Rapid airway stenosis due to ruptured occipital artery in a patient with neurofibromatosis type I.

Background: Neurofibromatosis type I is rarely associated with vascular abnormalities. Here, we report a case of rapid airway stenosis caused by a ruptured occipital artery that was treated with surgical airway management. Case Presentation: A 40-year-old woman, with no medical history, presented with a chief complaint of a sudden neck pain on the left side. She had a prominent mass in the outer left side of the neck. After arrival at the emergency room, the patient complained of severe dyspnea and experienced a rapid drop in oxygen saturation. Supplemental ventilation was ineffective, and tracheal intubation was attempted; however, laryngeal expansion could not be observed because of the enlarged cervical mass. Therefore, to manage the surgical airway, a cricothyrotomy was first carried out, which resulted in an immediate increase in oxygen saturation. Two percutaneous embolizations and one surgical procedure were carried out, and the patient was discharged without any complications. Conclusion: For a sudden onset cervical mass, airway management should be undertaken, keeping in mind the possibility of worsening rapid airway narrowing due to bleeding.

Transformation of double-hit follicular lymphoma to plasmablastic lymphoma: a partial role of MYC gene rearrangement.

Follicular lymphoma (FL) is genetically characterized by BCL2/IGH translocation. Some FL cases histologically transform to high-grade lymphoma, and the majority of cases transform to diffuse large B-cell lymphoma. We report herein an unusual FL case that transformed to plasmablastic lymphoma (PBL) with MYC gene rearrangement as early as 12 months after FL diagnosis. IGH/MYC translocation, the most common cytogenetic abnormality seen in de novo PBL, was also detected in the transformed tumor (double-hit lymphoma). The patient became resistant to chemotherapy and died 4 months after transformation. We speculate that the "second hit" of MYC rearrangement played a crucial role in PBL transformation (PBL-T) in this case. Highly specific three-color FISH analysis demonstrated the presence of BCL2/IGH/MYC triple fusion signals on a single chromosome as we expected, but BCL2/IGH and IGH/MYC fusion signals also coexisted in a single nucleus. The PBL-T tumor was genetically heterogeneous, despite being histologically quite homogeneous PBL. Surprisingly, three-color FISH analysis revealed that the preceding FL tumor was also genetically heterogeneous, simultaneously harboring BCL2/IGH, IGH/MYC and BCL2/IGH/MYC fusion signals (i.e. double-hit lymphoma), despite being histologically quite homogeneous FL. This suggests that MYC rearrangement played a partial role in PBL-T. Genetic instability including MYC rearrangement in the preceding FL tumor would contribute to PBL-T and poor outcome in this case. This study will broaden our understanding of the pathogenesis of high-grade transformation of FL and help improve patient outcome.

Magnified endoscopic observation of small depressed gastric lesions using linked color imaging with indigo carmine dye.

BACKGROUND AND STUDY AIMS: Magnifying linked color imaging with indigo carmine dye (M-Chromo-LCI) enables sterically enhanced and color image-magnified observation of the superficial gastric mucosa. This study investigated the usefulness of M-Chromo-LCI for the differential diagnosis of gastric lesions. PATIENTS AND METHODS: 100 consecutive small depressed lesions were examined with conventional white-light imaging (C-WLI), magnifying blue-laser imaging (M-BLI), and M-Chromo-LCI. Endoscopic images were reviewed by three experts and three non-experts. Diagnostic accuracy and interobserver agreement were compared among the modalities. RESULTS: For experts, M-BLI showed a significantly higher diagnostic accuracy than C-WLI (82.7 % vs. 67.0 %; P < 0.001). The diagnostic accuracy of M-Chromo-LCI was not different from M-BLI (87.7 % vs. 82.7 %; P = 0.31). For non-experts, M-BLI showed a significantly higher diagnostic accuracy than C-WLI (69.3 % vs. 52.3 %; P < 0.001). M-Chromo-LCI additionally showed a significantly higher diagnostic accuracy than M-BLI (79.7 % vs. 69.3 %; P = 0.005). M-Chromo-LCI had the highest interobserver agreement for each group. CONCLUSIONS: M-Chromo-LCI is expected to become a useful modality for the accurate diagnosis of gastric lesions.

