Unique macrophage phenotypes activated by BMP signaling in breast cancer bone metastases

Metastatic breast cancer (mBC) tissue in bone was systematically profiled to define the composition of the tumor microenvironment. Gene expression identified a high myeloid signature of patients with improved survival outcomes. Bone metastases were profiled by spatial proteomics to examine myeloid populations within the stroma that correlated with macrophage functions. Single-cell spatial analysis uncovered macrophage activation in the stroma of mBC bone lesions. Matched BC patient samples of primary breast tumor and bone metastasis tissues were compared for gene expression in the bone, where bone morphogenetic protein 2 (BMP2) was most significantly upregulated. Immune cell changes from breast to bone demonstrated a loss of lymphoid cells but a consistent population of macrophages. BMP-activated macrophages were increased uniquely in bone. Bone marrow-derived macrophage activation coupled with BMP inhibition increased inflammatory responses. Using experimental mouse models of mBC bone metastasis and trained immunity, we found that BMP inhibition restricts progression of metastases early in the macrophage activation state but not after tumors were established in the bone. This study revealed unique myeloid BMP activation states that are distinctly integrated with bone metastases.

Polymorphonuclear myeloid-derived suppressor cells and phosphatidylinositol-3 kinase gamma are critical to tobacco-mimicking oral carcinogenesis in mice

BACKGROUND

Oral squamous cell carcinoma (OSCC) is a devastating disease most often associated with tobacco consumption that induces a field of mutations from which a tumor arises. Identification of ways to prevent the emergence of cancer in high-risk patients is an ultimate goal for combatting all types of cancer, including OSCC.

METHODS

Our study employs a mouse model of tongue carcinogenesis induced by tobacco carcinogen mimetic, 4-nitroquinoline 1-oxide (4NQO), to establish tongue dysplasia and OSCC. We use conventional histology, immunohistochemistry, multispectral imaging, mass cytometry, novel cell lines, pharmaceutical inhibition of PI3Kγ, T-cell suppression assays and mouse transplant models in our functional experimentation.

RESULTS

In our study, we identify Ly6G+ granulocytes as the most abundant immune cell type in a model of tongue carcinogenesis induced by tobacco carcinogen mimetic 4NQO. Targeting Ly6G+ granulocytes with a pharmacologic inhibitor of PI3Kγ, an isoform of PI3K exclusively expressed by myeloid cells, resulted in reduced tongue dysplasia severity, and reduced rates of OSCC. Importantly, we performed functional assays with the Ly6G+ granulocytes induced in cell line models of 4NQO carcinogenesis to demonstrate that these granulocytes have increased polymorphonuclear myeloid-derived suppressor cells (PMN-MDSC) activity against T-cell proliferation and these PMN-MDSCs play a functional role in promoting tumor formation by inhibiting tumor regression in a PI3Kγ-dependent manner.

CONCLUSIONS

Overall, our data suggest that recruitment of PMN-MDSCs to sites of dysplasia is critical to immune suppression of CD8 T cells, thereby permitting malignancy, and PI3Kγ inhibitors are one mechanism to reduce PMN-MDSC recruitment, immunosuppression and tumorigenesis in OSCC.

Bone morphogenetic protein pathway responses and alterations of osteogenesis in metastatic prostate cancers

BACKGROUND

Prostate cancer is a common cancer in men that annually results in more than 33 000 US deaths. Mortality from prostate cancer is largely from metastatic disease, reflecting on the great strides in the last century of treatments in care for the localized disease. Metastatic castrate resistant prostate cancer (mCRPC) will commonly travel to the bone, creating unique bone pathology that requires nuanced treatments in those sites with surgical, radio and chemotherapeutic interventions. The bone morphogenetic protein (BMP) pathway has been historically studied in the capacity to regulate the osteogenic nature of new bone. New mineralized bone generation is a frequent and common observation in mCRPC and referred to as blastic bone lesions. Less common are bone destructive lesions that are termed lytic.

METHODS

We queried the cancer genome atlas (TCGA) prostate cancer databases for the expression of the BMP pathway and found that distinct gene expression of the ligands, soluble antagonists, receptors, and intracellular mediators were altered in localized versus metastatic disease. Human prostate cancer cell lines have an innate ability to promote blastic- or lytic-like bone lesions and we hypothesized that inhibiting BMP signaling in these cell lines would result in a distinct change in osteogenesis gene expression with BMP inhibition.

RESULTS

We found unique and common changes by comparing these cell lines response and unique BMP pathway alterations. We treated human PCa cell lines with distinct bone pathologic phenotypes with the BMP inhibitor DMH1 and found distinct osteogenesis responses. We analyzed distinct sites of metastatic PCa in the TCGA and found that BMP signaling was selectively altered in commons sites such as lymph node, bone and liver compared to primary tumors.

CONCLUSIONS

Overall we conclude that BMPs in metastatic prostate cancer are important signals and functional mediators of diverse processes that have potential for individualized precision oncology in mCRPC.

Abstract 2512: The metastatic breast cancer microenvironment in bone exhibits unique BMP signaling

