Abstract 3978: The growth inhibitory effect of MDV3100 on hormone receptor-positive, HER2-negative breast cancer cell lines with low DYRK2 expression

Introduction: Tumor progression is the main cause of death in patients with breast cancer. Accumulating evidence suggests that dual-specificity tyrosine-regulated kinase 2 (DYRK2) functions as a tumor suppressor by regulating cell survival, differentiation, proliferation and apoptosis. Recently, we reported for the first time that DYRK2 inhibits breast cancer stem cells and tumor cell proliferation through transcriptional downregulation of KLF4 and CDK14, respectively.Our previous study showed that Androgen receptor (AR) was a DYRK2-dependent transcriptional activator. In this context, we hypothesized that MDV3100, an inhibitor of AR, may be effective for breast cancer with low DYRK2 expression.

Methods: We established stable DYRK2-depleted cells. MCF-7 cells, hormone receptor-positive, HER2-negative breast cancer cell line, were transfected with pSuper-puro vector (pSuper control) or pSuper-puro DYRK2 shRNAs (shDYRK2) along with puromycin to isolate stable cell lines.These manipulated cells were compared with the control cells by various assays. We analyzed the activity of AR by Androgen receptor reporter assay. MTS assays were used to assess growth inhibition after treatment with MDV3100.

Results: Androgen receptor reporter assay showed that knocking down DYRK2 induced AR transcription activity in MCF-7 cells.In MCF-7 DYRK2-depleted cells, MTS assays revealed that the treatment by MDV3100 was more effective than that in MCF-7 control cells.

Conclusion: These findings demonstrate that reduced DYRK2 expression in hormone receptor-positive, HER2-negative breast cancer increases the activity of AR and significantly inhibits the growth by treatment with MDV3100.

Citation Format: Yoshimi Imawari, Rei Mimoto, Kiyotsugu Yoshida. The growth inhibitory effect of MDV3100 on hormone receptor-positive, HER2-negative breast cancer cell lines with low DYRK2 expression. [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 3978.

Abstract P6-03-14: Conditional reprogrammed cells enable us to examine the drug resistance for recurrent metastatic hormone receptor-positive, human epidermal receptor 2-negative breast cancer

Objectives: Various new drugs have been developed for treating recurrent hormone receptor-positive/human epidermal receptor 2-negative breast cancer. However, directly identifying effective drugs remains difficult. In this study, we elucidated the clinical relevance of cultured cells derived from patients with recurrent hormone receptor-positive/human epidermal receptor 2-negative metastatic breast cancer. Methods: We generated conditional reprogrammed cells from primary and metastatic breast cancer. CR cells were co-cultured with irradiated mouse fibroblast feeder cells in the presence of the Rho kinase inhibitor Y-27632. We performed microarray analysis using a SurePrint G3 Human GE microarray kit Ver. 2.0, and DNA target sequence using QIAseq Targeted DNA Panels to analyze the genetic variants of the 93 most commonly mutated genes in human breast cancer samples. We examined the pathological features by xenograft model. For drug screening assay, we used Cambridge Cancer Compound Library. Results: The results of microarray analysis, DNA target sequencing and xenograft experiments indicated that the mutation status and pathological features were preserved in CR cells, whereas RNA expression was different from that in the primary tumor cells, especially with respect to cell adhesion-associated pathways. The results of drug sensitivity assays involving the use of primary breast cancer CR cells were consistent with the result of Oncotype Dx. We performed drug screening assays using liver metastases, which were sensitive to 66 drugs. The result reflected the actual clinical course of this patient, resistant to taxanes and sensitive to fulvestrant plus palbociclib. Conclusion: These results supported the use of CR cells obtained from the metastatic lesions of patients with HR+/HER2− breast cancer for predicting the clinical drug efficacy.

Citation Format: Rei Mimoto, Satomi Yogosawa, Atsushi Fushimi, Hiroko Nogi, Tadashi Asakura, Kiyotsugu Yoshida, Hiroshi Takeyama. Conditional reprogrammed cells enable us to examine the drug resistance for recurrent metastatic hormone receptor-positive, human epidermal receptor 2-negative breast cancer [abstract]. In: Proceedings of the 2019 San Antonio Breast Cancer Symposium; 2019 Dec 10-14; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2020;80(4 Suppl):Abstract nr P6-03-14.

