Ethinylestradiol is beneficial for postmenopausal patients with heavily pre-treated metastatic breast cancer after prior aromatase inhibitor treatment: a prospective study.

BACKGROUND: Oestrogens usually stimulate the progression of oestrogen receptor (ER)-positive breast cancer. Paradoxically, high-dose oestrogens suppress the growth of these tumours in certain circumstances. METHODS: We prospectively examined the efficacy and safety of ethinylestradiol treatment (3 mg per day oral) in postmenopausal patients with advanced or recurrent ER-positive breast cancer who had previously received endocrine therapies, especially those with resistance to aromatase inhibitors. RESULTS: Eighteen patients were enrolled with the median age of 63 years and the mean observation time of 9.2 months. Three cases withdrew within 1 week due to oestrogen flare reactions with nausea, fatigue and muscle-skeletal pain. The response rate was 50% (9 out of 18), and the clinical benefit rate was 56% (10 out of 18). The stable disease (<6 months) was 17% (3 out of 18) and another 2 cases were judged as progressive disease. Time-to-treatment failure including 2 on treatment was a median of 5.6 months (range 0.1 to 14.5(+)). Although vaginal bleeding or endometrial thickening was observed in patients receiving long-term treatment, there were no severe adverse events, such as deep venous thrombosis or other malignancies. CONCLUSION: Although the mechanism of this treatment has not been fully understood, our data may contribute to change the common view of late-stage endocrine therapy.

Aberrant activation of the mTOR pathway and anti-tumour effect of everolimus on oesophageal squamous cell carcinoma.

BACKGROUND: The mammalian target of rapamycin (mTOR) protein is important for cellular growth and homeostasis. The presence and prognostic significance of inappropriate mTOR activation have been reported for several cancers. Mammalian target of rapamycin inhibitors, such as everolimus (RAD001), are in development and show promise as anti-cancer drugs; however, the therapeutic effect of everolimus on oesophageal squamous cell carcinoma (OSCC) remains unknown. METHODS: Phosphorylation of mTOR (p-mTOR) was evaluated in 167 resected OSCC tumours and 5 OSCC cell lines. The effects of everolimus on the OSCC cell lines TE4 and TE11 in vitro and alone or in combination with cisplatin on tumour growth in vivo were evaluated. RESULTS: Mammalian target of rapamycin phosphorylation was detected in 116 tumours (69.5%) and all the 5 OSCC cell lines. Everolimus suppressed p-mTOR downstream pathways, inhibited proliferation and invasion, and induced apoptosis in both TE4 and TE11 cells. In a mouse xenograft model established with TE4 and TE11 cells, everolimus alone or in combination with cisplatin inhibited tumour growth. CONCLUSION: The mTOR pathway was aberrantly activated in most OSCC tumours. Everolimus had a therapeutic effect both as a single agent and in combination with cisplatin. Everolimus could be a useful anti-cancer drug for patients with OSCC.

Differential expression of two basement membrane collagen genes, COL4A6 and COL4A5, demonstrated by immunofluorescence staining using peptide-specific monoclonal antibodies.

Genes for the human alpha 5(IV) and alpha 6(IV) collagen chains have a unique arrangement in that they are colocalized on chromosome Xq22 in a head-to-head fashion and appear to share a common bidirectional promoter. In addition we reported a novel observation that the COL4A6 gene is transcribed from two alternative promoters in a tissue-specific manner (Sugimoto, M., T. Oohashi, and Y. Ninomiya. 1994. Proc. Natl. Acad. Sci. USA. 91:11679-11683). To know whether the translation products of both genes are colocalized in various tissues, we raised alpha 5(IV) and alpha 6(IV) chain-specific rat monoclonal antibodies against synthetic peptides reflecting sequences near the carboxy terminus of each noncollagenous (NC)1 domain. By Western blotting alpha 6(IV) chain-specific antibody recognized 27-kD monomers and associated dimers of the human type IV collagen NC1 domain, which is the first demonstration of the presence in tissues of the alpha 6(IV) polypeptide as predicted from its cDNA sequence. Immunofluorescence studies using anti-alpha 6(IV) antibody demonstrated that in human adult kidney the alpha 6(IV) chain was never detected in the glomerular basement membrane, whereas the basement membranes of the Bowman's capsules and distal tubules were positive. The staining pattern of the glomerular basement membrane was quite different from that obtained with the anti-alpha 5(IV) peptide antibody. The alpha 5(IV) and alpha 6(IV) chains were colocalized in the basement membrane in the skin, smooth muscle cells, and adipocytes; however, little if any reaction was seen in basement membranes of cardiac muscles and hepatic sinusoidal endothelial cells. Thus, both genes are expressed in a tissue-specific manner, perhaps due to the unique function of the bidirectional promoter for both genes, which is presumably different from that for COL4A1 and COL4A2.