In 2021, an estimated 281,550 women will be diagnosed with breast cancer (BC) in the U.S., and 43,600 BC patients will succumb to the disease. BC patient prognosis has improved for localized BC, yet metastatic BC continues to cause high mortality with a 5 year survival rate of only 27%. Approximately 70% of BC metastases occur in the bone, with a tumor microenvironment (TME) composed primarily of BC cells, immune cells, and bone cells. In these cellular compartments, bone morphogenetic protein (BMP) signaling exhibits unique TME dependent tumor promoter and suppressor effects. Previous studies in our lab have found BMPs promote myeloid progenitors, polarization of M2 macrophages, and tumor progression in a BMPR1a LysMCre conditional knockout mouse model. Yet to establish BMPs as a viable target for the treatment of metastatic bone, the mechanisms behind BMPs promoting BC bone metastases must be investigated. To further investigate BMP dependent myeloid heterogeneity in cancer, we have utilized a cohort of non-treatment naïve BC patient bone biopsies to unveil the distinct myeloid populations in the TME of BC bone metastases. Differential gene expression analysis revealed a subset of patient samples with a high myeloid gene signature, corresponding with increased chemokine, cytokine and JAK/STAT signaling gene pathways in addition to enhanced BMP signaling. Digital Spatial Profiling via the NanoString GeoMx platform and multiplexed immunohistochemistry staining via the AKOYA Vectra Polaris platform were used to analyze the spatial context of the TME in our cohort of patient bone. We found enhanced myeloid cell infiltration, myeloid heterogeneity and M2 macrophage polarization in the TME of high myeloid gene signature patient samples. This precision oncology analysis into the unique landscape of the metastatic bone TME revealed BMP driven phenotypes in distinct TME cellular components. To then determine if the TME features observed in the metastatic bone samples was reflective of altered innate trained immunity regulated by BMPs, we investigated the requirement for BMP signaling in myeloid inflammatory responses both in vitro and in a mouse model of BC bone metastasis. We found BMPs alter the ability for macrophages to undergo innate trained immunity functions and BC bone metastases alter myeloid inflammatory responses in mice. Investigating the heterogeneity and functions of myeloid cells in the TME of bone metastatic BC will help advance therapeutic target development for BC patients with bone lesions. Expanding therapeutic options for metastatic BC patients will improve patient quality of life and reduce deaths caused by metastasis.

Citation Format: Claire Louise Ihle, Desiree Straign, Philip Owens. The metastatic breast cancer microenvironment in bone exhibits unique BMP signaling [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 2512.

Neoadjuvant endocrine therapy expands stromal populations that predict poor prognosis in estrogen receptor-positive breast cancer

The tumor microenvironment (TME) is an important modulator of response and resistance to endocrine therapy in estrogen receptor alpha (ER) positive breast cancer. Endocrine therapy is highly effective at reducing tumor burden and preventing recurrence in most estrogen receptor alpha (ER) positive breast cancers. Existing drugs work either directly by targeting tumor-cell ER or indirectly by inhibiting estrogen production in stromal cells with aromatase inhibitors (AI). However, many stromal cells also express ER and the direct impact of endocrine therapies on ER + stromal cells remain unclear. In this study, we investigated how neoadjuvant endocrine therapy (NET) directly effects stromal cells by measuring changes in stomal components of the TME that favor tumor progression. We previously defined two major subsets of tumor-associated stromal cells (TASCs): CD146 positive/CDCP1 negative (TASC^CD146 ), CD146 negative/CDCP1 positive (TASC^CDCP1 ), and generated a differentially expressed genes list associated with each type. Here, we applied the TASC gene list for classification and an algorithm that estimates immune cell abundance (TIMEx) to METABRIC transcriptomic data for ER + breast cancer patients coupled with multiplex imaging and analysis of paired tissue samples pre- and post- NET with the AI exemestane. TASC^CDCP1 composition predicted for decreased patient survival in the METABRIC cohort. Exemestane treatment significantly increased expression of TASC^CDCP1 and decreased expression of TASC^CD146 . The posttreatment shift toward TASC^CDCP1 composition correlated with increased macrophage infiltration and increased CD8+ T-cell, B cell, and general stromal components. The effectiveness of NET is currently based solely on the reduction of ER+ breast cancer cells. Here, we show NET displays clear TME effects that promote the expansion of the less favorable TASC^CDCP1 population which are correlated with TME remodeling and reshaping immune infiltration supportive of tumor progression. Our findings highlight the need to further understand the role of endocrine therapy on TME remodeling, tumor progression, and patient outcomes.

Mechanobiology of Bone Metastatic Cancer

PURPOSE OF REVIEW

In this review, we provide an overview of what is currently known about the impacts of mechanical stimuli on metastatic tumor-induced bone disease (TIBD). Further, we focus on the role of the osteocyte, the skeleton's primary mechanosensory cell, which is central to the skeleton's mechanoresponse, sensing and integrating local mechanical stimuli, and then controlling the downstream remodeling balance as appropriate.

RECENT FINDINGS

Exercise and controlled mechanical loading have anabolic effects on bone tissue in models of bone metastasis. They also have anti-tumorigenic properties, in part due to offsetting the vicious cycle of osteolytic bone loss as well as regulating inflammatory signals. The impacts of metastatic cancer on the mechanosensory function of osteocytes remains unclear. Increased mechanical stimuli are a potential method for mitigating TIBD.

Does patient age and BMI affect temporal changes in depth-force relationship during CPR?

Introduction

A strong non-linear relationship exists between chest compression (CC) force and depth during cardiopulmonary resuscitation (CPR) in out-of-hospital cardiac arrest events. A decrease in the depth-force (DF) relationship over time and cumulative number of CC has been described for both human and animal subjects. The effect of patient demographics such as age and body mass index (BMI) in the DF relationship during CPR is not as widely explored.

Purpose

The aim of the present study was to analyse the temporal effect of patient demographics (i.e. age and BMI) in the DF relationship during the performance of CPR.

Methods

Data were collected from a first responder group based in Texas, USA. Responders were instructed to use a CPR depth feedback device (Laerdal CPRmeter) and an automated external defibrillator (AED; HeartSine SAM 350P) when attending sudden cardiac arrest events. The AED was configured with a shock protocol separated by 2-minute episodes of CPR and rescuer CC depth and rate were guided by the CPR depth feedback device. Patient demographic data was captured at the cardiac arrest scene.

CC depth and force data were extracted from Laerdal CPRmeter and processed for 171 patient events. The depth-force ratio (DFR) was calculated as mean depth local maxima divided by mean force local maxima (mm/kgf). Data processing and statistical analyses were performed with R version 3.7.3.

Patient age was available for 169 events (median (IQR) = 63 (53–76) years). Age was categorised in two groups: 18–64 (n=87) and 65+ years (n=82). Patient BMI was estimated for 149 patients (median (IQR) = 25.84 (22.58–31.05) kg/m2). BMI was categorised as: Underweight (gUW, BMI <18.5, n=13), Normal (gN, 18.5 ≤ BMI <25, n=54), Overweight (gOW, 25 ≤ BMI <30, n=37) and Obese (gOB, BMI ≥30, n=45).

