CD271 promotes proliferation and migration in bladder cancer.

Bladder cancer is a urothelial cancer and effective therapeutic strategies for its advanced stages are limited. Here, we report that CD271, a neurotrophin receptor, promotes the proliferation and migration of bladder cancer cells. CD271 knockdown decreased proliferation in both adherent and spheroid cultures, and vice versa when CD271 was overexpressed in bladder cancer cell lines. CD271 depletion impaired tumorigenicity in vivo. Migration activity was reduced by CD271 knockdown and TAT-Pep5, a known CD271-Rho GDI-binding inhibitor. Apoptosis was induced by CD271 knockdown. Comprehensive gene expression analysis revealed alterations in E2F- and Myc-related pathways upon CD271 expression. In clinical cases, patients with high CD271 expression showed significantly shortened overall survival. In surgically resected specimens, pERK, a known player in proliferation signaling, colocalizes with CD271. These data indicate that CD271 is involved in bladder cancer malignancy by promoting cell proliferation and migration, resulting in poor prognosis.

FAXC interacts with ANXA2 and SRC in mitochondria and promotes tumorigenesis in cholangiocarcinoma.

Cholangiocarcinoma (CCA) is one of the most difficult malignancies to treat as the therapeutic options are limited. Although several driver genes have been identified, most remain unknown. In this study, we identified a failed axon connection homolog (FAXC), whose function is unknown in mammals, by analyzing serially passaged CCA xenograft models. Knockdown of FAXC reduced subcutaneous tumorigenicity in mice. FAXC was bound to annexin A2 (ANXA2) and c-SRC, which are tumor-promoting genes. The FAXC/ANXA2/c-SRC complex forms in the mitochondria. FAXC enhances SRC-dependent ANXA2 phosphorylation at tyrosine-24, and the C-terminal amino acid residues (351-375) of FAXC are required for ANXA2 phosphorylation. Transcriptome data from a xenografted CCA cell line revealed that FAXC correlated with epithelial-mesenchymal transition, hypoxia, and KRAS signaling genes. Collectively, these findings advance our understanding of CCA tumorigenesis and provide candidate therapeutic targets.

CD271 mRNA/hnRNPA2B1 complex promotes proliferation and stemness in oral and head and neck squamous cell carcinoma.

RNAs, such as noncoding RNA, microRNA, and recently mRNA, have been recognized as signal transduction molecules. CD271, also known as nerve growth factor receptor, has a critical role in cancer, although the precise mechanism is still unclear. Here, we show that CD271 mRNA, but not CD271 protein, facilitates spheroid cell proliferation. We established CD271-/- cells lacking both mRNA and protein of CD271, as well as CD271 protein knockout cells lacking only CD271 protein, from hypopharyngeal and oral squamous cell carcinoma lines. Sphere formation was reduced in CD271-/- cells but not in CD271 protein knockout cells. Mutated CD271 mRNA, which is not translated to a protein, promoted sphere formation. CD271 mRNA bound to hnRNPA2B1 protein at the 3'-UTR region, and the inhibition of this interaction reduced sphere formation. In surgical specimens, the CD271 mRNA/protein expression ratio was higher in the cancerous area than in the noncancerous area. These data suggest CD271 mRNA has dual functions, encompassing protein-coding and noncoding roles, with its noncoding RNA function being predominant in oral and head and neck squamous cell carcinoma.

BEX2 is poor prognostic factor and required for cancer stemness in gastric cancer.

Gastric cancer is the fifth most common malignancy worldwide. However, targeted therapy for advanced gastric cancer is still limited. Here, we report BEX2 (Brain expressed X-linked 2) as a poor prognostic factor in two gastric cancer cohorts. BEX2 expression was increased in spheroid cells, and its knockdown decreased aldefluor activity and cisplatin resistance. BEX2 was found to upregulate CHRNB2 (Cholinergic Receptor Nicotinic Beta 2 Subunit) expression, a cancer stemness-related gene, in a transcriptional manner, and the knockdown of which also decreases aldefluor activity. Collectively, these data are suggestive of the role of BEX2 in the malignant process of gastric cancer, and as a promising therapeutic target.

Evaluation of the meropenem dosage and administration schedule in patients with bacteremia initial therapy.