Abstract P4-08-04: Downregulation of DYRK2 contributes to tumor cell proliferation by enhancing CDK14 expression in breast cancer

Introduction: Tumor progression is the main cause of death in patients with breast cancer. Accumulating evidence suggests that dual-specificity tyrosine-regulated kinase 2 (DYRK2) functions as a tumor suppressor by regulating cell survival, differentiation, proliferation and apoptosis. However, little is known about the mechanisms of transcriptional regulation by DYRK2 in cancer progression, particularly with respect to cancer proliferation and invasion. Here, using a comprehensive expression profiling approach, we show that cyclin-dependent kinase 14 (CDK14) is a target of DYRK2.

The aim of this study is to clarify whether DYRK2 suppresses the proliferation of breast cancer cells through CDK14 expression.

Methods: Cell lines: We established stable DYRK2-depleted cells. MCF-7 cells were transfected with pSuper-puro vector (pSuper control) or pSuper-puro DYRK2 shRNAs (shDYRK2) along with puromycin to isolate stable cell lines.

We generated stable DYRK2-overexpressing MDA-MB-231 cells using GFP-DYRK2 (GFP-DYRK2 cells). A GFP vector was transfected as a vehicle control (GFP control cells) with G418 to isolate stable cell lines.

Moreover, we established both stable DYRK2- and CDK14-depleted cells. The shDYRK2 cells were transfected with the pSuper-neo vector (shDYRK2-pSuper control) or pSuper-neo CDK14 shRNAs (shDYRK2-shCDK14). The pSuper control cells were transfected with the pSuper-neo vector (pSuper control-pSuper control cells) as a vehicle control with puromycin and G418 to isolate stable cell lines.

These manipulated cells were compared with the control cells by various assays.

Immunohistological staining: Sixty samples from surgically treated breast cancer patients were obtained from the Surgery Department at the Jikei University Hospital between 2001 and 2002. The Jikei University School of Medicine Ethics Review Committee approved the study protocol, and informed consent was obtained.

Results: We analyzed cancer cell proliferation by MTS and colony formation assays. We investigated the effects of CDK14 in DYRK2-depleted cells in a breast tumor xenograft model. We found that reduced DYRK2 expression increased CDK14 expression to promote cancer cell proliferation in vitro and tumorigenicity in vivo.

We further identified androgen receptor (AR) as a candidate of DYRK2-dependent transcription factors to control CDK14. Real-time RT-PCR and western blotting revealed that inhibition of AR activity using an AR inhibitor MDV3100 decreased both mRNA and protein levels of CDK14 in shDYRK2 and GFP control cells. In contrast, knocking down DYRK2 induced AR transcription activity in MCF-7 cells. shDYRK2 cells were more sensitive to MDV3100 compared with pSuper control cells.

Immunohistological staining of sixty samples from surgically treated breast cancer patients showed an inverse correlation between DYRK2 and CDK14 expression.

Conclusion: These findings demonstrate that reduced DYRK2 expression in breast cancer promotes tumor cell proliferation by modulating CDK14 expression via AR.

Citation Format: Yoshimi Imawari, Rei Mimoto, Noriko Yamaguchi, Makiko Kamio, Hiroko Nogi, Ken Uchida, Hiroshi Takeyama, Kiyotsugu Yoshida. Downregulation of DYRK2 contributes to tumor cell proliferation by enhancing CDK14 expression in breast cancer [abstract]. In: Proceedings of the 2019 San Antonio Breast Cancer Symposium; 2019 Dec 10-14; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2020;80(4 Suppl):Abstract nr P4-08-04.

Clinical implications of drug-screening assay for recurrent metastatic hormone receptor-positive, human epidermal receptor 2-negative breast cancer using conditionally reprogrammed cells

Various new drugs have been developed for treating recurrent hormone receptor-positive (HR+)/human epidermal receptor 2-negative (HER2−) breast cancer. However, directly identifying effective drugs remains difficult. In this study, we elucidated the clinical relevance of cultured cells derived from patients with recurrent HR+/HER2− metastatic breast cancer. The recently established conditionally reprogrammed (CR) cell system enables us to examine heterogeneity, drug sensitivity and cell function using patient-derived tumour samples. The results of microarray analysis, DNA target sequencing and xenograft experiments indicated that the mutation status and pathological features were preserved in CR cells, whereas RNA expression was different from that in the primary tumour cells, especially with respect to cell adhesion-associated pathways. The results of drug sensitivity assays involving the use of primary breast cancer CR cells were consistent with gene expression profiling test data. We performed drug-screening assays using liver metastases, which were sensitive to 66 drugs. Importantly, the result reflected the actual clinical course of this patient. These results supported the use of CR cells obtained from the metastatic lesions of patients with HR+/HER2− breast cancer for predicting the clinical drug efficacy.

