Terry J. Shackleford

JAB1/CSN5: a new player in cell cycle control and cancer

Abstractc-Jun activation domain-binding protein-1 (Jab1) acts as a modulator of intracellular signaling and affects cellular proliferation and apoptosis, through its existence as a monomer or as the fifth component of the constitutive photomorphogenic-9 signalosome (CSN5). Jab1/ CSN5 is involved in transcription factor specificity, deneddylation of NEDD8, and nuclear-to-cytoplasmic shuttling of key molecules. Jab1/CSN5 activities positively and negatively affect a number of pathways, including integrin signaling, cell cycle control, and apoptosis. Also, more recent studies have demonstrated the intriguing roles of Jab1/CSN5 in regulating genomic instability and DNA repair. The effects of Jab1/CSN5s multiple protein interactions are generally oncogenic in nature, and overexpression of Jab1/CSN5 in cancer provides evidence that it is involved in the tumorigenic process. In this review, we highlight our current knowledge of Jab1/CSN5 function and the recent discoveries in dissecting the Jab1 signaling pathway. Further, we also discuss the regulation of Jab1/CSN5 in cancers and its potential as a therapeutic target.

Effect of low-fat diets on plasma levels of NF-κB-regulated inflammatory cytokines and angiogenic factors in men with prostate cancer.

Diet, nutritional status, and certain dietary supplements are postulated to influence the development and progression of prostate cancer. Angiogenesis and inflammation are central to tumor growth and progression, but the effect of diet on these processes remains uncertain. We explored changes in 50 plasma cytokines and angiogenic factors (CAF) in 145 men with prostate cancer enrolled in a preoperative, randomized controlled phase II trial with four arms: control (usual diet), low-fat (LF) diet, flaxseed-supplemented (FS) diet, and FS+LS diet. The mean duration of dietary intervention was 30 to 31 days. Among the individual arms, the largest number of significant changes (baseline vs. preoperative follow-up) was observed in the LF arm, with 19 CAFs decreasing and one increasing (P < 0.05). Compared with the control arm, 6 CAFs—including proangiogenic factors (stromal-cell derived-1α) and myeloid factors (granulocyte-colony-stimulating factor, macrophage colony-stimulating factor)—all decreased in the LF arm compared with controls; three and four CAFs changed in the FS and FS+LF arms, respectively. Weight loss occurred in the LF arms and significantly correlated with VEGF decreases (P < 0.001). The CAFs that changed in the LF arm are all known to be regulated by NF-κB, and a pathway analysis identified NF-κB as the most likely regulatory network associated with these changes in the LF arm but not in the FS-containing arms. These results suggest that a LF diet without flaxseed may reduce levels of specific inflammatory CAFs and suggests that the NF-κB pathway may be a mediator of these changes. Cancer Prev Res; 4(10); 1590–8. ©2011 AACR.

Abstract PR-09: Low-fat diet reduces NF-κB regulated inflammatory cytokines and angiogenic factors in plasma of men with prostate cancer

Purpose: Diet and certain dietary supplements are postulated to influence the development and progression of prostate cancer. Angiogenesis and inflammation are central to tumor growth and progression, but the effect of diet on these processes remains uncertain. Procedure: We examined changes in 50 plasma cytokines and angiogenic factors (CAFs) in 145 men with prostate cancer enrolled in a pre-operative, randomized controlled phase-II trial with four arms: control (usual diet); low-fat (LF) diet; flaxseed-supplemented (FS) diet; and flaxseed-supplemented, low-fat diet. The mean duration of dietary intervention was 30 days. While two CAFS changed significantly in the FS arm (eotaxin and IL-16), 11 CAFs, including proangiogenic factors (vascular endothelial growth factor [VEGF], stromal-cell derived-1α) and myeloid factors (granulocyte-colony-stimulating factor, granulocyte-macrophage colony-stimulating factor, macrophage-colony-stimulating factor) changed significantly in the LF arm compared to controls with virtually all of these factors decreasing. Results: Significant decreases in body mass index occurred in the LF arms and correlated with VEGF decreases (P Conclusions: Low-fat diets may reduce levels of specific inflammatory cytokines and angiogenic factors via the NF-κB mediated pathway. Citation Information: Cancer Prev Res 2010;3(12 Suppl):PR-09.