Immunocytochemical analyses and targeted gene disruption of GTPBP1.

We previously identified a gene encoding a putative GTPase, GTPBP1, which is structurally related to elongation factor 1alpha, a key component of protein biosynthesis machinery. The primary structure of GTPBP1 is highly conserved between human and mouse (97% identical at the amino acid level). Expression of this gene is enhanced by gamma interferon in a monocytic cell line, THP-1. Although counterparts of this molecule in Caenorhabditis elegans and Ascaris suum have also been identified, the function of this molecule remains to be clarified. In the present study, our immunohistochemical analyses on mouse tissues revealed that GTPBP1 is expressed in some neurons and smooth muscle cells of various organs as well as macrophages. Immunofluorescence analyses revealed that GTPBP1 is localized exclusively in cytoplasm and shows a diffuse granular network forming a gradient from the nucleus to the periphery of the cells in smooth muscle cell lines and macrophages. To investigate the physiological role of GTPBP1, we used targeted gene disruption in embryonic stem cells to generate GTPBP1-deficient mice. The mutant mice were born at the expected Mendelian frequency, developed normally, and were fertile. No manifest anatomical or behavioral abnormality was observed in the mutant mice. Functions of macrophages, including chemotaxis, phagocytosis, and nitric oxide production, in mutant mice were equivalent to those seen in wild-type mice. No significant difference was observed in the immune response to protein antigen between mutant mice and wild-type mice, suggesting normal function of antigen-presenting cells of the mutant mice. The absence of an eminent phenotype in GTPBP1-deficient mice may be due to functional compensation by GTPBP2, a molecule we recently identified which is similar to GTPBP1 in structure and tissue distribution.

Eosinophil chemotactic factors from granuloma of Kimura's disease, with special reference to T lymphocyte-derived factors.

The granuloma of patients with Kimura's disease characterized by tissue and peripheral blood eosinophilia was reviewed with respect to eosinophil infiltration. An infiltrate of inflammatory cells with histiocytes and a sprinkling of eosinophils were observed in the fibrous stroma surrounding the newly formed vessels. Mast cells were rarely seen in the areas where eosinophils were grouped together. Three different eosinophil chemotactic factors (ECF) were isolated from the granulomas of Kimura's disease. They were termed as low molecular weight (LMW), intermediate molecular weight (IMW), and high molecular weight (HMW)-ECF according to the profile on gel filtration (LMW-ECF, about 500; IMW-ECF, about 12,500; HMW-ECF, 45,000-70,000). In terms of their activity when extracted from the granuloma, LMW-ECF and HMW-ECF seemed to be major natural mediators for the tissue eosinophilia, whereas IMW-ECF was a minor one. In an in vitro system, it was shown that granuloma lymphoid cells produce spontaneously at least two ECF having similar properties to LMW- and HMW-ECF, respectively. By analysis with monoclonal antibodies, granuloma T cells, probably OKT4-positive cells, were shown to be responsible for the production of those two ECF. It was thus suggested that prolonged synthesis of LMW- and HMW-ECF by OKT4-positive T cells plays a crucial role in the local eosinophilia of Kimura's disease.

Spatiotemporal pattern of the mouse chondromodulin-I gene expression and its regulatory role in vascular invasion into cartilage during endochondral bone formation.