Successful treatment with biweekly CHOP for bone marrow relapse of blastic plasmacytoid dendritic cell neoplasm.

Blastic plasmacytoid dendritic cell neoplasm (BPDCN) is a rare and aggressive hematological malignancy derived from precursors of plasmacytoid dendritic cells. The majority of patients initially respond to multi-agent chemotherapy, though most relapse within a year and the prognosis is very poor. We report a 67-year-old man with erythema on the right chest and a nasopharyngeal mass. Histological examination revealed a mass of tumor cells expressing CD4, CD56, and CD123, but neither CD3 nor CD20. He was diagnosed with BPDCN. Bone marrow involvement was not seen at diagnosis. He achieved complete remission (CR) with CHOP-like chemotherapy. After 1 year, he relapsed with a cutaneous tumor on the head, a nasopharyngeal tumor, and massive bone marrow involvement. Relapsed BPDCN is generally resistant to chemotherapy and the prognosis is dismal. However, he was successfully treated with biweekly CHOP therapy and achieved a second CR lasting 16 months.

Frequent Presence of Lymphovascular Invasion in Small Rectal Neuroendocrine Tumors on Immunohistochemical Analysis.

Rectal neuroendocrine tumors (RNETs) have become common in recent years and are good candidates for endoscopic resection (ER). To achieve clear resection margins, more advanced techniques such as endoscopic submucosal dissection, endoscopic submucosal resection with a ligation device, and cap-assisted endoscopic mucosal resection are available for ER. After ER, lymphovascular invasion (LVI) is regarded as an important predictor of nodal metastasis. Previous studies have shown that small RNETs with LVI were uncommon (0-8.3%). However, using immunohistochemical analysis, a recent study revealed the frequent occurrence of LVI in small RNETs in a systematic manner (46.7%). There is a possibility that the actual detection rate of LVI in small RNETs is not always evaluated accurately because of the limited detection sensitivity of conventional hematoxylin-eosin staining. In addition, the correlation between LVI detected using immunohistochemical analysis and the development of metastasis remains unclear. Further prospective studies are required to clarify the role of LVI detected using immunohistochemical analysis.

Enhanced detection of lymphovascular invasion in small rectal neuroendocrine tumors using D2-40 and Elastica van Gieson immunohistochemical analysis.

Rectal neuroendocrine tumor (RNET) lymphovascular invasion (LVI) is regarded as an important predictor of nodal metastasis after endoscopic resection (ER). However, little is known about the frequency of immunohistochemical detection of LVI in RNETs. This study was performed to establish the actual detection of LVI rate in RNETs ≤10 mm and to evaluate associated clinical outcomes. We retrospectively reviewed the records for 98 consecutive patients treated by ER with a total of 102 RNETs ≤10 mm. Tissue sections were labeled with hematoxylin-eosin (HE) stain, the D2-40 monoclonal antibody to evaluate lymphatic invasion, and Elastica van Gieson (EVG) stain to detect venous invasion. LVI detection rate by HE versus immunohistochemical analysis was compared. Follow-up findings and clinical outcomes were also evaluated for 91 patients who were followed for ≥12 months. Lymphatic and venous invasion were detected using HE staining alone in 6.9% and 3.9% of patients, respectively, whereas they were detected using D2-40 and EVG staining in 20.6% and 47.1% of the patients, respectively. Thus, the LVI detection frequency using D2-40 and EVG staining (56.9%) was significantly higher than with HE (8.8%). Two out of seven patients who required additional surgery had regional lymph node metastases. However, among the 84 patients who were followed up without surgery, no distant metastases or recurrences were detected. Compared with HE staining, immunohistochemical analysis significantly increased the frequency of LVI detection in RNETs ≤10 mm. However, the clinical impact of LVIs detected using immunohistochemical analysis remains unclear. Clarification of the actual role of LVI using immunohistochemical analysis requires a patient long-term follow-up and outcomes.

