Watchman device migration and embolization: a report from the NCDR LAAO registry

Background

Incomplete anchoring of the Watchman left atrial appendage closure (LAAO) device can result in substantial device migration or device embolization requiring percutaneous or surgical retrieval.

Purpose

To report rates and characteristics of in-hospital and post-discharge Watchman device migration and embolization events in the United States.

Methods

We performed a retrospective analysis of Watchman procedures (January 2016 through March 2021) reported to the National Cardiovascular Data Registry LAAO Registry. We excluded patients with prior LAAO interventions, no device released, and missing device information. In-hospital events were assessed among all patients and post-discharge events were assessed among patients with 45-day follow-up.

Results

Of 120,278 Watchman procedures, device migration or embolization occurred in 0.07% of patients (n=84) during the index hospitalization and surgery was performed in 39 patients. The in-hospital mortality rate was 14% among patients with device migration or embolization and 20.5% among patients who underwent surgery. In-hospital migration or embolization was more common: at hospitals with a lower median annual procedure volume (24 vs. 41 procedures, p<0.0001), with first-generation Watchman versus next-generation Watchman FLX devices (0.08% vs. 0.04%, p=0.0048), with larger LAA ostia (median 23 mm vs. 21 mm, p=0.004), and with a smaller difference between device and LAA ostial size (median difference 4 mm vs. 5 mm, p=0.04). There were no differences by age, sex, hospital type, hospital size, or teaching versus non-teaching status. Of 98,147 patients with 45-day follow-up, device migration or embolization after discharge occurred in 0.06% (n=54) patients and cardiac surgery was performed in 7.4% (n=4) of cases. The 45-day mortality rate was 3.7% (n=2) among patients with post-discharge device migration or embolization. Post-discharge migration or embolization was more common among men (79.7% of events but 58.9% of all procedures, p=0.0019), taller patients (177.9 cm vs. 172 cm, p=0.0005), and those with greater body mass (99.9 kg vs. 85.5 kg, p=0.0055); in contrast to in-hospital events, there were no differences in hospital volume, device characteristics, or LAA characteristics.

Conclusions

Watchman device migration or embolization is rare but associated with high mortality (Figure 1) and frequently requires surgical retrieval. A substantial proportion of all device migration or embolization cases occur after discharge and different patient and procedure characteristics are associated with in-hospital versus post-discharge cases. Given the morbidity and mortality associated with device migration or embolization, risk mitigation strategies and on-site cardiac surgical back-up are of paramount importance.

Funding Acknowledgement

Type of funding sources: Public grant(s) – National budget only. Main funding source(s): National Institutes of Health

Enhanced design considerations on the buckling and dynamics of Gannet-inspired systems during water entry

To provide a more complete analysis of Gannet birds and Gannet-inspired drones during diving, this work considers an improved beam model to describe the static and dynamic characteristics of Gannet and Gannet-like drones at impact. The beam model consists of two different geometric and material property beams under continuity conditions to better understand the geometrical and material parameters' influence on the structural statics and dynamics of these kinds of systems. Using Hamilton's principle, the equations of motion, continuity, and boundary conditions considering Euler-Bernoulli and Timoshenko theories are derived. Then, applying the continuity and boundary conditions, the static and dynamic analyses are conducted to examine the impact buckling speeds, the buckled shapes, the natural frequencies at different impact velocities for bioinspired drone design, and the post-buckled mode shapes. The buckled configurations suggest that the body of the Gannet most likely has a different bending and torsional stiffness than the neck. The results indicate that the amount of softening in the joints contributes significantly to not only the speed at which the bird will buckle, but also the buckling profile of the bird. To obtain a physical buckling profile of the Gannet, a stiffer boundary condition at the end of the bird body model is needed due to the increased bending stiffness properties of the body compared to the neck as well as the position of the wings and feet surpassing the end of the body. The results also demonstrate that to build a bioinspired diving drone that falls within a smaller air-vehicle range, the amount of error between theories in predicting the static and dynamic buckling behavior of the system becomes significantly more evident. The dynamic characteristics and mode shapes of the Gannet-like systems are provided for further drone design insight on the impact speeds the drone can achieve without responding to an external excitation frequency from a propeller or actuator.

Investigations on the buckling and dynamics of diving-inspired systems when entering water

This work provides comparative modeling approaches to determine the velocities and natural frequencies of plunge-diving bird and bioinspired drone systems when entering water. These systems are chosen to further explain the survival of diving birds as they impact water and to provide insight into the design geometry and material choice of bioinspired diving drones. A nonlinear reduced-order model is developed and utilized to analyze the dive at impact considering both Timoshenko and Euler-Bernoulli beam theories. Using Hamilton's principle, the equations of motion are first derived. Then, static and dynamic buckling analyses are conducted. For this study, a geometrically simplified cone-beam system is considered, where the cone represents the head and the beam represents both the neck and body of the plunge-diving systems. The first study is to analyze the effects different diving drone materials and cone dimensions play on the sensitivity of the system. The second study applies geometric parameters to the cone-beam system representative of a plunge-diving bird (Northern gannet) and a surface-diving bird (Double-crested cormorant). The results show that choosing a material with a higher Young's modulus and a cone with a smaller half angle increase the velocity at which buckling occurs. The buckling velocities of the predicted Northern gannet model appear to be much greater than the average recorded diving speeds, suggesting that the bird is capable of plunge-diving at more extreme conditions. The natural frequencies are found for the aforementioned plunge-diving systems to predict failure if any external frequencies are known to act on the system while on a mission, such as conditions dependent on the climate or environment. It is shown in all buckling studies that the Euler-Bernoulli beam theory consistently overestimates the responses when compared with the Timoshenko beam theory. In the dynamic responses, Euler-Bernoulli beam theory overestimates for the pre-buckling region, then underestimates at the start of the post-buckling region until a point where the two theories cross paths. The amount of error with Euler-Bernoulli beam theory depends heavily on the slenderness ratio of the beam due to the theory being a simplification of the Timoshenko beam theory. It is noted that as the development of a more realistic bird model improves, the thickness will become significant and the use of Euler-Bernoulli beam theory at the point of impact will no longer be a valid assumption.

The growth of a xenograft breast cancer tumor model with engineered hyaluronan-accumulating stroma is dependent on hyaluronan and independent of CD44

Hyaluronan accumulation in the tumor microenvironment is associated with poor prognosis in several solid human cancers. To understand the role of stromal hyaluronan in tumor progression, we engineered 3T3HAS3, a hyaluronan-producing fibroblast cell line, by lentiviral transduction of Balb/c 3T3 cells with the human hyaluronan synthase 3(HAS3) gene. 3T3HAS3 cells significantly enhanced tumor growth when co-grafted with MDA-MB-468 cells in nude mice. Immunohistochemical analysis of the xenograft tumors showed that MDA-MB-468 cells were surrounded by hyaluronan-accumulating stroma, closely resembling the morphology observed in human breast cancer specimens. Tumor growth of MDA-MB-468 + 3T3HAS3 co-grafts was greatly reduced upon hyaluronan degradation by lentiviral transduction of a human hyaluronidase gene in 3T3HAS3 cells, or by systemic administration of pegvorhyaluronidase alfa (PEGPH20). In contrast, the growth of the co-graft tumors was not inhibited when CD44 expression was reduced or ablated by small hairpin RNA-mediated CD44 knockdown in MDA-MB-468 cells, CD44 CRISPR knockout in 3T3HAS3 cells, or by grafting these cells in CD44 knockout nude mice. Collectively, these data demonstrate that tumor growth of an engineered xenograft breast cancer model with hyaluronan-accumulating stroma can be dependent on hyaluronan and independent of CD44.