Results

No statistically significant differences in mean event duration were found in the age groups (t-test, p=0.368) or the BMI groups (ANOVA, p=0.309).

A multiple linear regression model was applied to the data to assess the effect of time and age or BMI on the DFR. At the beginning of the events, no statistically significant differences were found in DFR between age groups (p=0.092). Time had no effect on the change in DFR for 18–64 age group (p=0.110) but the rate of change between the 18–64 and 65+ age groups was significantly different (p<0.010).

For BMI and using gN as reference, there were significant differences in DFR between all BMI groups except gUW at the beginning of the events. Time had a significant effect in DFR during events for gUW, gN and gOB (p<0.050), but no common trend in temporal change was identified.

Conclusions

Temporal changes in DFR appear to be significantly affected by patient age. Tailoring CC force or depth to patient demographics during CPR events may be required for some patients.

Funding Acknowledgement

Type of funding sources: Private company. Main funding source(s): HeartSine Technologies Ltd, Belfast, UK

Protection of bone mineral density in heart failure patients:audit on current clinical practice in a busy tertiary care hospital cardiology department in Ireland

Background

The strong association between heart failure (HF) and osteoporosis is well recognised. Heart failure, due to its multiple risk factors and common pathogenesis with osteoporosis can lead to low bone mineral density (BMD) and increase the risk of fragility fractures. The mortality of HF patients following these fractures is high. Current National Osteoporosis Foundation Guidelines recommend that pharmacological therapy should be reserved for postmenopausal women and men aged 50 years or older who present with a hip or vertebral fracture, where the vertebral fractures may be clinical or identified on a radiograph alone.

Methods

Most HF patients have frequent chest radiographs over their course years. We aimed to audit the prevalence of osteoporosis and current practice of prescribing BMD-protection in patients attending the HF clinic in a busy tertiary care hospital in Ireland. 100 patients attending the clinic in the last one year were randomly selected and clinical, medication and chest radiograph information on this cohort was collected via the hospital electronic information system. All those patients with Radiologist confirmed vertebral compression fractures (VCF) on their plain chest radiographs were audited regarding osteoporosis screening and bone protection prescription.

Results

Due to limited penetration,18 out of 100 chest radiographs were inconclusive,reducing the sample size to 82. 9 out of the remaining 82 patients had radiologist confirmed VCF on their plain chest radiographs whereas 2 patients had VCF incidentally picked up on their lumbar spine x-rays. All patients were aged more than 50. 4 were female and 7 male. Median ejection fraction calculated was 35%. 3 out of 11 were smokers,8 had atrial fibrillation and were on anticoagulation,4 had DM-II and 2 had CKD. 10 were on loop diuretics. Of note,4 patients were on calcium and vitamin D supplements but only 1 patient was on antiresorptive therapy for osteoporosis.

Conclusion

Despite its strong association with heart failure,Osteoporosis remains undertreated in this patient cohort.Due to the significant mortality and morbidity associated with major osteoporotic fractures, doctors should carefully assess and screen heart failure patients for osteoporosis and initiate specific therapy where indicated.

Funding Acknowledgement

Type of funding sources: None.

Abstract 114: Loss of BMPR1a in fibroblasts restricts breast cancer progression and alters the immune tumor microenvironment

The Bone Morphogenetic Protein (BMP) pathway is a member of the TGFβ signaling family and has complex roles in cancer. The dichotomous role of BMPs as both tumor promoters and suppressors appears to be largely context based in both the cancer cell and the surrounding microenvironment. Fibroblasts who are activated in the tumor microenvironment to become cancer associated fibroblasts (CAFs) also carry out diverse functions to support tumor progression, including matrix generation and remodeling as well as angiogenesis and immune cell regulation. We found that conditional deletion of the BMP signaling receptor BMPR1a in mammary fat pad derived fibroblasts (via FSP-Cre) restricts tumor progression in a C57BL/6 syngeneic mammary fat pad MMTV-PyMT breast cancer mouse model. Specific changes in the architecture of collagen were found in the tumors with loss of BMPR1a signaling in CAFs. We analyzed these mammary fat pad tumors using Vectra multiplexed immunohistochemistry (mIHC) to evaluate differential cell phenotypes, spatial distribution, and high-dimensional cell clustering dependent on BMP signaling in CAFs. Vectra mIHC panels were designed to perform tumor and stromal cell classification, immune cell profiling, immune cell function, cell signaling and vascular analysis. Based on Vectra mIHC, changes in myeloid cell populations and immune cell interactions in the tumors were observed with differential BMPR1a expression in CAFs. We profiled the secretome of mammary fat pad fibroblasts and found distinct chemokine and cytokine secretion was altered related on BMPR1a loss. These results indicate a unique necessity for BMP signaling in fibroblasts during tumor progression to influence the stroma, matrix, and immune components of the tumor microenvironment.

Citation Format: Claire Louise Ihle, Meredith D. Provera, Parvanee A. Karimpour, Desiree M. Straign, Erin Smith, Philip Owens. Loss of BMPR1a in fibroblasts restricts breast cancer progression and alters the immune tumor microenvironment [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr 114.