Impact of host and histopathological factors on the discrepancies in estrogen receptor, and progesterone receptor, and HER2 status between core needle biopsy and surgically excised tumors.

PURPOSE: The high reliability and utility of core needle biopsy (CNB) have been previously described. Our aim in this study was to clarify the host and histopathological factors influencing the discrepancies in ER, PgR, and HER2 status between CNB and surgically excised tumors (SET). METHODS: All patients diagnosed with operable invasive breast cancer in our hospital between January 2005 and April 2015 were included in the study; patients who required neoadjuvant chemotherapy were excluded. ER, PgR, and HER2 expression were assessed between paired CNB and SET samples. ER and PgR status were determined using immunohistochemistry(IHC). HER2 status was determined using IHC and scored from 0 to 3+. Fluorescence in-situ hybridization analysis was carried out in HER2 2+ cases. The cut off point for ER and PgR positivity was set at 1%. RESULTS: A total of 1307 patients were assessed. The concordance rates of ER, PgR, and HER2 status in CNB and SET were 95%, 84% and 97%, respectively. Factors of discrepancy were nuclear grade, histological type, and menopausal status for ER and PgR, and none detected for HER2. The discrepancy factors were assessed with univariate and multivariate analysis. CONCLUSIONS: Using the largest known dataset to date of paired samples from a single institution, we evaluated the accuracy of CNB and the discrepancy factors between CNB and SET in breast cancer patients. We conclude that CNB for ER and PgR assessment in postmenopausal patients before treatment should be used with caution. Further research will contribute to increased CNB accuracy, improving patient treatment decisions.

Impact of infiltrative growth on the outcome of patients with undifferentiated pleomorphic sarcoma and myxofibrosarcoma.

BACKGROUND AND OBJECTIVES: Infiltrative growth, frequently observed in undifferentiated pleomorphic sarcoma (UPS) and myxofibrosarcoma (MFS), is often associated with a positive surgical margin as well as a local failure. The purpose of our study was to determine whether the radiographic growth patterns were associated with the outcomes of patients with UPS and MFS. METHODS: We reviewed 89 patients diagnosed with UPS or MFS and underwent initial surgery at our institute between 1994 and 2011. Growth patterns were assessed radiographically on preoperative MRI. Clinicopathological factors were collected and uni- and multivariate analyses were performed for survival. RESULTS: Infiltrative growth was observed in 21 patients (24%), which correlated with superficial tumors and positive surgical margin. Infiltrative growth correlated with poor disease-specific and distant failure-free survivals relative to non-infiltrative growth. Multivariate analysis confirmed that these factors remained as significant factors. Patients with non-infiltrative tumors resected inadequately exhibited slightly more favorable local control with postoperative radiotherapy, although no clinical benefit was seen for those with infiltrative tumors. CONCLUSIONS: Infiltrative growth was an adverse prognostic factor for not only local control, but also disease-specific and metastasis-free survival in patients with UPS and MFS. Radiotherapy could not salvage inadequately resected infiltrative tumors.

Successful treatment of histiocytic sarcoma with induction chemotherapy consisting of dose-escalated CHOP plus etoposide and upfront consolidation auto-transplantation.

Histiocytic sarcoma (HS) is an extremely rare malignant neoplasm that often exhibits an aggressive clinical presentation. In this report, we describe the case of a 38-year-old female with advanced-stage HS who was found to have a subcutaneous tumor in the left calf and enlarged lymph nodes in the left inguinal and internal iliac regions. The subcutaneous tumor and inguinal nodes were resected operatively. Immunohistochemistry of the surgical specimens showed that the malignant cells stained positive for CD163, CD68, and related markers; a diagnosis of HS was established. Following the administration of induction chemotherapy consisting of dose-escalated CHOP plus etoposide, the remaining internal iliac tumors disappeared. At that point, high-dose chemotherapy with autologous stem cell transplantation was performed as consolidation treatment. The patient remains alive with no evidence of disease for 30 months post-treatment. This report provides valuable insight into the treatment of advanced HS.

