Targeting cis-regulatory elements of FOXO family is a novel therapeutic strategy for induction of leukemia cell differentiation

Differentiation therapy has been proposed as a promising therapeutic strategy for acute myeloid leukemia (AML); thus, the development of more versatile methodologies that are applicable to a wide range of AML subtypes is desired. Although the FOXOs transcription factor represents a promising drug target for differentiation therapy, the efficacy of FOXO inhibitors is limited in vivo. Here, we show that pharmacological inhibition of a common cis-regulatory element of forkhead box O (FOXO) family members successfully induced cell differentiation in various AML cell lines. Through gene expression profiling and differentiation marker-based CRISPR/Cas9 screening, we identified TRIB1, a complement of the COP1 ubiquitin ligase complex, as a functional FOXO downstream gene maintaining an undifferentiated status. TRIB1 is direct target of FOXO3 and the FOXO-binding cis-regulatory element in the TRIB1 promoter, referred to as the FOXO-responsive element in the TRIB1 promoter (FRE-T), played a critical role in differentiation blockade. Thus, we designed a DNA-binding pharmacological inhibitor of the FOXO-FRE-T interface using pyrrole-imidazole polyamides (PIPs) that specifically bind to FRE-T (FRE-PIPs). The FRE-PIPs conjugated to chlorambucil (FRE-chb) inhibited transcription of TRIB1, causing differentiation in various AML cell lines. FRE-chb suppressed the formation of colonies derived from AML cell lines but not from normal counterparts. Administration of FRE-chb inhibited tumor progression in vivo without remarkable adverse effects. In conclusion, targeting cis-regulatory elements of the FOXO family is a promising therapeutic strategy that induces AML cell differentiation.

RHEB is a potential therapeutic target in T cell acute lymphoblastic leukemia

T cell acute lymphoblastic leukemia (T-ALL) is an aggressive malignancy of immature T lymphocytes. Although various therapeutic approaches have been developed, refractoriness of chemotherapy and relapse cause a poor prognosis of the disease and further therapeutic strategies are required. Here, we report that Ras homolog enriched in brain (RHEB), a critical regulator of mTOR complex 1 activity, is a potential target for T-ALL therapy. In this study, we established an sgRNA library that comprehensively targeted mTOR upstream and downstream pathways, including autophagy. CRISPR/Cas9 dropout screening revealed critical roles of mTOR-related molecules in T-ALL cell survival. Among the regulators, we focused on RHEB because we previously found that it is dispensable for normal hematopoiesis in mice. Transcriptome and metabolic analyses revealed that RHEB deficiency suppressed de novo nucleotide biosynthesis, leading to human T-ALL cell death. Importantly, RHEB deficiency suppressed tumor growth in both mouse and xenograft models. Our data provide a potential strategy for efficient therapy of T-ALL by RHEB-specific inhibition.

Therapeutic advantage of targeting lysosomal membrane integrity supported by lysophagy in malignant glioma

Lysosomes function as the digestive system of a cell and are involved in macromolecular recycling, vesicle trafficking, metabolic reprogramming, and progrowth signaling. Although quality control of lysosome biogenesis is thought to be a potential target for cancer therapy, practical strategies have not been established. Here, we show that lysosomal membrane integrity supported by lysophagy, a selective autophagy for damaged lysosomes, is a promising therapeutic target for glioblastoma (GBM). In this study, we found that ifenprodil, an FDA‐approved drug with neuromodulatory activities, efficiently inhibited spheroid formation of patient‐derived GBM cells in a combination with autophagy inhibition. Ifenprodil increased intracellular Ca²⁺ level, resulting in mitochondrial reactive oxygen species–mediated cytotoxicity. The ifenprodil‐induced Ca²⁺ elevation was due to Ca²⁺ release from lysosomes, but not endoplasmic reticulum, associated with galectin‐3 punctation as an indicator of lysosomal membrane damage. As the Ca²⁺ release was enhanced by ATG5 deficiency, autophagy protected against lysosomal membrane damage. By comparative analysis of 765 FDA‐approved compounds, we identified another clinically available drug for central nervous system (CNS) diseases, amoxapine, in addition to ifenprodil. Both compounds promoted degradation of lysosomal membrane proteins, indicating a critical role of lysophagy in quality control of lysosomal membrane integrity. Importantly, a synergistic inhibitory effect of ifenprodil and chloroquine, a clinically available autophagy inhibitor, on spheroid formation was remarkable in GBM cells, but not in nontransformed neural progenitor cells. Finally, chloroquine dramatically enhanced effects of the compounds inducing lysosomal membrane damage in a patient‐derived xenograft model. These data demonstrate a therapeutic advantage of targeting lysosomal membrane integrity in GBM.

Pillar[6]arene acts as a biosensor for quantitative detection of a vitamin metabolite in crude biological samples

Metabolic syndrome is associated with obesity, hypertension, and dyslipidemia, and increased cardiovascular risk. Therefore, quick and accurate measurements of specific metabolites are critical for diagnosis; however, detection methods are limited. Here we describe the synthesis of pillar[n]arenes to target 1-methylnicotinamide (1-MNA), which is one metabolite of vitamin B3 (nicotinamide) produced by the cancer-associated nicotinamide N-methyltransferase (NNMT). We found that water-soluble pillar[5]arene (P5A) forms host-guest complexes with both 1-MNA and nicotinamide, and water-soluble pillar[6]arene (P6A) selectively binds to 1-MNA at the micromolar level. P6A can be used as a "turn-off sensor" by photoinduced electron transfer (detection limit is 4.38 × 10^-6 M). In our cell-free reaction, P6A is used to quantitatively monitor the activity of NNMT. Moreover, studies using NNMT-deficient mice reveal that P6A exclusively binds to 1-MNA in crude urinary samples. Our findings demonstrate that P6A can be used as a biosensor to quantify 1-MNA in crude biological samples.