Abstract P3-10-18: Factors associated with mammographic density in Japanese women

Background: Increased mammographic breast density decreases the sensitivity and the specificity of mammography screening and is associated with a significant risk factor for breast cancer. No studies were identified that examined the impact of supplemental screening on breast cancer recurrence rates or mortality for women with dense breasts. The aim of this study is to examine factors associating with breast density in Japanese women.

Data sources and methods: We used mammography check-up participants (n=5159, women aged 40 years or older) between Apr 2014 and Mar 2017 as our baseline data. Using a self-administered questionnaire, data of life style were collected. Logistic regression was used to estimate the odds of having dense breasts by age, body mass index (BMI), alcohol consumption, smoking, parity, menopausal status, dysmenorrhea, hormone replacement therapy (HRT), family history of breast cancer, physical exercise, fried foods intake, brightly colored vegetables intake, coffee intake, tea intake and bone mineral density. Breast densities were divided into four categories based on BI-RADS classification. BI-RADS 3 and 4 were defined as dense breast. All statistical tests were two-sided.

Results: Dense breast accounted for 62.3% of mammography screening participants. Dense breast at an early age was more frequent as 78.0% in the 40's. Alcohol intake (20 g or more a day, OR=1.62, 0.026) in post-menopausal women showed statistically significant positive interaction with dense breast. Weak positive interaction was seen in bone mineral density>80% (OR=0.63, 0.086, n=775). On the other, age (OR=0.97, <0.001), BMI (OR=0.78, <0.001), number of live birth (one; OR=0.77, <0.030, two or more; OR=0.37, <0.001) and post-menopause (OR=0.60, <0.001) showed statistically significant negative interactions with dense breast.

Conclusion: Dense breast accounted for 62.3% of all participants. Dense breast was more frequent at early age as 78.0% in their 40's. Alcohol consumption and bone mineral density in post-menopausal women were positive interaction with mammographic breast density. On the contrary, age, BMI, number of live birth and post-menopause were negative interaction with mammographic breast density.

Citation Format: Uchida K, Ohashi H, Hiroko N, Mimoto R. Factors associated with mammographic density in Japanese women [abstract]. In: Proceedings of the 2017 San Antonio Breast Cancer Symposium; 2017 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2018;78(4 Suppl):Abstract nr P3-10-18.

Downregulation of dual-specificity tyrosine-regulated kinase 2 promotes tumor cell proliferation and invasion by enhancing cyclin-dependent kinase 14 expression in breast cancer

Tumor progression is the main cause of death in patients with breast cancer. Accumulating evidence suggests that dual-specificity tyrosine-regulated kinase 2 (DYRK2) functions as a tumor suppressor by regulating cell survival, differentiation, proliferation and apoptosis. However, little is known about the mechanisms of transcriptional regulation by DYRK2 in cancer progression, particularly with respect to cancer proliferation and invasion. Here, using a comprehensive expression profiling approach, we show that cyclin-dependent kinase 14 (CDK14) is a target of DYRK2. We found that reduced DYRK2 expression increases CDK14 expression, which promotes cancer cell proliferation and invasion in vitro, in addition to tumorigenicity in vivo. CDK14 and DYRK2 expression inversely correlated in human breast cancer tissues. We further identified androgen receptor (AR) as a candidate of DYRK2-dependent transcription factors regulating CDK14. Taken together, our findings suggest a mechanism by which DYRK2 controls CDK14 expression to regulate tumor cell proliferation and invasion in breast cancer. Targeting of this pathway may be a promising therapeutic strategy for treating breast cancer.