During endochondral bone formation, vascular invasion into cartilage initiates the replacement of cartilage by bone. Chondromodulin-I, a 25 kDa glycoprotein purified from bovine epiphyseal cartilage, was recently identified as a novel endothelial cell growth inhibitor. Here we cloned the mouse chondromodulin-I cDNA from a mouse whole embryo cDNA library. Northern blot analysis revealed that the chondromodulin-I transcripts were expressed in association with the formation of cartilage expressing type II collagen from days 11 to 17 of gestation in mouse embryos, at which time cartilaginous bone rudiments were gradually replaced by bone. Chondromodulin-I mRNA was also detected in the thymus and eyes at a lower level. In situ hybridization revealed significant expression in all cartilaginous tissues in the embryos at days 13.5 and 16 of gestation. However, the expression was completely abolished in the hypertrophic cartilage zone prior to calcification. Upon chondrogenic differentiation of mouse ATDC5 cells in vitro, the expression of chondromodulin-I transcripts was induced concomitantly with the formation of type II collagen-expressing chondrocytes. The expression of the transcripts then declined as type X collagen-expressing hypertrophic chondrocytes appeared in the culture. Purified chondromodulin-I protein inhibited the vascular invasion into cartilage ectopically induced by demineralized bone matrix in nude mice, leading to the suppression of bone formation in vivo. These results suggest that chondromodulin-I is involved in the anti-angiogenic property of cartilage, and that the withdrawal of its expression allows the vascular invasion which triggers the replacement of cartilage by bone during endochondral bone development.

Variations in site and levels of expression of chondrocyte nucleotide pyrophosphohydrolase with aging.

The aim of this study was to identify changes in cartilage intermediate layer protein/nucleotide pyrophosphohydrolase (CILP/NTPPH) expression in articular cartilage during aging. Adult (3-4 years old) and young (7-10 days old) porcine articular hyaline cartilage and fibrocartilage were studied by Northern blot analysis, in situ hybridization, and immunohistochemistry using a complementary DNA (cDNA) probe encoding porcine CILP/NTPPH and antibody to a synthetic peptide corresponding to a CILP/NTPPH sequence. Northern blot analysis of chondrocytes showed lower expression of CILP/NTPPH messenger RNA (mRNA) in young cartilage than in adult cartilage. In adult cartilage, extracellular matrix from the surface to the middeep zone was immunoreactive for CILP/NTPPH, especially in the pericellular matrix surrounding the middeep zone chondrocytes. In young cartilage, chondrocytes were moderately immunoreactive for CILP/NTPPH throughout all zones except the calcified zone. The matrix of young cartilage was negative except in the superficial zone. In young cartilage, CILP/NTPPH mRNA expression was undetectable. In adult cartilage, chondrocytes showed strong mRNA expression for CILP/NTPPH throughout middeep zones. Protein and mRNA signals were not detectable below the tidemark. CILP/NTPPH secretion into matrix around chondrocytes increases with aging. In this extracellular site it may generate inorganic pyrophosphate and contribute to age-related calcium pyrophosphate dihydrate crystal deposition disease.

Differential expression of two exons of the alpha1(XI) collagen gene (Col11a1) in the mouse embryo.

The amino terminal domain of collagen XI has a unique structure, which is believed to participate in the regulation of matrix assembly. Interestingly, several distinct isoforms of the amino terminal domain of alpha1(XI) and alpha2(XI) collagen chains exist as a result of alternative splicing. Here we report the analysis of the alternative splicing pattern of the mouse alpha1(XI) collagen gene (Col11a1). Like other vertebrate species, the mutually exclusive expression of exons 6A and 6B of Col11a1 results in the inclusion in the alpha1 chain of either an acidic peptide (pI 3.14) or a basic peptide (pI 11.66). Expression of these two exons was monitored in several tissues of the 16.5-day mouse embryo by in situ hybridization and immunohistochemistry, with exon-specific cDNA probes and peptide-specific antibodies, respectively. The results documented that isoforms containing the exon 6B-encoded peptide accumulate predominantly in the vertebrae, skeletal muscles and intestinal epithelium. By contrast, exon 6A products were found to be most abundant in the smooth muscle cells of the intestine, aorta and lung. The results using in situ hybridization confirmed those using immunohistochemistry. Albeit correlative, the evidence suggests distinct contributions of the two peptides to the differential assembly of tissue-specific matrices.

Immunohistochemical localization of procollagen types I and III during placentation in pregnant rats by type-specific procollagen antibodies.