Autophagy inhibition synergizes with calcium mobilization to achieve efficient therapy of malignant gliomas

Autophagy plays a critical role in tumorigenesis, but how autophagy contributes to cancer cells' responses to chemotherapeutics remains controversial. To investigate the roles of autophagy in malignant gliomas, we used CRISPR/CAS9 to knock out the ATG5 gene, which is essential for autophagosome formation, in tumor cells derived from patients with glioblastoma. While ATG5 disruption inhibited autophagy, it did not change the phenotypes of glioma cells and did not alter their sensitivity to temozolomide, an agent used for glioblastoma patient therapy. Screening of an anticancer drug library identified compounds that showed greater efficacy to ATG5-knockout glioma cells compared to control. While several selected compounds, including nigericin and salinomycin, remarkably induced autophagy, potent autophagy inducers by mTOR inhibition did not exhibit the ATG5-dependent cytoprotective effects. Nigericin in combination with ATG5 deficiency synergistically suppressed spheroid formation by glioma cells in a manner mitigated by Ca2+ chelation or CaMKK inhibition, indicating that, in combination with autophagy inhibition, calcium-mobilizing compounds contribute to efficient anticancer therapeutics. ATG5-knockout cells treated with nigericin showed increased mitochondria-derived reactive oxygen species and apoptosis compared to controls, indicating that autophagy protects glioma cells from mitochondrial reactive oxygen species-mediated damage. Finally, using a patient-derived xenograft model, we demonstrated that chloroquine, a pharmacological autophagy inhibitor, dramatically enhanced the efficacy of compounds selected in this study. Our findings propose a novel therapeutic strategy in which calcium-mobilizing compounds are combined with autophagy inhibitors to treat patients with glioblastoma.

Spred1 Safeguards Hematopoietic Homeostasis against Diet-Induced Systemic Stress

Stem cell self-renewal is critical for tissue homeostasis, and its dysregulation can lead to organ failure or tumorigenesis. While obesity can induce varied abnormalities in bone marrow components, it is unclear how diet might affect hematopoietic stem cell (HSC) self-renewal. Here, we show that Spred1, a negative regulator of RAS-MAPK signaling, safeguards HSC homeostasis in animals fed a high-fat diet (HFD). Under steady-state conditions, Spred1 negatively regulates HSC self-renewal and fitness, in part through Rho kinase activity. Spred1 deficiency mitigates HSC failure induced by infection mimetics and prolongs HSC lifespan, but it does not initiate leukemogenesis due to compensatory upregulation of Spred2. In contrast, HFD induces ERK hyperactivation and aberrant self-renewal in Spred1-deficient HSCs, resulting in functional HSC failure, severe anemia, and myeloproliferative neoplasm-like disease. HFD-induced hematopoietic abnormalities are mediated partly through alterations to the gut microbiota. Together, these findings reveal that diet-induced stress disrupts fine-tuning of Spred1-mediated signals to govern HSC homeostasis.

[Regulation of hematopoietic stem cell homeostasis by Spred1]

Various types of stresses account for the dysregulation of the self-renewal activity of stem cells, resulting in the functional failure of tissues or tumorigenesis promotion. Although diets also affect our health, the effect of harmful dietary stresses on the tissue or stem cell homeostasis remains unclear. Recent research has revealed that Spred1, which negatively regulates RAS-MAPK signaling, protects hematopoietic stem cell (HSC) homeostasis against high-fat diet (HFD) -induced systemic stress. In steady-state conditions, Spred1 negatively regulates HSC self-renewal in a manner supported by the Rho kinase (ROCK) activity. In addition, Spred1 deficiency in mice mitigates HSC dysfunction induced by aging or lipopolysaccharide treatment, enhances the HSC self-renewal capacity, and prolongs HSC lifespan, but does not induce leukemia because of the compensatory upregulation of Spred2-the other Spred family member. Conversely, HFD triggers ERK hyperactivation and aberrant self-renewal in Spred1-deficient HSCs, resulting in HSC dysfunction, severe anemia, and the development of lethal myeloproliferative neoplasm-like disease. The depletion of the gut microbiota by antibiotics restored myeloproliferation, anemia, and HSC reconstitution ability in HFD-fed Spred1-deficient mice, suggesting that HFD-induced hematopoietic abnormalities were partially because of alterations in the gut microbiota composition. Thus, HFD-induced systemic stress affects the regulation of HSC self-renewal, and Spred1 safeguards HSC homeostasis against the diet-induced systemic stress.

Distinct roles of Rheb and Raptor in activating mTOR complex 1 for the self-renewal of hematopoietic stem cells

The mammalian target of rapamycin (mTOR) complex 1 (mTORC1) senses a cell's energy status and environmental levels of nutrients and growth factors. In response, mTORC1 mediates signaling that controls protein translation and cellular metabolism. Although mTORC1 plays a critical role in hematopoiesis, it remains unclear which upstream stimuli regulate mTORC1 activity in the context of hematopoietic stem cells (HSC) maintenance in vivo. In this study, we investigated the function of Rheb, a critical regulator of mTORC1 activity controlled by the PI3K-AKT-TSC axis, both in HSC maintenance in mice at steady-state and in HSC-derived hematopoiesis post-transplantation. In contrast to the severe hematopoietic dysfunction caused by Raptor deletion, which completely inactivates mTORC1, Rheb deficiency in adult mice did not show remarkable hematopoietic failure. Lack of Rheb caused abnormalities in myeloid cells but did not have impact on hematopoietic regeneration in mice subjected to injury by irradiation. As previously reported, Rheb deficiency resulted in defective HSC-derived hematopoiesis post-transplantation. However, while Raptor is essential for HSC competitiveness in vivo, Rheb is dispensable for HSC maintenance under physiological conditions, indicating that the PI3K-AKT-TSC pathway does not contribute to mTORC1 activity for sustaining HSC self-renewal activity at steady-state. Thus, the various regulatory elements that impinge upstream of mTORC1 activation pathways are differentially required for HSC homeostasis in vivo.

Functional dissection of hematopoietic stem cell populations with a stemness-monitoring system based on NS-GFP transgene expression

Hematopoietic stem cells (HSCs) in a steady state can be efficiently purified by selecting for a combination of several cell surface markers; however, such markers do not consistently reflect HSC activity. In this study, we successfully enriched HSCs with a unique stemness-monitoring system using a transgenic mouse in which green florescence protein (GFP) is driven by the promoter/enhancer region of the nucleostemin (NS) gene. We found that the phenotypically defined long-term (LT)-HSC population exhibited the highest level of NS-GFP intensity, whereas NS-GFP intensity was strongly downregulated during differentiation in vitro and in vivo. Within the LT-HSC population, NS-GFP^high cells exhibited significantly higher repopulating capacity than NS-GFP^low cells. Gene expression analysis revealed that nine genes, including Vwf and Cdkn1c (p57), are highly expressed in NS-GFP^high cells and may represent a signature of HSCs, i.e., a stemness signature. When LT-HSCs suffered from remarkable stress, such as transplantation or irradiation, NS-GFP intensity was downregulated. Finally, we found that high levels of NS-GFP identified HSC-like cells even among CD34⁺ cells, which have been considered progenitor cells without long-term reconstitution ability. Thus, high NS-GFP expression represents stem cell characteristics in hematopoietic cells, making this system useful for identifying previously uncharacterized HSCs.