Dual-specificity tyrosine-regulated kinase 2 is a suppressor and potential prognostic marker for liver metastasis of colorectal cancer

Colorectal cancer is a common cancer and a leading cause of cancer-related death worldwide. The liver is a dominant metastatic site for patients with colorectal cancer. Molecular mechanisms that allow colorectal cancer cells to form liver metastases are largely unknown. Activation of epithelial-mesenchymal transition is the key step for metastasis of cancer cells. We recently reported that dual-specificity tyrosine-regulated kinase 2 (DYRK2) controls epithelial-mesenchymal transition in breast cancer and ovarian serous adenocarcinoma. The aim of this study is to clarify whether DYRK2 regulates liver metastases of colorectal cancer. We show that the ability of cell invasion and migration was abrogated in DYRK2-overexpressing cells. In an in vivo xenograft model, liver metastatic lesions were markedly diminished by ectopic expression of DYRK2. Furthermore, we found that patients whose liver metastases expressed low DYRK2 levels had significantly worse overall and disease-free survival. Given the findings that DYRK2 regulates cancer cell metastasis, we concluded that the expression status of DYRK2 could be a predictive marker for liver metastases of colorectal cancer.

Impairment of DYRK2 augments stem-like traits by promoting KLF4 expression in breast cancer

Whereas accumulating studies have supported the cancer stem cell theory, a specific therapy targeting a cancer stem cell subpopulation has not been established. Here, we show that dual-specificity tyrosine phosphorylation-kinase 2 (DYRK2) is a novel negative regulator for formation of breast cancer stem cells. Downregulation of DYRK2 promotes cancer stem-like traits in vitro, tumourigenesis in vivo and the proportion of the cancer stem cell population in human breast cancer tissues. We found that Krupple-like factor 4 (KLF4) serves as a key mediator of DYRK2's control over the cancer stem phenotype. Reduced DYRK2 expression increases KLF4 expression, which induces cancer stem-like properties. We identified androgen receptor (AR) as a transcription factor binding to the KLF4 promoter region; this process is dependent on DYRK2 kinase activity. Our findings delineate a mechanism of cancer stem cell regulation by the DYRK2-AR-KLF4 axis in breast cancer. Targeting of this pathway may be a promising strategy against breast cancer stem cells.

Diminished DYRK2 sensitizes hormone receptor-positive breast cancer to everolimus by the escape from degrading mTOR

Mammalian target of rapamycin (mTOR) inhibitor, everolimus, provides benefit for metastatic hormone receptor positive breast cancer after failure of the endocrine therapy. The present report highlights Dual Specificity Tyrosine Phosphorylation Regulated Kinase 2 (DYRK2) as a predictive marker for everolimus sensitivity. The key node and KEGG pathway analyses revealed that mTORC1 pathway is activated in DYRK2-depleted cells. Everolimus was more effective in DYRK2-depleted cells compared with control cells. In xenograft model, everolimus treatment significantly inhibited tumor growth compared with vehicle or eribulin treatment. In clinical analysis, patients with low DYRK2 expression acquired longer treatment period and had higher clinical benefit rate than those with high DYRK2 expression (171 vs 82 days; P < 0.05 and 50% vs 12.5%, respectively). We further investigated the underlying mechanism by which DYRK2 regulates mTORC1 pathway. The ectopic expression of DYRK2 promoted phosphorylation of Thr631 for the ubiquitination and degradation of mTOR. DYRK2 expression levels may thus predict clinical responses to everolimus.

DYRK2 regulates epithelial-mesenchymal-transition and chemosensitivity through Snail degradation in ovarian serous adenocarcinoma

Epithelial-mesenchymal-transition (EMT) plays essential roles in ovarian cancer invasion, metastasis, and drug resistance. A hallmark of EMT is the loss of E-cadherin, which is regulated by Snail. Recently, it was shown that dual-specificity tyrosine-regulated kinase 2 (DYRK2) controls Snail degradation in breast cancer. The aim of this study is to clarify whether DYRK2 regulates EMT through Snail degradation in ovarian serous adenocarcinoma (SA). Expression of DYRK2 and Snail in two pairs of cisplatin-resistant and the original cisplatin-sensitive ovarian cancer cell line were analyzed by immunoblotting and real-time RT-PCR analysis. Morphological change, invasion ability, and chemosensitivity were evaluated by using DYRK2 stable knockdown cell line in 2008 (2008 shDYRK2). Immunohistochemical analyses for DYRK2 and Snail were performed with surgical specimens. The correlations between the expression of these proteins and the clinicopathological parameters, including prognosis, were determined. Moreover, we conducted a hypodermic administration test in nude mice and examined reproductive and cisplatin response activities. DYRK2 protein expression was posttranslationally reduced in cisplatin-resistant SA cell lines. 2008 shDYRK2 showed mesenchymal phenotype and resistant to cisplatin. Immunohistochemistry demonstrated that DYRK2 expression inversely correlated with Snail expression, and reduced expression of DYRK2 was associated with shorter overall survival in SA. DYRK2 may regulate EMT through Snail degradation in ovarian SA and might be a predictive marker for a favorable prognosis in the treatment of this cancer.