Diagnosis of pancreatic neoplasms using a novel method of DNA methylation analysis of mucin expression in pancreatic juice.

Mucins (MUC) play crucial roles in carcinogenesis and tumor invasion in pancreatic ductal adenocarcinoma (PDAC) and intraductal papillary mucinous neoplasms (IPMNs). Our immunohistochemistry (IHC) studies have shown a consensus position on mucin expression profiles in pancreatic neoplasms as follows: MUC1-positive but MUC2-negative expression in PDACs; MUC1-negative but MUC2-positive expression in intestinal-type IPMNs (dangerous type); MUC1-negative and MUC2-negative expression in gastric-type IPMNs (safe type); High MUC4 expression in PDAC patients with a poor outcome; and MUC4-positive expression in intestinal-type IPMNs. We also showed that three mucin genes (MUC1, MUC2 and MUC4) expression in cancer cell line was regulated by DNA methylation. We have developed a novel 'methylation-specific electrophoresis (MSE)' method to analyze the DNA methylation status of mucin genes by high sensitivity and resolution. By using the MSE method, we evaluated pancreatic juice samples from 45 patients with various pancreatic lesions. The results were compared with final diagnosis of the pancreatic lesions including IHC of mucin expression in the paired pancreatic tissues. The results indicated that the DNA methylation status of MUC1, MUC2 and MUC4 in pancreatic juice matched with the mucin expression in tissue. Analyses of the DNA methylation status of MUC1, MUC2 and MUC4 were useful for differential diagnosis of human pancreatic neoplasms, with specificity and sensitivity of 87% and 80% for PDAC; 100% and 88% for intestinal-type IPMN; and 88% and 77% for gastric-type IPMN, respectively. In conclusion, MSE analysis of human pancreatic juice may provide useful information for selection of treatment for pancreatic neoplasms.

Pulmonary artery sarcoma diagnosed by endobronchial ultrasound-guided transbronchial needle aspiration.

Pulmonary artery sarcoma (PAS) is a rare tumor that is often detected at an advanced stage, when disease is so widespread that a radical surgical procedure is no longer indicated. Therefore, less invasive biopsy techniques are required to establish a definitive preoperative diagnosis. Endobronchial ultrasound (EBUS) is useful for producing real-time images of both lymph nodes and the interior of pulmonary arteries adjacent to the bronchi. We report a case with masslike lesions in the pulmonary artery that were observed by EBUS and from which tissue was obtained by endobronchial ultrasound-guided transbronchial needle aspiration (EBUS-TBNA) to establish a diagnosis of PAS.

Preoperative histological subtype classification of intraductal papillary mucinous neoplasms (IPMN) by pancreatic juice cytology with MUC stain.

OBJECTIVE: To prospectively evaluate the diagnostic value of preoperative histological subtyping of intraductal papillary mucinous neoplasms (IPMNs) by pancreatic juice cytology (PJC) with mucin (MUC) stain. BACKGROUND: IPMNs are classified into four subtypes based on their histomorphology and mucin phenotype, and varied degrees of malignant nature and prognosis among these subtypes have been shown. METHODS: The subjects were 36 patients with surgically confirmed IPMNs, who underwent PJC preoperatively by endoscopic retrograde cholangiopancreatography. Histological subtyping of cytological samples with or without MUC stain (MUC1, MUC2, and MUC5AC) was compared with that of resected specimens. RESULTS: Histologically, low-grade dysplasia was found in 4 patients, intermediate in 10, high grade in 11, and invasive carcinoma in 11. Gastric, intestinal, pancreatobiliary, and oncocytic subtypes corresponded to 16, 14, 5, and 1 patient, respectively. The rate of high-grade dysplasia (HGD) and/or invasive IPMNs was 25% for gastric subtype, 85.7% for intestinal subtype, and 100% for both pancreatobiliary and oncocytic subtypes, showing a significant correlation between histological subtype and rate of HGD and/or invasive IPMN (P < 0.01 for gastric vs nongastric).Histological subtype was successfully diagnosed by PJC in 42% (15/36) without MUC stain, and the rate was significantly improved to 89% (32/36) with MUC stain (P < 0.01). The sensitivity, specificity, and overall accuracy of PJC with MUC stain were 86%, 100%, and 94% for intestinal subtype, respectively. When cytological grade was combined with MUC stain, the diagnosis of HGD/invasive IPMN showed 77.2% sensitivity, 85.7% specificity, and 80.5% accuracy. CONCLUSIONS: Preoperative PJC with MUC stain proved to be highly reliable for identifying the histological subtype of IPMN and may provide useful information for deciding surgical indication.