Clinical pattern of primary systemic therapy and outcomes of estrogen receptor-positive, HER2-negative metastatic breast cancer: a review of a single institution

PURPOSE

In the management of estrogen receptor-positive, human epidermal growth factor receptor 2-negative metastatic breast cancer (ER+HER2-MBC) patients, endocrine therapy (ET) is preferred to chemotherapy (CT) as a primary systemic therapy (PST) when tumor burden is not high. However, there are no definite criteria for choosing a PST, transitioning from ET to CT or using maintenance ET subsequent to CT.

METHODS

We reviewed the medical records of 311 ER+HER2-MBC patients who underwent CT from September 2002 to December 2016 and assessed their outcomes.

RESULTS

Of the 311 patients, 178 (57%) received ET as a PST (ET-first group), and 133 (43%) received CT prior to ET (CT-first group). The ET-first group showed a median overall survival (OS) from the diagnosis of MBC (OS_MBC) of 1593 days, and the median OS from the initiation of CT (OS_CT) was 938 days. Patients with visceral involvement, liver metastasis, soft tissue metastasis, ≥3 organ involvement, or primary advanced BC at the MBC diagnosis showed a significantly higher tendency to be assigned to the CT-first group (P < 0.01 for any visceral involvement, P < 0.05 for all others). Maintenance ET was available in 74 (55.6%) patients in the CT-first group, who showed a significantly better OS_MBC and OS_CT than patients without maintenance ET (median OS_MBC 1423 and 867 days, respectively, P < 0.0001; median OS_CT 1350 and 637 days, respectively, P < 0.0001).

CONCLUSION

Our findings suggest the possibility for changing the treatment paradigm of patients with ER+HER2-MBC, so a randomized prospective study is warranted to determine the optimum sequence of systemic therapies.

Therapeutic Strategy for Targeting Aggressive Malignant Gliomas by Disrupting Their Energy Balance

Although abnormal metabolic regulation is a critical determinant of cancer cell behavior, it is still unclear how an altered balance between ATP production and consumption contributes to malignancy. Here we show that disruption of this energy balance efficiently suppresses aggressive malignant gliomas driven by mammalian target of rapamycin complex 1 (mTORC1) hyperactivation. In a mouse glioma model, mTORC1 hyperactivation induced by conditional Tsc1 deletion increased numbers of glioma-initiating cells (GICs) in vitro and in vivo Metabolic analysis revealed that mTORC1 hyperactivation enhanced mitochondrial biogenesis, as evidenced by elevations in oxygen consumption rate and ATP production. Inhibition of mitochondrial ATP synthetase was more effective in repressing sphere formation by Tsc1-deficient glioma cells than that by Tsc1-competent glioma cells, indicating a crucial function for mitochondrial bioenergetic capacity in GIC expansion. To translate this observation into the development of novel therapeutics targeting malignant gliomas, we screened drug libraries for small molecule compounds showing greater efficacy in inhibiting the proliferation/survival of Tsc1-deficient cells compared with controls. We identified several compounds able to preferentially inhibit mitochondrial activity, dramatically reducing ATP levels and blocking glioma sphere formation. In human patient-derived glioma cells, nigericin, which reportedly suppresses cancer stem cell properties, induced AMPK phosphorylation that was associated with mTORC1 inactivation and induction of autophagy and led to a marked decrease in sphere formation with loss of GIC marker expression. Furthermore, malignant characteristics of human glioma cells were markedly suppressed by nigericin treatment in vivo Thus, targeting mTORC1-driven processes, particularly those involved in maintaining a cancer cell's energy balance, may be an effective therapeutic strategy for glioma patients.

Association of a murine leukaemia stem cell gene signature based on nucleostemin promoter activity with prognosis of acute myeloid leukaemia in patients

Acute myeloid leukaemia (AML) is a heterogeneous neoplastic disorder in which a subset of cells function as leukaemia-initiating cells (LICs). In this study, we prospectively evaluated the leukaemia-initiating capacity of AML cells fractionated according to the expression of a nucleolar GTP binding protein, nucleostemin (NS). To monitor NS expression in living AML cells, we generated a mouse AML model in which green fluorescent protein (GFP) is expressed under the control of a region of the NS promoter (NS-GFP). In AML cells, NS-GFP levels were correlated with endogenous NS mRNA. AML cells with the highest expression of NS-GFP were very immature blast-like cells, efficiently formed leukaemia colonies in vitro, and exhibited the highest leukaemia-initiating capacity in vivo. Gene expression profiling analysis revealed that cell cycle regulators and nucleotide metabolism-related genes were highly enriched in a gene set associated with leukaemia-initiating capacity that we termed the 'leukaemia stem cell gene signature'. This gene signature stratified human AML patients into distinct clusters that reflected prognosis, demonstrating that the mouse leukaemia stem cell gene signature is significantly associated with the malignant properties of human AML. Further analyses of gene regulation in leukaemia stem cells could provide novel insights into diagnostic and therapeutic approaches to AML.

Loss of Tsc1 accelerates malignant gliomagenesis when combined with oncogenic signals

Glioblastomas frequently harbour genetic lesions that stimulate the activity of mammalian target of rapamycin complex 1 (mTORC1). Loss of heterozygosity of tuberous sclerosis complex 1 (TSC1) or TSC2, which together form a critical negative regulator of mTORC1, is also seen in glioblastoma; however, it is not known how loss of the TSC complex affects the development of malignant gliomas. Here we investigated the role of Tsc1 in gliomagenesis in mice. Tsc1 deficiency up-regulated mTORC1 activity and suppressed the proliferation of neural stem/progenitor cells (NSPCs) in a serial neurosphere-forming assay, suggesting that Tsc1-deficient NSPCs have defective self-renewal activity. The neurosphere-forming capacity of Tsc1-deficient NSPCs was restored by p16(Ink4a)p19(Arf) deficiency. Combined Tsc1 and p16(Ink4a)p19(Arf) deficiency in NSPCs did not cause gliomagenesis in vivo. However, in a glioma model driven by an active mutant of epidermal growth factor receptor (EGFR), EGFRvIII, loss of Tsc1 resulted in an earlier onset of glioma development. The mTORC1 hyperactivation by Tsc1 deletion accelerated malignant phenotypes, including increased tumour mass and enhanced microvascular formation, leading to intracranial haemorrhage. These data demonstrate that, although mTORC1 hyperactivation itself may not be sufficient for gliomagenesis, it is a potent modifier of glioma development when combined with oncogenic signals.

