A case of AML characterized by a novel t(4;15)(q31;q22) translocation that confers a growth-stimulatory response to retinoid-based therapy

Here we report the case of a 30-year-old woman with relapsed acute myeloid leukemia (AML) who was treated with all-transretinoic acid (ATRA) as part of investigational therapy (NCT02273102). The patient died from rapid disease progression following eight days of continuous treatment with ATRA. Karyotype analysis and RNA-Seq revealed the presence of a novel t(4;15)(q31;q22) reciprocal translocation involving theTMEM154andRASGRF1genes. Analysis of primary cells from the patient revealed the expression ofTMEM154-RASGRF1mRNA and the resulting fusion protein, but no expression of the reciprocalRASGRF1-TMEM154fusion. Consistent with the response of the patient to ATRA therapy, we observed a rapid proliferation of t(4;15) primary cells following ATRA treatment ex vivo. Preliminary characterization of the retinoid response of t(4;15) AML revealed that in stark contrast to non-t(4;15) AML, these cells proliferate in response to specific agonists of RARα and RARγ. Furthermore, we observed an increase in the levels of nuclear RARγ upon ATRA treatment. In summary, the identification of the novel t(4;15)(q31;q22) reciprocal translocation opens new avenues in the study of retinoid resistance and provides potential for a new biomarker for therapy of AML

Abstract 1363: Inhibition of the PI3K/AKT/mTOR Pathway Leads to Down-Regulation of c-Myc and Overcomes Resistance to ATRA in Acute Myeloid Leukemia.

Acute Promyelocytic Leukemia (APL) accounts for 5% of all cases of acute myeloid leukemia (AML). This disease is highly curable with all-trans-retinoic acid (ATRA) based therapy. In non-APL AML, ATRA has limited activity, and little is known about mechanisms of ATRA resistance. The apparent selective efficacy of ATRA in PML/RARα-associated APL poses an important question as to whether the presence of this fusion protein renders APL uniquely susceptible. Two compelling arguments can be made to counter this view. First, experiments in vitro show that ATRA effectively differentiates HL-60 cell lines, which lack the PML/RARα fusion protein. Second, clinical studies with ATRA in previously untreated older AML patients (excluding APL) have reported clinical activity. These observations confirm the therapeutic potential of ATRA beyond APL. In this context, our group has previously identified the lysine demethylase LSD-1, as a therapeutic target to re-sensitize leukemic blasts to ATRA. A clinical investigation of ATRA combined with LSD-1 inhibition is currently underway (NCT02273102). It is likely that other defects leading to ATRA resistance will be similarly amenable to pharmacologic manipulation. Defects in the proto-oncogene c-Myc have been widely implicated in the initiation and maintenance of AML. Over-expression of c-Myc in leukemic blasts enhances clonogenic survival and blocks ATRA induced differentiation. We hypothesized that down-regulation of c-Myc might increase the anti-leukemic effects of ATRA in AML. To date, c-Myc has been an evasive target for direct pharmacologic inhibition however, inhibitors of the PI3K/AKT/mTOR pathway have been shown to indirectly lower levels of c-Myc in leukemic blasts. In the current study, we show that the pro-differentiation effects of ATRA are markedly potentiated when combined with agents that target PI3K/AKT/mTOR signalling. In AML cell lines and primary patient samples, we observed additive pro-differentiation effects when ATRA was combined with inhibitors of PI3K (ZSTK474) and mTOR complex proteins (Torin-1, WYE-125132). However, when combined with the bromodomain inhibitor NVP-BEZ235, a dual inhibitor of PI3K and mTOR, we observed synergistic induction of CD11b by FACS analysis. Combination studies revealed loss of cell viability, cell cycle arrest in G1 phase, and impaired clonogenic survival, which was more prominent for ATRA combination treatments than with any agent used alone (Figure 1). To assess the role of c-Myc in mediating these effects, we measured c-Myc protein levels and PI3K/AKt/mTOR pathway markers at different time-points following treatment with ATRA alone and in combination with the inhibitors described above (Figure 2). Our findings suggest that ATRA alone quickly down-regulates c-Myc (within 6 hours) through transcriptional repression. Disruption of the PI3K/AKT/mTOR pathway further down-regulates c-Myc (within 3 hours) through destabilization and enhanced degradation. ATRA combined with NVP-BEZ235 produced maximal c-Myc suppression, and led to more cell kill than any other combination tested. Detailed analysis of changes in the transcriptome in MV-411 cells following treatment with ATRA and NVP-BEZ235 revealed that both agents act jointly on the regulation of the same biological pathways and processes, but regulate different sets of genes within these pathways. Updated mechanism based studies will be presented. In conclusion, suppression of c-Myc levels through disruption of PI3K/AKT/mTOR signalling augments the anti-leukemic effects of ATRA. These data support the clinical investigation of ATRA combined with rapalogs or bromodomain inhibitors

Characterization of the 5′-flanking region of the gene encoding the 50 kDa subunit of human DNA polymerase δ