ALK fusion gene positive lung cancer and 3 cases treated with an inhibitor for ALK kinase activity.

BACKGROUND: Anaplastic lymphoma kinase (ALK) fusion gene-positive lung cancer accounts for 4-5% of non-small cell lung carcinoma. A clinical trial of the specific inhibitor of ALK fusion-type tyrosine kinase is currently under way. METHODS: ALK fusion gene products were analyzed immunohistochemically with the materials obtained by surgery or by endobronchial ultrasound-guided transbronchial needle aspiration (EBUS-TBNA). The echinoderm microtubule-associated protein-like 4(EML4)-ALK or kinesin family member 5B (KIF5B)-ALK translocation was confirmed by the reverse transcription polymerase chain reaction (RT-PCR) and fluorescence in situ hybridization (FISH). After eligibility criteria were met and informed consent was obtained, 3 patients were enrolled for the Pfizer Study of Crizotinib (PF02341066), Clinical Trial A8081001, conducted at Seoul National University. RESULTS: Out of 404 cases, there were 14 of EML4-ALK non-small cell carcinoma (NSCLC) and one KIF5B-ALK NSCLC case (8 men, 7 women; mean age, 61.9 years, range 48-82). Except for 2 light smokers, all patients were non-smokers. All cases were of adenocarcinoma with papillary or acinar subtypes. Three were of stage IA, 5 of stage IIIA, 1 of stage IIIB and 6 of stage IV. Ten patients underwent thoracotomy, 3 received chemotherapy and 2 only best supportive care (BSC). One BSC and 2 chemotherapy cases were enrolled for the clinical trial. Patients with advanced stages who received chemotherapy or best supportive care were younger (54.0±6.3) than those who were surgically treated (65.8±10.1) (p<0.05). The powerful effect of ALK inhibitor on EML4-ALK NSCLC was observed. Soon after its administration, almost all the multiple bone and lymph node metastases quickly disappeared. Nausea, diarrhea and the persistence of a light image were the main side effects, but they diminished within a few months. CONCLUSION: ALK-fusion gene was found in 3.7% (15/404) NSCLC cases and advanced disease with this fusion gene was correlated with younger generation. The ALK inhibitor presented in this study is effective in EML4-ALK NSCLC cases. A further study will be necessary to evaluate the clinical effectiveness of this drug.

Overexpression of the transcription factor Yin-Yang-1 suppresses differentiation of HaCaT cells in three-dimensional cell culture.

Yin-Yang-1 (YY1) is a member of the GLI-Krüppel family of transcription factors, and both YY1 mRNA and protein expression have been identified in a number of different tissues and cell types suggesting that it is expressed both constitutively and ubiquitously. In epidermal tissue, however, we reported previously that YY1 protein is expressed at high levels in undifferentiated basal keratinocytes and is downregulated during differentiation toward the suprabasal layers. This differential expression pattern during keratinocyte differentiation suggests that YY1 may have an important role in regulating keratinocyte differentiation. In this study, we examined the role of YY1 in differentiation of the human keratinocyte cell line HaCaT using air-liquid interface three-dimensional culture. The constitutive overexpression of YY1 in HaCaT cells during air exposure-induced differentiation resulted in an undifferentiated phenotype, thickening of the stratified layers, suppression of differentiation marker expression, and retention of proliferative activity. These findings suggested that YY1 may have an important role in maintenance of the undifferentiated phenotype of keratinocytes in the basal epidermal layer, and that reduction of YY1 expression in the suprabasal layers may allow keratinocytes to differentiate and move toward the upper layers of the epidermis.