Abstract 97: The effect of hyaluronan degradation on the uptake and cytotoxic activity of liposome-encapsulated doxorubicin in 3D tumor spheroid models

The accumulation of hyaluronan (HA) in the solid tumor microenvironment (TME) can be associated with poor prognosis in several human cancers. Accumulation of HA in the TME can increase interstitial pressure that compresses local blood vessels and impairs the access of anti-cancer therapy. In preclinical models, enzymatic degradation of HA by pegvorhyaluronidase alfa (PEGPH20; PVHA), a PEGylated form of recombinant human hyaluronidase PH20 (rHuPH20), is associated with decreased tumor interstitial pressure, improved tumor vascular perfusion, and increased access and anti-tumor efficacy of cytotoxic and immunotherapies.

The functional effect of HA degradation on the TME has been mostly characterized in animal tumor models. Here, we describe the utilization of 3D tumor spheroid models to evaluate the effects of HA degradation on the cytotoxic effect of anti-cancer therapies. A number of commonly used human colorectal cancer (CRC) cell lines were assessed for HA accumulation and tumor spheroid morphology: HCT 116, HT-29 parental, and HT-29/HAS3 (HT-29 cells engineered to over-express hyaluronan synthase 3). CRC 3D tumor spheroid models were developed to evaluate the uptake and cytotoxic activity of liposome-encapsulated doxorubicin (DOX) using the IncuCyte® S3 Live-Cell Analysis System. The effect of HA degradation on DOX uptake and cytotoxic activity was initially tested with rHuPH20 treatment in all three models, and further evaluated with PVHA treatment in HT-29 parental and HT-29/HAS3 models.

A dose-dependent uptake and cytotoxic activity of DOX was observed in HCT 116 tumor spheroids. HA degradation after rHuPH20 treatment enhanced DOX uptake by an average of 6.1% (up to 7.7%) and cytotoxicity by an average of 37.9% (up to 58.2%) over the 5-day duration of the experiment compared with DOX alone. Dose-dependent uptake and cytotoxic activity of DOX in HT-29/HAS3 tumor spheroids were enhanced with rHuPH20 treatment to a greater extent than in HT-29 parental tumor spheroids. Specifically, rHuPH20 treatment led to an average increase in DOX uptake of 9.2% (up to 14.6%) with HT-29/HAS3 spheroids and 2.6% (up to 5.1%) with HT-29 parental spheroids. The addition of rHuPH20 resulted in an average increase in DOX cytotoxicity of 101% (up to 227.6%) with HT-29/HAS3 spheroids and 24.9% (up to 63.9%) with HT-29 parental spheroids. Enhanced uptake and cytotoxic activity of DOX was also observed with PVHA treatment in HT-29 and HT-29/HAS3 models.

These data corroborate our previous findings with in vivo tumor models, in which the combination of PVHA-mediated HA degradation and other anti-cancer therapies display enhanced anti-tumor activity compared with either agent alone. Further, 3D tumor spheroid models may be used to evaluate the effect of extracellular matrix remodeling such as HA degradation and serve as a bridge between 2D cell-based assays and in vivo tumor models.

Citation Format: Feng Gao, Susan Zimmerman, Kelly Chen, Daniel C. Maneval, Chunmei Zhao. The effect of hyaluronan degradation on the uptake and cytotoxic activity of liposome-encapsulated doxorubicin in 3D tumor spheroid models [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 97.

Nonlinear modeling and experimental verification of Gannet-inspired beam systems during diving

A nonlinear model is proposed to answer at which diving speeds and beak angles will cause injury to Gannet-inspired beam systems during plunge-diving. In doing so, the critical velocities at which buckling occurs with various types of boundary conditions are first obtained for vertical dives and the resulting forces at the point of impact are determined. The Gannet-inspired system is modeled as an Euler-Bernoulli beam to represent the neck and body of the Gannet, while the head of the Gannet is modeled as a cone with varying half-angles. The experimental investigations of Gannet-like diving systems are first introduced to present the varying parameters and assumptions of the simplified model. Next, the resulting forces during impact are investigated and a study is conducted to compare various approximations of the drag coefficient for the cone-shaped head. Considering the mid-plane stretching nonlinearity, the equations of motion for the structural system under various types of boundary conditions are derived using the Hamilton's principle. The characteristic equations, buckled configurations, and critical velocities are determined for each set of boundary conditions. The results show that the system with the smallest half-beak angle and thus the lowest drag force and beam length delays the critical velocity and is most representative of a Gannet during diving. The obtained results demonstrate great agreement with the conducted experiments. For clamped-clamped boundary conditions, the critical velocity is found to be the greatest because of the increased stability at both ends of the beam. It is also noted that a nonlinear approximation for the coefficient of drag offers the best fit with the provided experimental values when compared to a hyperbolic tangent approximation, which predicts the coefficient of drag to be less than that obtained in experiments, and thus predicts that the systems will buckle at higher velocities.

Abstract 2101: The growth of a xenograft breast cancer tumor model with engineered hyaluronan-accumulating stroma is dependent on hyaluronan and independent of CD44

The abnormal accumulation of hyaluronan in the solid tumor microenvironment is associated with poor prognosis in several human cancers. Hyaluronan often accumulates in the tumor stroma. To understand the role of hyaluronan-accumulating stroma in tumor progression, we engineered a hyaluronan-producing fibroblast cell line 3T3HAS3 by lentiviral transduction of the human hyaluronan synthase 3 gene into Balb/c 3T3 cells. The 3T3HAS3 cells produced significant amounts of hyaluronan in vitro, which bind to the cell surface of the human breast cancer cell line MDA-MB-468. When co-grafted with MDA-MB-468 cells in nude mice, 3T3HAS3 significantly enhanced tumor growth. Immunohistochemical analysis of tumor xenografts showed that MDA-MB-468 cells were surrounded by hyaluronan-accumulating stroma, closely resembling the morphology observed in human breast cancer specimens. Tumor growth of this co-graft model required hyaluronan production from 3T3HAS3 cells, as demonstrated by the delayed tumor growth upon hyaluronan removal by expression of the human PH20 gene in 3T3HAS3 cells, or by systemic administration of PEGylated recombinant human PH20 (PEGPH20). In contrast, neither the expression of CD44, a well-characterized hyaluronan receptor, in tumor and stromal fibroblasts, nor the binding of hyaluronan to CD44 in MDA-MB-468 tumor cells was essential for tumor growth. Small scale screening of signaling changes in xenograft tumors suggested that the AMPK/mTOR pathway may respond to hyaluronan removal by PEGPH20. Collectively, these data demonstrate that the growth of an engineered breast cancer xenograft model with hyaluronan-accumulating stroma is dependent on hyaluronan, and that hyaluronan-CD44 interaction may not be the main mechanism through which hyaluronan promotes tumor progression in certain tumors.

