Ryan J. Ice

NEDD9 Depletion Destabilizes Aurora A Kinase and Heightens the Efficacy of Aurora A Inhibitors: Implications for Treatment of Metastatic Solid Tumors

Aurora A kinase (AURKA) is overexpressed in 96% of human cancers and is considered an independent marker of poor prognosis. While the majority of tumors have elevated levels of AURKA protein, few have AURKA gene amplification, implying that posttranscriptional mechanisms regulating AURKA protein levels are significant. Here, we show that NEDD9, a known activator of AURKA, is directly involved in AURKA stability. Analysis of a comprehensive breast cancer tissue microarray revealed a tight correlation between the expression of both proteins, significantly corresponding with increased prognostic value. A decrease in AURKA, concomitant with increased ubiquitination and proteasome-dependent degradation, occurs due to depletion or knockout of NEDD9. Reexpression of wild-type NEDD9 was sufficient to rescue the observed phenomenon. Binding of NEDD9 to AURKA is critical for AURKA stabilization, as mutation of S296E was sufficient to disrupt binding and led to reduced AURKA protein levels. NEDD9 confers AURKA stability by limiting the binding of the cdh1-substrate recognition subunit of APC/C ubiquitin ligase to AURKA. Depletion of NEDD9 in tumor cells increases sensitivity to AURKA inhibitors. Combination therapy with NEDD9 short hairpin RNAs and AURKA inhibitors impairs tumor growth and distant metastasis in mice harboring xenografts of breast tumors. Collectively, our findings provide rationale for the use of AURKA inhibitors in treatment of metastatic tumors and predict the sensitivity of the patients to AURKA inhibitors based on NEDD9 expression.

NEDD9 Regulates Actin Dynamics through Cortactin Deacetylation in an AURKA/HDAC6–Dependent Manner

The prometastatic protein NEDD9 (neural precursor cell expressed, developmentally downregulated 9) is highly expressed in many cancers and is required for mesenchymal individual cell migration and progression to the invasive stage. Nevertheless, the molecular mechanisms of NEDD9-driven migration and the downstream targets effecting metastasis are not well defined. In the current study, knockdown of NEDD9 in highly metastatic tumor cells drastically reduces their migratory capacity due to disruption of actin dynamics at the leading edge. Specifically, NEDD9 deficiency leads to a decrease in the persistence and stability of lamellipodial protrusions similar to knockdown of cortactin (CTTN). Mechanistically, it was shown that NEDD9 binds to and regulates acetylation of CTTN in an Aurora A kinase (AURKA)/HDAC6–dependent manner. The knockdown of NEDD9 or AURKA results in an increase in the amount of acetylated CTTN and a decrease in the binding of CTTN to F-actin. Overexpression of the deacetylation mimicking (9KR) mutant of CTTN is sufficient to restore actin dynamics at the leading edge and migration proficiency of the tumor cells. Inhibition of AURKA and HDAC6 activity by alisertib and Tubastatin A in xenograft models of breast cancer leads to a decrease in the number of pulmonary metastases. Collectively, these findings identify CTTN as the key downstream component of NEDD9-driven migration and metastatic phenotypes. Implications: This study provides a mechanistic platform for therapeutic interventions based on AURKA and HDAC6 inhibition for patients with metastatic breast cancer to prevent and/or eradicate metastases. Mol Cancer Res; 12(5); 681–93. ©2014 AACR.

NEDD9 Depletion Leads to MMP14 Inactivation by TIMP2 and Prevents Invasion and Metastasis.

The scaffolding protein NEDD9 is an established prometastatic marker in several cancers. Nevertheless, the molecular mechanisms of NEDD9-driven metastasis in cancers remain ill-defined. Here, using a comprehensive breast cancer tissue microarray, it was shown that increased levels of NEDD9 protein significantly correlated with the transition from carcinoma in situ to invasive carcinoma. Similarly, it was shown that NEDD9 overexpression is a hallmark of highly invasive breast cancer cells. Moreover, NEDD9 expression is crucial for the protease-dependent mesenchymal invasion of cancer cells at the primary site but not at the metastatic site. Depletion of NEDD9 is sufficient to suppress invasion of tumor cells in vitro and in vivo, leading to decreased circulating tumor cells and lung metastases in xenograft models. Mechanistically, NEDD9 localized to invasive pseudopods and was required for local matrix degradation. Depletion of NEDD9 impaired invasion of cancer cells through inactivation of membrane-bound matrix metalloproteinase MMP14 by excess TIMP2 on the cell surface. Inactivation of MMP14 is accompanied by reduced collagenolytic activity of soluble metalloproteinases MMP2 and MMP9. Reexpression of NEDD9 is sufficient to restore the activity of MMP14 and the invasive properties of breast cancer cells in vitro and in vivo. Collectively, these findings uncover critical steps in NEDD9-dependent invasion of breast cancer cells. Implications: This study provides a mechanistic basis for potential therapeutic interventions to prevent metastasis. Mol Cancer Res; 12(1); 69–81. ©2013 AACR.

