phantom consisting of axisymmetric double cylinders were experimentally obtained with the TEAM and time-gating and continuous-wave (CW) methods. The reconstructed TEAM images are compared with those obtained with the time-gating and CW methods and are found to have better spatial resolution.

Involvement of human interleukin 6 in experimental cachexia induced by a human uterine cervical carcinoma xenograft.

A human tumor xenograft model for cancer cachexia was established by growing a uterine cervical carcinoma, Yumoto, in nude mice. The tumor transplanted into the mice induced severe body weight loss (30% of body weight) when the tumor weight was only 1 g. In addition, other indicators for cachexia, such as adipose tissue and muscle wasting and hypoglycemia, were also observed in the tumor-bearing mice, suggesting that this is a proper model for experimental cachexia induced by a human tumor. We then examined the association of this model with various cytokines, such as tumor necrosis factor alpha, interleukin (IL)-1alpha, IL-1beta, IFN-gamma, IL-6, and leukemia inhibitory factor, and identified human IL-6, which was produced by the tumor cells, as a mediator of cachexia. A neutralizing antibody against hIL-6 administered to the mice after the development of cachexia symptoms significantly improved body weight loss, adipose tissue wasting, hypoglycemia, acute phase reaction, and leukocytosis, although it did not suppress the tumor growth. These results demonstrate that the hIL-6 produced by the tumor cells is an essential mediator of the cachexia induction in this model.

[Antitumor activity of various cytostatics in mice bearing murine advanced tumors].

Antitumor activities of cytostatics such as 5-FU, 5'-DFUR, cyclophosphamide (CPA), ACNU, CDDP, mitomycin C (MMC) and doxorubicin (DXR) were compared in mice bearing four different murine-tumor models at two different stages of the tumor growth. All cytostatics tested suppressed the tumor growth in most of the four tumors, colon 26 carcinoma, UV 2237 fibrosarcoma, Ehrlich carcinoma and Meth A fibrosarcoma, when the tumor sizes were small (early transplant). When given to mice bearing advanced tumors, 5-FU, CDDP, MMC and DXR were effective only at the higher doses, showing toxicity. In contrast, 5'-DFUR was equally effective against both most of early and advanced tumors except for advanced Meth A against which higher doses of 5'-DFUR were needed. CPA and ACNU equally suppressed the growth of early transplant and advanced tumors of Meth A, although higher doses were needed against advanced tumors of three others. 5'-DFUR was also effective against tumor cachexia (colon 26) and spontaneous metastasis (Lewis lung carcinoma), which are characteristically observed in mice bearing advanced tumors. CPA also showed an anticachectic activity, though the activity was weaker than that of 5'-DFUR. These results suggest that 5'-DFUR and CPA can be used in both intensive and adjuvant chemotherapies.

Cytokines induce uridine phosphorylase in mouse colon 26 carcinoma cells and make the cells more susceptible to 5'-deoxy-5-fluorouridine.

The antiproliferative activity of 5-fluorouracil (5-FUra) and 5'-deoxy-5-fluorouridine (5'-dFUrd), used in combination with typical cytokines and growth factors, was investigated in mouse colon 26 carcinoma cells. Tumor necrosis factor alpha (TNF alpha), interleukin-1 alpha (IL-1 alpha), and interferon gamma (IFN gamma) at low doses showing < 50% inhibition of cell growth by themselves enhanced the susceptibility of the cells to the activity of 5'-dFUrd. In particular, a mixture of these cytokines greatly enhanced the activity of 5'-dFUrd and 5-FUra by up to 12.4- and 2.7-fold, respectively, whereas the activity of other cytostatics was only slightly changed (< 1.5-fold). Basic fibroblast growth factor also increased the susceptibility, but only to 5'-dFUrd. This preferential enhancement of the activity of 5'-dFUrd would be due to induction by the cytokines of uridine phosphorylase (Urd Pase), by which 5'-dFUrd is converted to 5-FUra. TNF alpha, IL-1 alpha, IFN gamma, and a mixture of these factors increased the enzyme activity by up to 3.7-fold in colon 26 cells. Consequently, the anabolism of 5'-dFUrd to fluoronucleotides and the incorporation of 5-FUra into RNA in colon 26 cells were increased by TNF alpha treatment. In addition, the increase by the cytokine mixture in the susceptibility to 5'-dFUrd was abolished by an inhibitor of Urd Pase, 2,2'-anhydro-5-ethyluridine. These results indicate that induction of Urd Pase activity by cytokines is a critical event that increases the susceptibility to 5'-dFUrd.

Cytokines induce thymidine phosphorylase expression in tumor cells and make them more susceptible to 5'-deoxy-5-fluorouridine.

The present study shows that various cytokines such as tumor necrosis factor (TNF alpha), interleukin-1 alpha (IL-1 alpha), and interferon-gamma (IFN gamma) make tumor cells much more susceptible to the cytostatic 5'-deoxy-5-fluorouridine (5'-dFUrd) than to 5-fluorouracil (5-FUra) and other cytostatics. These three cytokines increased the susceptibility of human cancer cell lines (COLO201, MKN45 and WiDr) but did not affect that of normal fibroblast WI38 cells. The cytokine mixture induced a 50-fold increase in the susceptibility of COLO201 to 5'-dFUrd, whereas a 12-fold increase and a less than 5-fold enhancement in the susceptibility to 5-FUra and other cytostatics, respectively, were observed. The increased susceptibility would be a result of the induction of thymidine phosphorylase (TdR Pase), which is the essential enzyme for the conversion of 5'-dFUrd to 5-FUra. The cytokine mixture increased TdR Pase activity by up to 47 times and greatly induced its mRNA expression in the cancer cell lines. These results suggest that the therapeutic benefit of 5'-dFUrd would be improved by its use in combination with the cytokines.