Citation Format: Chunmei Zhao, Benjamin J. Thompson, Kelly Chen, Mathieu Marella, Susan Zimmerman, Trevor Kimbler, Barbara Blouw, Sheryl Garrovillo, Lei Huang, Adrian Radi, Zhongdong Huang, H. Michael Shepard, Sanna Rosengren, Christopher D. Thanos, Daniel C. Maneval. The growth of a xenograft breast cancer tumor model with engineered hyaluronan-accumulating stroma is dependent on hyaluronan and independent of CD44 [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 2101.

Abstract 3036: PEGylated hyaluronidase increases tumor uptake of 89Zr-DFO-HuMab-5B1 (MVT-2163) in a CA19-9 positive hyaluronan-accumulating pancreatic cancer model

Hyaluronan (HA) accumulates in the extracellular matrix of many solid tumors, and is associated with poor prognosis in pancreatic ductal adenocarcinoma. In non-clinical models, enzymatic degradation of HA with PEGylated recombinant human hyaluronidase PH20 (PEGPH20) has been shown to remodel the tumor stroma, reduce tumor interstitial fluid pressure, and expand tumor blood vessels, resulting in enhanced delivery of therapeutic and imaging agents, such as monoclonal antibodies. 89Zr-DFO-HuMab-5B1 (MVT-2163) is a targeted ImmuoPET imaging agent for CA19-9 positive malignancies currently in clinical evaluation. CA19-9 plays a role in tumor adhesion and metastasis, and is an independent prognostic indicator of cancer survival. CA19-9 is expressed in pancreatic and other cancers, including small cell lung and colon. In this study, we aimed to show the effects of PEGPH20 on the biodistribution of MVT-2163 in a CA19-9 positive HA-rich human pancreatic tumor xenograft model.

Nude mice were peritibially implanted on the right hind limb with 5x106 human pancreatic tumor cells engineered to overexpress hyaluronan synthase 3 (BxPC3/HAS3). Tumor volumes were measured by MR imaging, and mice were staged when average tumor size reached 320 mm3. The control group received intravenous (IV) vehicle, and the test group received PEGPH20 (IV, 1 mg/kg). Both control and test groups also received MVT-2163 (IV, 3 mg/kg) 24 hours later. PET images were captured from 2 to 120 hours post MVT-2163, and region of interest (ROI) of tumor and liver were analyzed (N=6/group). After the final PET image, tumors and livers were harvested for ex vivo gamma counting.

Ex vivo gamma counting demonstrated improved MVT-2163 accumulation in animals treated with PEGPH20, with a 50.9% increase in counts in the excised tumors. ROI analysis of the tumors showed increased tumor SUV of 8.0, 9.4, and 24.1% at 72, 96, and 120 hours post-injection, respectively, with PEGPH20 compared to vehicle. ROI analysis of liver regions showed an 11.4 to 26.4% reduction in SUV in the PEGPH20 group compared to control. Ex vivo counts of liver tissue confirmed the PET signal reduction with PEGPH20. Analysis of tumor-to-liver ratios showed average increases of 34.1, 35.7, and 58.5% at 72, 96, and 120 hours, respectively, post MVT-2163 injection in PEGPH20 treated mice.

In summary, as measured by SUV, PEGPH20 increased both the tumor uptake and the tumor-to-liver ratios of MVT-2163 in a CA19-9 positive xenograft mouse model of HA accumulating pancreatic cancer. Ex vivo analysis confirmed in vivo results. Taken together, the increased tumor uptake and the decreased liver uptake support further investigation into the potential clinical utility for the combination of PEGPH20 and MVT-2163.

Citation Format: Jonah Rainey, Paul Maffuid, Wolfgang W. Scholz, Jack Ostrowski, H Toni Jun, Paul Resnick, Xiaoming Li, Jesse D. Bahn, Susan Zimmerman, Kelly Chen, Barbara Blouw, Curtis B. Thompson, Daniel C. Maneval, David W. Kang. PEGylated hyaluronidase increases tumor uptake of 89Zr-DFO-HuMab-5B1 (MVT-2163) in a CA19-9 positive hyaluronan-accumulating pancreatic cancer model [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 3036.

Abstract B46: Varying the inoculation site of mouse syngeneic tumors can result in aberrant inclusion of lymph node tissue at tumor harvest

In recent years, growing interest in immunotherapies for the treatment of cancer has led to increased reliance on murine syngeneic tumor models for preclinical study in immunocompetent animals. These studies typically examine changes in the quantities and phenotypes of tumor-infiltrating immune cells; thus, it is crucial to distinguish between these cells and extratumoral immune cells during tumor harvest. Here, we show that 4T1 breast tumors inoculated in mammary fat pads (MFP) numbers 4 or 9 (4/9) contained greater frequencies of B cells and naïve T cells than tumors inoculated in MFP numbers 5 or 10 (5/10). Immunohistochemical analysis for B-cell presence demonstrated that MFP 4/9 tumors encroached on, and often encapsulated, inguinal lymph nodes, such that lymph node tissue was unknowingly collected during tumor harvest. This prevented accurate enumeration and phenotyping of infiltrating immune cells by flow cytometry, as the majority of lymphocytes in the affected samples derived from lymph nodes, and had not infiltrated the tumor per se. We observed the same phenomenon in peritibial tumors using immunohistochemical analysis, which began to encapsulate popliteal lymph nodes at large tumor volumes (>1500 mm3). Our data highlight the importance of choosing an appropriate inoculation site for obtaining accurate and consistent results when evaluating immune cell infiltration in syngeneic tumor models.

Citation Format: Renee Clift, Barbara Blouw, Susan Zimmerman, Sanna Rosengren, Curt Thompson, Benjamin Thompson. Varying the inoculation site of mouse syngeneic tumors can result in aberrant inclusion of lymph node tissue at tumor harvest [abstract]. In: Proceedings of the AACR Special Conference: Advances in Modeling Cancer in Mice: Technology, Biology, and Beyond; 2017 Sep 24-27; Orlando, Florida. Philadelphia (PA): AACR; Cancer Res 2018;78(10 Suppl):Abstract nr B46.

Neurologial Interpretations and the Information in the Cognitive Pupillary Response

It has been known for 70 years that the human pupil dilates when a person responds to a cognitive task. Further, it is known that parasympathetic pupillary innervation decreases with raised attention state while sympathetic innervation increases. But the information the pupil transmits during elevated attention states about such neurological dynamics and a quantitative measure of this information have defied statistical modelling. Now we describe experiments using a short-term memory task called an acoustic impulse test in which the pupillary dynamics in response to random acoustic impulses are recorded with a high resolution (0.01mm) pupillometer with the result that parasympathetic and sympathetic pupillary dilation components are quantifiable, as is the information transmitted by these components.