Abstract P2-06-14: Clinical relevance and biological properties of oligometastatic breast cancer in lung; prognostic impact of CD44+/CD24−/low cells

Background: Metastatic breast cancer is a systemic disease. Our aim was to evaluate the clinical outcomes of pulmonary metastasectomy of recurrent breast tumors and to identify possible prognostic factors.

Methods: We reviewed data from a registry of patients with lung metastases from breast tumors who received pulmonary metastasectomy in Jikei University Hospital between 2004 and 2011. We analyzed prognostic factors for overall survival (OS) and progression free survival (PFS) after metastasectomy. We also investigated lung metastases for the prevalence of CD44+/CD24−/low tumor cells and evaluated their prognostic significance.

Results: Among 17 patients with lung metastasis of breast tumors, 5-year OS and PFS were 72% and 36%, respectively. Better OS was observed among patients with oligometastatic breast cancer (OMBC). Patients with OMBC, estrogen receptor (ER) positive cells, and disease free intervals (DFI) of &gt;8 years had better PFS. The average prevalence of CD44+/CD24−/low tumor cells in lung metastases of breast cancer was 21%, ranging from 0 to 90%. The presence of CD44+/CD24−/low tumor cells influenced the progression after lung metastasectomy, with median PFS times of only 6 months in patients with high-prevalence of cancer-initiating cells. CD44+/CD24−/low cells with cancer-initiating properties were present in only 9% ± 12 of patients with OMBC but were found in 73% ± 21 of patients with non-OMBC.

Conclusion: Pulmonary metastasectomy may be a treatment option for OMBC patients with lung metastases. Better prognosis of OMBC may be related to low levels of cancer-initiating cells.

Citation Format: Rei Mimoto, Tadashi Kobayashi, Yoshimi Imawari, Makiko Kamio, Kumiko Kato, Hiroko Nogi, Yasuo Toriumi, Ken Uchida, Hiroshi Takeyama. Clinical relevance and biological properties of oligometastatic breast cancer in lung; prognostic impact of CD44+/CD24−/low cells [abstract]. In: Proceedings of the Thirty-Seventh Annual CTRC-AACR San Antonio Breast Cancer Symposium: 2014 Dec 9-13; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2015;75(9 Suppl):Abstract nr P2-06-14.

Clinical relevance and low tumor-initiating properties of oligometastatic breast cancer in pulmonary metastasectomy

Metastatic breast cancer is a systemic disease. However, certain subsets of patients, such as those with oligometastatic breast cancer (OMBC), have long-term survival prospects. Our aim was to evaluate the clinical relevance of OMBC in pulmonary metastasectomy of recurrent breast cancer. We also investigated lung metastases for the prevalence of CD44+/CD24-/low tumor cells and evaluated their prognostic significance. We reviewed data from a registry of breast cancer patients with lung metastases who underwent pulmonary metastasectomy at Jikei University Hospital. We analyzed prognostic factors for overall survival (OS) and progression-free survival (PFS) after metastasectomy and examined the prognostic difference between OMBC and non-OMBC patients. CD44+/CD24-/low tumor cells were detected by immunohistochemical analysis of lung metastases sites. Among 17 breast cancer patients with lung metastasis, 5-year OS and PFS rates were 72 and 36 %, respectively. Better OS was observed among patients with OMBC. Patients with OMBC, estrogen receptor-positive cells, and disease-free intervals of >8 years had better PFS. The presence of CD44+/CD24-/low tumor cells influenced progression after lung metastasectomy, with median PFS of only 6 months in patients with a high prevalence of cancer-initiating cells. CD44+/CD24-/low cells with cancer-initiating properties were present in only 9 % ± 3 of patients with OMBC, but were found in 73 % ± 12 of patients with non-OMBC. Pulmonary metastasectomy may be a treatment option for OMBC patients with lung metastases. Better prognosis of OMBC may be associated with low levels of cancer-initiating cells.