Abstract 1825: Jab1/Csn5 a new target in the resistant mechanism to HER2-targeted therapies for breast cancer

Proceedings: AACR Annual Meeting 2014; April 5-9, 2014; San Diego, CA Her2 positive (Her2+) breast cancer (BC) accounts for 20% of all breast cancer subtypes and is associated with high risk of death. Trastuzumab (Ttzm), first FDA-approved targeted therapy for BC, represents a key milestone in the personalized treatment of Her2+ metastatic disease (MBC). However, 75% of Her2+ MBC are or become resistant to Ttzm and experience relapse or disease progression. This suggests that tumors acquire or possess an intrinsic mechanism of resistance that prevents from Her2 inhibition. Therefore, it is important to identify novel pathway to overcome the resistance. Recent studies have proposed various potential mechanisms leading to the resistance, including p27 rapid degradation. Jab1/Csn5 a novel candidate oncogene that we identified contributes to the progression of BC and is correlated with poor prognosis. Our study demonstrated that Jab1/Csn5 degrades p27 in MBC. These findings suggest that Jab1 overexpression contributes to Ttzm-resistance by facilitating p27-degradation. Jab1/Csn5 is overexpressed in 50% of primary and 90% of MBC while its expression is low or absent in normal adult breast tissues. We previously identified that high expression of Jab1 is associated with shorter progression-free survival in MBC patients. In this study, we showed that the knockdown of Jab1 sensitizes to Ttzm-treatment. Mechanistically, we found that Jab1/Csn5 overexpression is significantly correlated with the activation of Akt pathway in Her2+ MBC and xenograft models. Interestingly, activated Akt, due to PTEN-loss or PI3K activating mutation has been widely implicated in the potential mechanism to Ttzm-resistance. Therefore, our results suggest that targeting Jab1/Csn5 overcomes the resistance to Ttzm via interfering with PI3K/Akt pathway. Our study identifies Jab1 as a novel contributor to Ttzm-resistance and elucidates its potential mechanisms of actions. Jab1 could be used as a predictive marker of tumor response to Ttzm, which could assist clinicians in selecting the best treatment modalities for patients with MBC. Note: This abstract was not presented at the meeting. Citation Format: Francois X. Claret, Thuy Vu, Terry J. Shackleford, Jennifer Allensworth, Qingxiu Zhang, Ling Tian, Ronghua Zhang. Jab1/Csn5 a new target in the resistant mechanism to HER2-targeted therapies for breast cancer. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 1825. doi:10.1158/1538-7445.AM2014-1825

Abstract B231: Jab1/Csn5 a new player driving the resistance to Her2-targeted therapies for breast cancer.

