Kari B. Wisinski

CARM1 Methylates Chromatin Remodeling Factor BAF155 to Enhance Tumor Progression and Metastasis

Coactivator-associated arginine methyltransferase 1 (CARM1), a coactivator for various cancer-relevant transcription factors, is overexpressed in breast cancer. To elucidate the functions of CARM1 in tumorigenesis, we knocked out CARM1 from several breast cancer cell lines using Zinc-Finger Nuclease technology, which resulted in drastic phenotypic and biochemical changes. The CARM1 KO cell lines enabled identification of CARM1 substrates, notably the SWI/SNF core subunit BAF155. Methylation of BAF155 at R1064 was found to be an independent prognostic biomarker for cancer recurrence and to regulate breast cancer cell migration and metastasis. Furthermore, CARM1-mediated BAF155 methylation affects gene expression by directing methylated BAF155 to unique chromatin regions (e.g., c-Myc pathway genes). Collectively, our studies uncover a mechanism by which BAF155 acquires tumorigenic functions via arginine methylation.

Identification of Estrogen Receptor Dimer Selective Ligands Reveals Growth-Inhibitory Effects on Cells That Co-Express ERα and ERβ

Estrogens play essential roles in the progression of mammary and prostatic diseases. The transcriptional effects of estrogens are transduced by two estrogen receptors, ERα and ERβ, which elicit opposing roles in regulating proliferation: ERα is proliferative while ERβ is anti-proliferative. Exogenous expression of ERβ in ERα-positive cancer cell lines inhibits cell proliferation in response to estrogen and reduces xenografted tumor growth in vivo, suggesting that ERβ might oppose ERαs proliferative effects via formation of ERα/β heterodimers. Despite biochemical and cellular evidence of ERα/β heterodimer formation in cells co-expressing both receptors, the biological roles of the ERα/β heterodimer remain to be elucidated. Here we report the identification of two phytoestrogens that selectively activate ERα/β heterodimers at specific concentrations using a cell-based, two-step high throughput small molecule screen for ER transcriptional activity and ER dimer selectivity. Using ERα/β heterodimer-selective ligands at defined concentrations, we demonstrate that ERα/β heterodimers are growth inhibitory in breast and prostate cells which co-express the two ER isoforms. Furthermore, using Automated Quantitative Analysis (AQUA) to examine nuclear expression of ERα and ERβ in human breast tissue microarrays, we demonstrate that ERα and ERβ are co-expressed in the same cells in breast tumors. The co-expression of ERα and ERβ in the same cells supports the possibility of ERα/β heterodimer formation at physio- and pathological conditions, further suggesting that targeting ERα/β heterodimers might be a novel therapeutic approach to the treatment of cancers which co-express ERα and ERβ.

Tumor Cell–Driven Extracellular Matrix Remodeling Drives Haptotaxis during Metastatic Progression

UNLABELLED Fibronectin (FN) is a major component of the tumor microenvironment, but its role in promoting metastasis is incompletely understood. Here, we show that FN gradients elicit directional movement of breast cancer cells, in vitro and in vivo Haptotaxis on FN gradients requires direct interaction between α5β1 integrin and MENA, an actin regulator, and involves increases in focal complex signaling and tumor cell-mediated extracellular matrix (ECM) remodeling. Compared with MENA, higher levels of the prometastatic MENA(INV) isoform associate with α5, which enables 3-D haptotaxis of tumor cells toward the high FN concentrations typically present in perivascular space and in the periphery of breast tumor tissue. MENA(INV) and FN levels were correlated in two breast cancer cohorts, and high levels of MENA(INV) were significantly associated with increased tumor recurrence as well as decreased patient survival. Our results identify a novel tumor cell-intrinsic mechanism that promotes metastasis through ECM remodeling and ECM-guided directional migration. SIGNIFICANCE Here, we provide new insight into how tumor cell:ECM interactions generate signals and structures that promote directed tumor cell migration, a critical component of metastasis. Our results identify a tumor cell-intrinsic mechanism driven by the actin regulatory protein MENA that promotes ECM remodeling and haptotaxis along FN gradients. Cancer Discov; 6(5); 516-31. ©2016 AACR.See related commentary by Santiago-Medina and Yang, p. 474This article is highlighted in the In This Issue feature, p. 461.

The role of molecular markers in predicting response to therapy in patients with colorectal cancer

Advances in systemic therapy for colorectal cancer have dramatically improved prognosis. While disease stage has traditionally been the main determinant of disease course, several molecular characteristics of tumor specimens have recently been shown to have prognostic significance. Although to date no molecular characteristics have emerged as consistent predictors of response to therapy, retrospective studies have investigated the role of a variety of biomarkers, including microsatellite instability, loss of heterozygosity of 18q, type II transforming growth factor β receptor, thymidylate synthase, epidermal growth factor receptor, and Kirsten-ras (KRAS). This paper reviews the current literature, ongoing prospective studies evaluating the role of these markers, and novel techniques such as gene profiling, which may help to uncover the more complex molecular interactions that will predict response to chemotherapy in patients with colorectal cancer.