Abstract P4-06-11: HER2 type DCIS acquires histological diversity by p53 mutation

[Introduction]

It is widely known that breast cancer is a heterogeneous disease of various phenotypes and biological characteristics.

Several studies have identified distinct subtypes of invasive ductal carcinoma by gene expression profiling or staining pattern of estrogen receptor (ER), progesterone receptor (PR), and HER2/neu protein.

Ductal carcinoma in situ (DCIS) is a non-invasive form of breast cancer, and is thought to be the precursor of invasive breast cancer.

One of the most well-known hypothesis shows that breast cancer occurs in a normal terminal duct lobular unit, and a histological continuity exists between the precursor and breast cancer.

The aim of this analysis is to reveal how DCIS acquires histological diversity and progresses to invasive ductal carcinoma.

We hypothesized that p53 gene mutation is responsible for this acquisition of histological diversity, and performed immunohistochemical analysis to pursue this hypothesis.

[Material and methods]

The participants of this study were taken from a database established by Jikei University School of Medicine. Between the period of April 2000 and April 2011, 84 cases of pure DCIS patients underwent operation.

Patients were classified into 4 subtypes by a combination of hormone receptor (HR) status and HER2 status.

The status of ER, PR, HER2, and p53 was determined by immunohistochemical staining.

Tumors with Allred score above 2 ER / PR nuclear staining were classified as ER / PR positive. Tumors with HER2 membranous staining equivalent to 3+ intensity with Hercep test in more than 30% of the cells were scored as overexpression. p53 was defined as positive when nuclear staining was equal to or greater than 10%.

We evaluated histological nuclear atypia to assess histological diversity of DCIS. When DCIS included different type of atypia cells more than 10%, we judged the histological diversity as positive.

[Results]

Patient characteristics are presented in table1.

Patient characteristics number%Age  median (range)55 (31-83)    Receptor status  ER / PR  positive6780negative1720HER2  positive1821negative6679   Subtype  HR+ / HER2-6274HR+ / HER2+56HR- / HER2+1315HR- / HER2-45

The classifications by the immunohistochemical subtype of DCIS are as follows: HR+/HER2- 62 cases (74%), HR+/HER2+ 5 cases (6%), HR-/HER2+ 13 cases (15%), HR-/HER2- 4 cases (5%).

p53 expression in HR-/HER2+ and HR-/HER2- subtype was significantly higher than HR+/HER2- and HR+/HER2+ subtype (p&lt;0.001).

The frequency of histological diversity by nuclear atypia was high in HR+/HER2- and HR-HER2+ subtype (p = 0.009).

In HR-HER2+ subtype, p53 expression was associated with histological diversity (p = 0.021). But in HR-HER2+ subtype, there was no association with p53 expression and histological diversity.

p53 status and histological diversity of DCIS HR+/HER2-HR+/HER2+HR-/HER2+HR-/HER2-pp53     positive5193&lt;0.001negative57441       histological diversity     positive481910.009negative14443       p0.3310.5760.0210.501 

[Conclusion]

This analysis demonstrates that HR-HER2+ subtype DCIS acquires histological diversity by p53 mutation.

Citation Information: Cancer Res 2013;73(24 Suppl): Abstract nr P4-06-11.

DYRK2 controls the epithelial-mesenchymal transition in breast cancer by degrading Snail

The epithelial-mesenchymal transition (EMT) plays a fundamental role in the early stages of breast cancer invasion. Snail, a zinc finger transcriptional repressor, is an important regulator of EMT. Snail is phosphorylated by GSK3β and is subsequently degraded by βTrCP-mediated ubiquitination. We identified an additional kinase, DYRK2, that regulates Snail stability. Knockdown of DYRK2 promoted EMT and cancer invasion in vitro and in vivo. Consistent with these results, DYRK2 was found to be down-regulated in human breast cancer tissue. Patients with low DYRK2-expressing tumors had a worse outcome than those with high DYRK2-expressing tumors. These findings revealed that DYRK2 regulates cancer invasion and metastasis by degrading Snail.