NEDD9/Arf6-dependent endocytic trafficking of matrix metalloproteinase 14: a novel mechanism for blocking mesenchymal cell invasion and metastasis of breast cancer.

NEDD9 is an established marker of invasive and metastatic cancers. NEDD9 downregulation has been shown to dramatically reduce cell invasion and metastasis in multiple tumors. The mechanisms by which NEDD9 regulates invasion are largely unknown. In the current study, we have found that NEDD9 is required for matrix metalloproteinase 14 (MMP14) enzymatic recovery/recycling through the late endosomes to enable disengagement of tissue inhibitor of matrix metalloproteinase 2 (TIMP2) and tumor invasion. Depletion of NEDD9 decreases targeting of the MMP14/TIMP2 complex to late endosomes and increases trafficking of MMP14 from early/sorting endosomes back to the surface in a small GTPase ADP ribosylation factor-6 (Arf6)-dependent manner. NEDD9 directly binds to Arf6-GTPase-activating protein, ARAP3 and Arf6-effector GGA3, thereby facilitating the Arf6 inactivation required for MMP14/TIMP2 targeting to late endosomes. Re-expression of NEDD9 or a decrease in Arf6 activity is sufficient to restore MMP14 activity and the invasive properties of tumor cells. Importantly, NEDD9 inhibition by Vivo-Morpholinos, an antisense therapy, decreases primary tumor growth and metastasis in xenograft models of breast cancer. Collectively, our findings uncover a novel mechanism to control tumor-cell dissemination through NEDD9/Arf6-dependent regulation of MMP14/TIMP2 trafficking, and validate NEDD9 as a clinically relevant therapeutic target to treat metastatic cancer.

Kruppel-like factor 4 signals through microRNA-206 to promote tumor initiation and cell survival

Tumor cell heterogeneity poses a major hurdle in the treatment of cancer. Mammary cancer stem-like cells (MaCSCs), or tumor-initiating cells, are highly tumorigenic sub-populations that have the potential to self-renew and to differentiate. These cells are clinically important, as they display therapeutic resistance and may contribute to treatment failure and recurrence, but the signaling axes relevant to the tumorigenic phenotype are poorly defined. The zinc-finger transcription factor Kruppel-like factor 4 (KLF4) is a pluripotency mediator that is enriched in MaCSCs. KLF4 promotes RAS-extracellular signal-regulated kinase pathway activity and tumor cell survival in triple-negative breast cancer (TNBC) cells. In this study, we found that both KLF4 and a downstream effector, microRNA-206 (miR-206), are selectively enriched in the MaCSC fractions of cultured human TNBC cell lines, as well as in the aldehyde dehydrogenase-high MaCSC sub-population of cells derived from xenografted human mammary carcinomas. The suppression of endogenous KLF4 or miR-206 activities abrogated cell survival and in vivo tumor initiation, despite having only subtle effects on MaCSC abundance. Using a combinatorial approach that included in silico as well as loss- and gain-of-function in vitro assays, we identified miR-206-mediated repression of the pro-apoptotic molecules programmed cell death 4 (PDCD4) and connexin 43 (CX43/GJA1). Depletion of either of these two miR-206-regulated transcripts promoted resistance to anoikis, a prominent feature of CSCs, but did not consistently alter MaCSC abundance. Consistent with increased levels of miR-206 in MaCSCs, the expression of both PDCD4 and CX43 was suppressed in these cells relative to control cells. These results identify miR-206 as an effector of KLF4-mediated prosurvival signaling in MaCSCs through repression of PDCD4 and CX43. Consequently, our study suggests that a pluripotency factor exerts prosurvival signaling in MaCSCs, and that antagonism of KLF4-miR-206 signaling may selectively target the MaCSC niche in TNBC.

