Browsing by Author "Christensen, Brock C."

Now showing 1 - 4 of 4
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    A phase 1 study of combined guadecitabine and cisplatin in platinum refractory germ cell cancer
    (Wiley, 2021) Albany, Costantine; Fazal, Zeeshan; Singh, Ratnakar; Bikorimana, Emmanuel; Adra, Nabil; Hanna, Nasser H.; Einhorn, Lawrence H.; Perkins, Susan M.; Sandusky, George E.; Christensen, Brock C.; Keer, Harold; Fang, Fang; Nephew, Kenneth P.; Spinella, Michael J.; Medicine, School of Medicine
    Purpose: Germ cell tumors (GCTs) are cured with therapy based on cisplatin, although a clinically significant number of patients are refractory and die of progressive disease. Based on preclinical studies indicating that refractory testicular GCTs are hypersensitive to hypomethylating agents (HMAs), we conducted a phase I trial combining the next-generation HMA guadecitabine (SGI-110) with cisplatin in recurrent, cisplatin-resistant GCT patients. Methods: Patients with metastatic GCTs were treated for five consecutive days with guadecitabine followed by cisplatin on day 8, for a 28-day cycle for up to six cycles. The primary endpoint was safety and toxicity including dose-limiting toxicity (DLT) and maximum tolerated dose (MTD). Results: The number of patients enrolled was 14. The majority of patients were heavily pretreated. MTD was determined to be 30 mg/m2 guadecitabine followed by 100 mg/m2 cisplatin. The major DLTs were neutropenia and thrombocytopenia. Three patients had partial responses by RECIST criteria, two of these patients, including one with primary mediastinal disease, completed the study and qualified as complete responses by serum tumor marker criteria with sustained remissions of 5 and 13 months and survival of 16 and 26 months, respectively. The overall response rate was 23%. Three patients also had stable disease indicating a clinical benefit rate of 46%. Conclusions: The combination of guadecitabine and cisplatin was tolerable and demonstrated activity in patients with platinum refractory germ cell cancer.
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    Hypermethylation and global remodelling of DNA methylation is associated with acquired cisplatin resistance in testicular germ cell tumours
    (Taylor & Francis, 2021-10) Fazal, Zeeshan; Singh, Ratnakar; Fang, Fang; Bikorimana, Emmanuel; Baldwin, Hannah; Corbet, Andrea; Tomlin, Megan; Yerby, Cliff; Adra, Nabil; Albany, Costantine; Lee, Sarah; Freemantle, Sarah J.; Nephew, Kenneth P.; Christensen, Brock C.; Spinella, Michael J.; Medicine, School of Medicine
    Testicular germ cell tumours (TGCTs) respond well to cisplatin-based therapy. However, cisplatin resistance and poor outcomes do occur. It has been suggested that a shift towards DNA hypermethylation mediates cisplatin resistance in TGCT cells, although there is little direct evidence to support this claim. Here we utilized a series of isogenic cisplatin-resistant cell models and observed a strong association between cisplatin resistance in TGCT cells and a net increase in global CpG and non-CpG DNA methylation spanning regulatory, intergenic, genic and repeat elements. Hypermethylated loci were significantly enriched for repressive DNA segments, CTCF and RAD21 sites and lamina associated domains, suggesting that global nuclear reorganization of chromatin structure occurred in resistant cells. Hypomethylated CpG loci were significantly enriched for EZH2 and SUZ12 binding and H3K27me3 sites. Integrative transcriptome and methylome analyses showed a strong negative correlation between gene promoter and CpG island methylation and gene expression in resistant cells and a weaker positive correlation between gene body methylation and gene expression. A bidirectional shift between gene promoter and gene body DNA methylation occurred within multiple genes that was associated with upregulation of polycomb targets and downregulation of tumour suppressor genes. These data support the hypothesis that global remodelling of DNA methylation is a key factor in mediating cisplatin hypersensitivity and chemoresistance of TGCTs and furthers the rationale for hypomethylation therapy for refractory TGCT patients.