Her2 a key member in the epidermal growth factor receptor (EGFR) family, is one of the most dominant oncogenes in breast cancer. It is overexpressed in approximately 25%-30% of human breast cancers, which confers a more aggressive tumor phenotype and is associated with poor prognosis. The most effective FDA-approved therapy targeting Her2 is the monoclonal antibody trastuzumab (Ttzm; Herceptin). Ttzm inhibits Her2 activation and blocks downregulation of PI3K/Akt activities, which ultimately leads to increased expression of the cyclin-dependent kinase inhibitor p27, cell cycle arrest, and/or apoptosis. However, about 75% of Her2-positive breast tumors are or become resistant to Ttzm and experience relapse or disease progression. This suggests that tumors acquire or possess an intrinsic mechanism of resistance that prevents from Her2 inhibition. Therefore, it is important for the clinic to identify novel pathway to overcome the resistance. Clinicians cannot predict which patients with Her2-positive breast cancer will benefit from this treatment. Despite extensive studies, the mechanisms and genes responsible for resistance to trastuzumab (Ttzm) have not been entirely identified. Thus, novel strategies for treating Her2-positive disease are urgently needed. Recent studies have proposed that resistance to Ttzm is related to IGF-1R overexpression, rapid p27 degradation, PTEN loss, and PI3K mutations, but a clear target for modifying its resistance has yet to be identified. The cytostatic effect of Ttzm correlates with downregulation of Akt activity, which ultimately leads to increased expression of the cyclin-dependent kinase inhibitor p27, cell cycle arrest and/or apoptosis. c-Jun activation domain-binding protein 1 (Jab1/Csn5), a novel candidate oncogene that we identified, contributes to the progression of breast carcinoma and is correlated with poor prognosis. Jab1/Csn5 expression is low or absent in normal adults breast tissues, but over-expressed in 50% of primary breast tumor and 90% of metastatic breast cancer and other tumor types (ovarian cancer, pancreatic, non-small-cell lung carcinoma, and non-Hodgkins lymphomas). Jab1/Csn5 negatively regulates p27 tumor suppressor gene, mediates p27 nuclear-to-cytoplasmic export and degradation. Jab1 levels are inversely associated with p27 expression in vitro and in vivo, which means that its up-regulation may contribute to trastuzumab (Ttzm) resistance by promoting p27 degradation. This study was conducted to investigate the role of Jab1 in modulating trastuzumab (Ttzm) resistance. We hypothesize that overexpression of Jab1 plays a crucial role in resistance to Ttzm through negative regulation of the cell-cycle inhibitor p27. Using molecular approaches and pre-clinical studies we identified the pathway leading to resistance the Ttzm. In this study, we will test a novel paradigm that inhibition of Jab1 expression renders Ttzm-resistant cells sensitive to Ttzm by stabilizing nuclear p27 expression levels. Finally Jab1 could be used as a predictive marker of tumor response to Ttzm, which could assist clinicians in selecting the best treatment modalities for patients with breast cancer Citation Information: Mol Cancer Ther 2013;12(11 Suppl):B231. Citation Format: Thuy T. Vu, Terry J. Shackleford, Qingxiu Zhang, Francisco J. Esteva, Elias Drakos, Ling Tian, Timothy Kute, Aysegul A. Sahin, George Z. Rassidakis, Francois X. Claret. Jab1/Csn5 a new player driving the resistance to Her2-targeted therapies for breast cancer. [abstract]. In: Proceedings of the AACR-NCI-EORTC International Conference: Molecular Targets and Cancer Therapeutics; 2013 Oct 19-23; Boston, MA. Philadelphia (PA): AACR; Mol Cancer Ther 2013;12(11 Suppl):Abstract nr B231.

Abstract P5-08-02: New target in the resistant mechanism to trastuzumab

Her2 positive (Her2+) breast cancer (BC) accounts for 18-20% of all breast cancer subtypes and is associated with high risk of death. Trastuzumab, the first Food and Drug Administration-approved targeted therapy for BC, represents a key milestone in the personalized treatment of Her2+ metastatic disease (Her2+ MBC). However, the median duration of response is less than a year, due to either primary or acquired resistance to the therapy. In addition, there is currently no conclusive biomarker for the response of patients to trastuzumab. Therefore, understanding the development of resistance to trastuzumab is of our interest. Recent studies have proposed various potential mechanisms leading to the resistance, including p27 rapid degradation. Previously, our study and other research demonstrated that Jab1 degrades p27 in breast cancer. These findings suggest that Jab1 over-expression contributes to trastuzumab resistance by facilitating p27 degradation. Jab1/CSN5 (c-Jun activation domain-binding protein 1) is over-expressed in 50% of primary and 90% of metastatic breast cancers, while its expression is low or absent in normal adult breast tissues. We previously identified that high expression of Jab1 is associated with shorter progression-free survival in breast cancer patients. In this study, our preliminary data showed that the knockdown of Jab1 sensitizes the breast cancer cells to trastuzumab treatment in a dose-dependent manner. Mechanistically, we found that Jab1 over-expression is significantly correlated with the activation of Akt pathway in Her2+ breast cancer cells and xenograft model. Interestingly, activated Akt, due to PTEN loss or PI3K activating mutation has been widely implicated in the potential mechanism to trastuzumab resistance. Therefore, our results suggest that targeting Jab1 overcomes the resistance to trastuzumab via interfering with PI3K/Akt pathway. In general, our study identifies Jab1 as a novel contributor to trastuzumab resistance and elucidates its potential mechanisms of actions. The successful completion of the study can potentially be translated to the clinic for the benefit of patients refractory to the therapy. Also our study suggests Jab1 expression level can be used as a predictive marker for trastuzumab treatment. Citation Information: Cancer Res 2013;73(24 Suppl): Abstract nr P5-08-02.