BACKGROUND: The standard meropenem (MEPM) regimen allowed by insurance in Japan is 0.5 g two or three times a day. Differences in dosages and administration schedules in Japan were evaluated. METHODS: Patients with bacteremia for whom MEPM was used as the initial treatment at our institution between 2016 and 2021 were included. We retrospectively investigated patients classified into two groups: those treated according to severe infections (high-dose groupand others (low-dose group). After propensity score matching, we compared the probability of achieving free drug blood levels above the minimum inhibitory concentration (MIC) in 24 h (%fT > MIC) and outcomes. RESULTS: The probability of 100% fT > MIC was significantly higher in the high-dose group (96.4% vs 74.5%, odds ratio [OR] = 0.3, 95% confidence interval [CI] = 0.2-0.4, P = < 0.001). Regarding outcomes, the 30-day mortality rate was significantly lower in the high-dose group (1.4% vs. 11.4%, OR = 8.0, 95% CI = 1.5-43.7, P = 0.019). CONCLUSIONS: To improve outcomes in patients with bacteremia treated with MEPM, support for appropriate antimicrobial use is necessary for compliance with the dosage and administration schedule according to severe infections in initial treatment.

Establishment of a monoclonal antibody against glycosylated CD271 specific for cancer cells in immunohistochemistry.

Various proteins are highly expressed in cancer (e.g., epidermal growth factor receptor); however, the majority are also expressed in normal cells, although they may differ in expression intensity. Recently, we reported that CD271 (nerve growth factor receptor), a glycosylated protein, increases malignant behavior of cancer, particularly stemlike phenotypes in squamous cell carcinoma (SCC). CD271 is expressed in SCC and in normal epithelial basal cells. Glycosylation alterations generally occur in cancer cells; therefore, we attempted to establish a cancer-specific anti-glycosylated CD271 antibody. We purified recombinant glycosylated CD271 protein, immunized mice with the protein, and screened hybridomas using an ELISA assay with cancer cell lines. We established a clone G4B1 against CD271 which is glycosylated with O-glycan and sialic acid. The G4B1 antibody reacted with the CD271 protein expressed in esophageal cancer, but not in normal esophageal basal cells. This specificity was confirmed in hypopharyngeal and cervical cancers. G4B1 antibody recognized the fetal esophageal epithelium and Barrett's esophagus, which possess stem cell-like characteristics. In conclusion, G4B1 antibody could be useful for precise identification of dysplasia and cancer cells in SCC.

Improving patient outcomes by promoting antimicrobial stewardship for patients with positive blood cultures: Investigation of patients with gram negative bacterium.

WHAT IS KNOWN AND OBJECTIVE: In this study, changes in patient outcomes were analysed to evaluate the effects of prospective audit and feedback (PAF), which was promoted under a new system of antimicrobial stewardship (AS), in patients with gram-negative rod (GNR)-positive blood cultures. METHODS: This study included patients with positive blood cultures treated at Kagawa University Hospital between 2019 and 2020. The effects of PAF, as promoted in 2020 and performed within a few days of treatment initiation, were examined in terms of patient prognosis and estimated cost of extra hospital stay associated with GNR infection. RESULTS AND DISCUSSION: As AS activities under the new system, proposals were made for targeted therapy based on susceptibility results and for the duration of antimicrobial therapy, escalation and dose increases, and imaging evaluation. Between 2019 and 2020, there was no difference in the rate of de-escalation in the form of switching to a narrower-spectrum intravenous antimicrobial, the rate of image inspection, but the rate of switching to oral therapy after receiving culture results increased from 19.7% to 31.3%, the rate of sensitivity-based treatment increased from 76.4% to 92.2%. Regarding patient outcomes, the 90-day mortality rate and the duration of hospital stay were similar between the groups. The rate of recurrent bloodstream infections decreased from 8.7% to 0.9%. WHAT IS NEW AND CONCLUSION: Most of the changes in the indicators related to patient outcomes analysed in this study suggest that the increased use of PAF in AS activities improved patient outcomes.

BEX2 is required for maintaining dormant cancer stem cell in hepatocellular carcinoma.