Abstract 50: HTI-1511, a novel anti-EGFR-ADC, overcomes mutation resistance and demonstrates significant activity against multiple tumor types in preclinical studies

Multiple solid tumor types over-express epidermal growth factor receptor (EGFR). Antibodies that target the receptor are often accompanied by adverse skin reactions due to interaction with receptors expressed in normal tissue. Additionally, downstream mutations (KRAS, BRAF) within tumors can result in EGFR-independent activation and resistance to treatment. We have previously described HTI-1511, an antibody-drug conjugate in pre-clinical development that targets EGFR. HTI-1511 carries the potent cytotoxin MMAE and a novel bis-alkylating linker, connected to a monoclonal antibody engineered to have improved specificity for EGFR in the tumor microenvironment (Huang et. al. AACR National Meeting, 2016, New Orleans, LA). Here we screened a panel of over 70 tumor cell lines derived from various solid tumor malignancies for both EGFR expression by flow cytometry and sensitivity to cell growth inhibition by HTI-1511 in vitro. Cell lines derived from head and neck squamous cell carcinoma (SCC15, CAL27, FaDu, CAL33, SCC25 [IC50 0.52 nM - 3.1 nM]), non-small cell lung cancer (HCC827, NCI-H1666, PC-9, NCI-H1650 [IC50 0.04 nM - 6.2 nM]), and pancreatic carcinoma (BxPC-3, PANC-1, AsPC-1 [IC50 0.99 nM - 4.44 nM]) showed particular sensitivity to HTI-1511. In conjunction, HTI-1511 efficacy was assessed in vivo for tumor growth inhibition (TGI) in several human tumor xenograft models. Evaluations in the human xenografts A431 (epidermoid, 93% TGI at 3.0 mg/kg, p<0.05), BxPC3 (pancreatic, >100% TGI at 3.0 mg/kg, p<0.05), AsPC-1 (pancreatic, >100% TGI at 3.0 mg/kg, p<0.05), and FaDu (HNSCC, >100% TGI at 3.0 mg/kg, p<0.05) indicated dose dependent tumor regressions in all cases, and no observed toxicity when administered weekly at dose levels up to 3 mg/kg for up to eight weeks. HTI-1511 anti-tumor activity was also investigated in a group of patient derived xenograft (PDX) models. An initial study evaluated weekly administration of a single dose level of 2.5 mg/kg HTI-1511 in three different PDX models. TGI of 83% (p<0.05) was observed in a BRAFmut colorectal cancer model and 57% (p<0.05) in a wildtype colorectal cancer model, as well as 46% (not significant) TGI seen in a wild type renal cell carcinoma model. A separate study in a NSCLC (KRASmut) PDX model demonstrated a dose dependent response with greater than 100% TGI at 1.0 and 3.0 mg/kg (both p<0.05, and also p<0.05 to a non-cognate antibody ADC control). The non-cognate antibody control yielded 67.4% (not significant) TGI by itself compared to the vehicle control group. These results support further development of HTI-1511 as a possible treatment for EGFR overexpressing tumors, including those with downstream activating mutations in the KRAS/BRAF pathway.

Citation Format: Jesse D. Bahn, Feng Gao, Lei Huang, Barbara Blouw, Chunmei Zhao, Kelly Chen, Susan Zimmerman, Erin K. Wise, Maria L. Mancini, Matthew Bird, William McDowell, Curtis B. Thompson, Sanna Rosengren, Christopher D. Thanos. HTI-1511, a novel anti-EGFR-ADC, overcomes mutation resistance and demonstrates significant activity against multiple tumor types in preclinical studies [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 50. doi:10.1158/1538-7445.AM2017-50

Abstract A46: Hyaluronan-dependent growth of human triple negative breast cancer MDA-MB-468 in a mouse xenograft model with HA-high stroma

Hyaluronan (also known as hyaluronic acid or HA) is a megadalton sized glycosaminoglycan present in the extracellular matrix. The abnormal accumulation of HA in the solid tumor microenvironment (TME) of several human cancers, including pancreatic, breast, colon and prostate, has been well studied and is associated with poor prognosis. In certain breast cancer specimens with a HA-high status, HA is found to be significantly associated with the stromal compartment rather than with tumor cells. To understand the interaction between tumor cells and a HA containing stromal compartment, we engineered a HA-high stromal cell line by lentiviral transduction of the human HAS3 gene into Balb/c 3T3 fibroblast cells. The 3T3/HAS3 cells produced significant amounts of HA in vitro, which was shown to bind to the HA-low/CD44-high breast cancer cell line MDA-MB-468 at the cell surface. When co-grafted with MDA-MB-468 cells in mice, 3T3/HAS3 cells promoted the in vivo growth of MDA-MB-468 cells. Immunohistochemical analysis of tumor xenograft samples showed that MDA-MB-468 cells were surrounded by HA-high stromal cells, closely resembling the tumor morphology observed in human breast cancer specimens. Tumor growth in this co-grafting model was highly dependent on the presence of 3T3/HAS3 cells, and required HA produced by 3T3/HAS3 cells. Ganciclovir blocked the growth of MDA-MB-468 co-inoculated with 3T3/HAS3/hsv-TK, as did HA removal either by the expression of the HA degrading enzyme PH20, directly in 3T3/HAS3 cells or by exogenous administration of PEGPH20, a pegylated version of PH20 engineered for extended half-life. Interestingly, the presence of 3T3/HAS3 cells was found to be most critical during early stages of tumor progression and was non-essential for tumor maintenance once tumors were fully established, as ganciclovir had little impact on tumor growth when tumor size was larger than 500 mm3 but prevented tumor growth when administered at inoculation and inhibited tumor growth when treatment started at a smaller tumor size (200 mm3, 90.4% TGI). We have developed a tumor xenograft model that mimics breast cancer with a HA-high status in the tumor stromal compartment. Further characterization of this model will provide insight into the mechanisms by which increased levels of HA and the associated changes in the TME promote disease progression in breast cancer.

Citation Format: Chunmei Zhao, Mathieu Marella, Lei Huang, Anne Kultti, Susan Zimmerman, Caroline EN Chou, Jesse Bahn, Adrian Radi, Zhongdong Huang, H Michael Shepard, Christopher D. Thanos. Hyaluronan-dependent growth of human triple negative breast cancer MDA-MB-468 in a mouse xenograft model with HA-high stroma. [abstract]. In: Proceedings of the AACR Special Conference: Function of Tumor Microenvironment in Cancer Progression; 2016 Jan 7–10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2016;76(15 Suppl):Abstract nr A46.