Abundant nucleostemin expression supports the undifferentiated properties of germ cell tumors

Nucleostemin (NS) is a nucleolar GTP-binding protein that is involved in ribosomal biogenesis and protection of telomeres. We investigated the expression of NS in human germ cell tumors and its function in a mouse germ cell tumor model. NS was abundantly expressed in undifferentiated, but not differentiated, types of human testicular germ cell tumors. NS was expressed concomitantly with OCT3/4, a critical regulator of the undifferentiated status of pluripotent stem cells in primordial germ cells and embryonal carcinomas. To investigate the roles of NS in tumor growth in vivo, we used a mouse teratoma model. Analysis of teratomas derived from embryonic stem cells in which the NS promoter drives GFP expression showed that cells highly expressing NS were actively proliferating and exhibited the characteristics of tumor-initiating cells, including the ability to initiate and propagate tumor cells in vivo. NS-expressing cells exhibited higher levels of GTP than non-NS-expressing cells. Because NS protein is stabilized by intracellular GTP, metabolic changes may contribute to abundant NS expression in the undifferentiated cells. OCT3/4 deficiency in teratomas led to loss of NS expression, resulting in growth retardation. Finally, we found that teratomas deficient in NS lost their undifferentiated characteristics, resulting in defective tumor proliferation. These data indicate that abundant expression of NS supports the undifferentiated properties of germ cell tumors.

mTORC1 is essential for leukemia propagation but not stem cell self-renewal

Although dysregulation of mTOR complex 1 (mTORC1) promotes leukemogenesis, how mTORC1 affects established leukemia is unclear. We investigated the role of mTORC1 in mouse hematopoiesis using a mouse model of conditional deletion of Raptor, an essential component of mTORC1. Raptor deficiency impaired granulocyte and B cell development but did not alter survival or proliferation of hematopoietic progenitor cells. In a mouse model of acute myeloid leukemia (AML), Raptor deficiency significantly suppressed leukemia progression by causing apoptosis of differentiated, but not undifferentiated, leukemia cells. mTORC1 did not control cell cycle or cell growth in undifferentiated AML cells in vivo. Transplantation of Raptor-deficient undifferentiated AML cells in a limiting dilution revealed that mTORC1 is essential for leukemia initiation. Strikingly, a subset of AML cells with undifferentiated phenotypes survived long-term in the absence of mTORC1 activity. We further demonstrated that the reactivation of mTORC1 in those cells restored their leukemia-initiating capacity. Thus, AML cells lacking mTORC1 activity can self-renew as AML stem cells. Our findings provide mechanistic insight into how residual tumor cells circumvent anticancer therapies and drive tumor recurrence.

Hair follicle stem cells provide a functional niche for melanocyte stem cells

In most stem cell systems, the organization of the stem cell niche and the anchoring matrix required for stem cell maintenance are largely unknown. We report here that collagen XVII (COL17A1/BP180/BPAG2), a hemidesmosomal transmembrane collagen, is highly expressed in hair follicle stem cells (HFSCs) and is required for the maintenance not only of HFSCs but also of melanocyte stem cells (MSCs), which do not express Col17a1 but directly adhere to HFSCs. Mice lacking Col17a1 show premature hair graying and hair loss. Analysis of Col17a1-null mice revealed that COL17A1 is critical for the self-renewal of HFSCs through maintaining their quiescence and immaturity, potentially explaining the mechanism underlying hair loss in human COL17A1 deficiency. Moreover, forced expression of COL17A1 in basal keratinocytes, including HFSCs, in Col17a1-null mice rescues MSCs from premature differentiation and restores TGF-β signaling, demonstrating that HFSCs function as a critical regulatory component of the MSC niche.

NKX2.2 suppresses self-renewal of glioma-initiating cells

Glioblastoma (GBM) is the most aggressive and destructive form of brain cancer. Animal models that can unravel the mechanisms underlying its progression are needed to develop rational and effective molecular therapeutic approaches. In this study, we report the development of mouse models for spontaneous gliomas representing distinct progressive stages of disease that are governed by defined genetic alterations. Neural stem/progenitor cell (NPC)-specific constitutive Ras activation in vivo plus p53 deficiency led to development of primarily anaplastic astrocytoma (grade III), whereas combined loss of p53 plus p16(Ink4a)/p19(Arf) led to development of GBM (grade IV) at 100% penetrance within 6 weeks. These glioma models showed enhanced stem cell properties (stemness) accompanied by malignant progression. Notably, we determined that, in our models and in human specimens, downregulation of the homeodomain transcription factor NKX2.2, which is essential for oligodendroglial differentiation, was correlated with increased tumor malignancy. NKX2.2 overexpression by GBM-derived glioma-initiating cells (GIC) induced oligodendroglial differentiation and suppressed self-renewal capacity. By contrast, Nkx2.2 downregulation in mouse NPCs accelerated GBM formation. Importantly, the inhibitory effects of NXK2.2 on GIC self-renewal were conserved in human cells. Thus, our mouse models offer pathobiologically significant advantages to investigate the nature of brain tumors, with improved opportunities to develop novel mechanism-based therapeutic approaches.

Abstract P6-11-13: Phase I Study of Combined S-1 Plus Weekly Paclitaxel Therapy in Patients with Metastatic Breast Cancer

Introduction: S-1, a novel anticancer compound, contains tegafur, a prodrug of fluorouracil (FU), 5-chloro-2.4-dihydroxypyridine, which prevents FU degradation, and potassium oxonate, which prevents drug-induced diarrhea, has a broad spectrum of activity against gastric, colorectal, head & neck, and breast cancers. While combined S-1 with cisplatin or paclitaxel (PAC) therapy is feasible and highly active against gastrointestinal cancer, the feasibility in breast cancer patients has not yet been clarified. We conducted a phase I study of combined S-1 plus weekly PAC therapy (S-1/PAC) to determine the maximum tolerated dose (MTD), recommended dose (RD) and dose-limiting toxicities (DLT) in patients (pts) with HER2-negative, taxane-naïve metastatic breast cancer (MBC).

Methods: S-1 was administered orally from day 1 through day 14 and PAC was administered intravenously on days 1, 8 and 15 of each 28-day cycle. Since S-1 is prescribed at the dose of 80mg/m2 in monotherapy, the primary dose levels (level 1) were set at 65 and 70mg/m2, respectively. The final dose (level 3) was set at 80mg/m2 for each drugs. DLT was defined over 2 cycles.

Results: Ten MBC pts were enrolled in the study. No DLTs were documented. Although grade 1 or 2 adverse events were seen in all pts, no cases of febrile neutropenia or Gr 4 neutropenia were observed. Of the 8 evaluable pts, 3 pts achieved partial response and 4 pts had stable disease.

Conclusion: Based on the results of this study, RD was determined to be 80mg/m2 for either drugs. We conclude that S-1/PAC was well-tolerated and highly active against HER2-negative MBC.