Bach2 represses plasma cell gene regulatory network in B cells to promote antibody class switch.

Two transcription factors, Pax5 and Blimp-1, form a gene regulatory network (GRN) with a double-negative loop, which defines either B-cell (Pax5 high) or plasma cell (Blimp-1 high) status as a binary switch. However, it is unclear how this B-cell GRN registers class switch DNA recombination (CSR), an event that takes place before the terminal differentiation to plasma cells. In the absence of Bach2 encoding a transcription factor required for CSR, mouse splenic B cells more frequently and rapidly expressed Blimp-1 and differentiated to IgM plasma cells as compared with wild-type cells. Genetic loss of Blimp-1 in Bach2(-/-) B cells was sufficient to restore CSR. These data with mathematical modelling of the GRN indicate that Bach2 achieves a time delay in Blimp-1 induction, which inhibits plasma cell differentiation and promotes CSR (Delay-Driven Diversity model for CSR). Reduction in mature B-cell numbers in Bach2(-/-) mice was not rescued by Blimp-1 ablation, indicating that Bach2 regulates B-cell differentiation and function through Blimp-1-dependent and -independent GRNs.

EML4-ALK fusion gene assessment using metastatic lymph node samples obtained by endobronchial ultrasound-guided transbronchial needle aspiration.

PURPOSE: Anaplastic lymphoma kinase (ALK) fusion genes represent novel oncogenes for non-small cell lung cancers (NSCLC). Several ALK inhibitors have been developed, and are now being evaluated in ALK-positive NSCLC. The feasibility of detecting ALK fusion genes in samples obtained by endobronchial ultrasound-guided transbronchial needle aspiration (EBUS-TBNA) was determined. The clinicopathologic characteristics of ALK-positive lung cancer were also analyzed. EXPERIMENTAL DESIGN: From April 2008 to July 2009, NSCLC cases with hilar/mediastinal lymph node metastases detected by EBUS-TBNA were enrolled. Positive expression of ALK fusion protein was determined using immunohistochemistry, and ALK gene rearrangements were further examined to verify the translocation between ALK and partner genes using fluorescent in situ hybridization and reverse transcription-PCR. Direct sequencing of PCR products was performed to identify ALK fusion variants. RESULTS: One hundred and nine cases were eligible for the analysis using re-sliced samples. Screening of these specimens with immunohistochemistry revealed ALK positivity in seven cases (6.4%), all of which possessed echinoderm microtubule-associated protein-like 4-ALK fusion genes as detected by fluorescent in situ hybridization and reverse transcription-PCR. All ALK-positive cases had an adenocarcinoma histology and possessed no EGFR mutations. Compared with ALK-negative cases, ALK-positive cases were more likely to have smaller primary tumors (P < 0.05), to occur at a younger age (<60 years; P < 0.05), and to occur in never/light smokers (smoking index < 400; P < 0.01). Mucin production was frequently observed in ALK-positive adenocarcinomas (29.4%; P < 0.01). CONCLUSIONS: EBUS-TBNA is a practical and feasible method for obtaining tissue from mediastinal and hilar lymph nodes that can be subjected to multimodal analysis of ALK fusion genes in NSCLC.

Suppression of keratinocyte stratification by a dominant negative JunB mutant without blocking cell proliferation.