Cancer stem cells (CSCs) are responsible for therapy resistance and share several properties with normal stem cells. Here, we show that brain-expressed X-linked gene 2 (BEX2), which is essential for dormant CSCs in cholangiocarcinoma, is highly expressed in human hepatocellular carcinoma (HCC) lesions compared with the adjacent normal lesions and that in 41 HCC cases the BEX2high expression group is correlated with a poor prognosis. BEX2 localizes to Ki67-negative (nonproliferative) cancer cells in HCC tissues and is highly expressed in the dormant fraction of HCC cell lines. Knockdown of BEX2 attenuates CSC phenotypes, including sphere formation ability and aldefluor activity, and BEX2 overexpression enhances these phenotypes. Moreover, BEX2 knockdown increases cisplatin sensitivity, and BEX2 expression is induced by cisplatin treatment. Taken together, these data suggest that BEX2 induces dormant CSC properties and affects the prognosis of patients with HCC.

Discovery of a chemical compound that suppresses expression of BEX2, a dormant cancer stem cell-related protein.

Cancer stem cells (CSCs) are believed to cause cancer metastasis and recurrence. BEX2 (brain expressed X-linked gene 2) is a CSC-related gene that is expressed in dormant CSCs in cholangiocarcinoma and induces resistance against chemotherapy. The aim of the present study was to identify small compounds that have activity to inhibit BEX2 expression and result in the attenuation of CSC-related phenotypes. We screened 9600 small chemical compounds in high-throughput screening using cholangiocarcinoma cell line HuCCT1 expressing BEX2 protein fused with NanoLuc, and identified a compound, BMPP (1, 3-Benzenediol, [4-(4-methoxyphenyl)-1H-pyrazol-3-yl]). BMPP was found to exert decreasing effects on BEX2 protein expression and G0 phase population of the tumor cells, and increasing effects on ATP levels and chemotherapeutic sensitivity of the cells. These findings indicate that BMPP is a valuable chemical compound for reducing dormant CSC-related phenotypes. Thus, the identification of BMPP as a potential CSC suppressor provides scope for the development of novel therapeutic modalities for the treatment of cancers with BEX2 overexpressing CSCs.

Novel activating KRAS mutation candidates in lung adenocarcinoma.

Lung adenocarcinoma (LUAC) is a unique lung cancer subtype that is responsive to several therapeutic agents. The KRAS gene is the second most frequently mutated gene in LUAC and the majority of KRAS mutations are one of three classical activating mutations (G12, G13, and Q61). Recently, other types of "minor" KRAS mutation have been identified among LUAC patients and some may have similar transforming activities to those of the classical KRAS mutations. Here we describe minor KRAS mutations in LUAC patients, some of which (A66T, A66V, and G75E) may have tumor-forming activity in mouse embryonic fibroblasts in an allograft model. RNA-Seq analysis revealed that mouse embryonic fibroblasts overexpressing these three minor KRAS mutations have distinct expression profiles compared with overexpression of the wild type but similar expression profiles compared with overexpression of the classical KRAS mutants. Our results indicate that some of the minor KRAS mutations cause varying tumor formation activity and are important targets for developing anti-RAS agents as chemotherapeutic agents.

CD109 promotes the tumorigenic ability and metastatic motility of pancreatic ductal adenocarcinoma cells.

BACKGROUND: Accumulating evidence indicates that CD109, a glycosylphosphatidylinositol-anchored glycoprotein, is highly expressed in human epithelial carcinomas of multiple organs including the pancreas, but its functional role in carcinoma development has not yet been fully clarified. The aim of this study was to investigate the role of CD109 in the malignancy of pancreatic ductal adenocarcinoma (PDAC). METHODS: PDAC specimens of 145 cases were immunostained for CD109, and correlations between CD109 expression and clinicopathological conditions were analyzed. CD109 expression in PANC-1 cells, a PDAC-derived cell line, was decreased by siRNA or shRNA and its effect on the malignancy of PANC-1 cells was examined. RESULTS: Suppression of CD109 expression in PANC-1 cells resulted in reduction of in vitro cell motility and tumorigenicity in xenografts. Based on these results, we investigated the relationship between CD109 expression and metastasis of PDAC using tumor tissue specimens. Among 106 recurrent cases of 145 PDAC, there was a tendency for CD109-positive cases to be accompanied by distant metastasis. CONCLUSIONS: CD109 plays a critical role in the promotion of tumorigenic ability and cellular motility relating to metastasis of PDAC cells.

CD271 is a negative prognostic factor and essential for cell proliferation in lung squamous cell carcinoma.

