Dependence receptor UNC5A restricts luminal to basal breast cancer plasticity and metastasis

Background

The majority of estrogen receptor-positive (ERα⁺) breast cancers respond to endocrine therapies. However, resistance to endocrine therapies is common in 30% of cases, which may be due to altered ERα signaling and/or enhanced plasticity of cancer cells leading to breast cancer subtype conversion. The mechanisms leading to enhanced plasticity of ERα-positive cancer cells are unknown.

Methods

We used short hairpin (sh)RNA and/or the CRISPR/Cas9 system to knockdown the expression of the dependence receptor UNC5A in ERα⁺ MCF7 and T-47D cell lines. RNA-seq, quantitative reverse transcription polymerase chain reaction, chromatin immunoprecipitation, and Western blotting were used to measure the effect of UNC5A knockdown on basal and estradiol (E2)-regulated gene expression. Mammosphere assay, flow cytometry, and immunofluorescence were used to determine the role of UNC5A in restricting plasticity. Xenograft models were used to measure the effect of UNC5A knockdown on tumor growth and metastasis. Tissue microarray and immunohistochemistry were utilized to determine the prognostic value of UNC5A in breast cancer. Log-rank test, one-way, and two-way analysis of variance (ANOVA) were used for statistical analyses.

Results

Knockdown of the E2-inducible UNC5A resulted in altered basal gene expression affecting plasma membrane integrity and ERα signaling, as evident from ligand-independent activity of ERα, altered turnover of phosphorylated ERα, unique E2-dependent expression of genes effecting histone demethylase activity, enhanced upregulation of E2-inducible genes such as BCL2, and E2-independent tumorigenesis accompanied by multiorgan metastases. UNC5A depletion led to the appearance of a luminal/basal hybrid phenotype supported by elevated expression of basal/stem cell-enriched ∆Np63, CD44, CD49f, epidermal growth factor receptor (EGFR), and the lymphatic vessel permeability factor NTN4, but lower expression of luminal/alveolar differentiation-associated ELF5 while maintaining functional ERα. In addition, UNC5A-depleted cells acquired bipotent luminal progenitor characteristics based on KRT14⁺/KRT19⁺ and CD49f⁺/EpCAM⁺ phenotype. Consistent with in vitro results, UNC5A expression negatively correlated with EGFR expression in breast tumors, and lower expression of UNC5A, particularly in ERα⁺/PR⁺/HER2⁻ tumors, was associated with poor outcome.

Conclusion

These studies reveal an unexpected role of the axon guidance receptor UNC5A in fine-tuning ERα and EGFR signaling and the luminal progenitor status of hormone-sensitive breast cancers. Furthermore, UNC5A knockdown cells provide an ideal model system to investigate metastasis of ERα⁺ breast cancers.

Electronic supplementary material

The online version of this article (10.1186/s13058-018-0963-5) contains supplementary material, which is available to authorized users.

Pharmacological Dual Inhibition of Tumor and Tumor-Induced Functional Limitations in a Transgenic Model of Breast Cancer

Breast cancer progression is associated with systemic effects, including functional limitations and sarcopenia without the appearance of overt cachexia. Autocrine/paracrine actions of cytokines/chemokines produced by cancer cells mediate cancer progression and functional limitations. The cytokine-inducible transcription factor NF-κB could be central to this process, as it displays oncogenic functions and is integral to the Pax7:MyoD:Pgc-1β:miR-486 myogenesis axis. We tested this possibility using the MMTV-PyMT transgenic mammary tumor model and the NF-κB inhibitor dimethylaminoparthenolide (DMAPT). We observed deteriorating physical and functional conditions in PyMT⁺ mice with disease progression. Compared with wild-type mice, tumor-bearing PyMT⁺ mice showed decreased fat mass, impaired rotarod performance, and reduced grip strength as well as increased extracellular matrix (ECM) deposition in muscle. Contrary to acute cachexia models described in the literature, mammary tumor progression was associated with reduction in skeletal muscle stem/satellite-specific transcription factor Pax7. Additionally, we observed tumor-induced reduction in Pgc-1β in muscle, which controls mitochondrial biogenesis. DMAPT treatment starting at 6 to 8 weeks age prior to mammary tumor occurrence delayed mammary tumor onset and tumor growth rates without affecting metastasis. DMAPT overcame cancer-induced functional limitations and improved survival, which was accompanied with restoration of Pax7, Pgc-1β, and mitochondria levels and reduced ECM levels in skeletal muscles. In addition, DMAPT restored circulating levels of 6 out of 13 cancer-associated cytokines/chemokines changes to levels seen in healthy animals. These results reveal a pharmacological approach for overcoming cancer-induced functional limitations, and the above-noted cancer/drug-induced changes in muscle gene expression could be utilized as biomarkers of functional limitations. Mol Cancer Ther; 16(12); 2747-58. ©2017 AACR.