Citation Information: Cancer Res 2010;70(24 Suppl):Abstract nr P6-11-13.

Abstract 4237: Foxo3a is essential for survival of leukemia-initiating cells in chronic myeloid leukemia

Chronic myelogenous leukemia (CML) is caused by a defined genetic abnormality, BCR-ABL, a constitutively active protein tyrosine kinase. Although the introduction of imatinib, a small molecule inhibitor of ABL, represented a breakthrough in the treatment of CML, major part of patients treated in chronic-phase CML are not off therapy due to resistance or intolerance. Recent studies have suggested that imatinib is a potent inhibitor of the production of differentiated leukemic cells, but does not deplete leukemia-initiating cells (LICs). To date, therapeutics that can eradicate CML LICs, however, have remained under investigation. To overcome these clinical problems, we here evaluated molecular mechanisms on survival of the CML LICs.

We first generated a mouse CML model by using retroviral induction of BCR-ABL-ires-GFP gene into mouse immature hematopoietic cells, and the cells were subsequently transplanted into irradiated recipient mice. These experiments showed that CML LICs were highly enriched in c-Kit+Lin-Sca-1+ (KLS+) population in BCR-ABL+ CML cells, as previously reported. Unexpectedly, phosphorylation levels of Akt in CML LICs appeared to be lower than that in non-LICs, KLS- cells, despite it is widely believed that BCR-ABL induces activation of Akt signal. Since Forkhead O (Foxo) transcription factors, which are important downstream targets of PI3K-Akt signaling, are essential for the maintenance of self-renewal capacity of normal HSCs, we focused on analysis of Foxo3a in CML. Consistent with Akt phosphorylation status, we found that cells with nuclear localization of Foxo3a were enriched in the CML LICs, whereas non-LICs showed the cytoplasmic localization, suggesting that Foxo3a is activated via Akt inactivation in the CML LICs, but not in majority of CML cells. Serial transplantation experiments for CML LICs originated from Foxo3a-deficient mice and littermate wild-type mice indicated that Foxo3a-deficiency reduced lethality of recipient mice at 3rd transplantation. Although recipients that transplanted with wild-type LICs developed CML and acute lymphocytic leukemia (ALL) at 3rd transplantation, we did not observe development of ALL or CML in recipients of Foxo3a deficient LICs after 45 days post-3rd transplantation, suggesting that the Foxo3a deficient LICs lose their potential to generate malignancies. Furthermore, deficiency of Foxo3a led to enhanced efficiency in elimination of CML LICs in combination with imatinib treatment. These results demonstrate a critical role of Foxo pathway in survival of CML LICs, and provide a novel therapeutics approach for CML patients by suppression of FOXO signaling.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 4237.

TGF-beta-FOXO signalling maintains leukaemia-initiating cells in chronic myeloid leukaemia

Chronic myeloid leukaemia (CML) is caused by a defined genetic abnormality that generates BCR-ABL, a constitutively active tyrosine kinase. It is widely believed that BCR-ABL activates Akt signalling that suppresses the forkhead O transcription factors (FOXO), supporting the proliferation or inhibiting the apoptosis of CML cells. Although the use of the tyrosine kinase inhibitor imatinib is a breakthrough for CML therapy, imatinib does not deplete the leukaemia-initiating cells (LICs) that drive the recurrence of CML. Here, using a syngeneic transplantation system and a CML-like myeloproliferative disease mouse model, we show that Foxo3a has an essential role in the maintenance of CML LICs. We find that cells with nuclear localization of Foxo3a and decreased Akt phosphorylation are enriched in the LIC population. Serial transplantation of LICs generated from Foxo3a(+/+) and Foxo3a(-/-) mice shows that the ability of LICs to cause disease is significantly decreased by Foxo3a deficiency. Furthermore, we find that TGF-beta is a critical regulator of Akt activation in LICs and controls Foxo3a localization. A combination of TGF-beta inhibition, Foxo3a deficiency and imatinib treatment led to efficient depletion of CML in vivo. Furthermore, the treatment of human CML LICs with a TGF-beta inhibitor impaired their colony-forming ability in vitro. Our results demonstrate a critical role for the TGF-beta-FOXO pathway in the maintenance of LICs, and strengthen our understanding of the mechanisms that specifically maintain CML LICs in vivo.

Structural and functional changes of sulfated glycosaminoglycans in Xenopus laevis during embryogenesis

Xenopus laevis is an excellent animal for analyzing early vertebrate development. Various effects of glycosaminoglycans (GAGs) on growth factor-related cellular events during embryogenesis have been demonstrated in Xenopus. To elucidate the relationship between alterations in fine structure and changes in the specificity of growth factor binding during Xenopus development, heparan sulfate (HS) and chondroitin/dermatan sulfate (CS/DS) chains were isolated at four different embryonic stages and their structure and growth factor-binding capacities were compared. The total amounts of both HS and CS/DS chains decreased from the pre-midblastula transition to the gastrula stage, but increased exponentially during the following developmental stages. The length of HS chains was not significantly affected by development, whereas that of CS/DS chains increased with development. The disaccharide composition of GAGs in embryos also changed during development. The degree of sulfation of the HS chains gradually decreased with development. The predominant sulfation position in the CS/DS chains shifted from C4 to C6 of GalNAc during embryogenesis. Growth factor-binding experiments using a BIAcore system demonstrated that GAGs bound growth factors including fibroblast growth factors-1 and -2, midkine, and pleiotrophin, with comparable affinities. These affinities significantly varied during development, although the correlation between the structural alterations of GAGs and the change in the ability to bind growth factors remains to be clarified. The expression of saccharide sequences, which specifically interact with a growth factor, might be regulated during development.

Adult mouse hematopoietic stem cells: purification and single-cell assays

Mouse hematopoietic stem cells (HSCs) are the best-studied stem cells because functional assays for mouse HSCs were established earliest and purification techniques for mouse HSCs have progressed furthest. Here we describe our current protocols for the purification of CD34-/lowc-Kit+Sca-1+lineage marker- (CD34-KSL) cells, the HSC population making up approximately 0.005% of bone marrow cells in adult C557BL/6 mice. Purified HSCs have been characterized at cellular and molecular levels. Since clonal analysis is essential for the study of self-renewal and lineage commitment in HSCs, here we present our single-cell colony assay and single-cell transplantation procedures. We also introduce our immunostaining procedures for small numbers of HSCs, which are useful for signal transduction analysis. The purification of CD34-KSL cells requires approximately 6 h. Initialization of single-cell culture requires approximately 1 h. Single-cell transplantation requires approximately 6 h. Single-cell immunostaining requires approximately 2 d.