Adenosine/TGFβ axis in regulation of mammary fibroblast functions

Cancer associated fibroblasts (CAF) play a key role in cancer progression and metastasis. Diminished TGFβ response on CAF correlates with poor outcome and recurrence in cancer patients. Mechanisms behind lost TGFβ signaling on CAF are poorly understood, but, utilizing MMTV-PyMT mouse model, we have previously demonstrated that in tumor microenvironment myeloid cells, producing adenosine, contribute to downregulated TGFβ signaling on CAFs. In the current work, we performed serial in vitro studies to investigate the role of adenosine/TGFβ axis in mouse mammary fibroblast functions, i.e., proliferation, protein expression, migration, and contractility. We found that adenosine analog NECA diminished TGFβ-induced CCL5 and MMP9 expression. Additionally, we discovered that NECA completely inhibited effect of TGFβ to upregulate αSMA, key protein of cytoskeletal rearrangements, necessary for migration and contractility of fibroblasts. Our results show that TGFβ increases contractility of mouse mammary fibroblasts and human fibroblast cell lines, and NECA attenuates theses effects. Using pharmacological approach and genetically modified animals, we determined that NECA effects on TGFβ pathway occur via A_2A/A_2B adenosine receptor—AC—PKA dependent manner. Using isolated CD11b⁺ cells from tumor tissue of CD73-KO and CD39-KO animals in co-culture experiments with ATP and AMP, we confirmed that myeloid cells can affect functions of mammary fibroblasts through adenosine signaling. Our data suggest a novel mechanism of interaction between adenosine and TGFβ signaling pathways that can impact phenotype of fibroblasts in a tumor microenvironment.

Correlation of STOP-bang obstructive sleep apnoea screening tool to apnoea-hypopnea index in a general cardiology population

Funding Acknowledgements

Type of funding sources: None.

Introduction

The link between obstructive sleep apnoea (OSA) and cardiovascular disease is well known. Prevalence can be very high in this population, sharing many pathophysiological drivers in addition to being a risk factor. More concerning however is the increasing number of patients with undiagnosed OSA, who are at higher risk of long-term complications such as coronary artery disease, hypertension, atrial fibrillation, heart failure or stroke. There are several OSA screening tools available to clinicians, with variable sensitivities and specificities depending on patient demographics.

Predictive efficacy of the STOP-Bang screening tool in a general cardiology population with mixed cardiovascular disease has not been established.

Proposal

To identify the correlation between the STOP-Bang assessment score (1-8) and real-world Apnoea-Hypopnoea Index (AHI) in a general cardiology clinic population.

Methods

250 successive patients in a general cardiology clinic were asked to complete a STOP-Bang assessment. Of those, 50 patients with a variety of STOP-Bang scores were randomly selected to undergo sleep studies. A STOP-Bang value of ≥ 5 was taken as high-risk for moderate-severe OSA. Statistical linear regression analysis was performed in IBM SPSS version 26.

Results

Of n = 50 patients, mean STOP-Bang score =3.7 (SD +/-2.17) with mean AHI =15.8, (SD +/- 14.3). See Table 1 for categories 1-8. N = 44 (88%) had AHI ≥ 5 (At least mild OSA). N = 18 (36%) had an AHI ≥ 15 (Moderate-severe OSA). N = 29 (58%) had symptoms such as sleepiness, loud snoring or witnessed apnoea. Correlation between STOP-Bang score and AHI was high, with an  R value of 0.704, R2 = 0.496 (p < 0.01). A STOP-Bang score increase of 1 corresponded with a mean AHI rise of 4.648. When taking a STOP-Bang value of ≥ 5 as "positive", we demonstrated a sensitivity of 83.33% (95% C.I. 58.58-96.42) and specificity of 93.94% (95% C.I. 79.77-99.26%) for moderate-severe OSA (AHI ≥ 15). 

Conclusion

We discovered a very high number of patients with undiagnosed OSA of at least mild severity. We found a strong correlation between STOP-Bang score and real-world AHI in a general cardiology population with mixed cardiovascular disease with 5 as an acceptable screening score for moderate-severe OSA.

Table 1 STOP-Bang Value 1 2 3 4 5 6 7 8 Patients (N=) 12 5 7 9 5 5 5 2 AHI (Mean) 6.67 6.62 9.97 11.95 24.44 22.20 39.54 35.25 Standard Deviation (±) 3.29 2.74 3.45 4.63 12.87 5.69 27.2 6.72 Summary of mean apnoea-hypopnoea index and standard deviation for each STOP-Bang patient category.

Abstract Figure 1

miR-31 Displays Subtype Specificity in Lung Cancer

miRNA rarely possess pan-oncogenic or tumor-suppressive properties. Most miRNAs function under tissue-specific contexts, acting as either tumor suppressors in one tissue, promoting oncogenesis in another, or having no apparent role in the regulation of processes associated with the hallmarks of cancer. What has been less clear is the role of miRNAs within cell types of the same tissue and the ability within each cell type to contribute to oncogenesis. In this study, we characterize the role of one such tissue-specific miRNA, miR-31, recently identified as the most oncogenic miRNA in lung adenocarcinoma, across the histologic spectrum of human lung cancer. Compared with normal lung tissue, miR-31 was overexpressed in patient lung adenocarcinoma, squamous cell carcinoma, and large-cell neuroendocrine carcinoma, but not small-cell carcinoma or carcinoids. miR-31 promoted tumor growth in mice of xenografted human adenocarcinoma and squamous cell carcinoma cell lines, but not in large- or small-cell carcinoma lines. While miR-31 did not promote primary tumor growth of large- and small-cell carcinoma, it did promote spontaneous metastasis. Mechanistically, miR-31 altered distinct cellular signaling programs within each histologic subtype, resulting in distinct phenotypic differences. This is the first report distinguishing diverse functional roles for this miRNA across the spectrum of lung cancers and suggests that miR-31 has broad clinical value in human lung malignancy. SIGNIFICANCE: These findings demonstrate the oncogenic properties of miR-31 in specific subtypes of lung cancer and highlight it as a potential therapeutic target in these subtypes. GRAPHICAL ABSTRACT: http://cancerres.aacrjournals.org/content/canres/81/8/1942/F1.large.jpg.