Abstract 1873: Intraoperative assessment of breast tumor margins using multimodal photoacoustic tomography (MarginPAT)

Radical mastectomies are progressively becoming a surgery of the past. Women today are increasingly opting for lumpectomies, a less invasive treatment option. Clinical data has shown no difference in survival or clinical outcomes between the two surgical groups in early stages of breast cancer. There is, however, an undesired outcome yet to be adequately addressed. Lumpectomies have, in some cases, failed to remove marginal malignant tumor cells left as a product from surgery.

Following surgery, tumor biopsies are analyzed for marginal tumor cells. Biopsies are cut in, fixed, processed in a tissue processor, embedded into a paraffin block, and stained with H&E. After processing, presence of marginal cancerous tissue is determined by a pathologist. This process takes 3-5 days, ultimately requiring the patient to undergo reoperation if a positive margin is discovered. Presently, the reoperation rate is 20-30%.

A device capable of imaging removed tissue to determine remaining marginal tumor during surgery would greatly reduce the reoperation rate. Multiple intraoperative imaging tools existing or are emerging for breast tumor margin assessment. Current devices fail to meet acceptable clinical specifications due to either long procedure time (15 mins+), or low sensitivity (~70%), and low specificity (~68%). An unmet need exists in developing an intraoperative margin assessment device that is rapid, sensitive, capable of measuring the entire tissue surface, and images a depth of 2mm+.

The MarginPAT device presents a multi-modal photoacoustic/ultrasound imaging system for rapid and highly sensitive breast cancer margin assessment. After surgical removal of tumor, tissue is inserted, via cartridge, into MarginPAT for imaging. An automatic scan (<3 mins) provides 3D images of the excised tissue, providing margin status. Such immediate feedback allows the surgeon to re-operate immediately or allow the patient to return home based on the marginal results from MarginPAT.

Our preliminary study on 40 patient samples, showed 93% sensitivity and 90% specificity in margin assessment by precise localization of adipose tissue using PA imaging and further RF spectrum analysis of ultrasound signaling. Other than the superior sensitivity and specificity, the unique features of MarginPAT include deep tissue sensing (>3 mm) and high surface scanning speed (20 cm2/per min).

These achieved specifications meet the needs of intraoperative margin assessment, which are expected to surpass similar platforms. More importantly, MarginPAT supports conventional ultrasound imaging, allowing for use in ultrasound-guided wire localization. These multimodality functions allow MarginPAT to be utilized in multiple fields of breast cancer diseases, another advantage over other platforms. In conclusion, current clinical results show through both verification and validation that MarginPAT competently performs in the operating room.

Citation Format: Kyle McElyea, George Sandusky, Rui Li, Lu Lan, Ji-Xin Cheng, Linda K. Han, Pu Wang. Intraoperative assessment of breast tumor margins using multimodal photoacoustic tomography (MarginPAT) [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 1873. doi:10.1158/1538-7445.AM2017-1873

Abstract P6-08-02: Disruption of the estradiol-regulated NTN1-UNC5A dependence receptor signaling axis causes a hybrid basal/luminal molecular phenotype in estrogen receptor-positive breast cancer cells

Luminal subtype of breast cancers that express the estrogen receptor alpha (ERα) represents approximately two-thirds of all breast cancer cases. ER+ tumors tend to have the most favorable prognoses when treated with endocrine therapy. However, a relapse or endocrine therapy resistance is often seen in ER+ breast tumors. UNC5A belongs to the dependence receptor family which can mediate two different intracellular signals: cell survival, differentiation or migration when engaged with its ligand (such as Netrin-1; NTN1) or cell death/apoptosis in the absence of the ligand. Here we demonstrate that, depending upon the cell type, UNC5A and NTN1 are estradiol (E2)-inducible genes. Using shRNA or CRISPR knockdown strategies, we show that the disruption of the NTN1-UNC5A signaling axis in ER+ (MCF7 and T-47D) cells generates a mixed basal-like/luminal phenotype with stem cell-like characteristics. RNA-seq of UNC5A knockdown cells showed deregulated expression of several E2-target genes in both cell lines. Moreover, knockdown of UNC5A resulted in increased cell proliferation, and elevated expression of the E2-inducible anti-apoptotic, BCL2. Furthermore, the expression of ΔNp63 was enhanced in UNC5A knockdown cells. ΔNp63 is a TP53 family transcription factor that promotes breast epithelial stem cell maintenance and basal-like breast cancer. Accordingly, UNC5A knockdown cells displayed cancer stem cell phenotype as evident from ~3-fold increase in the number of CD44+/CD24+, CD44+/EPCAM+ and ITGA6+/EPCAM+ subpopulation compared with control cells. In addition, the expression of NTN4, a pro-angiogenic and lymphangiogenic factor, was increased upon UNC5A knockdown. In vivo, UNC5A knockdown cells implanted in nude mice were able to form tumors in the mammary fat pad independent of E2 supplementation and were able to colonize and develop into overt metastasis in multiple organs such as lungs, ovaries and adrenal glands. Consequently, analysis of mammary fat pad tumors from animals that received UNC5A knockdown cells revealed an increased expression of PECAM1 (CD31), a marker for endothelial cells used to evaluate tumor angiogenesis. In contrast to UNC5A, knocking down NTN1, decreased the expression of BCL2 and TP63 in both cell lines. Thus, knockdown of UNC5A resulted in deregulated expression of E2-regulated genes, E2-independent and anti-estrogen-resistant growth in vitro, and E2-independent tumor formation in xenograft models. Consistent with results of in vitro studies, analysis of tissue samples from breast cancer patients (n=196) revealed that lower expression of UNC5A is associated with lower overall survival (P < 0.05). Thus, loss or mutational inactivation of UNC5A could lead to unrestricted E2:ERα signaling and anti-estrogen resistant growth while simultaneously enabling ERα-positive luminal breast cancer cells to acquire basal-like and cancer stem cell-like features.