Nuclear Epidermal Growth Factor Receptor Is a Functional Molecular Target in Triple-Negative Breast Cancer

Triple-negative breast cancer (TNBC) is a subclass of breast cancers (i.e., estrogen receptor–negative, progesterone receptor–negative, and HER2-negative) that have poor prognosis and very few identified molecular targets. Strikingly, a high percentage of TNBCs overexpresses the EGF receptor (EGFR), yet EGFR inhibition has yielded little clinical benefit. Over the last decade, advances in EGFR biology have established that EGFR functions in two distinct signaling pathways: (i) classical membrane-bound signaling and (ii) nuclear signaling. Previous studies have demonstrated that nuclear EGFR (nEGFR) can enhance resistance to anti-EGFR therapies and is correlated with poor overall survival in breast cancer. On the basis of these findings, we hypothesized that nEGFR may promote intrinsic resistance to cetuximab in TNBC. To examine this question, a battery of TNBC cell lines and human tumors were screened and found to express nEGFR. Knockdown of EGFR expression demonstrated that TNBC cell lines retained dependency on EGFR for proliferation, yet all cell lines were resistant to cetuximab. Furthermore, Src Family Kinases (SFKs) influenced nEGFR translocation in TNBC cell lines and in vivo tumor models, where inhibition of SFK activity led to potent reductions in nEGFR expression. Inhibition of nEGFR translocation led to a subsequent accumulation of EGFR on the plasma membrane, which greatly enhanced sensitivity of TNBC cells to cetuximab. Collectively, these data suggest that targeting both the nEGFR signaling pathway, through the inhibition of its nuclear transport, and the classical EGFR signaling pathway with cetuximab may be a viable approach for the treatment of patients with TNBC. Mol Cancer Ther; 13(5); 1356–68. ©2014 AACR.

Leveraging Electronic Health Record Systems to Create and Provide Electronic Cancer Survivorship Care Plans: A Pilot Study

PURPOSE The Institute of Medicine (IOM) recommends cancer survivors receive survivorship care plans after completing active cancer treatment. However, care plan creation requires significant time and effort, contributing to diminished adoption of this recommendation. Electronic health record (EHR) systems have been proposed as a solution. We assessed the feasibility of creating and delivering care plans within an EHR system. METHODS Thirty-eight breast cancer survivors without existing care plans were recruited during a follow-up visit to their primary oncologist. Using an EHR template, an oncologist created an individualized care plan for each participant. Time spent creating each plan was recorded. Participant use and feedback were collected. RESULTS Participants enrolled a median of 19.7 months after diagnosis (range, 4.3 to 57 months). A minority of IOM-recommended plan elements could be automatically imported without any manual entry. The majority of elements required interpretation and manual import by the clinician. However, with an established infrastructure for importing elements, the time needed to create a care plan electronically was short (median, 3 minutes; range 2 to 12 minutes). Most survivors (n = 36; 95%) successfully accessed their care plans online and spent a median of 12 minutes (range, 0.5 to 61.9 minutes) reviewing them. Survivors perceived the plans as useful and did not generally report difficulty in accessing them online or understanding content. CONCLUSION Rapid care plan creation and delivery within an EHR is possible. Plans were available to all (survivors, oncologists, primary care physicians) via the EHR. Further research is required to explore the barriers to automating data importation into plans as well as the impact of EHR-integrated plans.

Research Resource: Global Identification of Estrogen Receptor β Target Genes in Triple Negative Breast Cancer Cells

Breast cancers that are negative for estrogen receptor α (ERα), progesterone receptor, and human epidermal growth factor receptor 2 are known as triple-negative breast cancers (TNBC). TNBCs are associated with an overall poor prognosis because they lack expression of therapeutic targets like ERα and are biologically more aggressive. A second estrogen receptor, ERβ, has been found to be expressed in 50% to 90% of ERα-negative breast cancers, and ERβ expression in TNBCs has been shown to correlate with improved disease-free survival and good prognosis. To elucidate the role of ERβ in regulating gene expression and cell proliferation in TNBC cells, the TNBC cell line MDA-MB-468 was engineered with inducible expression of full-length ERβ. In culture, ERβ expression inhibited cell growth by inducing a G1 cell cycle arrest, which was further enhanced by 17β-estradiol treatment. In xenografts, ERβ expression also inhibited tumor formation and growth, and 17β-estradiol treatment resulted in rapid tumor regression. Furthermore, genomic RNA sequencing identified both ligand-dependent and -independent ERβ target genes, some of which were also regulated by ERβ in other TNBC cell lines and correlated with ERβ expression in a cohort of TNBCs from the Cancer Genome Atlas Network. ERβ target genes were enriched in genes that regulate cell death and survival, cell movement, cell development, and growth and proliferation, as well as genes involved in the Wnt/β-catenin and the G1/S cell cycle phase checkpoint pathways. In addition to confirming the anti-proliferative effects of ERβ in TNBC cells, these data provide a comprehensive resource of ERβ target genes and suggest that ERβ may be targeted with ligands that can stimulate its growth inhibitory effects.