Targeting the BMP Pathway in Prostate Cancer Induced Bone Disease

From the 33,000 men in the U.S. who die from prostate cancer each year, the majority of these patients exhibit metastatic disease with bone being the most common site of metastasis. Prostate cancer bone metastases are commonly blastic, exhibiting new growth of unhealthy sclerotic bone, which can cause painful skeletal related events. Patient's current care entails androgen deprivation therapy, anti-resorptive agents, radiation, and chemotherapy to help control the spread of the cancer but little intervention is available to treat blastic bone disease. The transforming growth factor beta (TGFβ) and bone morphogenetic protein (BMP) pathways are known to regulate bone growth and resorption of destructive lytic bone lesions, yet the role of TGFβ/BMP signaling in prostate cancer blastic vs lytic bone lesions are not fully understood. We hypothesized that to target the BMP/TGFβ pathway, a useful biomarker of bone lytic or blastic pathology would have superior response. We show distinct BMP vs. TGFβ signaling in clinical samples of human prostate cancer bone metastases with either lytic or blastic pathologies. BMPs exhibit distinct effects on bone homeostasis, so to examine the effect of BMP inhibition on healthy bone, we treated mice with the BMP receptor small molecule antagonist DMH1 and saw a modest temporary improvement in bone health, with increased trabecular bone. We next sought to use the BMP inhibitor DMH1 to treat bone metastasis engraftment seeded by a caudal artery injection of the lytic human prostate cell line PC3 in immunodeficient mice. The colonization by PC3 cells to the bone were restricted with DMH1 treatment and bone health was importantly preserved. We next proceeded to test BMP inhibition in an injury model of established bone metastasis via intratibial injection of the MYC-CaP mouse prostate cell line into FVBN syngeneic mice. DMH1 treated mice had a modest decrease in trabecular bone and reduced lymphocytes in circulation without affecting tumor growth. Taken together we show unique responses to BMP inhibition in metastatic prostate cancer in the bone. These studies suggest that profiling bone lesions in metastatic prostate cancer can help identify therapeutic targets that not only treat the metastatic tumor but also address the need to better treat the distinct tumor induced bone disease.

Integrating intravenous frusemide treatment into the community for heart failure patients

Background

A structured pathway was developed to allow patients to safely receive intravenous (i/v) frusemide at home.

This pathway was implemented by an integrated team consisting of primary and tertiary care.

This allowed the traditional acute hospital treatment to be now delivered in the community.

Purpose

This concept has been used on an individual case basis by a minority of acute hospitals.

Previously there was no structured pathway that would allow this treatment to become a standard part of heart failure treatment by acute hospitals.

The pathway would ensure that the treatment would be delivered safely to a cohort of patients who meet certain criteria.

Methods

A pathway was developed by a consultant cardiologist, heart failure (HF) nurses and the Community Intervention Team (CIT)/CareDoc. The Caredoc Community Intervention Team (CIT) is a nurse led professional team that provides acute nursing care to patients in the community setting.

The HF nurse would identify the suitable patient for i/v frusemide as per pathway.

A referral would be sent to the CIT team who would administer the frusemide at the patients home.

The CIT team would take a renal profile daily, check vital signs, check symptoms of HF and check daily weight on the patient while they were receiving i/v frusemide.

The bloods results would be reviewed daily by the HF nurse.

The HF nurse would liaise daily with the CIT team and patient for symptoms, daily weights and vital signs. The patient would then be reviewed in the HF clinic post treatment.

Results

Single centre retrospective analysis was undertaken of the patients who received i/v frusemide at home over a 3 year period.

83 patients meet the inclusion criteria and received the treatment. 70 male and 13 female.

Average age 78 years old.

Average length of treatment 3 days.

Treatment was given twice daily, average daily dose was 137 mg. Majority of treatment was 80mg bd or 60 mg bd.

No failure cannulating any patient as CIT had high cannulation skills due to regular cannulation as part of workload.

3 episodes of hypokalaemia, lowest potassium was 3.1 mmols, all 3 episodes were effectively treated with oral potassium supplements.

No significant acute kidney injury was noted that required change to treatment.

6 patients required heart failure associated admission to hospital, 3 had hypotension, 1 has fast A-flutter and 2 remained resistance to i/v frusemide and required inotropes.

Both patient and carers reported a high satisfaction rate with the service.

Conclusion

National length of stay for a HF patient in Ireland is 11 days.This novel structured pathway successfully selected appropriate patients who can safely receive i/v frusemide at home. 93% avoided hospital admission.This reduces the need for acute hospital admission and significant associated costs. Patients and carers rated 95% satisfaction with service.Sustainability of the project is driven by an integration team approach.

Funding Acknowledgement

Type of funding source: None

Abstract 1580: Distinct pathways of lytic and blastic bone metastases in prostate cancer patients

The most common metastatic lesions of prostate cancer are in the bone and can be classified into three distinct pathologic subtypes: lytic, blastic, and an indeterminate mixture of both. There is no immunotherapy guidance for treating patients based on lytic or blastic tumor induced bone disease. To identify distinct tumor and stroma in lytic and blastic prostate cancer bone metastases, we investigated a cohort of decalcified formalin-fixed and paraffin-embedded (FFPE) patient bone biopsy specimens that contained metastatic prostate cancer with lytic or blastic features. Tissue sections were utilized for immunohistochemistry (IHC) staining, isolation of RNA for gene expression, and Digital Spatial Profiling (DSP) of changes in both the tumor and microenvironment. A diverse set of unique immune cell populations and signaling pathways to both lytic and blastic types of prostate cancer metastases were present. High proportions of macrophages were present in lytic tumor induced bone disease, and T cells were present in lytic and blastic samples. In blastic lesions, immune cells were enriched for pSTAT3 and components of the JAK-STAT pathway. In lytic lesions, immune cells exhibited enhanced pAKT activity and components of the PI3K-AKT pathway. Expression of key immune checkpoint targets were identified in blastic prostate cancer, providing new therapeutic targets for patients with bone metastases. To further investigate which individual cells comprising the stroma and tumor have active JAK-STAT signaling, we performed fluorescent multiplex-IHC (mIHC). A tumor and myeloid panel of antibodies was used to identify on a single cell resolution which specific cell types are enriched for pSTAT3 in the tumor microenvironment. The identification of pAKT or pSTAT3 as promising therapeutic targets could be rationally employed to individual patients. The presence of macrophages and T cells in samples suggest that conventionally “cold” prostate cancer bone metastases warrant reappraisal as capable immunotherapy responders. Biopsies could guide selection of patients into appropriate therapeutic interventions based on protein levels and RNA expression of desired targets in metastatic disease.