Combination of Eribulin and Aurora A Inhibitor MLN8237 Prevents Metastatic Colonization and Induces Cytotoxic Autophagy in Breast Cancer

Recent findings suggest that the inhibition of Aurora A (AURKA) kinase may offer a novel treatment strategy against metastatic cancers. In the current study, we determined the effects of AURKA inhibition by the small molecule inhibitor MLN8237 both as a monotherapy and in combination with the microtubule-targeting drug eribulin on different stages of metastasis in triple-negative breast cancer (TNBC) and defined the potential mechanism of its action. MLN8237 as a single agent and in combination with eribulin affected multiple steps in the metastatic process, including migration, attachment, and proliferation in distant organs, resulting in suppression of metastatic colonization and recurrence of cancer. Eribulin application induces accumulation of active AURKA in TNBC cells, providing foundation for the combination therapy. Mechanistically, AURKA inhibition induces cytotoxic autophagy via activation of the LC3B/p62 axis and inhibition of pAKT, leading to eradication of metastases, but has no effect on growth of mammary tumor. Combination of MLN8237 with eribulin leads to a synergistic increase in apoptosis in mammary tumors, as well as cytotoxic autophagy in metastases. These preclinical data provide a new understanding of the mechanisms by which MLN8237 mediates its antimetastatic effects and advocates for its combination with eribulin in future clinical trials for metastatic breast cancer and early-stage solid tumors. Mol Cancer Ther; 15(8); 1809–22. ©2016 AACR.

Prometastatic NEDD9 Regulates Individual Cell Migration via Caveolin-1-Dependent Trafficking of Integrins.

The dissemination of tumor cells relies on efficient cell adhesion and migration, which in turn depends upon endocytic trafficking of integrins. In the current work, it was found that depletion of the prometastatic protein, NEDD9, in breast cancer cells results in a significant decrease in individual cell migration due to impaired trafficking of ligand-bound integrins. NEDD9 deficiency does not affect the expression or internalization of integrins but heightens caveolae-dependent trafficking of ligand-bound integrins to early endosomes. Increase in mobility of ligand-bound integrins is concomitant with an increase in tyrosine phosphorylation of caveolin-1 (CAV1) and volume of CAV1-vesicles. NEDD9 directly binds to CAV1 and colocalizes within CAV1 vesicles. In the absence of NEDD9, the trafficking of ligand-bound integrins from early to late endosomes is impaired, resulting in a significant decrease in degradation of ligand–integrin complexes and an increase in recycling of ligand-bound integrins from early endosomes back to the plasma membrane without ligand disengagement, thus leading to low adhesion and migration. Reexpression of NEDD9 or decrease in the amount of active, tyrosine 14 phosphorylated (Tyr14) CAV1 in NEDD9-depleted cells rescues the integrin trafficking deficiency and restores cellular adhesion and migration capacity. Collectively, these findings indicate that NEDD9 orchestrates trafficking of ligand-bound integrins through the attenuation of CAV1 activity. Implications: This study provides valuable new insight into the potential therapeutic benefit of NEDD9 depletion to reduce dissemination of tumor cells and discovers a new regulatory role of NEDD9 in promoting migration through modulation of CAV1-dependent trafficking of integrins. Mol Cancer Res; 13(3); 423–38. ©2014 AACR.

Abstract B20: Development of metastatic patient-derived xenografts (PDXs) for accurate assessment of anti-metastatic therapeutics in pre-clinical settings

Background: Although advances in treating early stage breast cancers have increased the overall survival rate, once the disease has metastasized treatment options subside to palliative care. The limited access to metastatic biopsies and disease-relevant pre-clinical models to test new therapeutics targeted against advanced metastatic cancers limits progress and translation of investigational therapeutics to the clinic. Methods: To address this deficiency we developed a collection of metastatic patient derived xenograft models via direct transplantation of metastatic biopsy or residual surgical material in immunocompromised mice. We successfully collected and established triple negative as well as ER/PR positive patient xenografts which are available for collaborative research. We further characterized and utilized the PDXs to assess the efficacy of new combination therapy to treat distant metastases. Results: The efficacy of Aurora A kinase inhibition by small molecule inhibitor MLN8237 (Alisertib) as monotherapy and in combination with microtubule targeting drug, eribulin, on different stages of metastasis and potential mechanisms of its action was defined. Our work using PDX models indicates that Alisertib does not limit growth of the primary tumor. These findings are similar to the results of clinical trials with Alisertib in breast cancer. Importantly, we found that Alisertib dramatically decreases growth of the established metastases and prevents further dissemination via inactivation of AKT and activation of cytotoxic autophagy. Combination of Alisertib with eribulin led to a synergistic decrease in metastases to distant organs and provided additional local control of mammary tumor growth. Conclusion: Metastatic PDX models provide new, accurate assessment of anti-metastatic regiment9s efficacy. MLN8237 plus eribulin combination shows synergistic inhibition of metastatic spread, growth of established metastases and prolongs overall survival. Future clinical trials are needed to further test this regiment in clinic to improve survival of metastatic cancer patients. Citation Format: Ryan Ice, Anna Kiseleva, Yuriy Loskutov, Matthew Smolkin, Adham Salkeni, Hannah Hazard, Ginger Layne, Elena Pugacheva{Authors}. Development of metastatic patient-derived xenografts (PDXs) for accurate assessment of anti-metastatic therapeutics in pre-clinical settings. [abstract]. In: Proceedings of the AACR Special Conference: Patient-Derived Cancer Models: Present and Future Applications from Basic Science to the Clinic; Feb 11-14, 2016; New Orleans, LA. Philadelphia (PA): AACR; Clin Cancer Res 2016;22(16_Suppl):Abstract nr B20.