Constitutively decreased TGFBR1 allelic expression is a common finding in colorectal cancer and is associated with three TGFBR1 SNPs

PurposeConstitutively decreased TGFBR1 allelic expression is emerging as a potent modifier of colorectal cancer risk in mice and humans. This phenotype was first observed in mice, then in lymphoblastoid cell lines from patients with microsatellite stable colorectal tumors.Patients and MethodsWe assessed the frequency of constitutively decreased TGFBR1 allelic expression and association with SNPs covering the TGFBR1 locus using RNA and DNA extracted from the peripheral blood lymphocytes of 118 consecutive patients with biopsy-proven adenocarcinoma of the colon or the rectum.ResultsWe found that 11(9.3%) of 118 patients exhibited decreased TGFBR1 allelic expression (TGFBR1 ASE). TGFBR1 ASE was strongly associated with three SNPs in linkage disequilibrium with each other: rs7034462 (p = 7.2 × 10-4), TGFBR1* 6A (p = 1.6 × 10-4) and rs11568785 (p = 1.4 × 10-4).ConclusionThese results confirm the high prevalence of constitutively decreased TGFBR1 allelic expression among patients with colorectal cancer. The association of this phenotype with TGFBR1*6A, rs7034462 and rs1156875 suggests an association between TGFBR1 SNPs and colorectal cancer, which warrants additional studies.

Phase I Study of an AKT Inhibitor (MK-2206) Combined with Lapatinib in Adult Solid Tumors Followed by Dose Expansion in Advanced HER2+ Breast Cancer

Purpose: Preclinical data support combining AKT inhibitors with HER2-targeted therapies to overcome resistance to treatment. This phase I study combined the investigational AKT inhibitor, MK-2206, with lapatinib to determine the MTD. Experimental Design: The dose escalation cohort enrolled adults with advanced solid tumors, who received MK-2206 dosed 30 to 60 mg every other day and lapatinib 1,000 to 1,500 mg daily continuously, escalated using a 3+3 design. Cycles were 28 days except cycle 1 (35 days, including an initial 8 days of MK-2206 alone to evaluate pharmacokinetic interactions). The dose expansion cohort enrolled adults with advanced HER2+ breast cancer. Results: Twenty-three participants enrolled in the dose escalation cohort. Dose-limiting toxicities were hyponatremia, fatigue, rash, hypocalcemia, and mucositis. Common toxicities included diarrhea, nausea, and rash. The MTD was reached at MK-2206 45 mg orally every other day and lapatinib 1,500 mg orally daily. Two participants maintained stable disease for >4 months, including a colorectal cancer participant with substantial carcinoembryonic antigen decrease. Of 5 participants in the dose expansion cohort, 2 maintained stable disease for >6 months, including one with prior progression on single-agent lapatinib. Plasma MK-2206 concentrations decreased after addition of lapatinib, but in vitro studies indicate lapatinib increases the intracellular levels of MK-2206. Conclusions: MK-2206 combined with lapatinib can be tolerated with both drugs above biologically active single-agent doses. Overlapping toxicities result in significant diarrhea and rash, which can be managed medically. Antitumor activity was promising and supports evaluation of AKT inhibitors combined with HER2-targeted therapies. Clin Cancer Res; 22(11); 2659–67. ©2016 AACR.

Two Isoforms of the RNA Binding Protein, Coding Region Determinant-binding Protein (CRD-BP/IGF2BP1), Are Expressed in Breast Epithelium and Support Clonogenic Growth of Breast Tumor Cells

Background: The RNA binding protein, coding region determinant-binding protein (CRD-BP), is expressed by tumor cells and protects key mRNAs. Results: This study identifies a novel variant of CRD-BP and finds that CRD-BP is required for breast tumor cell clonogenicity. Conclusion: CRD-BP has tumorigenic activity and is ubiquitously expressed in breast epithelium. Significance: Under-reporting of CRD-BP isoforms suggests that published studies may be incomplete. CRD-BP/IGF2BP1 has been characterized as an “oncofetal” RNA binding protein typically highly expressed in embryonic tissues, suppressed in normal adult tissues, but induced in many tumor types. In this study, we show that adult breast tissues express ubiquitous but low levels of CRD-BP protein and mRNA. Although CRD-BP mRNA expression is induced in breast tumor cells, levels remain ∼1000-fold lower than in embryonic tissues. Despite low expression levels, CRD-BP is required for clonogenic growth of breast cancer cells. We reveal that because the most common protein isoform in normal adult breast and breast tumors has an N-terminal deletion (lacking two RNA recognition motif (RRM) domains) and is therefore missing antibody epitopes, CRD-BP expression has been under-reported by previous studies. We show that a CRD-BP mutant mouse strain retains expression of the shorter transcript (ΔN-CRD-BP), which originates in intron 2, suggesting that the impact of complete ablation of this gene in mice is not yet known. Either the full-length CRD-BP or the N-terminally truncated version can rescue the clonogenicity of CRD-BP knockdown breast cancer cells, suggesting that clonogenic function is served by either CRD-BP isoform. In summary, although CRD-BP expression levels are low in breast cancer cells, this protein is necessary for clonogenic activity.