Abstract P4-03-10: Sonographic-pathological correlation in contrast-enhanced ultrasonography in the diagnosis of breast cancers

Background: As contrast-enhanced ultrasonography (CEUS) in the diagnosis of breast masses has been performed less frequently than other imaging modalities, it's efficacy evaluation has not been established. CEUS with Sonazoid, which is microbubble-based contrast agent, allows visualization of the mass bloodstream, therefore the classification of enhancement patterns in CEUS could increase diagnostic yield for breast masses. To achieve this, a clear standard for the CEUS evaluation is needed. The purpose of this study was to identify CEUS findings for malignancies and clarify sonographic-pathological correlation of breast cancers.

Material and Method: Present study included 20 patients with invasive ductal cancer who underwent operation for primary therapy without any chemotherapy or hormonal therapy. We contrasted CEUS features with Sonazoid with surgical specimens retrospectively. As malignant findings, the presence of focal perfusion defects inside masses and enhancement of outside masses were chosen.

Result: All of the 20 cases displayed focal perfusion defects. 9 cases of those could be successfully assessed in the same sections histopathologically and ultrasonographically. Histopathological findings showed those defects to be fibrotic foci inside masses in 7cases (77.7%). While, 6 cases of all (30%) showed stains outside tumor, and only one case was found out to be fibrotic growth with cancer cells.

Conclusion: focal perfusion defects of breast masses in CEUS were considered to be specific for malignancy, and they seemed to be fibrotic foci histopathologically. Desmoplastic reaction has been observed in epithelial solid tumor biology, and if those defects reflect the desmoplasia defects could be the proof of malignancy.

Citation Information: Cancer Res 2012;72(24 Suppl):Abstract nr P4-03-10.

Abstract P5-04-02: DYRK2 regulates breast cancer invasion via Snail/E-cadherin pathway

Introduction: Epithelial-Mesenchymal Transition (EMT) is characterized by the loss of cellular adhesion molecule E-cadherin, and plays a fundamental role during early steps of breast cancer invasion. An important regulator of E-cadherin expression is Snail, a zinc finger transcriptional repressor. Snail is posphorylated by GSK3β and then degraded by βTrCP mediated ubiquitination. Here we found another kinase, DYRK2, regulates the stability of Snail. Knockdown of DYRK2 promoted the EMT and cancer invasion both in vitro and in vivo experiments.

Methods: Cell lines: MCF-7 cells were transfected with pSuper vector (pSuper control) and pSuper shRNA DYRK2 (shRNA-DYRK2) with G418 to isolate stable cell lines.

Immunoblotting: Expression of pertinent molecular markers was determined by western blotting.

RT-PCR: RNA was extracted using TRIsure and 500 ng of total RNA was amplified using Primer Script One Step RT-PCR Kit Ver.2.

Invasion assay: Various cancer cell lines were seeded on the top of the upper chamber with serum free medium while the bottom chambers were filled with medium containing 10% FBS.

In vivo metastasis assay: Cells in PBS were injected into the left ventricle of 7-week-old female nude mice. Metastases to distant organs were confirmed by IVIS2000.

Immunohistochemistry: We acquired paraffin-embedded tissue sections from primary breast tumor cores and from Jikei University of Medicine. Immunohistochemistry for DYRK2 was performed.

Results: In MCF-7 cells, knockdown of DYRK2 increased Snail in the protein level but not in mRNA level. Upon DYRK2 knockdown, MG132 treatment had no effect on additional increase in Snail. DYRK2 knockdown decreased Snail ubiquitination. Stable DYRK2 depletion led to Snail accumulation and E-cadherin abrogation. Fibroblast marker, Vimentin, emerged in DYRK2 depleted cells. For further analysis, we carried out invasion assays. The invasion potential in DYRK2-depleted cells was substantially higher than that in control cells. In xenograft model, we used nude mice received intracardial injections of pSuper control or shRNA-DYRK2 cells. 6 weeks after injections, a significant increase in bone and lung metastasis was observed in shRNA-DYRK2 group. The patients with tumors expressed low DYRK2 showed significantly poor prognosis.

Conclusion: In breast cancer cells, Snail is phosphorylated by DYRK2 and then acquires the ability to be ubiquitinated. In the absence of DYRK2, Snail is unable to be degraded by ubiquitin-proteasome machinery. Accumulation of Snail promotes EMT and cancer invasion, so low expression of DYRK2 leads to poor prognosis in breast cancer.

Citation Information: Cancer Res 2012;72(24 Suppl):Abstract nr P5-04-02.