Citation Format: Claire L. Ihle, Meredith D. Provera, Desiree M. Straign, E. Erin Smith, Susan M. Edgerton, Adrie Van Bokhoven, M. Scott Lucia, Philip Owens. Distinct pathways of lytic and blastic bone metastases in prostate cancer patients [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 1580.

Myeloid Cell-Derived TGFβ Signaling Regulates ECM Deposition in Mammary Carcinoma via Adenosine-Dependent Mechanisms

TGFβ plays a crucial role in the tumor microenvironment by regulating cell-cell and cell-stroma interactions. We previously demonstrated that TGFβ signaling on myeloid cells regulates expression of CD73, a key enzyme for production of adenosine, a protumorigenic metabolite implicated in regulation of tumor cell behaviors, immune response, and angiogenesis. Here, using an MMTV-PyMT mouse mammary tumor model, we discovered that deletion of TGFβ signaling on myeloid cells (PyMT/TGFβRII^LysM) affects extracellular matrix (ECM) formation in tumor tissue, specifically increasing collagen and decreasing fibronectin deposition. These changes were associated with mitigated tumor growth and reduced metastases. Reduced TGFβ signaling on fibroblasts was associated with their proximity to CD73⁺ myeloid cells in tumor tissue. Consistent with these findings, adenosine significantly downregulated TGFβ signaling on fibroblasts, an effect regulated by A_2A and A_2B adenosine receptors. METABRIC dataset analysis revealed that patients with triple-negative breast cancer and basal type harbored a similar signature of adenosine and ECM profiles; high expression of A_2B adenosine receptors correlated with decreased expression of Col1 and was associated with poor outcome. Taken together, our studies reveal a new role for TGFβ signaling on myeloid cells in tumorigenesis. This discovered cross-talk between TGFβ/CD73 on myeloid cells and TGFβ signaling on fibroblasts can contribute to ECM remodeling and protumorigenic actions of cancer-associated fibroblasts. SIGNIFICANCE: TGFβ signaling on fibroblasts is decreased in breast cancer, correlates with poor prognosis, and appears to be driven by adenosine that accelerates tumor progression and metastasis via ECM remodeling.

Loss of Myeloid BMPR1a Alters Differentiation and Reduces Mouse Prostate Cancer Growth

The Bone Morphogenetic Protein (BMP) pathway is a member of the TGFβ signaling family and has complex roles in cancer. BMP signaling is rarely mutated and can be frequently overexpressed in many human cancers. The dichotomous role of BMPs as both tumor promoters and suppressors appears to be largely context based in both the cancer cell and the surrounding microenvironment. Myeloid cells including macrophages and neutrophils have been shown to be tumor promoting when stimulated from BMPs. We found that conditional deletion of BMPR1a in myeloid cells (LysMCre) restricts tumor progression in a syngeneic mouse prostate cancer model. Specific changes occurred in myeloid cells both in tumor bearing mice and tumor naïve mice throughout multiple tissues. We profiled myeloid subsets in the bone marrow, spleen and primary tumor and found myeloid BMPR1a loss altered the differentiation and lineage capability of distinct populations by histologic, flow cytometry and high dimensional mass cytometry analysis. We further confirmed the requirement for BMP signaling with pharmacologic inhibition of THP-1 and Raw264.7 activated into M2 macrophages with the BMP inhibitor DMH1. M2 polarized primary bone marrow derived cells from LysMCre BMPR1a knockout mice indicated a distinct requirement for BMP signaling in myeloid cells during M2 activation. These results indicate a unique necessity for BMP signaling in myeloid cells during tumor progression.

Integrating the immune microenvironment of prostate cancer induced bone disease

Prostate cancer (PCa) is the most frequently diagnosed cancer for men in the U.S. but does not impede patient survival until the disease is metastatic. Metastatic lesions most frequently occur in the bone, which exhibits a distinct microenvironment of immune and bone cell populations. Advances in the diagnosis and treatment of primary PCa allow for the use of tailored therapeutic approaches based on biomarkers, protein expression, and histopathology. Understanding the molecular and cellular characteristics of primary tumors has advanced therapeutic development and survival for patients with PCa. Personalized medicine has only recently emerged for the treatment of metastatic bone lesions. Tumor induced bone disease (TIBD) in patients with PCa can be classified into lytic, blastic, or mixed pathologies, with most patients exhibiting the blastic phenotype. Progress has been made in treating TIBD, but metastatic PCa has yet to be cured. Immune checkpoint inhibitors have exhibited limited responses in immunosuppressive PCa tumors, but have yet to be assessed in metastatic sites which may be susceptible to an increased inflammatory response. Recent discoveries have uncovered distinct tumor microenvironments (TMEs) of blastic and lytic bone metastases from patients with PCa, identifying actionable targets for therapeutic applications, including immune checkpoint inhibitors and targeted therapeutics. Enrichment for macrophages and T cells in patient samples suggests metastatic sites may be reappraised as immunologically targetable, despite their immunologically "cold" primary tumors. The practice of performing bone biopsies will help identify unique cellular and protein targets in the bone TME that can guide therapy decisions.

Fibroblast subtypes define a metastatic matrisome in breast cancer

Small primary breast cancers can show surprisingly high potential for metastasis. Clinical decision-making for tumor aggressiveness, including molecular profiling, relies primarily on analysis of the cancer cells. Here we show that this analysis is insufficient - that the stromal microenvironment of the primary tumor plays a key role in tumor cell dissemination and implantation at distant sites. We previously described 2 cancer-associated fibroblasts (CAFs) that either express (CD146+) or lack (CD146-) CD146 (official symbol MCAM, alias MUC18). We now find that when mixed with human breast cancer cells, each fibroblast subtype determines the fate of cancer cells: CD146- fibroblasts promoted increased metastasis compared with CD146+ fibroblasts. Potentially novel quantitative and qualitative proteomic analyses showed that CD146+ CAFs produced an environment rich in basement membrane proteins, while CD146- CAFs exhibited increases in fibronectin 1, lysyl oxidase, and tenascin C, all overexpressed in aggressive disease. We also show clinically that CD146- CAFs predicted for likelihood of lymph node involvement even in small primary tumors (<5 cm). Clearly small tumors enriched for CD146- CAFs require aggressive treatments.

