Background: Recurrent glioblastoma (GBM) is resistant to available treatments and continued growth of the tumor is inevitable; this process is facilitated by the expression of genes regulated by the Signal Transducer and Activator of Transcription (STAT) family of transcription factors, namely STAT5, active in the invasive rim of GBM tumors. Currently, there are no targeted therapies for recurrent GBM that increase the overall patient survival rate. This study aims to analyze the differential expression of genes regulated by STAT5 between primary and recurrent GBM.<br/>Methods: Analysis of whole exome and RNA sequencing were performed on matched bulk primary and multiple recurrent tumor samples from GBM patients who received the current standard care to determine significant changes in gene expression of STAT3/5 targets. <br/>Results: Statistical analysis reveals a decrease in Synaptotagmin 2 (SYT2) and Pleckstrin Homology Domain Containing A3 (PLEKHA3) at recurrence, previously identified as potential STAT5 targets. <br/>Conclusions: To get a better understanding of the roles of STAT5 in GBM recurrence, their downstream effects need to be better understood. The transcriptomic program initiated by STAT5 activation is distinct from that of STAT3 activation. The roles of STAT5 target genes in GBM are poorly characterized, so further research should focus on understanding the effects of altered expression of these genes as they relate to STAT3/5 in GBM recurrence.

Background: Esophageal adenocarcinoma (EAC) is one of the only malignancies whose incidence is rising in the United States. Current multidrug treatment for EAC has considerable toxic side effects that necessitate the development of less toxic, more specific target drugs. Recent large scale genomic analysis reveals that TP53 is the most frequently inactivated gene in EAC. One of the primary functions of TP53 and its gene product, the tumor suppressor p53, is in regulation of DNA repair in response to DNA damage. Inactivation of TP53 results in loss of the G1/S cell cycle checkpoint, and dependence on the G2/M checkpoint for DNA repair. Activity of cyclin-dependent kinase 1 (CDK1) is necessary for cells to exit the G2/M checkpoint and enter mitosis. Phosphorylation of CDK1 by the wee1 kinase inhibits CDK1 in response to DNA damage, allowing cells to maintain G2 arrest and repair the damaged DNA. Active in normal cells, wee1 kinase is critical in cancer cells to promote DNA repair and cell survival in response to DNA damage, particularly from commonly used DNA damaging therapies. AZD1775 is a small molecule inhibitor of wee1 kinase, currently under investigation in clinical trials. AZD1775 differentially targets cancer cells by blocking wee1 mediated inhibition of CDK1 and consequently preventing G2/M arrest in response to DNA damage. Combination of AZD1775 with DNA damaging agents is thought to push cancer cells with damaged DNA through to mitosis and initiate apoptosis instead of G2/M arrest and DNA repair. Based upon the incidence of TP53 mutation in EAC, we hypothesize that treatment with a DNA damaging agent in combination with AZD1775 will be as effective at eliciting DNA damage and cell death as the more toxic current standard of care, which is comprised of treatment with cisplatin, docetaxel, and radiation. Methods: p53 mutant EAC cell lines were dosed with cisplatin, AZD1775, and the combination of cisplatin and AZD1775, and then assayed for viability. Nude mice were implanted with p53 mutant patient derived xenograft esophageal adenocarcinoma tumors and randomized for treatment with AZD1775 alone, cisplatin and AZD1775, radiation and AZD1775, cisplatin, docetaxel, and radiation or vehicle (control). Tumor volume was measured over the five week treatment course. Results: In vitro and in vivo assays reveal a potent synergistic effect between AZD1775 and DNA damaging agents that is as efficacious as the standard of care therapy. The difference in AZD1775 sensitivity among TP53 mutant EAC cell lines indicates that TP53 alone may not be an adequate biomarker to assess for AZD1775- mediated toxicity.

Prevalence of esophageal adenocarcinoma (EAC) has increased six-fold in the United States over the past four decades due to increases in associated risk factors, namely obesity and gastroesophageal reflux disease. The most common genomic driver of EAC, tumor protein 53 (TP53) mutation, has previously been therapeutically intractable, affirming the unmet clinical need to deploy novel therapeutic strategies targeting this genomic driver in this tumor type. 72 percent of EAC patients have mutations in TP53, making tumors more reliant on the G2/M checkpoint to repair DNA damage, increasing likelihood of efficacious G2/M abrogation via targeting WEE1 G2 checkpoint kinase (WEE1), a modulator of this checkpoint. We hypothesize that the G2/M checkpoint represents a viable therapeutic avenue against the most common genomic driver of EAC. We investigated the efficacy of the WEE1 inhibitor AZD1775 on EAC cells. WEE1 mRNA expression levels in EAC are elevated compared to normal tissue controls. AZD1775 was shown to induce cyclin dependent kinase 1 (CDK1) mediated cell cycle progression and increased DNA damage markers as exposure increased via immunoblot analysis. SK-GT- 4 EAC cell line viability was significantly reduced by up to 30 percent when treated with AZD1775 and cisplatin when compared to cisplatin alone. AZD1775 monotherapy showed high efficacy in some EAC settings. Simultaneous dual therapy demonstrated the highest overall efficacy, and stepwise sequential treatments offered negligible benefit. Future research will explore the genomic contexts of the EAC celllines used in order to understand the different responses to AZD1775 monotherapy regimens. Ionizing radiotherapy will be employed in order to understand the DNA damage response timeline, providing more information on the mechanisms of G2/M checkpoint inhibitors in this disease setting. This research will provide insight into novel therapeutic targets for EAC leading to therapeutic testing and improved patient outcome.