Abstract 1912: Jab1/Csn5 as a novel driver for therapeutic resistance in HER2-positive breast cancer

Proceedings: AACR 103rd Annual Meeting 2012‐‐ Mar 31‐Apr 4, 2012; Chicago, IL Her2-positive (Her2+) breast cancer has the second worst prognosis of the five subtypes of breast cancer. The most successful targeted therapy for Her2+ breast cancer to date is trastuzumab (Herceptin)-based. However, the median duration of response to trastuzumab is shorter than 1 year, and about 75% of patients who initially responsed, has experienced resistance to the therapy after a year. Thus, better treatment strategies for Her2+ subtype are urgently needed. We and other researchers previously demonstrated that c-Jun activation domain-binding protein 1 (Jab1) negatively regulates p27, mediates p27 nuclear-to-cytoplasmic export and degradation and contributes to the loss of p27 that is seen in >50% of breast tumors and that correlates with poor clinical outcome in breast cancer cells. Thus, implicates the potential role of Jab1 in interfering with trastuzumab. We identified Jab1/Csn5 as a novel oncogene. Jab1 is amplified and overexpressed in elevated in 50% of primary and 90% of metastatic breast tumors, but is low or absent in normal adult breast tissue. In addition, high Jab1 expression is associated with short progression-free survival durations in breast cancer patients. Our preliminary data showed that inactivation of Jab1/Csn5 in trastuzumab-resistant breast cancer cells sensitized the cells to trastuzumab in a dose- and time-dependent manners. However, the ways in which Jab1 expression is up-regulated in Her2+ breast cancer cells and how this up-regulation drives trastuzumab resistance remain largely unclear. In this study, we will seek to analyze the cross-talk between Src/Stat3 or Akt signaling and Jab1 activation in breast carcinoma. We have found that Stat3 is a novel positive regulator of Jab1 expression in breast cancer cells and that Jab1 overexpression driven by the Src/Stat3 pathway compensates for trastuzumabs inhibition of Her2 signaling in Her2+ breast cancer cells. This suggests that activated Stat3, by up-regulating Jab1 expression, inhibits trastuzumab-induced cell-cycle arrest. In general, our proposed study elucidates Jab1 as a novel contributor to trastuzumab resistance and determine its potential as a prognostic and predictive marker as well as an important therapeutic target. The successful completion of our study would benefit breast cancer patients in three ways. 1) Because Jab1 is rarely expressed in mammary epithelial cells, targeting Jab1 would be less toxic to normal epithelial cells, compared to other agents. 2) Combining Jab1 with trastuzumab would interfere with both Src/Stat3 and Akt pathway. This would significantly benefit patients with Her2+ breast cancer refractory to this therapy due to PTEN loss or activating mutant Stat3. 3) Because Jab1 expression is higher in trastuzumab-resistant cells than in trastuzumab-sensitive cells, Jab1 could be used as a marker of tumor response to trastuzumab. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 1912. doi:1538-7445.AM2012-1912