Distinct tumor microenvironments of lytic and blastic bone metastases in prostate cancer patients

The most common metastatic lesions of prostate cancer are in bone and can be classified into three distinct pathology subtypes: lytic, blastic, and an indeterminate mixture of both. We investigated a cohort of decalcified formalin-fixed and paraffin-embedded (FFPE) patient specimens from the bone that contained metastatic prostate cancer with lytic or blastic features. These tissue sections were utilized for immunohistochemistry (IHC) staining, isolation of RNA for gene expression, and Digital Spatial Profiling (DSP) of changes in both the tumor and microenvironment. A diverse set of unique immune cell populations and signaling pathways to both lytic and blastic types of prostate cancer metastases were present. In blastic lesions immune cells were enriched for pSTAT3 and components of the JAK-STAT pathway. In lytic-type lesions, immune cells were enriched for pAKT activity and components of the PI3K-AKT pathway. Enrichment for immune checkpoints including PD-L1, B7-H4, OX40L, and IDO-1 were identified in blastic prostate cancer, providing new therapeutic targets for patients with bone metastases. Biopsies could guide selection of patients into appropriate therapeutic interventions based on protein levels and RNA expression of desired targets in metastatic disease. Molecular pathology has been an excellent complement to the diagnosis, treatment, and management of primary tumors and could be successfully extended to patients with metastatic lesions.

Pancreatic Tumor Microenvironment Modulation by EphB4-ephrinB2 Inhibition and Radiation Combination

PURPOSE

A driving factor in pancreatic ductal adenocarcinoma (PDAC) treatment resistance is the tumor microenvironment, which is highly immunosuppressive. One potent immunologic adjuvant is radiotherapy. Radiation, however, has also been shown to induce immunosuppressive factors, which can contribute to tumor progression and formation of fibrotic tumor stroma. To capitalize on the immunogenic effects of radiation and obtain a durable tumor response, radiation must be rationally combined with targeted therapies to mitigate the influx of immunosuppressive cells and fibrosis. One such target is ephrinB2, which is overexpressed in PDAC and correlates negatively with prognosis.Experimental Design: On the basis of previous studies of ephrinB2 ligand-EphB4 receptor signaling, we hypothesized that inhibition of ephrinB2-EphB4 combined with radiation can regulate the microenvironment response postradiation, leading to increased tumor control in PDAC. This hypothesis was explored using both cell lines and in vivo human and mouse tumor models.

RESULTS

Our data show this treatment regimen significantly reduces regulatory T-cell, macrophage, and neutrophil infiltration and stromal fibrosis, enhances effector T-cell activation, and decreases tumor growth. Furthermore, our data show that depletion of regulatory T cells in combination with radiation reduces tumor growth and fibrosis.

CONCLUSIONS

These are the first findings to suggest that in PDAC, ephrinB2-EphB4 interaction has a profibrotic, protumorigenic role, presenting a novel and promising therapeutic target.

Cytokine sensitivity screening highlights BMP4 pathway signaling as a therapeutic opportunity in ER+ breast cancer

Despite the success of approved systemic therapies for estrogen receptor α (ER)-positive breast cancer, drug resistance remains common. We hypothesized that secreted factors from the human tumor microenvironment could modulate drug resistance. We previously screened a library of 297 recombinant-secreted microenvironmental proteins for the ability to confer resistance to the anti-estrogen fulvestrant in 2 ER⁺ breast cancer cell lines. Herein, we considered whether factors that enhanced drug sensitivity could be repurposed as therapeutics and provide leads for drug development. Screening data revealed bone morphogenic protein (BMP)4 as a factor that inhibited cell growth and synergized with approved anti-estrogens and cyclin-dependent kinase 4/6 inhibitors (CDK4/6_i). BMP4-mediated growth inhibition was dependent on type I receptor activin receptor-like kinase (ALK)3-dependent phosphorylation (P) of mothers against decapentaplegic homolog (SMAD/P-SMAD)1 and 5, which could be reversed by BMP receptor inhibitors and ALK3 knockdown. The primary effect of BMP4 on cell fate was cell-cycle arrest, in which RNA sequencing, immunoblot analysis, and RNA interference revealed to be dependent on p21^WAF1/Cip1 upregulation. BMP4 also enhanced sensitivity to approved inhibitors of mammalian target of rapamycin complex 1 and CDK4/6 via ALK3-mediated P-SMAD1/5 and p21 upregulation in anti-estrogen-resistant cells. Patients bearing primary ER⁺ breast tumors, exhibiting a transcriptomic signature of BMP4 signaling, had improved disease outcome following adjuvant treatment with anti-estrogen therapy, independently of age, tumor grade, and tumor stage. Furthermore, a transcriptomic signature of BMP4 signaling was predictive of an improved biologic response to the CDK4/6_i palbociclib, in combination with an aromatase inhibitor in primary tumors. These findings highlight BMP4 and its downstream pathway activation as a therapeutic opportunity in ER⁺ breast cancer.-Shee, K., Jiang, A., Varn, F. S., Liu, S., Traphagen, N. A., Owens, P., Ma, C. X., Hoog, J., Cheng, C., Golub, T. R., Straussman, R., Miller, T. W. Cytokine sensitivity screening highlights BMP4 pathway signaling as a therapeutic opportunity in ER⁺ breast cancer.