Loss of diacylglycerol kinase epsilon in mice causes endothelial distress and impairs glomerular Cox-2 and PGE2 production

Thrombotic microangiopathy (TMA) is a disorder characterized by microvascular occlusion that can lead to thrombocytopenia, hemolytic anemia, and glomerular damage. Complement activation is the central event in most cases of TMA. Primary forms of TMA are caused by mutations in genes encoding components of the complement or regulators of the complement cascade. Recently, we and others have described a genetic form of TMA caused by mutations in the gene diacylglycerol kinase-ε (DGKE) that encodes the lipid kinase DGKε (Lemaire M, Fremeaux-Bacchi V, Schaefer F, Choi MR, Tang WH, Le Quintrec M, Fakhouri F, Taque S, Nobili F, Martinez F, Ji WZ, Overton JD, Mane SM, Nurnberg G, Altmuller J, Thiele H, Morin D, Deschenes G, Baudouin V, Llanas B, Collard L, Majid MA, Simkova E, Nurnberg P, Rioux-Leclerc N, Moeckel GW, Gubler MC, Hwa J, Loirat C, Lifton RP. Nat Genet 45: 531-536, 2013; Ozaltin F, Li BH, Rauhauser A, An SW, Soylemezoglu O, Gonul II, Taskiran EZ, Ibsirlioglu T, Korkmaz E, Bilginer Y, Duzova A, Ozen S, Topaloglu R, Besbas N, Ashraf S, Du Y, Liang CY, Chen P, Lu DM, Vadnagara K, Arbuckle S, Lewis D, Wakeland B, Quigg RJ, Ransom RF, Wakeland EK, Topham MK, Bazan NG, Mohan C, Hildebrandt F, Bakkaloglu A, Huang CL, Attanasio M. J Am Soc Nephrol 24: 377-384, 2013). DGKε is unrelated to the complement pathway, which suggests that unidentified pathogenic mechanisms independent of complement dysregulation may result in TMA. Studying Dgke knockout mice may help to understand the pathogenesis of this disease, but no glomerular phenotype has been described in these animals so far. Here we report that Dgke null mice present subclinical microscopic anomalies of the glomerular endothelium and basal membrane that worsen with age and develop glomerular capillary occlusion when exposed to nephrotoxic serum. We found that induction of cyclooxygenase-2 and of the proangiogenic prostaglandin E2 are impaired in Dgke null kidneys and are associated with reduced expression of the antithrombotic cell adhesion molecule platelet endothelial cell adhesion molecule-1/CD31 in the glomerular endothelium. Notably, prostaglandin E2 supplementation was able to rescue motility defects of Dgke knockdown cells in vitro and to restore angiogenesis in a test in vivo. Our results unveil an unexpected role of Dgke in the induction of cyclooxygenase-2 and in the regulation of glomerular prostanoids synthesis under stress.

Abstract P1-03-09: Pegylated recombinant human hyaluronidase PH20 (PEGPH20) enhances efficacy of eribulin mesylate (HALAVEN®) in triple negative breast cancer xenografts

Hyaluronan (hyaluronic acid, HA), a glycosaminoglycan found in tissue throughout the body, overaccumulates in the tumor microenvironment (TME) of many non-hematologic malignancies, including breast cancer. HA overaccumulation in breast cancer patients correlates with tumor progression and decreased survival (Tammi 2008). Pegylated recombinant human hyaluronidase PH20 (PEGPH20), an investigational therapeutic agent entering Phase 3 clinical development in pancreatic cancer, enzymatically removes HA from the TME. In preclinical animal models, PEGPH20-mediated HA degradation is associated with remodeling of the tumor stroma, reduction of tumor pressure, expansion of tumor blood vessels and facilitated delivery of chemotherapy (Thompson 2010, Provenzano 2012, Jacobetz 2013). Accordingly, preclinical studies investigated the combination of PEGPH20 with eribulin mesylate (ERI, HALAVEN®), a microtubule dynamics inhibitor with a novel mechanism of action (Towle 2001, Jordan 2005), currently approved for treatment of certain patients with advanced breast cancer. NCr nu/nu mice were inoculated subcutaneously with human triple-negative breast cancer (TNBC) HCC1806 or HCC1806/HAS3 cells; the latter subline was engineered to accumulate high HA levels, confirmed by immunohistochemistry, via overexpression of hyaluronan synthase 3 (HAS3). When tumors reached ∼350 mm3, animals were randomly assigned to four treatments groups: vehicle, ERI (0.7 mg/kg, IV, QW), PEGPH20 (37.5 µg/kg, IV, BIW), or ERI plus PEGPH20. In the parental HCC1806 model, addition of PEGPH20 did not significantly change the antitumor effects of ERI. In contrast, combining PEGPH20 with ERI in the HCC1806/HAS3 model increased the antitumor effects of ERI by 27% (94.5% vs. 119.7% TGI, ERI alone vs. ERI+PEGPH20, respectively; p=0.05) and resulted in 6 of 7 complete tumor regressions.

In a complementary study in HCC1806/HAS3 tumors evaluating ERI pharmacokinetics with and without PEGPH20, mice were assigned to three treatments groups: ERI (0.5 mg/kg, IV), simultaneous ERI plus PEGPH20 (37.5 µg/kg, IV); or ERI plus PEGPH20 predosed 24 h prior to ERI. Animals were sacrificed at 0.5, 1, 4, 24, 48, 72 and 96 h post ERI dose, and ERI levels in tumor, muscle, plasma and liver were subsequently analyzed by liquid/liquid extraction and LC-MS/MS chromatography. Simultaneous administration of ERI and PEGPH20 increased ERI maximum tumor concentration (Cmax) slightly and approximately doubled ERI tumor exposure (AUC); whereas the 24 h pretreatment with PEGPH20 approximately doubled ERI Cmax and increased ERI AUC more than two-fold. No significant differences in plasma ERI levels were observed between groups, and no significant differences in ERI levels in liver or muscle tissue were observed between groups. Taken together, these data suggest that PEGPH20-mediated HA removal significantly increases both ERI tumor concentrations and antitumor effectiveness in an HA-high TNBC model. A clinical phase 1b/2 clinical trial is planned to evaluate PEGPH20 plus ERI in first-line HER2-negative metastatic breast cancer.

Citation Format: Bahn JD, DesJardins C, Condon KB, Fathallah A, Zimmerman S, Maneval DC, Littlefield BA, Thompson CB. Pegylated recombinant human hyaluronidase PH20 (PEGPH20) enhances efficacy of eribulin mesylate (HALAVEN®) in triple negative breast cancer xenografts. [abstract]. In: Proceedings of the Thirty-Eighth Annual CTRC-AACR San Antonio Breast Cancer Symposium: 2015 Dec 8-12; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2016;76(4 Suppl):Abstract nr P1-03-09.

Abstract 2392: Hyaluronan-dependent growth of human triple negative breast cancer MDA-MB-468 in mouse xenograft models

Hyaluronan (also known as hyaluronic acid or HA) is a nonsulfated glycosaminoglycan in the extracellular matrix. Elevated levels of HA in the tumor microenvironment have been associated with poor prognosis of several human cancers, including pancreatic, breast, colon and prostate. In many cases of breast cancer, HA is found to be associated with the stromal compartment. To understand the interaction between tumor cells and HA containing stromal compartment, we engineered a HA-high stromal cell line by overexpressing the human HAS3 gene in Balb/c 3T3 fibroblast cells. In vitro, the 3T3/HAS3 cells produced and secreted HA, which was shown to bind to the HA-low/CD44-high breast cancer cell line MDA-MB-468 at the cell surface. When co-grafted with MDA-MB-468 cells in mice, 3T3/HAS3 cells promoted the in vivo growth of MDA-MB-468 cells. Furthermore, depletion of HA with PEGPH20 (a pegylated form of the recombinant human PH20 protein) significantly inhibited the growth of MDA-MB-468 cells co-grafted with 3T3/HAS3 cells, suggesting that the HA provided by 3T3/HAS3 cells is critical for the growth of MDA-MB-468 cells in vivo. Immunohistochemical analysis of tumor xenograft samples showed that HA-low MDA-MB-468 cells were surrounded by HA-high stromal cells, resembling the tumor morphology observed in certain breast cancer patients. To model for breast cancers with tumor cell-associated HA, we overexpressed the human HAS3 gene directly in MDA-MB-468 cells. The in vivo growth of MDA-MB-468 was significantly enhanced by HAS3 overexpression. Depletion of HA by PEGPH20 synergized with Abraxane and improved its anti-cancer efficacy in the MDA-MB-468/HAS3 xenograft model compared to PEGPH20 and Abraxane alone. Taken together, we have developed tumor xenograft models that mimic HA-high breast cancers and can be used to test the pharmacological activity of anticancer agents. Further characterization of these models will provide insights into the understanding of the mechanisms by which increased levels of HA and the associated changes in the tumor microenvironment promote the disease progression in breast cancer and how depletion of HA can interfere with this process and synergize with chemotherapies to inhibit tumor progression.