DNA polymerase δ consists of at least four subunits: p125, p68, p50, and p12 [Liu et al., J. Biol. Chem. 275 (2000) 18739–18744]. We have isolated genomic DNA clones covering the gene for the human DNA polymerase δ 50 kDa subunit (POLD2) and its 5′-flanking sequence. The POLD2 gene is composed of 11 exons and is distributed over 10 kb of genomic DNA. All exon–intron splice junctions conformed to the GT/AG consensus sequence. The 5′-flanking region of human POLD2 is G+C-rich and does not have a typical TATA box. A computer-based search for potential transcription factor binding sites revealed the existence of a number of motifs including those for AP1, AP2, Sp1, NF-1 and CREB. The functional activity of the regulatory region of the human POLD2 gene was demonstrated by its ability to drive the expression of a chloramphenicol acetyltransferase reporter gene in COS-7 cells

Cloning and characterization of the 5′ flanking region of the sialomucin complex/rat Muc4 gene: promoter activity in cultured cells

Sialomucin complex (SMC/Muc4) is a heterodimeric glycoprotein complex consisting of a mucin subunit ascites sialoglycoprotein-1 (ASGP-1) and a transmembrane subunit (ASGP-2), which is aberrantly expressed on the surfaces of a variety of tumour cells. SMC is transcribed from a single gene, translated into a large polypeptide precursor, and further processed to yield the mature ASGP-1/ASGP-2 complex. SMC has complex spatial and temporal expression patterns in the normal rat, suggesting that it has complex regulatory mechanisms. A crude exon/intron map of the 5' regions of the SMC/Muc4 gene generated from clones isolated from a normal rat liver genomic DNA library reveals that this gene has a small first exon comprising the 5' untranslated region and signal peptide, followed by a large intron. The second exon appears to be large, comprising the 5' unique region and a large part (probably all) of the tandem repeat domain. This structure is strikingly similar to that reported for the human MUC4 gene. Using PCR-based DNA walking, 2.4 kb of the 5'-flanking region of the SMC/Muc4 gene was cloned and characterized. Promoter-pattern searches yielded multiple motifs commonly found in tissue-specific promoters. Reporter constructs generated from this 2.4 kb fragment demonstrate promoter activity in primary rat mammary epithelial cells (MEC), the human colon tumour cell line HCT-116, and the human lung carcinoma cell line NCI-H292, but not in COS-7 cells, suggesting epithelial cell specificity. Deletion constructs of this sequence transfected into rat MEC or HCT-116 cells demonstrate greatly varying levels of activity, suggesting that there are positive and negative, as well as tissue-specific, regulatory elements in this sequence. Taken together, these data suggest that the rat SMC/Muc4 promoter has been identified, that it is tissue- (epithelial cell-) specific, and that there are both positive and negative, as well as tissue-specific, regulatory elements in the sequence

PEA3 transactivates the Muc4/sialomucin complex promoter in mammary epithelial and tumor cells

Sialomucin complex (SMC, rat Muc4) is a heterodimeric glycoprotein composed of two subunits, the mucin component ascites sialoglycoprotein ASGP-1 and the transmembrane subunit ASGP-2, which is aberrantly expressed on the surfaces of a variety of tumor cells. Up-regulation of the Muc4/SMC gene in the 13762 sublines of the rat mammary adenocarcinoma correlates with the overexpression of transcription factor PEA3 and the receptor tyrosine kinase ErbB2. Here we report that PEA3 is capable of transactivating the Muc4/SMC promoter in a dose-dependent manner via direct attachment to a PEA3 binding site. ERM and ER81, the other two members of the PEA3 subfamily of transcription factors, could not transactivate the Muc4/SMC promoter. Transcriptional activation of Muc4/SMC by PEA3 is potentiated by Ras and MEKK1 kinases. These data suggest that expression of PEA3 in mammary tumors leads to up-regulation of Muc4/SMC transcription, the gene product of which may contribute to the metastatic potential of mammary tumors

Abstract 3627: Head and neck squamous cell carcinoma in African Americans: A simple oral rinse detection test using solCD44 and total protein

