Interferon regulatory factor-1 (IRF-1) is a transcription factor that acts as a tumor suppressor and causes apoptosis in cancer cells. We evaluated IRF-1-induced apoptosis in gastric cancer cell lines. We established stable clones in AGS cells that have a tetracycline-inducible IRF-1 expression system. We used these clones and recombinant adenovirus expressing IRF-1 to explore the mechanism of IRF-1-induced apoptosis in gastric cancer. Expression of IRF-1 causes apoptosis in gastric cancer cell lines as shown by phosphatidylserine exposure and cleavage of caspase-8, caspase-3, and Bid with the mitochondrial release of cytochrome c. However, inhibition of caspase-8 and Bid did not inhibit apoptosis and did not decrease cleaved caspase-9 or mitochondrial release of cytochrome c. We then show that IRF-1 upregulates PUMA (p53 upregulated modulator of apoptosis), which is known to activate apoptosis by the intrinsic pathway; this can be p53-independent. IRF-1 binds to distinct sites in the promoter of PUMA and activates PUMA transcription. Moreover, molecular markers of mitochondrial apoptosis are eliminated in PUMA knockout and knockdown cells and phosphatidylserine exposure is decreased dramatically. Finally, we show that IFN-γ induces IRF-1-mediated upregulation of PUMA in cancer cells. We conclude that IRF-1 can induce apoptosis by the intrinsic pathway independent of the extrinsic pathway by upregulation of PUMA.

The EGFR signaling pathway is frequently activated in human ovarian cancer and associated with poor prognosis. However, inhibition of EGFR signaling in patients with recurrent ovarian cancer has been disappointing. It remains to be addressed whether ovarian cancer patients could benefit from targeting EGFR signaling. Here we investigated the mechanisms underlying the resistance to EGFR inhibition in ovarian cancer and developed a strategy to overcome it. We found that treatment of human ovarian cancer cells with an EGFR inhibitor, gefitinib, resulted in increased STAT3 phosphorylation in a dose- and time-dependent manner. Inhibiting STAT3 activation with a small molecule inhibitor of JAK, an upstream kinase that phosphorylates and activates STAT3, synergistically increased the anti-tumor activity of gefitinib in vitro. Similar results were obtained when STAT3 or JAK1 expression was knocked down. In contrast, inhibiting other signaling pathways, such as AKT/mTOR, MEK or SRC, was relatively less effective. The combined treatment resulted in simultaneous attenuation of multiple survival pathways and increased inhibition of ERK pathway. In addition, the dual inhibition showed a stronger suppression of xenograft tumor growth than either single inhibition. Our findings demonstrate that feedback activation of STAT3 pathway might contribute to the resistance to EGFR inhibition. Combined blockade of both pathways appears to be more effective against human ovarian cancer than inhibition of each pathway alone both in vitro and in vivo. This study may provide a strategy to improve clinical benefit of targeting EGFR pathway in ovarian cancer patients.

JAK/STAT3 is one of the major signaling pathways that is aberrantly activated in ovarian cancer and associated with tumor progression and poor prognosis in patients with ovarian cancer. In this study, we evaluated the therapeutic potential of targeting JAK/STAT3 signaling in ovarian cancer using a peritoneal dissemination mouse model. We developed this mouse model by injecting a metastatic human ovarian cancer cell line, SKOV3-M-Luc, into the peritoneal cavity of immunodeficient mice. This model displayed a phenotype similar to late-stage ovarian cancer, including extensive peritoneal metastasis and ascites production. The constitutive activation of STAT3 in human ovarian cancer cells appeared to be mediated by an autocrine cytokine loop involving the IL6 family of cytokines and JAK1 kinase. shRNA-mediated knockdown of JAK1 or STAT3 in ovarian cancer cells led to reduced tumor growth, decreased peritoneal dissemination, and diminished ascites production, suggesting a critical role of STAT3 in ovarian cancer progression. Similar results were obtained when a small-molecule inhibitor (JAKi) of the JAK1 kinase was used to treat ovarian cancer in this model. In addition, we found that the expression level of IL6 was correlated with activation of STAT3 in ovarian cancer cells both in vitro and in vivo, suggesting a potential application of IL6 as a biomarker. Altogether, our results demonstrate that targeting JAK1/STAT3, using shRNA knockdown or a small-molecule inhibitor, effectively suppressed ovarian tumor progression and, therefore, could be a potential novel therapeutic approach for treating advanced ovarian cancer. Mol Cancer Ther; 13(12); 3037–48. ©2014 AACR.