De novo DNA methyltransferase is essential for self-renewal, but not for differentiation, in hematopoietic stem cells

DNA methylation is an epigenetic modification essential for development. The DNA methyltransferases Dnmt3a and Dnmt3b execute de novo DNA methylation in gastrulating embryos and differentiating germline cells. It has been assumed that these enzymes generally play a role in regulating cell differentiation. To test this hypothesis, we examined the role of Dnmt3a and Dnmt3b in adult stem cells. CD34^−/low, c-Kit⁺, Sca-1⁺, lineage marker⁻ (CD34⁻ KSL) cells, a fraction of mouse bone marrow cells highly enriched in hematopoietic stem cells (HSCs), expressed both Dnmt3a and Dnmt3b. Using retroviral Cre gene transduction, we conditionally disrupted Dnmt3a, Dnmt3b, or both Dnmt3a and Dnmt3b (Dnmt3a/Dnmt3b) in CD34⁻ KSL cells purified from mice in which the functional domains of these genes are flanked by two loxP sites. We found that Dnmt3a and Dnmt3b function as de novo DNA methyltransferases during differentiation of hematopoietic cells. Unexpectedly, in vitro colony assays and in vivo transplantation assays showed that both myeloid and lymphoid lineage differentiation potentials were maintained in Dnmt3a-, Dnmt3b-, and Dnmt3a/Dnmt3b-deficient HSCs. However, Dnmt3a/Dnmt3b-deficient HSCs, but not Dnmt3a- or Dnmt3b-deficient HSCs, were incapable of long-term reconstitution in transplantation assays. These findings establish a critical role for DNA methylation by Dnmt3a and Dnmt3b in HSC self-renewal.

Lnk negatively regulates self-renewal of hematopoietic stem cells by modifying thrombopoietin-mediated signal transduction

One of the central tasks of stem cell biology is to understand the molecular mechanisms that control self-renewal in stem cells. Several cytokines are implicated as crucial regulators of hematopoietic stem cells (HSCs), but little is known about intracellular signaling for HSC self-renewal. To address this issue, we attempted to clarify how self-renewal potential is enhanced in HSCs without the adaptor molecule Lnk, as in Lnk-deficient mice HSCs are expanded in number >10-fold because of their increased self-renewal potential. We show that Lnk negatively regulates self-renewal of HSCs by modifying thrombopoietin (TPO)-mediated signal transduction. Single-cell cultures showed that Lnk-deficient HSCs are hypersensitive to TPO. Competitive repopulation revealed that long-term repopulating activity increases in Lnk-deficient HSCs, but not in WT HSCs, when these cells are cultured in the presence of TPO with or without stem cell factor. Single-cell transplantation of each of the paired daughter cells indicated that a combination of stem cell factor and TPO efficiently induces symmetrical self-renewal division in Lnk-deficient HSCs but not in WT HSCs. Newly developed single-cell immunostaining demonstrated significant enhancement of both p38 MAPK inactivation and STAT5 and Akt activation in Lnk-deficient HSCs after stimulation with TPO. Our results suggest that a balance in positive and negative signals downstream from the TPO signal plays a role in the regulation of the probability of self-renewal in HSCs. In general, likewise, the fate of stem cells may be determined by combinational changes in multiple signal transduction pathways.

Selective activation of STAT5 unveils its role in stem cell self-renewal in normal and leukemic hematopoiesis

Although the concept of a leukemic stem cell system has recently been well accepted, its nature and the underlying molecular mechanisms remain obscure. Constitutive activation of signal transducers and activators of transcription 3 (STAT3) and STAT5 is frequently detected in various hematopoietic tumors. To evaluate their role in normal and leukemic stem cells, we took advantage of constitutively active STAT mutants to activate STAT signaling selectively in hematopoietic stem cells (HSCs). Activation of STAT5 in CD34- c-Kit+ Sca-1+ lineage marker- (CD34- KSL) HSCs led to a drastic expansion of multipotential progenitors and promoted HSC self-renewal ex vivo. In sharp contrast, STAT3 was demonstrated to be dispensable for the HSC maintenance in vivo, and its activation facilitated lineage commitment of HSCs in vitro. In a mouse model of myeloproliferative disease (MPD), sustained STAT5 activation in CD34- KSL HSCs but not in CD34+ KSL multipotential progenitors induced fatal MPD, indicating that the capacity of STAT5 to promote self-renewal of hematopoietic stem cells is crucial to MPD development. Our findings collectively establish a specific role for STAT5 in self-renewal of normal as well as leukemic stem cells.

In vivo and in vitro constant expression of GATA-4 in mouse postnatal Sertoli cells

In the mammalian postnatal testis, the biochemical and structural features of Sertoli cells change, depending on developmental stage and spermatogenic cycle, to support efficient spermatogenesis. Consequently, basic transcription factors that determine fundamental properties should be strictly maintained in postnatal Sertoli cells. We have confirmed that GATA-4 expression is kept at a constant level in mouse Sertoli cells during postnatal development, and is also maintained at a constant level in primary cultures, independent of treatment with hormones or the addition of germ cell fractions. In transient transfection assays with the testicular cell line TM3, established from Leydig cells, GATA-4 induced several Sertoli cell-specific genes. In the Sertoli cell line TM4, and in Sertoli cells in primary culture, GATA-4 slightly up-regulated these genes. These results suggest that GATA-4 plays an important role in the regulation of Sertoli cell function, and is exactly regulated in these cells.

Characterization of histone H2A.X expression in testis and specific labeling of germ cells at the commitment stage of meiosis with histone H2A.X promoter-enhanced green fluorescent protein transgene

To study the complex molecular mechanisms of mammalian spermatogenesis, it would be useful to be able to isolate cells at each stage of differentiation, especially at the stage in which the cells switch from mitosis to meiosis. Currently, no useful marker proteins or gene promoters specific to this important stage are known. We report here a transgenic mouse line that under the control of the promoter for a histone variant, H2A.X, expressed an enhanced green fluorescent protein (EGFP) in cells at the stage of the mitosis-meiosis switch. Endogenous H2A.X is expressed in type A spermatogonia through meiotic prophase spermatocytes in testis and in some somatic cells. However, despite the fact that its expression was driven by the H2A.X promoter, the EGFP expressed in the transgenic mice specifically labeled only the intermediate spermatogonia stage through the meiotic prophase spermatocyte stage in transgenic mice containing the -600-base pair H2A.X promoter/EGFP construct. Type A spermatogonia and somatic cells of other organs were not labeled. This expression pattern made it possible to isolate living cells from the testis of the transgenic mice at the stage of the mitosis-meiosis switch in spermatogenesis using EGFP fluorescence.