Abstract The burden of head and neck squamous cell carcinoma (HNSCC) is greater for African Americans (AA) than for Whites with both incidence and disease-specific mortality higher in AA. Early detection tests are needed because the majority of patients present in late stage when cure rates reach only 40%. Our group has developed a prototype early detection test based on soluble CD44 (solCD44) and total protein levels that is simple, inexpensive and noninvasive. Subjects included 21 HNSCC AA patients and 68 AA controls recruited from the University of Miami Hospital and Clinics, Jackson Memorial Hospital and Liberty City Community in Miami-Dade County. The majority of cases and controls come from underserved populations of low SES. A one-way ANOVA of the two cancer types and controls followed by pairwise comparisons using the Student t-test, and comparison of all cases vs. controls using the contrast method were computed. The effects of solCD44 and total protein on the risk of being a case was evaluated using univariate and multivariate logistic regression analyses. We report odds ratio (OR) estimates with corresponding 95% confidence interval (95% CI) and area under the curve (AUC) of the operating characteristic curve (ROC) for all fitted models. The groups did not differ in regards to gender (p=0.684), but did differ significantly in age (cases were older, mean 60 vs. 50, p&amp;lt;.0001) and ethnicity (19% Hispanic in cases vs. none in controls, p=.003). Log2solCD44 and total protein showed significantly elevated levels in cases compared to controls (2.12 vs. 0.76, p&amp;lt;.0001 and 1.19 vs. 0.72, p=.001, respectively). Lip/oral cavity and oropharynx cancer cases and controls were significantly different with respect to log2solCD44 and total protein at p&amp;lt;0.05. Among cancer patients, difference in means by disease site was only statistically significant for log2solCD44 (lower for oropharynx than lip/oral cavity (1.86 vs. 3.21) at p&amp;lt;0.05). Univariately, both markers seemed to have good predictive ability (log2solCD44 AUC=0.814, OR=4.52, p=.0001 and total protein AUC=0.714, OR=5.66, p=.0015). The best models were log2solCD44 (OR=3.66) adjusted for age and gender (AUC=0.930), total protein (OR=5.25) adjusted for age and gender (AUC=0.899), and log2solCD44 (OR=3.17) and protein (OR=1.80) together adjusted for age and gender (AUC=0.930). In this last model, log2solCD44 maintained its effect in the presence of protein; however log2solCD44 appears to be a confounder for protein, reducing considerably its effect. Tests of effect modification (interactions) of ethnicity and age on log2 solCD44, on total protein, and between markers were carried out, and there were no interactions found. Our preliminary data on AA underserved populations show great promise for detecting HNSCC. In addition, our findings strongly suggest that race, gender and age are very important components for HNSCC early detection studies. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 3627. doi:1538-7445.AM2012-3627</jats:p

Abstract 279: Small interfering RNA targeting CD44 blocks EGFR signaling in head and neck squamous cell carcinoma (HNSCC)

Abstract INTRODUCTION: Head and Neck Squamous Cell Carcinoma (HNSCC) is a disease that accounts for 90% of the 600,000 new diagnoses of head and neck cancers worldwide each year. CD44 is a purported cancer stem cell (CSC) marker, and its colocalization with EGFR has been proposed to activate tyrosine kinase (TK) and mitogen-activated protein kinase (MAPK). Therapies tend to have dismal cure rates. Understanding the interaction between CD44 and EGFR may result in improved therapies for HNSCC. METHODS: To evaluate the effect of CD44 on EGFR, we inhibited CD44 expression in a CD44-overexpressing HNSCC cell line, CAL27, using the siRNA method. The cell line was stably transfected with a DNA plasmid designed to knock down the expression of CD44. We then performed western blots examining CD44 and phosphorylated EGFR (Y1068) in siRNA knockdown clones and in scrambled sequence, followed by implantation of the CD44siRNA clones and scramble controls in nude mice. The mice were sacrificed, and the tumors were embedded in paraffin for IHC analysis. CD44 and EGFR colocalization was examined in 5 HNSCC cases and in CAL 27 xenografts by immunohistochemistry (IHC) and laser scanning confocal microscopy (LSCM). RESULTS: Downregulation of CD44 by siRNA in CAL 27 cells inhibited constitutive EGFR phosphorylation in vitro and in vivo. Knocking down of CD44 by siRNA reduced the tumor growth in mice compared to CAL 27 and scrambled siRNA. CD44 and EGFR coexpression and colocalization were observed in 80% (4/5) of HNSCC cases and in CAL 27 xenografts. CONCLUSION: Based on these studies, targeting CD44 may provide an additional therapeutic option for HNSCC that does not respond favorably to other treatments. Anti- CD44 therapy in HNSCC may target the cancer stem cell population and alter EGFR signaling. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 279. doi:1538-7445.AM2012-279</jats:p

Muc4/Sialomucin Complex in the Mammary Gland and Breast Cancer

MUC4 is a one of the membrane mucins of the mucin gene (MUC) family, characterized by mucin tandem repeat domains and a transmembrane domain which associates it with the cell plasma membrane. Although MUC4 is encoded by a single gene, it is produced by epithelial cells as a heterodimer through a proteolytic cleavage mechanism. This heterodimer is found in both membrane and soluble forms associated with epithelia. Functionally, MUC4 is proposed to provide a protective mechanism for vulnerable epithelia, such as those of the airway, eye, female reproductive tract and mammary gland. The protective mechanism(s) may be highjacked by some carcinomas, such as those of the breast, to increase tumor progression. Two mechanisms are proposed to contribute to the MUC4 functions. First, MUC4 acts as an anti-adhesive or anti-recognition barrier at epithelial or tumor cell surfaces. Second, MUC4 can bind the receptor tyrosine kinase ErbB2 and alter its cellular signaling. Expression of MUC4 in mammary gland is repressed by posttranscriptional mechanisms involving basement membrane and TGF-β, which are relieved during pregnancy to permit secretion of MUC4 into milk. These mechanisms are also abrogated in some breast cancers, providing a scenario for promotion of tumor progression. These observations imply important functions for MUC4 in both normal mammary function and in breast cancer