CD8 ⁺ tumor-infiltrating lymphocytes (TILs) are associated with improved survival in triple-negative breast cancer (TNBC) yet have no association with survival in estrogen receptor–positive (ER ⁺ ) BC. The basis for these contrasting findings remains elusive. We identified subsets of BC tumors infiltrated by CD8 ⁺ T cells with characteristic features of exhausted T cells (T _EX ). Tumors with abundant CD8 ⁺ T _EX exhibited a distinct tumor microenvironment marked by amplified interferon-γ signaling–related pathways and higher programmed death ligand 1 expression. Paradoxically, higher levels of tumor-infiltrating CD8 ⁺ T _EX associated with decreased overall survival of patients with ER ⁺ BC but not patients with TNBC. Moreover, high tumor expression of a CD8 ⁺ T _EX signature identified dramatically reduced survival in premenopausal, but not postmenopausal, patients with ER ⁺ BC. Finally, we demonstrated the value of a tumor T _EX signature score in identifying high-risk premenopausal ER ⁺ BC patients among those with intermediate Oncotype DX Breast Recurrence Scores. Our data highlight the complex relationship between CD8 ⁺ TILs, interferon-γ signaling, and ER status in BC patient survival. This work identifies tumor-infiltrating CD8 ⁺ T _EX as a key feature of reduced survival outcomes in premenopausal patients with early-stage ER ⁺ BC.

Age is an important prognostic factor in papillary thyroid cancer (PTC), with better survival observed in patients < 45 years of age, regardless of stage. Although the impact of increasing age on PTC-related survival is well-known, previous studies have focused on survival relative to age 45 years only. As the number of patients entering their 7th decade of life increases, PTC-related survival in this demographic becomes increasingly important. Survival in patients ≥ 60 years specifically compared to other groups has not previously been examined. We sought to determine whether age ≥ 60 years is an adverse prognostic factor for disease-specific survival and recurrence in patients with PTC. The California Cancer Registry database was linked to inpatient and ambulatory patient records from the Office of Statewide Health Planning and Development for the years 2000–2011. This linked database was queried for patients diagnosed with papillary thyroid cancer and treated with surgery. We then identified prognostic factors related to both 5-year and 10-year disease-specific survival and disease-free survival in patients ≤ 45, 45–59, and ≥ 60 years. Multivariable Cox proportional hazard models were created to test the effect of age ≥ 60 on disease-specific and disease-free survival, controlling for clinical, treatment, and demographic factors. The final cohort included 15,675 patients. Of the group, 46.3% were between 18 and 44 years of age, 33.6% were 45–59 years, and 20.1% were ≥ 60. Univariate analysis showed that compared to other groups, patients ≥ 60 were more likely to be male (p < 0.001), present with tumors > 5 cm (p < 0.001), more likely to have metastatic disease (p < 0.001), less likely to receive radioactive iodine (p < 0.001), and more likely to receive external beam radiation therapy (p < 0.001). In multivariable Cox proportional hazards models for 5 and 10-year disease-free survival, age ≥ 60 was associated with higher risk of disease at 5 and 10-years (HR 2.3 and 1.9 respectively, p < 0.001). Similar results were observed for 5 and 10-year disease-specific survival (HR 38.0 and 30.0 respectively, p < 0.001) after controlling for gender, race, co-morbidity, stage, surgical procedure, radioactive iodine, insurance, and hospital volume. Patients ≥ 60 years of age have worse DSS and DFS after a diagnosis of PTC, across all stages of disease. Given that patients over the age of 45 years have progressively worse survival as they age, these data support having three age groups, 18–44 years of age, 45–59 years, and ≥ 60 as an independent predictor of survival and recurrence to current staging guidelines.