Dramatic expansion of germinal stem cells by ectopically expressed human glial cell line-derived neurotrophic factor in mouse Sertoli cells

Although the mammalian germinal stem cell (GSC) provides a good model to investigate the regulation of stem cells, the small number of these cells currently available hampers elucidation of the regulatory mechanism. Here, we show the dramatic amplification of GSCs in mouse testis following transfection of human glial cell line-derived neurotrophic factor cDNA into Sertoli cells using an efficient, in vivo electroporation technique. Transplantation analysis demonstrated not only GSC enrichment but also differentiation from stem cells into sperm. The GSC population, as estimated using a colony-formation assay, was approximately 20-fold greater than in cryptorchid testis, or approximately 500- to 1000-fold greater than in normal adult testis. This system should provide sufficient quantities of GSCs to accelerate our understanding of GSC properties, regulation mechanisms, and behavior control.

Novel actin-like proteins T-ACTIN 1 and T-ACTIN 2 are differentially expressed in the cytoplasm and nucleus of mouse haploid germ cells

We isolated cDNA clones for the novel actin-like proteins T-ACTIN 1 and T-ACTIN 2, which are expressed specifically in the mouse testis. These clones were from a subtracted cDNA library that was enriched for haploid germ cell-specific cDNAs. The mRNA sizes and deduced molecular masses of t-actin 1/mACTl7b and t-actin 2/mACTl7a were 2.2 kilobases (kb) and 1.8 kb, and Mr 43.1 x 10(3) and Mr 47.2 x 10(3), respectively. The two deduced amino acid sequences had 60% homology, and they had approximately 40% homology with other actins. The T-ACTINs contained some of the conserved regions seen in other actins. Although the cellular locations of these two proteins are quite different (T-ACTIN-1 was found in the cytoplasm and T-ACTIN-2 was located in the nucleus), the expression of their proteins and mRNAs is controlled during development and limited during spermiogenesis. In contrast, only T-ACTIN-2 was present in sperm heads and tails. These results suggest that T-ACTINs play important roles in sperm function and in the specific morphogenesis of spermatozoa during spermiogenesis.

The effect of cigarette smoke exposure and ascorbic acid intake on gene expression of antioxidant enzymes and other related enzymes in the livers and lungs of Shionogi rats with osteogenic disorders

Cigarette smoking causes many chronic diseases but is a preventable risk factor in developing countries. However, it may be possible to relieve the smoke-induced damage by increasing the protective defense system. As vitamin C intake reduces smoking risk, it is recommended that smokers should take more vitamin C. However, the molecular mechanism of vitamin C intake on smokers has not been thoroughly investigated. We have found there to be suppression of smoke-induced cytochrome P-450 1A1 (CYP1A1) mRNA expression by high-dose ascorbic acid administration. Therefore, we surveyed other genes, the expressions of which were altered by the administration of high-dose ascorbic acid. As cigarette smoking increases oxidative stress, we investigated the effect on antioxidative enzyme expression. The osteogenic disorder Shionogi (ODS) rat, which lacks ascorbic acid synthesis enzyme, was administered either minimal amounts (4 mg/day, S4) or high-dose amounts (40 mg/day, S40) of ascorbic acid, and were exposed to cigarette smoke daily for 25 days. The effect on antioxidative enzymes mRNA expression in the liver was measured by competitive reverse transcription-polymerase chain reaction method (competitive RT-PCR). CuZn-superoxide dismutase (SOD), MnSOD, catalase and protein disulfide isomerase (PDI) were significantly decreased by high-dose ascorbic acid administration, and plasma glutathione peroxidase was also decreased, but not significantly. Cigarette smoke exposure slightly increased gene expression of PDI and catalase, but not significantly. The differently expressed 27 genes in the liver were found by differential display methods. From 27 genes, altered expression of plasma proteinase inhibitor, alpha-1-inhibitor III and CYP1A2 were confirmed by competitive RT-PCR. These results show that ascorbic acid intake influences gene expression of antioxidative enzymes, an ascorbic acid recycle enzyme, and xenobiotic metabolizing enzymes.

Homeostatic regulation of germinal stem cell proliferation by the GDNF/FSH pathway

Stem cell regulatory mechanisms are difficult to study because self-renewal and production of differentiated progeny, which are both strictly controlled, occur simultaneously in these cells. To focus on the self-renewal mechanism alone, we investigated the behavior of germinal stem cells (GSCs) in progeny-deficient testes with defective GSC differentiation. In these testes, we found that the proliferation of undifferentiated spermatogonia, some of which are GSCs, was accelerated by high concentrations of glial cell line-derived neurotrophic factor (GDNF). Furthermore, we found that follicle-stimulating hormone (FSH) stimulation via homeostatic control was one of the major regulators of GDNF concentration. These results suggest that in mammalian testes, GSC proliferation and population size are regulated homeostatically by the GDNF/FSH pathway.

Regulation of cigarette smoke-induced cytochrome P4501A1 gene expression in osteogenic disorder Shionogi rat liver and in lung by large ascorbic acid dose

The effects of a large ascorbic acid dose on cytochrome P4501A1 gene expression induced by cigarette smoke exposure was studied in Osteogenic Disorder Shionogi rats, which lack ascorbic acid biosynthesis. The rats were divided into four groups and were administered either a minimal amount (4 mg/day, 4S and 4C) or a large amount (40 mg/day, 40S and 40C) of ascorbic acid. The 4S group and 40S group were daily exposed to cigarette smoke for 2 hours, while the 4C group and 40C group were not. At the end of the 25-day experiment, the rats were killed. The cytochrome P4501A1 mRNA level both in the liver and lung was measured by a competitive reverse transcription-polymerase chain reaction method. When a minimal amount of ascorbic acid was administered, the cytochrome P4501A1 mRNA increased in the liver of the cigarette smoke-exposed group (4S) compared with the control group (4C). On the other hand, when a large amount of ascorbic acid was administered, this increase was not observed in the cigarette smoke-induced group (40S) in liver. On the other hand, in lung, an increased mRNA level in 4S group was not decreased by large ascorbic acid administration (40S). This is the first direct mRNA-level evidence of the effects of a large ascorbic acid dose on the gene expression stimulated by cigarette smoke.

Two mouse piwi-related genes: miwi and mili

Genes belonging to the piwi family are required for stem cell self-renewal in diverse organisms. We cloned mouse homologues of piwi by RT-PCR using degenerative primers. The deduced amino acid sequences of mouse homologues MIWI and MILI showed that each contains a well-conserved C-terminal PIWI domain and that each shares significant homology with PIWI and their human counterparts HIWI. Both miwi and mili were found in germ cells of adult testis by in situ hybridization, suggesting that these genes may function in spermatogenesis. Furthermore, mili was expressed in primordial germ cells (PGCs) of developing mouse embryos and may therefore play a role during germ cell formation. MIWI may be involved in RNA processing or translational regulation, since MIWI was found to possess RNA binding activity. Our data suggest that miwi and mili regulate spermatogenesis and primordial germ cell production.