Squamous cell carcinoma is a major type of cancer in the lung. While several therapeutic target molecules for lung adenocarcinoma have been identified, little is known about lung squamous cell carcinoma (LSCC). We recently reported that CD271 (p75 neurotrophin receptor) serves as a marker for tumor initiation and is a key regulator of cell proliferation in hypopharyngeal squamous cell carcinoma. In this study, we found that CD271 was also expressed in squamous cell carcinoma, but not in adenocarcinoma, of several tissues, including the lung, and the expression of CD271 was associated with a poor prognosis in LSCC. To examine CD271's role in LSCC, we established xenograft cell lines from LSCC patients. Within the sorted live LSCC cell population, the CD271high cells were primarily cycling through the G2/M phase, while the CD271low cells were mostly in the G0 phase. CD271 knockdown in the LSCC cells completely suppressed their proliferation and tumor-formation capability, and increased their cell-cycle arrest in the G0 phase. In the CD271-knockdown cells, ERK-phosphorylation was decreased, while no change was observed in the IκBα-phosphorylation, p65-phosphorylation, or Akt-phosphorylation. Treatment with the MEK inhibitor U0126 decreased the LSCC cells' proliferation capability. Microarray analysis revealed that CD271 knockdown attenuated the RAS-related pathways. The knockdown of TrkB, which forms a heterodimer with CD271 and accelerates its downstream signaling, partially inhibited the LSCC cell proliferation. These results indicated that LSCC exclusively depends on CD271 for cell proliferation, in part through ERK-signaling activation, and CD271 is a promising target for LSCC therapy.

Neuraminidases 3 and 4 regulate neuronal function by catabolizing brain gangliosides.

Gangliosides (sialylated glycolipids) play an essential role in the CNS by regulating recognition and signaling in neurons. Metabolic blocks in processing and catabolism of gangliosides result in the development of severe neurologic disorders, including gangliosidoses manifesting with neurodegeneration and neuroinflammation. We demonstrate that 2 mammalian enzymes, neuraminidases 3 and 4, play important roles in catabolic processing of brain gangliosides by cleaving terminal sialic acid residues in their glycan chains. In neuraminidase 3 and 4 double-knockout mice, GM3 ganglioside is stored in microglia, vascular pericytes, and neurons, causing micro- and astrogliosis, neuroinflammation, accumulation of lipofuscin bodies, and memory loss, whereas their cortical and hippocampal neurons have lower rate of neuritogenesis in vitro Double-knockout mice also have reduced levels of GM1 ganglioside and myelin in neuronal axons. Furthermore, neuraminidase 3 deficiency drastically increased storage of GM2 in the brain tissues of an asymptomatic mouse model of Tay-Sachs disease, a severe human gangliosidosis, indicating that this enzyme is responsible for the metabolic bypass of ß-hexosaminidase A deficiency. Together, our results provide the first in vivo evidence that neuraminidases 3 and 4 have important roles in CNS function by catabolizing gangliosides and preventing their storage in lipofuscin bodies.-Pan, X., De Britto Pará De Aragão, C., Velasco-Martin, J. P., Priestman, D. A., Wu, H. Y., Takahashi, K., Yamaguchi, K., Sturiale, L., Garozzo, D., Platt, F. M., Lamarche-Vane, N., Morales, C. R., Miyagi, T., Pshezhetsky, A. V. Neuraminidases 3 and 4 regulate neuronal function by catabolizing brain gangliosides.

Voriconazole concentration is inversely correlated with corticosteroid usage in immunocompromised patients.