Citation Format: Padua MB, Bhat-Nakshatri P, Anjanappa M, Hao Y, Liu Y, McElyea K, Sandusky G, Althouse S, Perkins S, Nakshatri H. Disruption of the estradiol-regulated NTN1-UNC5A dependence receptor signaling axis causes a hybrid basal/luminal molecular phenotype in estrogen receptor-positive breast cancer cells [abstract]. In: Proceedings of the 2016 San Antonio Breast Cancer Symposium; 2016 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2017;77(4 Suppl):Abstract nr P6-08-02.

A Phase II Trial of Dovitinib in BCG-Unresponsive Urothelial Carcinoma with FGFR3 Mutations or Overexpression: Hoosier Cancer Research Network Trial HCRN 12-157

Purpose: To assess the clinical and pharmacodynamic activity of dovitinib in a treatment-resistant, molecularly enriched non-muscle-invasive urothelial carcinoma of the bladder (NMIUC) population.Experimental Design: A multi-site pilot phase II trial was conducted. Key eligibility criteria included the following: Bacillus Calmette-Guerin (BCG)-unresponsive NMIUC (>2 prior intravesical regimens) with increased phosphorylated FGFR3 (pFGFR3) expression by centrally analyzed immunohistochemistry (IHC+) or FGFR3 mutations (Mut+) assessed in a CLIA-licensed laboratory. Patients received oral dovitinib 500 mg daily (5 days on/2 days off). The primary endpoint was 6-month TURBT-confirmed complete response (CR) rate.Results: Between 11/2013 and 10/2014, 13 patients enrolled (10 IHC+ Mut-, 3 IHC+ Mut+). Accrual ended prematurely due to cessation of dovitinib clinical development. Demographics included the following: median age 70 years; 85% male; carcinoma in situ (CIS; 3 patients), Ta/T1 (8 patients), and Ta/T1 + CIS (2 patients); median prior regimens 3. Toxicity was frequent with all patients experiencing at least one grade 3-4 event. Six-month CR rate was 8% (0% in IHC+ Mut-; 33% in IHC+ Mut+). The primary endpoint was not met. Pharmacodynamically active (94-5,812 nmol/L) dovitinib concentrations in urothelial tissue were observed in all evaluable patients. Reductions in pFGFR3 IHC staining were observed post-dovitinib treatment.Conclusions: Dovitinib consistently achieved biologically active concentrations within the urothelium and demonstrated pharmacodynamic pFGFR3 inhibition. These results support systemic administration as a viable approach to clinical trials in patients with NMIUC. Long-term dovitinib administration was not feasible due to frequent toxicity. Absent clinical activity suggests that patient selection by pFGFR3 IHC alone does not enrich for response to FGFR3 kinase inhibitors in urothelial carcinoma. Clin Cancer Res; 23(12); 3003-11. ©2016 AACR.

Critical role of phosphorylation of serine 165 of YBX1 on the activation of NF-κB in colon cancer

Y-box binding protein 1 [YBX1] is a multifunctional protein known to facilitate many of the hallmarks of cancer. Elevated levels of YBX1 protein are highly correlated with cancer progression, making it an excellent marker in cancer. The connection between YBX1 and the important nuclear factor κB [NF-κB] has never been reported. Here, we show that overexpression of wild type YBX1 [WT-YBX1] activates NF-κB, suggesting that YBX1 is a potential NF-κB activator. Furthermore, using mass spectrometry analysis we identified novel phosphorylation of serine 165 [S165] on YBX1. Overexpression of the S165A-YBX1 mutant in either HEK293 cells or colon cancer HT29 cells showed dramatically reduced NF-κB activating ability as compared with that of WT-YBX1, confirming that S165 phosphorylation is critical for the activation of NF-κB by YBX1. We also show that expression of the S165A-YBX1 mutant dramatically decreased the expression of NF-κB-inducible genes, reduced cell growth, and compromised tumorigenic ability as compared with WT-YBX1. Taken together, we provide the first evidence that YBX1 functions as a tumor promoter via NF-κB activation, and phosphorylation of S165 of YBX1 is critical for this function. Therefore, our important discovery may lead to blocking S165 phosphorylation as a potential therapeutic strategy to treat colon cancer.