To examine the sequential localizations of procollagen Types I (Pro I) and III (Pro III) during chorioallantoic placental formation in pregnant rats, we prepared polyclonal anti-rat Pro I- and III-specific antibodies. Biochemical analysis of a fraction containing [14C]-glycine-incorporated collagen from pregnant rat uteri showed that collagen Types I and III were actively synthesized during placental development. We examined 8-, 9.5-, 13-, and 20-day gestation rat uteri immunohistochemically. At Days 8 and 9.5, in the basal decidua facing the fetal cytotrophoblastic giant cell layer and implantation site, the immunoreactivity for Pro I was higher than that for Pro III. On Day 13, the enlarged myometrium and cytotrophoblastic cell layer showed increased immunoreactivity for Pro III. Unexpectedly, polygonal trophoblastic cells invading and modifying the maternal central artery showed intense immunoreactivity for Pro III. On Day 20, the fetal mesenchyme, large fetal blood vessels, and subendothelial stroma, including fetal blood capillaries, were more immunoreactive to Pro III antibody than to Pro I antibody in the labyrinth. Pro I and III synthesis and processing appear to be developmentally regulated and may be related to control of the microenvironment for supporting the fetus, control of the maternal blood supply stabilizing the fetoplacental physiological functions, and parturition.

Rapid expression of collagen type X gene of non-hypertrophic chondrocytes in the grafted chick periosteum demonstrated by in situ hybridization.

We investigated the spatiotemporal localization of collagen Type I, II, and X mRNAs in the subcutaneously grafted chick periosteum by in situ hybridization. Five days after transplantation, we noted three types of histological findings in the grated tissue. (a) Developing trabecular bone exhibited proliferation of spindle-shaped fibroblastic cells and polygonal osteoblasts with moderate signals for collagen Type I mRNA. (b) Developing cartilage contained ovoid chondrocytes with a moderate level of both collagen Type I and II mRNAs. Differentiating chondrocytes with increased collagen Type X mRNA developed during the course of endochondral ossification. (c) An atypical mass of cartilage weakly stained with alcian blue was composed of a large number of non-hypertrophic chondrocytes exhibiting high signals for collagen Type X mRNA. At Day 9, we observed the typical histological features of both membranous and endochondral ossification. However, sparsely distributed chondrocytes with high signals for collagen Type X mRNA were also demonstrated in osteoid and/or woven bone. The phenotype of chondrocytes showing rapid expression of collagen Type X gene derived from grafted periosteum seems to participate in the important role of endochondral bone formation in the early stage of fracture repair.

Precise distribution of neuronal nitric oxide synthase mRNA in the rat brain revealed by non-radioisotopic in situ hybridization.

Regional distribution of neurons expressing neuronal nitric oxide synthase mRNA in the rat brain was examined by non-radioisotopic in situ hybridization, using digoxigenin-labeled complementary RNA probes. Clustering of intensely positive neurons was observed in discrete areas including the main and accessory olfactory bulbs, the islands of Calleja, the amygdala, the paraventricular nucleus of the thalamus, several hypothalamic nuclei, the lateral geniculate nucleus, the magnocellular nucleus of the posterior commissure, the superior and inferior colliculi, the laterodorsal and pedunculopontine tegmental nuclei, the nucleus of the trapezoid body, the nucleus of the solitary tract and the cerebellum. Strongly-stained isolated neurons were scattered mainly in the cerebral cortex, the basal ganglia and the brain stem, especially the medulla reticular formation. In the hippocampus, an almost uniform distribution of moderately stained neurons was observed in the granular cell layer of the dentate gyrus and in the pyramidal cell layer of the Ammon's horn, while more intensely stained isolated neurons were scattered over the entire hippocampal region. These observations can serve as a good basis for studies on function and gene regulation of neuronal nitric oxide synthase.

Epstein-Barr virus (EBV) subtype in EBV related oral squamous cell carcinoma in Okinawa, a subtropical island in southern Japan, compared with Kitakyushu and Kumamoto in mainland Japan.