BACKGROUND: Voriconazole (VRCZ) is a broad-spectrum antifungal agent that can be administered both orally and intravenously. A high level of intra- and interindividual variability in serum drug therapeutic concentrations has been reported. We analyzed the influence of corticosteroid use on serum VRCZ concentration by assessing the correlation between corticosteroid dose and VRCZ trough level. METHODS: Immunocompromised patients treated with VRCZ with or without corticosteroid use from June 2010 to March 2017 (6 years and 8 months) were reviewed in our institute. VRCZ and the corticosteroids were administered orally or intravenously. Corticosteroid treatment was considered as "concurrent" only if it was administered within 3 days before or after the initiation of VRCZ. All corticosteroids were converted to a prednisolone-based dosage according to their anti-inflammatory effect (relative glucocorticoid activity). VRCZ concentration was measured at the trough point on the day of steady state. RESULTS: A total of 85 samples were obtained from 38 patients. The medical records of 23 women and 15 men, with a median age of 61 years (range: 35-86), were reviewed. Twenty-one patients (55.3%, 21/38) received chemotherapy, and 28 (73.7%, 28/38) received corticosteroid therapy. The average and median daily doses of corticosteroids were 59.2 and 89.8 mg, respectively (range: 0.714-377). VRCZ concentration was inversely correlated with corticosteroid dose (r = -.26). The VRCZ concentration was significantly decreased in the corticosteroid user compared to nonuser (P = .013). We evaluated the association of VRCZ concentration and corticosteroid dose in 3 patients among our cohorts for whom more than 5 points of data were available. Intraindividual analysis revealed the trough level of VRCZ concentration decreased as the corticosteroid dose increased. The patients' underlying diseases were hematological diseases (n = 25) and immunological diseases (n = 13). Among accrual patients, no patients were undergoing stem cell transplantation, and no patients were treated with known confounders such as calcineurin inhibitors or phenytoin. CONCLUSIONS: VRCZ might be metabolized by an enzyme induced by corticosteroid treatment; therefore, intraindividual variation in VRCZ metabolism should be considered prior to concurrent treatment, especially for patients with hematological malignancies treated with corticosteroids.

Hypertension and Proteinuria as Predictive Factors of Effects of Bevacizumab on Advanced Breast Cancer in Japan.

Bevacizumab (BV), an inhibitor of vascular endothelial growth factor, is used in combination with paclitaxel (PTX) to treat advanced breast cancer. Hypertension and proteinuria are characteristic adverse events of BV therapy. We assessed the potential of these adverse events as predictors of BV treatment responses. Our results revealed that groups that developed hypertension and proteinuria early (by day 56) had a stronger antitumor response (Fisher's exact test p<0.05). However, no significant difference was observed in progression-free survival (the Kaplan-Meier method and Log-rank test). As a reference, age, the treatment line, subtypes, liver and renal function, diabetes mellitus and hyperlipidemia history, body mass index, influencing concomitant medicine, average relative dose intensity and hematotoxicity did not significantly differ between groups with or without hypertension and with or without proteinuria. These results indicate the potential of the development of hypertension and proteinuria as predictors of improved outcomes with PTX plus BV therapy in patients with breast cancer. However, since both adverse events may preclude the continuation of treatment, their earlier management may be required.

Crucial role of carbonic anhydrase IX in tumorigenicity of xenotransplanted adult T-cell leukemia-derived cells.

Carbonic anhydrase IX (CA9) is a membrane-associated carbonic anhydrase that regulates cellular pH, is upregulated in various solid tumors, and is considered to be a therapeutic target. Here, we describe the essential role of CA9 in the tumorigenicity of cells derived from human adult T-cell leukemia/lymphoma (ATL). We previously established the highly tumorigenic ST1-N6 subline from the ATL-derived ST1 cell line by serial xenotransplantation in NOG mice. In the present study, we first show that CA9 expression is strongly enhanced in ST1-N6 cells. We then sorted ST1 cells by high or low CA9 expression and established ST1-CA9high and ST1-CA9low sublines. ST1-CA9high cells, like ST1-N6 cells, were more strongly tumorigenic than ST1-CA9low or parental ST1 cells when injected into NOG mice. Knockdown of CA9 with shRNAs suppressed the ability of ST1-CA9high cells to initiate tumors, and the tumorigenicity of ST1 cells was significantly enhanced by introducing wild-type CA9 or a CA9 mutant with deletion of an intracytoplasmic domain. However, a CA9 with point mutations in the catalytic site did not increase the tumorigenicity of ST1 cells. Furthermore, we detected a small population of CA9+ CD25+ cells in lymph nodes of ATL patients. These findings suggest that CA9, and particularly its carbonic anhydrase activity, promotes the tumorigenicity of ATL-derived cells and may be involved in malignant development of lymphoma-type ATL.

Enhanced expression of the M2 isoform of pyruvate kinase is involved in gastric cancer development by regulating cancer-specific metabolism.