Abstract 3060: DYRK2-mediated phosphorylation of c-Jun and c-Myc is requisite for proper control of the G1/S transition

Transcription factors c-Jun and c-Myc are indispensable regulators for the G1/S transition and their expressions were tightly regulated at transcriptional and post-translational levels. Dysregulation of these expressions leads to tumor development and progression. Degradation of c-Jun/c-Myc, a critical event for the G1/S transition, is triggered by sequential phosphorylations by unknown priming kinase(s) and GSK3-beta. Here we show that DYRK2 (dual-specificity tyrosine-phosphorylation-regulated kinase 2) functions as a priming kinase for c-Jun/c-Myc and modifies its expression at the by post-translational level. In the absence of priming phosphorylation, c-Jun and c-Myc escape from GSK-3-mediated sequential phosphorylation and Fbw-7-mediated ubiquitination. Therefore, depletion of DYRK2 results in aberrant expression of c-Jun and c-Myc. Furthermore, in DYRK2 knockdown cells, up-regulated c-Jun and c-Myc facilitate cell proliferation and shorten the length of the G1 phase and prompts the G1/S transition. Furthermore, DYRK2 inactivation contributes to cell proliferation and tumor progression in vitro and in vivo. Pathological analysis demonstrated that DYRK2 expression is decreased in multiple cancerous tissues. Taken together, DYRK2 controls cell cycle progression at G1/S phase via phosphorylation of c-Jun and c-Myc

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 3060. doi:1538-7445.AM2012-3060

Abstract 4309: DYRK2 regulates cancer invasiveness via Snail/E-cadherin pathway

Epithelial-mesenchymal transition (EMT) is characterized by the loss of cellular adhesion molecule E-cadherin, and plays a fundamental role during early steps of invasion and metastasis. An important regulator of E-cadherin expression is Snail, a zinc-finger transcriptional repressor. Snail is phosphorylated by GSK3-α and then degraded by α-TrCP-mediated ubiquitination. Here we describe another kinase, DYRK2, acts as a priming kinase for snail whose phosphorylation is required for the subsequent GSK3&gamma phosphorylation and proteasomal degradation. Inhibition of DYRK2 expression by siRNA results in up-regulation of Snail and down-regulation of E-cadherin. The expression of fibroblast mrakers, vimentin and fibronectin, emerged in these cells. Furthermore, the invasiveness of MCF7 cells was increased by stable DYRK2 silencing by shRNA. Tumors expressing DYRK2-shRNA robustly formed metastases in nude mice bones, while those expressing control-shRNA little if any. In human breast cancer tissues, DYRK2 exhibits an inverse correlation with the expression of Snail. Conversely, low level expression of DYRK2 is associated with down regulation of E-cadherin. The patiens with tumors expressed low DYRK2 showed significantly poor prognosis and short disease-free survival. These results demonstrate that DYRK2 regulates cancer invasiveness and metastasis via Snail/E-cadherin pathway in human breast cancer.

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 4309. doi:1538-7445.AM2012-4309

DYRK2 priming phosphorylation of c-Jun and c-Myc modulates cell cycle progression in human cancer cells

Dysregulation of the G(1)/S transition in the cell cycle contributes to tumor development. The oncogenic transcription factors c-Jun and c-Myc are indispensable regulators at this transition, and their aberrant expression is associated with many malignancies. Degradation of c-Jun/c-Myc is a critical process for the G(1)/S transition, which is initiated upon phosphorylation by glycogen synthase kinase 3 β (GSK3β). However, a specific kinase or kinases responsible for priming phosphorylation events that precede this GSK3β modification has not been definitively identified. Here, we found that the dual-specificity tyrosine phosphorylation-regulated kinase DYRK2 functions as a priming kinase of c-Jun and c-Myc. Knockdown of DYRK2 in human cancer cells shortened the G(1) phase and accelerated cell proliferation due to escape of c-Jun and c-Myc from ubiquitination-mediated degradation. In concert with these results, silencing DYRK2 increased cell proliferation in human cancer cells, and this promotion was completely impeded by codeprivation of c-Jun or c-Myc in vivo. We also found marked attenuation of DYRK2 expression in multiple human tumor samples. Downregulation of DYRK2 correlated with high levels of unphosphorylated c-Jun and c-Myc and, importantly, with invasiveness of human breast cancers. These results reveal that DYRK2 regulates tumor progression through modulation of c-Jun and c-Myc.