Testosterone suppresses spermatogenesis in juvenile spermatogonial depletion (jsd ) mice

Male juvenile spermatogonial depletion (jsd/jsd) mice are sterile because of a failure of spermatogonial differentiation. We have previously reported the recovery of spermatogonial differentiation by suppressing the levels of gonadotropins and testosterone with Nal-Glu, a GnRH antagonist. To determine whether suppression of testosterone or the gonadotropins was responsible for spermatogenic recovery, we examined the effect of supplementation of LH or FSH along with Nal-Glu treatment. Systemic administration of flutamide, an androgen receptor antagonist, was also examined. LH supplementation elevated both serum and intratesticular testosterone levels and suppressed the recovery of spermatogonial differentiation in a dose-dependent manner. Supplementation with FSH did not affect either testosterone levels or spermatogonial differentiation. Furthermore, the mice treated with flutamide showed some recovery of spermatogonial differentiation. The overall findings revealed that testosterone action mediated by androgen receptors suppressed the spermatogonial differentiation in jsd/jsd mice and suggested that spermatogonial differentiation in the jsd mutant is highly sensitive to testosterone suppression.

Defect in germ cells, not in supporting cells, is the cause of male infertility in the jsd mutant mouse: proliferation of spermatogonial stem cells without differentiation

C57BL/6 (B6)-jsd/jsd male mice are sterile because of lack of spermatogenesis. To find the cause of the deficient spermatogenesis, we have examined whether the mutation phenotype is the result of a defect in germ cells or in supporting cells using germ cell transplantation. In the seminiferous tubules of B6-jsd/jsd mutant mice, donor germ cells derived from the wild type GFP transgenic mouse (B6-+/+GFP) were able to undergo complete spermatogenesis, indicating that the juvenile spermatogonial depletion (jsd/jsd) mouse possesses normal supporting cell functions. In contrast, undifferentiated spermatogonia derived from B6-jsd/jsd mice were unable to differentiate in the seminiferous tubules of W/W v mice, even if the mutant germ cells successfully settled in the tubules. These results demonstrate that the deficiency in spermatogenesis of B6-jsd/jsd mice can be ascribed to a defect in spermatogonia but not in their supporting cell environment. Furthermore, the defect in B6-jsd/jsd spermatogonia is not in their ability to proliferate, but in their differentiation and may result from their hypersensitivity to high concentrations of androgen in the testis.

The reliability of a video-enhanced Hirschberg test under clinical conditions

PURPOSE

To examine the reliability and usefulness of a video-based Hirschberg test under clinical conditions.

METHODS

The authors estimated ocular deviation in 87 patients with strabismus through automated analysis of corneal reflex displacement using a video refractor. The reproducibility of measurement, the comparison with the prism and alternate cover test (PACT), and the distribution of the Hirschberg ratio were investigated.

RESULTS

The 95% limits of agreement of the video-based Hirschberg test evaluated by repeated measurements were +/- 0.18 mm (equivalent to +/- 2.2 degrees or +/- 3.8 prism diopters [PD] of calculated strabismic deviation) for the horizontal deviation and +/- 0.28 mm (equivalent to +/- 3.4 degrees or +/- 5.9 PD) for the vertical deviation. The 95% limits of agreement between the Hirschberg measures and the PACT were within +/- 7.8 degrees or +/- 13.7 PD. The average (+/- SD) Hirschberg ratio was 12.3 +/- 1.2 degrees/mm or 21.8 +/- 2.1 PD/mm.

CONCLUSIONS

The video-enhanced Hirschberg measurement shows good reproducibility and ease of application, even in the testing of infants. In quantitative analysis, however, systematic measurement error resulting from intersubject variance of the Hirschberg ratio should be taken into consideration.

Advancement of medial rectus muscle to the original insertion for consecutive exotropia

Twenty-four patients who underwent surgery to correct consecutive exotropia that developed iatrogenically after surgical overcorrection were studied retrospectively. All patients underwent single or bilateral advancement of the medial rectus muscle to the original muscle insertion. The mean preoperative exodeviation was 26.7 prism diopters at distance and 35.2 delta at near. Postoperatively, in cases receiving advancement of a single medial rectus, the mean amount of correction was 23.2 delta at distance and 29.6 delta at near. In cases receiving bilateral medial rectus advancement, the mean amount of postoperative correction was 26.3 delta at distance and 39.8 delta at near. Adduction deficiency was normalized in five patients (71%), while convergence insufficiency was improved in only nine patients (45%) after surgery. Twelve (50%) patients had binocular single vision at distance on a normal or abnormal basis as determined by the Bagolini lens test.

Preoperative prism correction in patients with acquired esotropia

We performed a prospective study of preoperative prism adaptation in 77 patients with acquired esotropia. Sixty-three of them increased their angle of squint when wearing Fresnel press-on prisms for 5-7 days. After the angle had stabilized to a point that did not exceed the press-on prisms by more than 10 prism D, they were randomly divided into two groups. Thirty-two patients underwent surgery based on the prism-adapted angle. The other 31 patients underwent surgery based on their initially measured angle. Fourteen patients who did not respond to prism correction underwent surgery based on the angle before prism correction. Success rates with deviations between 0 and 10 prism diopters measured 1 year after surgery were highest in those in whom surgery was based on the prism-determined angle and were lowest in the nonresponders, who had no fusion response to the prisms.

[Evaluation of preoperative prism adaptation in patients with acquired esotropia]

A prospective study was carried out of the evaluation preoperative prism adaptation in 77 patients with acquired esotropia. Sixty-three patients who showed a stable esodeviation with prisms of 10 prism diopter or less by alternate prism cover test and fusion response to the prisms were classified as prism responders and were randomly classified into two groups. Thirty-one patients of prism responders underwent surgery based on the prism adapted angle. Patients in the other 32 cases were assigned to undergo surgery for their initially measured angle. On the other hand, 14 patients who did not respond to prism adaptation underwent surgery for their preoperative measured angle of deviation. Success rates with deviations of 0 to 10 prism diopters measured 1 year after surgery by the alternative prism cover test at 5 m and with fusion on Bagolini's striated glasses test were highest (26 [84%] of 31 patients) in prism adaptation responders who underwent surgery for prism determined angle and lowest (3 [21%] of 14 patients) in the prism adaptation nonresponder who showed no fusion response to the prisms.