Abstract 2013: NEDD9 depletion leads to MMP14 inactivation by TIMP2 and prevents invasion and metastasis

The scaffolding protein NEDD9 is an established pro-metastatic marker in several cancers. Nevertheless, the molecular mechanisms of NEDD9 driven metastasis in cancers remain ill defined. Here, using a comprehensive breast cancer (BCa) tissue microarray, we show that increased levels of NEDD9 protein significantly correlated with the transition from carcinoma in situ to invasive carcinoma. NEDD9 expression is crucial for the mesenchymal invasion of cancer cells at the primary site but not at the metastatic site. Depletion of NEDD9 is sufficient to suppress invasion, leading to decrease in circulating tumor cells (CTCs) and lung metastases in xenograft models. Mechanistically, NEDD9 localizes to invasive pseudopods and is required for local matrix degradation via regulation of MMP14 trafficking. Depletion of NEDD9 impaired invasion of cancer cells through inactivation of MMP14 by excess TIMP2 on the cell surface. Re-expression of NEDD9 is sufficient to restore the activity of MMP14 and the invasive properties of BCa cells. Collectively, these findings uncover critical steps in invasion of BCa cells with potential strategy to target metastasis through manipulation of NEDD9. Citation Format: Elena N. Pugacheva, Sarah McLaughlin, Ryan Ice, Anuradha Rajulapati, Polina Kozyulina, Ryan Livengood, Varvara Kozyreva, Yuriy Loskutov, Alexey Ivanov, Scott Weed. NEDD9 depletion leads to MMP14 inactivation by TIMP2 and prevents invasion and metastasis. [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 2013. doi:10.1158/1538-7445.AM2014-2013

Abstract A094: The influence of pro-metastatic protein NEDD9 expression in supporting distant breast cancer metastasis

Although advances in treating early stage breast cancer have increased the overall survival rate, once the disease has metastasized treatment options become severely limited. Neural precursor cell expressed developmentally downregulated 9, NEDD9, is a pro-metastatic protein known to play a role during invasion and is increased in many tumor types including ductal breast carcinomas. The purpose of our study is to understand how NEDD9 contributes to the survival of metastatic disease and to establish via therapeutically relevant means the impact of reducing NEDD9 in metastatic breast cancer. Utilizing breast tumor xenograft models and in situ Zymography we were able to conclude that the reduction of NEDD9 led to a decrease in matrix metalloproteinase activity in the tumor cells in the primary site and distant lung metastasis thus reducing the number of invading cells. Additionally our study shows, via fluorescent immunohistochemistry analysis of lung metastasis, that by reducing the levels of NEDD9 in vivo the levels of active caspase 3 increased, along with decreasing Ki67 and phosphorylated Akt levels. These changes led to decreased proliferation and survival and increased cell death at distant metastatic sites and dramatically reduced number and size of lung metastasis. Finally, we have demonstrated that the application of NEDD9 Vivo-morpholinos is a valid method for targeting NEDD9 in a clinically relevant setting to reduce the levels of NEDD9 for treatment of metastatic breast cancer. Taken together our data suggests that not only does NEDD9 play a role in primary tumor invasion but is necessary for sustaining metastatic disease and can be reduced in a clinically viable manner resulting in less metastasis. Citation Format: Ryan J. Ice, Sricharan A. Mahavadi, Elena N. Pugacheva. The influence of pro-metastatic protein NEDD9 expression in supporting distant breast cancer metastasis. [abstract]. In: Proceedings of the AACR Special Conference on Advances in Breast Cancer Research: Genetics, Biology, and Clinical Applications; Oct 3-6, 2013; San Diego, CA. Philadelphia (PA): AACR; Mol Cancer Res 2013;11(10 Suppl):Abstract nr A094.