PS02.047: TARGETED SILENCING OF SOX2 BY AN ARTIFICIAL TRANSCRIPTION FACTOR SUPPRESSED THE GROWTH OF ESOPHAGEAL CANCER CELLS

Abstract Background SOX2 is a transcription factor that is fundamental for early development and for the maintenance of stem cells in multiple adult tissues and also plays an important role in squamous cell differentiation. Amplification of chromosome 3q26 is the most common of the genetic alterations found in squamous cell carcinoma (SCC). SOX2 is a candidate oncogene present in this locus and amplification of SOX2 has been reported in lung and esophageal squamous cell SCC. In this study, we have developed a zinc finger-based artificial transcription factor (ATF) to selectively suppress SOX2 expression in cancer cells and termed the system ATF/SOX2. Methods We engineered the ATF using six zinc finger arrays designed to target a 19 bp site in the SOX2 distal promoter and a KOX transcriptional repressor domain. A recombinant adenoviral vector Ad-ATF/SOX2 that expresses ATF/SOX2 suppressed SOX2 at the mRNA and protein levels in esophageal SCC cells(TE1 and TE4) expressing SOX2. Results Ad-ATF/SOX2 decreased esophageal SCC cells proliferation and colony formation more effectively than the recombinant adenoviral vector Ad-shSOX2, which expresses SOX2 short hairpin RNA (shSOX2). Ad-ATF/SOX2 induced the cell cycle inhibitor CDKN1A more strongly than Ad-shSOX2. Moreover, Ad-ATF/SOX2 effectively inhibited tumor growth in a SCC xenograft mouse model. Conclusion In this study, we have shown that the targeted down-regulation of SOX2 using ATF based technologies can be used as an effective tool for the treatment of SCC in esophageal cancers that express SOX2. Our results indicate that ATF/SOX2 would lead to the development of an effective molecular-targeted therapy for esophageal SCC. Disclosure All authors have declared no conflicts of interest.

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Exploring the Role of a Novel Tumor Suppressor - OSR2 in T-ALL

Blood ◽

10.1182/blood-2020-142772 ◽

2020 ◽

Vol 136 (Supplement 1) ◽

pp. 26-26

Author(s):

Arpan A. Sinha ◽

Pilar I. Andrade ◽

Megan Malone-Perez ◽

Syed T Ahmed ◽

J. Kimble Frazer

Keyword(s):

Transcription Factor ◽

Tumor Suppressor ◽

Childhood Cancer ◽

Conflicts Of Interest ◽

Lymphoblastic Leukemia ◽

Expression Patterns ◽

Tumor Biology ◽

Transgenic Animals ◽

Genetic Alterations ◽

Allelic Loss

Acute lymphoblastic leukemia (ALL) is the most common childhood cancer, representing >25% of all cancers in children 0-14 years. Despite major advancements in pediatric ALL treatment, it remains the second most lethal childhood cancer, accounting for ~25% of deaths. The two types of ALL are precursor-B, or B-ALL, and precursor-T, or T-ALL, which have distinct molecular landscapes. Of these types, T-ALL comprises about 15% and 25% of pediatric and adult cases, respectively, and is historically considered more aggressive and treatment-resistant, with an inferior prognosis. In the precision medicine era, it is imperative to identify genetic alterations and aberrant gene expression patterns, to better understand tumor biology and improve treatment outcomes by identifying new therapeutic targets. Our study investigates a novel transcription factor, odd-skipped related transcription factor 2 (OSR2), which we hypothesize is a putative T-ALL tumor suppressor. We are using a zebrafish T-ALL model expressing transgenic human MYC (hMYC) regulated by a lymphoblast-specific promoter, rag2. Prior work in zebrafish and human T-ALL found low OSR2 levels in ~95% of T-ALL. Based on this, we then used RNA-seq to analyze 10 hMYC zebrafish T-ALL, confirming low-to-absent osr2 in all 10 T-ALL relative to wild-type (WT) T cells. We further confirmed decreased osr2 expression by qRT-PCR of additional T-ALL and WT thymocytes. We hypothesized that if OSR2 suppresses T-ALL, impaired zebrafish Osr2 function might increase T-ALL incidence and shorten latency. To test this, we bred osr2-mutant fish to rag2:hMYC transgenic animals to create three genotypes: heterozygous osr2-mutant (osr2het) fish, heterozygous hMYC (hMYChet) fish, and compound-heterozygote (osr2het;hMYChet) fish. We screened these genotypes for T-ALL incidence by serial fluorescence microscopy, with T-ALL subsequently confirmed by fluorescence-based flow cytometry. By 7 months of age, we found 9/18 (50%) of double-heterozygous fish developed T-ALL, compared to 0/7 hMYChet fish (p = 0.026); osr2het fish also did not develop T-ALL. Together, our findings suggest osr2 allelic loss accelerates MYC-driven T-ALL, supporting our hypothesis that osr2 is a T-ALL tumor suppressor. Disclosures No relevant conflicts of interest to declare.

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