Citation Format: Chunmei Zhao, Mathieu Marella, Susan Zimmerman, Lei Huang, H. Michael Shepard, Zhongdong Huang. Hyaluronan-dependent growth of human triple negative breast cancer MDA-MB-468 in mouse xenograft models. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 2392. doi:10.1158/1538-7445.AM2015-2392

Abstract P4-04-25: Naked mole rat hyaluronan synthase 2 displays similar effects as human hyaluronan synthase 2 and promotes tumor growth in a mouse xenograft model

Accumulation of hyaluronan (HA) is correlated with poor prognosis in many human cancer including breast cancer and pancreatic cancer. Hyaluronan synthase 2 (HAS2) is one of the three HA synthase genes (HAS1-3) found in mammals. Up-regulation of the HAS2 gene has been observed in breast cancer patients; and HAS2 expression correlates with the incidence of metastasis and lower rate of overall patient survival (Okuda et al 2012). Interestingly, a recent study suggested that the naked mole rat (nmr) HAS2 enzyme may function differently than the HAS2 proteins from mice and humans, and its expression had a tumor suppressor effect (Tian et al 2013). The nmrHAS2 protein sequence was distinct from other mammals in the cytoplasmic loop where the active site resides, which led to the hypothesis that nmrHAS2 may contribute to the production of extremely high molecular weight HA species. Furthermore, nmrHAS2 is required for the resistance of nmr skin fibroblasts to malignant transformation. In this study, we examined whether the nmrHAS2 gene can also render human cells resistant to tumor progression. We have previously observed that HA level in the pancreatic cancer model AsPC1 can be modulated by the over-expression of the human HAS3 protein (Osgood et al 2014). To compare and contrast the effect of nmrHAS2 and huHAS2 on HA production and tumor growth, nmrHAS2 and huHAS2 AsPC1 models were engineered using a recombinant lentivirus encoding the nmrHAS2 and huHAS2 genes respectively. Over-expression of nmrHAS2 and huHAS2 both significantly increased the HA level in AsPC1 cells. Both nmrHAS2 and huHAS2 promoted the growth of AsPC1 in an intramuscular xenograft tumor model. Ex vivo analysis of tumor xenografts showed that nmrHAS2 and huHAS2 AsPC1 tumors contain elevated levels of HA, and the size range of the HA in the nmrHAS2 tumors is similar to that in the huHAS2 AsPC1 tumors. Therefore, nmrHAS2 functions similarly as huHAS2 gene and promotes tumor growth in the human pancreatic tumor model AsPC1.

References:

Okuda H, Kobayashi A, Xia B, Watabe M, Pai SK et al. Hyaluronan synthase HAS2 promotes tumor progression in bone by stimulating the interaction of breast cancer stem-like cells with macrophages and stromal Cells. Cancer Research 72:537-47, 2012.

Tian X, Azpurua J, Hine C, Vaidya A, Myakishev-Rempel M et al. High-molecular-mass hyaluronan mediates the cancer resistance of the naked mole rat. Nature 499:346-349, 2013.

Osgood RJ, Skipper JF, Cowell JA, Chen Y, Zhu L et al. Pegylated recombinant human hyaluronidase PH20 (PEGPH20) enhances Nab-Paclitaxel plus gemcitabine efficacy in human pancreatic cancer xenografts. AACR Special Conference Pancreatic Cancer 2014.

Citation Format: Chunmei Zhao, Susan Zimmerman, Calvin T Vu, Michael Shepard, Zhongdong Huang. Naked mole rat hyaluronan synthase 2 displays similar effects as human hyaluronan synthase 2 and promotes tumor growth in a mouse xenograft model [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 P4-04-25.

Effect of home-based light treatment on persons with dementia and their caregivers

Sleep disorders are problematic for persons with dementia and their family caregivers. This randomized controlled trial with crossover evaluated the effects of an innovative blue-white light therapy on 17 pairs of home-dwelling persons with dementia and their caregivers. Subjects with dementia received blue-white light and control ('red-yellow' light) for six weeks separated by a four-week washout. Neither actigraphic nor most self-reported sleep measures significantly differed for subjects with dementia. For caregivers, both sleep and role strain improved. No evidence of retinal light toxicity was observed. Six weeks of modest doses of blue-white light appear to improve sleep in caregivers but not in persons with dementia. Greater or prolonged circadian stimulation may be needed to determine if light is an effective treatment for persons with dementia.

Abstract 4844: Extracellular hyaluronan accumulation by hyaluronan synthase 3 promotes pancreatic cancer growth and modulates tumor microenvironment via epithelial-mesenchymal transition

Pancreatic cancer is one of most deadly cancers with a 5-year survival rate of 6%. Accumulation of hyaluronan (HA) is found in about 87% of human pancreatic adenocarcinomas, and removal of HA suppresses tumor growth in HA-rich preclinical models. In a transgenic pancreatic cancer mouse model (LSL-KrasG12D/+;LSLTrp53R172H/+;Pdx-1-Cre, KPC), removal of HA by pegylated human recombinant PH20 hyaluronidase (PEGPH20) inhibits tumor growth and increases survival in combination with gemcitabine compared to gemcitabine monotherapy. In this study, we explored the role of HA synthesizing (HAS) enzymes HAS2 and HAS3 and HA accumulation in pancreatic cancer tumor growth and remodeling of tumor microenvironment.

HAS2 and HAS3 were overexpressed in BxPC3 human pancreatic cancer cells using lentiviral vectors. Stable HAS2 and HAS3 overexpressing pancreatic cancer cell lines secreted more HA to culture medium and produced larger pericellular HA matrices than parental BxPC3 cells. In vivo, overexpression of HAS2 or HAS3 led to an increase in BxPC3 xenograft tumor growth (peritibial i.m. tumor model) compared to parental cells. Interestingly, overexpression of HAS3 was more effective to enhance tumor growth than overexpression of HAS2. In addition, massive accumulation of extracellular HA was found in HAS3 overexpressing tumors while HAS2 overexpressing tumors contained both extracellular and intracellular HA. Treatment with PEGPH20 removed the majority of extracellular HA and induced a 87% reduction of tumor volume in BxPC3 HAS3 model (p<0.001) but had weaker effect on BxPC3 HAS2 (33%, p<0.001) and BxPC3 tumors (36%, p<0.01). Accumulation of extracellular HA was associated with enriched tumor stroma, loss of membranous E-cadherin and accumulation of cytoplasmic β-catenin in pancreatic cancer cells, suggesting HA-induced epithelial-mesenchymal transition (EMT). Removal of HA by PEGPH20 reversed the remodeling of the tumor stroma and induced translocation of E-cadherin and β-catenin to the plasma membrane.Translocation of E-cadherin was also observed in the KPC pancreatic tumors after PEGPH20 treatment.