Keratinocytes make a stratified epidermoid structure when cultured at an air-liquid interface. The three-dimensional (3D) culture of keratinocytes has been successfully used for more than 25 years, but it is still unclear why keratinocytes stratify in response to air exposure. AP-1 proteins are ubiquitous transcription factors that regulate many biological processes, including cell proliferation, differentiation and apoptosis. We established HaCaT-JunBDeltaN, a human keratinocyte cell line that expressed a mutant JunB with a dominant negative effect on AP-1 activity. Stratification of HaCaT-JunBDeltaN cells was markedly suppressed in a 3D culture condition, in which HaCaT cells stratified similarly to stratified squamous epithelia. However, HaCaT-JunBDeltaN cells had proliferation activities that were closely equivalent to those of HaCaT cells, under both two-dimensional (2D) and 3D culture conditions. To screen for the candidate gene responsible for the different stratification ability, we examined the gene expression profile of HaCaT cells before and after air exposure. Several genes with an antioxidative function, such as aldo-keto reductase and selenoprotein P were highly expressed after air exposure in HaCaT cells but not in HaCaT-JunBDeltaN cells. Our findings indicate the presence of a novel role of AP-1 activity when HaCaT cells make a stratified epidermoid structure under 3D culture conditions.

Synchronous unilateral parotid gland neoplasms of three different histological types.

A 67-year-old male with three synchronous tumors in the unilateral parotid gland is reported. Postoperative histological examinations confirmed the presence of three synchronous primary tumors, specifically pleomorphic adenoma, Warthin's tumor and salivary duct carcinoma, in the right parotid gland. To our knowledge, this is the first case report describing three different histological types in the unilateral parotid gland.

Nuclear positioning of the BACH2 gene in BCR-ABL positive leukemic cells.

BACH2 is a B-cell-specific transcription repressor and is also know as a tumor suppressor in B cell malignancy. Expression of BACH2 is induced in BCR-ABL positive lymphoid cell lines including BV173 by imatinib, a molecular targeting agent for the treatment of chronic myeloid leukemia (CML). Here we show that the activity of the BACH2 gene is related to the nuclear positioning of the gene loci. We examined the spatial association of the BACH2 gene with the centromeric heterochromatin, a transcriptionally repressive subnuclear compartment, by comparing cells with low (BV173 and K562) and high (NAMALWA) levels of BACH2 mRNA. The BACH2 gene was located closer to the centromeric heterochromatin in BV173 and K562 cells as compared to NAMALWA cells. In BV173 cells, the BACH2-centromere distance increased after imatinib treatment to levels similar to those in NAMALWA cells. We also found that diethylmaleate, an oxidative stressor, enhanced the antiproliferative effect of imatinib in only BV173 cells. Since BACH2 induces apoptosis by oxidative stress, these observations suggest that down-regulation of the BACH2 gene through the interaction with centromeric heterochromatin would take part in leukomogenesis of BCR-ABL positive lymphoid leukemia.

Bcr-Abl signaling through the PI-3/S6 kinase pathway inhibits nuclear translocation of the transcription factor Bach2, which represses the antiapoptotic factor heme oxygenase-1.

The malignant phenotype of chronic myeloid leukemia (CML) is due to the abnormal tyrosine kinase activity of the Bcr-Abl oncoprotein. We have previously reported that expression of the Bach2 transcription factor, which induces apoptosis in response to oxidative stress, is greatly reduced in CML cells. Because these cells are resistant to apoptosis, we tested whether Bach2 could also be regulated through posttranslational mechanisms that promote inhibition of the apoptotic response to mutagenic stimuli in CML. We found that Bach2 is phosphorylated on S521 via the phosphatidylinositol-3/S6 kinase pathway, and substitution of this site to alanine leads to nuclear accumulation of the protein, indicating that this phosphorylation is important for its subcellular localization. Ectopic expression of the S521 mutant imparts greater impairment to CML cell growth than the wild-type factor. Furthermore, we showed that Bach2 transcriptionally represses heme oxygenase-1, an antiapoptotic factor up-regulated in CML. Because CML cells are known to produce high levels of intracellular reactive oxygen species, overexpression of heme oxygenase-1 resulting from inhibition of Bach2 activity may contribute to their genomic instability and leukemic phenotype.