AIM: In Okinawa, a subtropical island located between the East China Sea and Pacific Ocean, 2000 km south of mainland Japan, the incidence of oral squamous cell carcinoma is 1.5 times higher than that seen in mainland Japan, and a large number of these patients have been reported to be infected with the Epstein-Barr virus (EBV). This study aimed to gain a better understanding of the pathogenesis of this malignancy in this area by carrying out genomic analysis of EBV. METHODS: Fifty four patients with oral squamous cell carcinoma reported from 1997 to 1999 in Okinawa were compared with 21 and 20 patients from Kitakyushu and Kumamoto in Kyushu, mainland Japan, respectively. Diagnosis was confirmed by conventional histological examination of paraffin wax sections. EBV was detected by non-isotopic in situ hybridisation (NISH) and the polymerase chain reaction (PCR) (Bam HI-F, EBV nuclear antigen 2 (EBNA2), and latent membrane protein 1 (LMP-1) regions). Sequence analysis of the PCR products was also carried out. RESULTS: In Okinawa, 25 patients were found to be infected with EBV type A by analysing the 3' sequence divergence of the EBNA2 genes. Six patients were positive for EBV type B, and eight for both type A and B. Therefore, type A virus infection was demonstrated in 33 of 54 patients, and type B in 14 of 54. In total, 39 of 54 patients were infected with EBV. However, the "f" variant was shown in only one patient, who was also infected with type A virus. In contrast, 97.0% of EBV type A infected patients showed a 30 bp deletion of the LMP-1 gene, but those infected with EBV type B did not. Sequence analysis of the type A virus EBNA2 gene revealed slight variations of the sequence (mutations)-(48991)G-->T and (48998)C-->A-in 18 of 33 cases compared with the B95-8 strain, and in 14 cases, in addition to these, a further mutation of (48917)T-->C was demonstrated; in the single remaining case, only one mutation at (49137)A-->G was detected. The mutations at 48991 (G-->T), and 49137 (A-->G) are associated with amino acid changes Arg-->Met and Thr-->Ala, respectively. In contrast, no mutation was seen in the EBNA2 DNA from the 14 cases of type B virus when compared with that of the Jijoye strain. In Kitakyushu and Kumamoto, only 10 of 41 patients (six in Kitakyushu and four in Kumamoto) were infected with EBV. Among them, nine patients were infected with type A virus, and only one patient from Kitakyushu was infected with type B virus. The (48991)G-->T and (48998)C-->A mutations of the EBNA2 region were demonstrated in type A virus, but the (48917)T-->C and (49137)A-->G mutations were not when compared with the B95-8 strain. In the case of type B virus no mutation was noted. A 30 bp deletion was found in these nine cases of type A, but not in type B. The sequence analysis of EBV type A in Okinawa, Kitakyushu, and Kumamoto showed slight variations when compared with B95-8, but EBV type B LMP-1 did not when compared with the Jijoye strains. CONCLUSION: In Okinawa, EBV infection was frequently demonstrated in oral squamous cell carcinoma (p < 0.001). However, in mainland Japan there was no significant correlation between EBV and oral squamous cell carcinoma. In Okinawa, EBV type B infection is approximately 10 times more common than in the mainland. However, in these areas-Okinawa, Kitakyushu, and Kumamoto-the frequency of the "f " variant was very low, whereas a high incidence of a 30 bp deletion of LMP-1 was noted. The number of EBV (including type A and/or B) infected oral squamous cell carcinomas in Okinawa was about three times higher than that seen in the mainland, although the frequency of oral squamous carcinoma was only 1.5 times higher than that seen in the mainland. A high prevalence of type B virus infection and slight differences in the EBNA2 gene sequence in the type A virus might influence the frequency of this carcinoma in Okinawa.

Endosteal new bone formation in the long bones of adjuvant treated rats.

Histopathological changes were examined mainly in the diaphyseal parts of long bones, especially femur in adjuvant-treated male Lewis-SPF rats, with reference to clinical symptoms of chronic osteoarthritis. The diaphyseal bone marrow of long bones in these rats sequentially showed three different processes of chronic pathological changes, which, however, partly overlapped each other. Initially, multiple epitheloid cell granulomas or granulomatous lesions containing fibrin deposits began to appear in the marrow space about 22 days after adjuvant injection, when the joint score of arthritis reached a peak in severity. Secondly, about a week after appearance of the granulomas, there occurred the intramembranous endosteal new bone formation proceeding from the endosteum towards the granulomatous lesions. The bone formation reached a maximum about 64 days after the treatment, when the redness of joints of feet and hands was already sedated. Finally, about 40 days after occurrence of the second event, the newly growing bone matrix began to be actively resorbed simultaneously. On the other hand, in the bone marrow of metaphyseal parts of long bones in these rats, severe acute osteomyelitis was observed from an early stage, with marked destruction of bone trabeculae and simultaneous new bone formation. In the diaphyseal bone marrow of affected long bones, the epitheloid cell granulomas appear to induce the endosteal new bone formation.

[Induction of tumor necrosis factor alpha by Mycoplasma penetrans isolated from patients with AIDS].

