The potential role of STAT3 In the APE1/NF-kB regulatory axis in K-rasLSL.G12D/+;Pdx-1-Cre (KC) pancreatic tumor model

APE1/Ref-1 (apurinic/apyrimidinic endonuclease-redox effector factor 1) is a multifunctional protein that has been shown to be overexpressed in multiple types of cancer. The overexpression of APE1/Ref-1 is linked to higher cancer cell survival and increased patient mortality. Furthermore, APE1/Ref-1 is a key regulator of transcription factors (TF) through redox signaling and protein-protein interaction. It is involved in proliferative and inflammatory signaling upregulated in cancer. Transcription factor NF-kB is involved in inflammatory cytokine expression and has been shown to be regulated by Ref-1. My project investigated how Ref-1 regulates NF-kB, specifically Rel-A, in a model using K-rasLSL.G12D/+; Pdx-1-Cre (KC) pancreatic tumor cells (KC3590) derived from genetically engineered mice. Additionally, I explored other TFs within the APE1/Ref-1 signaling pathway, such as STAT3, in this model. My work involved knocking down STAT3 levels within four variations of the KC3590 line. These were the KC3590/ΔNF-kB (parent) and KC3590/ΔNF-kB vector lines (vector) which contain exon deletions within the NF-kB gene rendering it nonfunctional. KC3590/13 and KC3590/15 are cell lines which are KC3590/ΔNF-B cells with functional full-length NF-kB added to the cells. Previous experiments demonstrated that the ΔNF-kB and ΔNF-kB vector lines are resistant to treatment by the specific Ref-1 inhibitors, including APX3330, which inhibit the redox signaling function of Ref-1. Initial data demonstrated that adding back functional NF-kB to the NF-kB deficient cells reestablished sensitivity to APX3330, presumably due to the reintroduction of the Ref-1 target, NF-kB. Knockdown of STAT3 expression in the ΔNF-kB and ΔNF-kB vector lines demonstrated some sensitivity to APX3330, however, in the C13/15 cell lines, no enhanced sensitivity was observed. These data support the hypothesis that NF-kB is the major TF driving the growth of KC pancreatic tumor cells. Subsequent studies will clarify further the role of APE1/Ref-1 regulation in the KC model and the relative importance of APE1/Ref-1’s target TFs.

Thioredoxin 1 (Trx1) is associated with poor prognosis in clear cell renal cell carcinoma (ccRCC): an example for the crucial role of redox signaling in ccRCC

Purpose Thioredoxins are major regulatory proteins of oxidative signaling. Trx1 is the most prominent thioredoxin and, therefore, the current study sought to evaluate the prognostic role of Trx1 in ccRCC. Methods and patients A tissue micro-array (TMA) study was carried out to evaluate the association of Trx1 with clinicopathological features and survival outcome. Data from the Cancer Genome Atlas (TCGA) were evaluated for the association of characteristics in the Trx1 gene with clinicopathological features and survival outcome. Results In the TMA, patients with ccRCC that had high Trx1 levels had lower T stages (p < 0.001), less often distant metastases (p = 0.018), lower nuclear grades (p < 0.001), and less often tumor necrosis (p = 0.037) or sarcomatoid features (p = 0.008). Patients with a combined score of ≥ 10 had better DSS than patients with a low combined score of < 10 (HR 95% CI 0.62 (0.39–0.98)). Interestingly, the survival outcome is compartment specific: ccRCC patients whose tumors had exclusively Trx1 expression in the cytoplasm had the worst survival outcome (HR 3.1; 95% CI 1.2–8.0). Genomic data from the TCGA demonstrated that patients with ccRCCs that had Trx1 losses had more advanced clinicopathological features and worse survival outcome in disease specific (p < 0.001), overall (p = 0.001), and progression free survival (p = 0.001) when compared to patients with ccRCCs without copy number variations (CNV) or gains. Conclusion The current study suggests a possible role of Trx1 in the tumor biology of ccRCC and thus, the current study strongly advises in depth investigations of redox signaling pathways in ccRCC.