In conclusion, accumulation of extracellular HA by HAS3 overexpression favors tumor growth and leads to a strong response to PEGPH20 in a pancreatic cancer xenograft model. Deposition of extracellular HA is associated with optimization of the tumor microenvironment and EMT. Depletion of HA by PEGPH20 reverses changes in the tumor stroma and induces translocation of epithelial markers to the plasma membrane.

Citation Format: Anne Kultti, Chunmei Zhao, Susan Zimmerman, Ryan J. Osgood, Yanling Chen, Rebecca Symons, Ping Jiang, Curtis B. Thompson, David A. Tuveson, Gregory I. Frost, H Michael Shepard, Zhongdong Huang. Extracellular hyaluronan accumulation by hyaluronan synthase 3 promotes pancreatic cancer growth and modulates tumor microenvironment via epithelial-mesenchymal transition. [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 4844. doi:10.1158/1538-7445.AM2014-4844

Abstract 3646: Pegylated recombinant human hyaluronidase PH20 (PEGPH20) enhances cetuximab efficacy in BxPC-3/HAS3 human pancreatic cancer xenografts

Hyaluronan (HA) over-accumulation in the extracellular matrix (ECM) of many solid tumors is associated with tumor progression and poor prognosis (Tammi 2008). In preclinical animal models, enzymatic removal of ECM HA with pegylated recombinant human hyaluronidase PH20 (PEGPH20) is associated with remodeling of the tumor stroma, reduction of tumor interstitial fluid pressure, expansion of tumor blood vessels and facilitated delivery of chemotherapy (Thompson 2010, Jacobetz 2012, Provenzano 2012). Additionally, epidermal growth factor receptor (EGFR), a tyrosine kinase essential for cell division and tumor growth, has been implicated in multiple epithelial malignancies and is over expressed in ∼60% of human pancreatic carcinomas (Frolov 2007). Cetuximab (CET), a chimeric monoclonal antibody (mAb), targets EGFR preventing tyrosine kinase mediated phosphorylation and subsequent signal transduction (Enrique 2012). As pancreatic ductal adenocarcinoma (PDA) has been identified as a cancer type that expresses high levels of HA (∼87%; Jiang 2010), studies were conducted to evaluate PEGPH20 enhancement in anti-tumor activity of CET in an EGFR positive HA-overexpressing PDA BxPC3/HAS3 xenograft model (Kultti 2013). In brief, NCr nu/nu mice were inoculated with PDA BxPC3/HAS3 cells adjacent to the tibial periosteum, and tumor growth was monitored with 3D high resolution ultrasonography. When tumors reached ∼200 mm3, mice were treated with: (1) vehicle control; (2) PEGPH20 alone, 1 mg/kg; (3) CET alone, 0.03 mg; (4) CET alone, 0.1 mg; (5) PEGPH20 plus CET, 0.03 mg; or (6) PEGPH20 plus CET, 0.1 mg. Vehicle control or PEGPH20 was given intravenously while CET was administered intraperitoneally starting on study day 0, and then dosed twice weekly for 3 weeks (BIWx3). At study termination, the average tumor growth inhibition (TGI) of CET (0.03 mg) was not significantly different from vehicle-treated animals; however, PEGPH20 alone (78%, p<0.05) and CET alone at 0.1 mg (61%, p<0.05) inhibited tumor growth. The addition of PEGPH20 to the 0.03 mg and 0.1 mg CET groups increased TGI to 88% (p<0.05) for both treatments, relative to vehicle. In a second study, when tumors reached ∼200 mm3, mice were treated with: (1) vehicle control; (2) PEGPH20 alone, 37.5 µg/kg (3 µg/kg human equivalent dose); (3) CET alone, 0.03 mg; or (4) PEGPH20 plus CET. Animals were dosed as described above. At study termination, the average TGI of CET alone was not significantly different from vehicle-treated animals; however, PEGPH20 alone significantly inhibited tumor growth (47%, p<0.05). The combination of PEGPH20 and CET increased TGI to 70% (p<0.05) relative to vehicle. In conclusion, PEGPH20 treatment of HA-overexpressing tumors potentiates the subsequent anti-tumor activity of mAbs, such as CET.

Citation Format: Ryan J. Osgood, James F. Skipper, Susan Zimmerman, Rebecca C. Symons, Harold M. Shepard, Daniel C. Maneval, Curtis B. Thompson, David W. Kang. Pegylated recombinant human hyaluronidase PH20 (PEGPH20) enhances cetuximab efficacy in BxPC-3/HAS3 human pancreatic cancer xenografts. [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 3646. doi:10.1158/1538-7445.AM2014-3646

Abstract 511: The role of hyaluronan-CD44 interaction in breast cancer

The tumor microenvironment is crucial for cancer cell survival and spreading. The glycosaminoglycan hyaluronan (HA) is accumulated in 50% of malignant breast cancer tumors and its accumulation correlates with poor survival of breast cancer patients. HA is synthesized at the cell surface by HA synthase enzymes (HAS1-3) and is extruded to the extracellular space where HA molecules can be attached to the cell surface via interactions with its receptors or HAS proteins. HA can also interact with its binding proteins and be incorporated into surrounding ECM. However, the origin and exact functions of HA in breast cancer are still unclear. The aim of this study was to explore the role of HA in the tumor microenvironment of breast cancer, especially in the interaction of tumor and stromal cells in vitro and in vivo. First, interaction of breast cancer cells and stromal cells were studied in mono- and co-cultures. Human bone marrow-derived mesenchymal stem cells (MSCs) and breast cancer-associated fibroblasts (CAFs) synthesized high amounts of HA, while this was the case for <5% MDA-MB-468 breast cancer cells. In co-culture with MSCs or CAFSs, MDA-MB-468 and MDA-MB-231 cells formed distinct pericellular HA coats. Similar HA coats were observed after addition of exogenous FITC-labeled high molecular weight HA (1,2 MDa) to MDA-MB-468 and MDA-MB-231 cell cultures. Interestingly, binding of FITC-labeled HA was not efficiently blocked by unlabeled HA below 500 kDa. In co-cultures, the high molecular weight HA coats around MDA-MB-468 and MDA-MB-231 cells were prevented by antibody blockade of the HA receptor CD44, indicating that formation of HA coats is CD44-mediated. Knockdown of CD44 by shRNA also inhibited the formation of HA coats when FITC-HA was added to the cultures or when breast cancer cells were co-cultured with MSCs. MSCs also increased proliferation and migration of MDA-MB-468 (parental/Luc) cells, analyzed by luciferin and Transwell migration assays, respectively. MDA-MB-468 cell proliferation was slightly inhibited by removal of HA with pegylated human recombinant hyaluronidase PH20 (PEGPH20), and migration towards exogenous HA could be inhibited by CD44 knockdown. Importance of HA coats around breast cancer cells was also studied in vivo using MDA-MB-468 cells over-expressing HAS3 which forms 4.7-fold larger HA coats than parental MDA-MB-468 cells. MDA-MB-468 HAS3 cells exhibited much enhanced in vivo growth compared to MDA-MB-468 cells, and tumor growth of MDA-MB-468 HAS3 xenografts was inhibited up to 85% by PEGPH20. The results suggest that HA in tumor microenvironment, produced by tumor or stromal cells, provides growth benefit for breast cancer cells via promoting their proliferation and migration. Both phenomena seem to be mediated by CD44, which highlights the importance of HA-CD44 interaction in the growth of breast cancer.