The activity of induce tumor necrosis factor alpha (TNF alpha) production of several mycoplasmas, including AIDS associated mycoplasmas was investigated. M. penetrans which was detected and isolated from urine and tissue of Kaposi's sarcoma of patients with AIDS markedly exhibited the induction of TNF alpha production of both THP-1 cells and murine peritoneal macrophages to compare to other mycoplasmas. Each amount of M. penetrans, M. fermentans, M. incognitus, Acholeplasma ladilawii, M. orale, M. salivarium, M. hominis required for induction of 50% cytotoxicity to L cells in the supernatants of mouse peritoneal macrophages cultured with those microorganisms was 0.65 micrograms/ml, 11.3 micrograms/ml, 19.6 micrograms/ml, 6.6 micrograms/ml, 7.7 micrograms/ml, 6.3 micrograms/ml, 5.7 micrograms/ml respectively. Next, the components of M. penetrans were extracted by Bligh-Dyer method, in order to investigate chemical component to induce TNF alpha-production. The activity of TNF alpha induction was mainly found in the methanol-phase, but not in the chloroform-phase, where lipid and glycolipid of the microorganisms were generally thought to be accumulated. The binding of the active component to concanavalin A-Sepharose was blocked in the presence of Methyl alpha-D-mannopyranoside and Methyl alpha-D-glucopyranoside. These results suggest that the component possess mannoside and glucoside active site.

[Remodeling of basement membrane in association with cancer invasion].

Type IV collagen the major component of basement membrane (BM), is composed of six genetically distinct alpha chains. In normal breast tissue, benign breast tumors, and in the intraductal components of invasive ductal carcinoma, alpha 1 (IV) and alpha 2 (IV) chains were stained in all BM, whereas alpha 5 (IV) and alpha 6 (IV) chains were restrictively localized in a linear pattern in the epithelial BM. However, in invasive ductal carcinoma, alpha 1 (IV) and alpha 2 (IV) chains were discontinuously or negatively stained in the cancer cell nest, and the assembly of alpha 5 (IV) and alpha 6 (IV) chains into the BM was completely inhibited. The results indicate that the mammary gland forms a second network of BM composed of alpha 5 (IV)/alpha 6 (IV) chains, in addition to the classic network of alpha 1 (IV)/alpha 2 (IV) chains. Remodeling of type IV collagen alpha chains during the development of invasive breast cancer seems to be differentially regulated, and to be associated with modification of histopathological findings.

[A case of ruptured distal aortic arch aneurysm with bronchiolitis obliterans organizing pneumonia].

We report a case of histologically proved bronchiolitis obliterans organizing pneumonia (BOOP) associated with ruptured distal aortic arch aneurysm (DAAA) into the lung. A 63-years-old male with preoperative episode of hemosputum and hemoptysis was diagnosed DAAA. Preoperative computed tomographic scanning demonstrated that the aneurysm was surrounded with the structure of 2 layers of the enhanced high density external layer and the not enhanced low density internal layer. Combined resection of the left upper lobe and the aneurysm was performed safely because of marked adhesion between the lung and the aneurysm. Postoperative histological examination revealed that the perianeurysmal structure was due to BOOP.

Splenic volume may be a useful indicator of the protective effect of bevacizumab against oxaliplatin-induced hepatic sinusoidal obstruction syndrome.

AIMS: The aim of this study was to investigate the relationship between the use of bevacizumab (Bmab) in addition to oxaliplatin (OX), the development of sinusoidal obstruction syndrome (SOS) and the changes in splenic volume as an indicator of the protective effect of Bmab against OX-induced SOS. METHODS: Seventy-nine patients who received OX-based chemotherapy with (OX + Bmab group: n = 48) or without Bmab (OX group: n = 31) for colorectal liver metastases were included in this study. The changes in splenic volume after chemotherapy were evaluated in the two groups. Furthermore, the relationship between the changes in splenic volume and SOS were analyzed in the 55 patients who underwent hepatectomy. RESULTS: A significant increase in the splenic volume was observed in the OX group, but not in the OX + Bmab group. The increase in the splenic volume relative to baseline was significantly higher in the OX group than in the OX + Bmab group (39.1% vs. 2.3%, p < 0.0001). The incidence of moderate or severe SOS was significantly higher in the OX group than in the OX + Bmab group (50.0% vs. 16.0%, p = 0.0068), and the increase in the splenic volume was significantly higher in the patients with SOS than in those without SOS (42.9% vs. 9.9%, p = 0.0001). A multivariate analysis identified the increase in the splenic volume as an independent predictor of the development of SOS. CONCLUSIONS: This study demonstrated that the inhibition of splenic volume enlargement might be a useful indicator of the protective effect of Bmab against OX-induced SOS.