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    Racial Differences in the Tumor Immune Landscape and Survival of Women with High-Grade Serous Ovarian Carcinoma
    (American Association for Cancer Research, 2022) Peres, Lauren C.; Colin-Leitzinger, Christelle; Sinha, Sweta; Marks, Jeffrey R.; Conejo-Garcia, Jose R.; Alberg, Anthony J.; Bandera, Elisa V.; Berchuck, Andrew; Bondy, Melissa L.; Christensen, Brock C.; Cote, Michele L.; Doherty, Jennifer Anne; Moorman, Patricia G.; Peters, Edward S.; Segura, Carlos Moran; Nguyen, Jonathan V.; Schwartz, Ann G.; Terry, Paul D.; Wilson, Christopher M.; Fridley, Brooke L.; Schildkraut, Joellen M.; Epidemiology, Richard M. Fairbanks School of Public Health
    Background: Tumor-infiltrating lymphocytes (TIL) confer a survival benefit among patients with ovarian cancer; however, little work has been conducted in racially diverse cohorts. Methods: The current study investigated racial differences in the tumor immune landscape and survival of age- and stage-matched non-Hispanic Black and non-Hispanic White women with high-grade serous ovarian carcinoma (HGSOC) enrolled in two population-based studies (n = 121 in each racial group). We measured TILs (CD3+), cytotoxic T cells (CD3+CD8+), regulatory T cells (CD3+FoxP3+), myeloid cells (CD11b+), and neutrophils (CD11b+CD15+) via multiplex immunofluorescence. Multivariable Cox proportional hazard regression was used to estimate the association between immune cell abundance and survival overall and by race. Results: Overall, higher levels of TILs, cytotoxic T cells, myeloid cells, and neutrophils were associated with better survival in the intratumoral and peritumoral region, irrespective of tissue compartment (tumor, stroma). Improved survival was noted for T-regulatory cells in the peritumoral region and in the stroma of the intratumoral region, but no association for intratumoral T-regulatory cells. Despite similar abundance of immune cells across racial groups, associations with survival among non-Hispanic White women were consistent with the overall findings, but among non-Hispanic Black women, most associations were attenuated and not statistically significant. Conclusions: Our results add to the existing evidence that a robust immune infiltrate confers a survival advantage among women with HGSOC; however, non-Hispanic Black women may not experience the same survival benefit as non-Hispanic White women with HGSOC. Impact: This study contributes to our understanding of the immunoepidemiology of HGSOC in diverse populations.
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    Refractory testicular germ cell tumors are highly sensitive to the second generation DNA methylation inhibitor guadecitabine
    (Impact Journals, 2017-01-10) Albany, Costantine; Hever-Jardine, Mary P.; von Herrmann, Katherine M.; Yim, Christina Y.; Tam, Janice; Warzecha, Joshua M.; Shin, Leah; Bock, Sarah E.; Curran, Brian S.; Chaudhry, Aneeq S.; Kim, Fred; Sandusky, George E.; Taverna, Pietro; Freemantle, Sarah J.; Christensen, Brock C.; Einhorn, Lawrence H.; Spinella, Michael J.; Medicine, School of Medicine
    Testicular germ cell tumors (TGCTs) are the most common cancers of young males. A substantial portion of TGCT patients are refractory to cisplatin. There are no effective therapies for these patients, many of whom die from progressive disease. Embryonal carcinoma (EC) are the stem cells of TGCTs. In prior in vitro studies we found that EC cells were highly sensitive to the DNA methyltransferase inhibitor, 5-aza deoxycytidine (5-aza). Here, as an initial step in bringing demethylation therapy to the clinic for TGCT patients, we evaluated the effects of the clinically optimized, second generation demethylating agent guadecitabine (SGI-110) on EC cells in an animal model of cisplatin refractory testicular cancer. EC cells were exquisitely sensitive to guadecitabine and the hypersensitivity was dependent on high levels of DNA methyltransferase 3B. Guadecitabine mediated transcriptional reprogramming of EC cells included induction of p53 targets and repression of pluripotency genes. As a single agent, guadecitabine completely abolished progression and induced complete regression of cisplatin resistant EC xenografts even at doses well below those required to impact somatic solid tumors. Low dose guadecitabine also sensitized refractory EC cells to cisplatin in vivo. Genome-wide analysis indicated that in vivo antitumor activity was associated with activation of p53 and immune-related pathways and the antitumor effects of guadecitabine were dependent on p53, a gene rarely mutated in TGCTs. These preclinical findings suggest that guadecitabine alone or in combination with cisplatin is a promising strategy to treat refractory TGCT patients.