Recent studies have indicated that increased expression of the M2 isoform of pyruvate kinase (PKM2) is involved in glycolysis and tumor development. However, little is known about the role of PKM2 in gastric cancer (GC). Therefore, we examined the expression and function of PKM2 in human GC. We evaluated PKM1 and PKM2 expression by quantitative RT-PCR in gastric tissues from 10 patients who underwent gastric endoscopic submucosal dissection, 80 patients who underwent gastrectomy, and seven healthy volunteers, and analyzed the correlation with clinicopathological variables. To assess the function of PKM2, we generated PKM2-knockdown GC cells, and investigated the phenotypic changes. Furthermore, we examined the induction of PKM2 expression by cytotoxin-associated gene A (CagA), a pathogenic factor of Helicobacter pylori, using CagA-inducible GC cells. We found that PKM2 was predominantly expressed not only in GC lesions but also in the normal gastric regions of GC patients and in the gastric mucosa of healthy volunteers. The PKM2 expression was significantly higher in carcinoma compared to non-cancerous tissue and was associated with venous invasion. Knockdown of PKM2 in GC cells caused significant decreases in cellular proliferation, migration, anchorage-independent growth, and sphere formation in vitro, and in tumor growth and liver metastasis in vivo. The serine concentration-dependent cell proliferation was also inhibited by PKM2 silencing. Furthermore, we found that PKM2 expression was upregulated by CagA by way of the Erk pathway. These results suggested that enhanced PKM2 expression plays a pivotal role in the carcinogenesis and development of GC in part by regulating cancer-specific metabolism.

Sialidase NEU3 defines invasive potential of human glioblastoma cells by regulating calpain-mediated proteolysis of focal adhesion proteins.

BACKGROUND: Glioblastoma multiforme is one of the most malignant tumors of the human central nervous system characterized by high degree of invasiveness. Focusing on this invasive nature, we investigated whether ganglioside-specific sialidase NEU3 might be involved, because gangliosides are major components of brain tissues, and cell surface sialic acids, as target residues of sialidase catalysis, are thought to be closely related to cell invasion. METHODS: NEU3 mRNA levels of human glioblastoma specimens were evaluated by quantitative RT-PCR. Human glioblastoma cell lines, U251, A172, and T98G were used for cell invasion and migration by transwell and cell scratching assay. The molecules involved in the signaling cascade were investigated by western blot and immunofluorescent microscopy. RESULTS: NEU3 expression was down-regulated in human glioblastoma specimens. In the human glioblastoma cell lines, NEU3 overexpression reduced invasion and migration by promoting the assembly of focal adhesions through reduced calpain-dependent proteolysis, but NEU3 silencing resulted in accelerating cell invasion via disassembly of focal adhesions. In NEU3-silenced cells, elevation of calpain activity and GM3 accumulation were observed, as results of reduced sialidase hydrolysis, localization of calpain and GM3 at the cell lamellipodium being demonstrated by immunofluorescence microscopy. CONCLUSION: Sialidase NEU3 was found to exert a great influence on cell invasion in regulation of calpain activity and focal adhesion disassembly and consequent invasive potential of glioblastoma cells. GENERAL SIGNIFICANCE: This first demonstration of sialidase involvement in invasive potential of gliolastoma cells may point to NEU3 as an attractive treatment target of human gliomas.

Xenotransplantation elicits salient tumorigenicity of adult T-cell leukemia-derived cells via aberrant AKT activation.

The transplantation of human cancer cells into immunodeficient NOD/SCID/IL-2Rγc(null) (NOG) mice often causes highly malignant cell populations like cancer stem cells to emerge. Here, by serial transplantation in NOG mice, we established two highly tumorigenic adult T-cell leukemia-derived cell lines, ST1-N6 and TL-Om1-N8. When transplanted s.c., these cells formed tumors significantly earlier and from fewer initial cells than their parental lines ST1 and TL-Om1. We found that protein kinase B (AKT) signaling was upregulated in ST1-N6 and TL-Om1-N8 cells, and that this upregulation was due to the decreased expression of a negative regulator, INPP5D. Furthermore, the introduction of a constitutively active AKT mutant expression vector into ST1 cells augmented the tumorigenicity of the cells, whereas treatment with the AKT inhibitor MK-2206 attenuated the progression of tumors induced by ST1-N6 cells. Collectively, our results reveal that the AKT signaling pathway plays a critical role in the malignancy of adult T-cell leukemia-derived cells.