Citation Format: Anne Kultti, Susan Zimmerman, Lei Huang, Yanling Chen, Jessica Cowell, Rebecca C. Symons, Laurence Jadin, Ping Jiang, Gregory I. Frost, Michael Shepard, John Huang. The role of hyaluronan-CD44 interaction in breast cancer. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 511. doi:10.1158/1538-7445.AM2013-511

Abstract 4999: Hyaluronan-rich ECM contributes to resistance to antibody-dependent cell-mediated cytotoxicity in solid tumors

Accumulation of Hyaluronan (HA), an important glycosaminoglycan of the extracellular matrix (ECM), has been detected in about 25% of human tumors, and 56% of breast cancers1-2. HA is produced by malignant and stromal cells and acts to cross-link ECM proteins, contributing to the desmoplastic phenotype. Aberrant accumulation of HA in tumors has been associated with more aggressive malignancy1-2. We have observed that >50% of human epidermal growth factor receptor 2 (HER2) triple-positive breast tumors have a high accumulation of HA (HA3+). Monoclonal antibodies (MAbs) have been developed successfully as part of the anticancer armamentarium. However, even in cases where the target of the antibody is stably and abundantly expressed, efficacy often falls below expectations. In this work, we present a novel HA-dependent ECM-mediated mechanism of resistance to antibody-dependent cell-mediated cytotoxicity (ADCC) and this resistance can be reduced by PEGPH20 (a pegylated human PH20) treatment. Human hyaluronan synthase 2 (HAS2)-overexpressing tumor cells formed an HA-rich pericellular matrix which can restrict human NK cells from accessing tumor cells. This HA-dependent ECM-mediated physical barrier in HAS2- overexpressing tumor cells contributed to resistance to trastuzumab/cetuximab-dependent ADCC. Removal of HA from ECM by PEGPH20 treatment sensitized HAS2-overexpressing tumor cells to trastuzumab/cetuximab-mediated ADCC in vitro. HAS2-overexpressing ovarian cancer cell SKOV3 showed more aggressive growth pattern (median survival on 42 days) compared to parental SKOV3 (median survival of 61 days) in an intra-peritoneal xenograft model. In the same model with HAS2-overexpressing SKOV3, PEGPH20 in combination with trastuzumab and NK cell treatment (to simulate ADCC in vivo) resulted in 70% tumor growth inhibition (TGI) in comparison to 40% TGI with trastuzumab and NK cell treatment, indicating that PEGPH20 enhanced in vivo ADCC by trastuzumab and NK cell. Our results demonstrated a mechanism of high HA-content pericellular matrix-mediated resistance to MAb-mediated ADCC. These results may help explain why tumors with high levels of HA (HA3+ phenotype) are more aggressive, and suggest that removal of HA by PEGPH20 treatment may be an effective combinatorial therapy together with anti-cancer MAbs.

1. Kultti A, Li X, Jiang P, Thompson C.B., Frost G.I., Shepard H.M. 2012. Therapeutic targeting of Hyaluronan in the tumor stroma. Cancers, 4:873-903; doi:10.3390/cancers4030873.

2. Sironen, R.K., Tammi, M., Tammi, R., Auvinen, P.K., Anttila, M., and Kosma, V.M. 2011. Hyaluronan in human malignancies. Exp. Cell. Res. 317:383-391. doi: 10.1016/j.yexcr.2010.11.017

Citation Format: Netai C. Singha, Tara Nekoroski, Susan Zimmerman, Chunmei Zhao, Ping Jiang, Robert Connor, Gregory I. Frost, Zhondong Huang, Michael H. Shepard. Hyaluronan-rich ECM contributes to resistance to antibody-dependent cell-mediated cytotoxicity in solid tumors. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 4999. doi:10.1158/1538-7445.AM2013-4999

De novo lumen formation and elongation in the developing nephron: a central role for afadin in apical polarity

A fundamental process in biology is the de novo formation and morphogenesis of polarized tubules. Although these processes are essential for the formation of multiple metazoan organ systems, little is known about the molecular mechanisms that regulate them. In this study, we have characterized several steps in tubule formation and morphogenesis using the mouse kidney as a model system. We report that kidney mesenchymal cells contain discrete Par3-expressing membrane microdomains that become restricted to an apical domain, coinciding with lumen formation. Once lumen formation has been initiated, elongation occurs by simultaneous extension and additional de novo lumen generation. We demonstrate that lumen formation and elongation require afadin, a nectin adaptor protein implicated in adherens junction formation. Mice that lack afadin in nephron precursors show evidence of Par3-expressing membrane microdomains, but fail to develop normal apical-basal polarity and generate a continuous lumen. Absence of afadin led to delayed and diminished integration of nectin complexes and failure to recruit R-cadherin. Furthermore, we demonstrate that afadin is required for Par complex formation. Together, these results suggest that afadin acts upstream of the Par complex to regulate the integration and/or coalescence of membrane microdomains, thereby establishing apical-basal polarity and lumen formation/elongation during kidney tubulogenesis.

Further Evidence of Contrasting Phenotypes Caused by Reciprocal Deletions and Duplications: Duplication of NSD1 Causes Growth Retardation and Microcephaly

Microduplications of the Sotos syndrome region containing NSD1 on 5q35 have recently been proposed to cause a syndrome of microcephaly, short stature and developmental delay. To further characterize this emerging syndrome, we report the clinical details of 12 individuals from 8 families found to have interstitial duplications involving NSD1, ranging in size from 370 kb to 3.7 Mb. All individuals are microcephalic, and height and childhood weight range from below average to severely restricted. Mild-to-moderate learning disabilities and/or developmental delay are present in all individuals, including carrier family members of probands; dysmorphic features and digital anomalies are present in a majority. Craniosynostosis is present in the individual with the largest duplication, though the duplication does not include MSX2, mutations of which can cause craniosynostosis, on 5q35.2. A comparison of the smallest duplication in our cohort that includes the entire NSD1 gene to the individual with the largest duplication that only partially overlaps NSD1 suggests that whole-gene duplication of NSD1 in and of itself may be sufficient to cause the abnormal growth parameters seen in these patients. NSD1 duplications may therefore be added to a growing list of copy number variations for which deletion and duplication of specific genes have contrasting effects on body development.