Allogeneic Mesenchymal Stromal Cells (MSCs) are of Comparable Efficacy to Syngeneic MSCs for Therapeutic Revascularization in C57BKSdb/db Mice Despite the Induction of Alloantibody

Intramuscular administration of mesenchymal stromal cells (MSCs) represents a therapeutic option for diabetic critical limb ischemia. Autologous or allogeneic approaches may be used but disease-induced cell dysfunction may limit therapeutic efficacy in the former. Our aim was to compare the efficacy of allogeneic and autologous MSC transplantation in a model of hindlimb ischemia in diabetes mellitus and to determine whether allogeneic transplantation would result in the activation of an immune response. MSCs were isolated from C57BL/6 (B6) and diabetic obese C57BKS^db/db mice. Phosphate-buffered saline (control group), and MSCs (1 × 10⁶) from B6 (allogeneic group) or C57BKS^db/db (syngeneic group) were administered intramuscularly into the ischemic thigh of C57BKS^db/db mice following the induction of hindlimb ischemia. MSCs derived from both mouse strains secrete several angiogenic factors, suggesting that the potential therapeutic effect is due to paracrine signaling. Administration of allogeneic MSCs significantly improved blood perfusion as compared with the control group on week 2 and 3, post-operatively. In comparison with the control group, syngeneic MSCs significantly improved blood perfusion at week 2 only. There was no statistical difference in blood perfusion between allogeneic and syngeneic MSC groups at any stages. There was no statistical difference in ambulatory and necrosis score among the three groups. Amputation of toes was only observed in the control group (one out of seven animals). Alloantibody was detected in three out of the eight mice that received allogeneic MSCs but was not observed in the other groups. In summary, we demonstrated comparable efficacy after transplantation of autologous and allogeneic MSCs in a diabetic animal model despite generation of an immune response.

Abstract 2119: Bone Morphogenetic Protein Receptor 1a in myeloid cells regulates mouse prostate cancer growth

The Bone Morphogenetic Protein (BMP) pathway is a member of the TGFβ signaling family and has mirrored the complex roles in diverse contexts during cancer development. BMP signaling is rarely mutated and can be frequently overexpressed in many human cancers. The dichotomous role of BMPs as both tumor promoters and suppressors appears to be largely context based in both the cancer cell and the surrounding microenvironment. Myeloid cells including macrophages and neutrophils have been shown to be tumor promoting when stimulated from BMP signaling. We discovered that conditional deletion of BMPR1a in myeloid cells (LysM-Cre) would affect tumor progression and found smaller tumors in a syngeneic FVBn prostate cancer model. Specific changes occurred in myeloid cells both in tumor-bearing mice and non-tumor naïve mice throughout multiple tissues. We profiled myeloid subsets both in the bone marrow, spleen and primary tumor. We found that BMPR1a loss in myeloid cells altered the differentiation and lineage capability of distinct populations by histologic, flow cytometry and high-dimensional mass cytometry analysis. These results indicate a distinct genetic requirement for BMP signaling in myeloid cells during tumor progression.

Citation Format: Desiree M. Straign, Sergey V. Novitskiy, Philip Owens. Bone Morphogenetic Protein Receptor 1a in myeloid cells regulates mouse prostate cancer growth [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 2119.

Engineered microfluidic bioreactor for examining the three-dimensional breast tumor microenvironment

The interaction of cancer cells with the stromal cells and matrix in the tumor microenvironment plays a key role in progression to metastasis. A better understanding of the mechanisms underlying these interactions would aid in developing new therapeutic approaches to inhibit this progression. Here, we describe the fabrication of a simple microfluidic bioreactor capable of recapitulating the three-dimensional breast tumor microenvironment. Cancer cell spheroids, fibroblasts, and endothelial cells co-cultured in this device create a robust microenvironment suitable for studying in real time the migration of cancer cells along matrix structures laid down by fibroblasts within the 3D tumor microenvironment. This system allows for ready evaluation of response to targeted therapy.

Effectiveness of Early Hematopoietic Stem Cell Transplantation in Preventing Neurocognitive Decline in Mucopolysaccharidosis Type II: A Case Series

The early progressive form of the X-linked disorder, Hunter syndrome or mucopolysaccharidosis type II (MPS II) (OMIM #309900), is characterized by cognitive decline, and pulmonary and cardiac complications that often cause death before 20 years of age. Deficiency of the lysosomal enzyme, iduronate-2-sulfatase (EC 3.1.6.13) results in deposition of the glycosaminoglycans, dermatan, and heparan sulfate in various tissues. In recent years, enzyme replacement therapy (ERT) has become the mainstay of treatment, but is expensive and ineffective in arresting cognitive decline. Hematopoietic stem cell transplantation (HSCT) also provides enzyme replacement, and may be effective in stabilizing neurocognitive function if initiated early, though data are limited. We present a case series of four patients who demonstrated neurocognitive stabilization with early HSCT. HSCT is a potentially underutilized treatment strategy for select groups of MPS II patients.

Abstract PD4-08: A microenvironment secretome screen reveals FGF2 as a mediator of resistance to anti-estrogens and PI3K/mTOR pathway inhibitors in ER+ breast cancer

Despite the clinical success of anti-estrogen therapies, phosphatidylinositol 3-kinase inhibitors (PI3Ki), and mechanistic target of rapamycin complex I inhibitors (mTORC1i) for the treatment of patients with ER+ breast cancer, disease recurrence and progression are common. We found that a tumor transcriptional profile reflecting high stromal fibroblast content was associated with poor outcome in 3 cohorts of patients with ER+ breast cancer. We hypothesized that individual factors in the tumor microenvironment (TME) significantly contribute to drug resistance.

To test this hypothesis, we screened 297 recombinant secreted proteins for ability to confer resistance to the anti-estrogen fulvestrant in MCF-7 and T47D ER+ breast cancer cells. Screen results were validated, and expansion screening included the anti-estrogen tamoxifen, the PI3Ki pictilisib, and the mTORC1i everolimus in 4 cell lines. To identify hits are most likely to be relevant to ER+ breast cancer, a bioinformatics filter was developed utilizing gene and protein expression in human tissues relevant to the TMEs of ER+ breast cancer. After filtering, the top screening hit was fibroblast growth factor 2 (FGF2), which confers resistance to anti-estrogens, PI3Ki, and mTORC1i, and is highly expressed in tissues and cell types associated with ER+ breast cancer. FGF2 did not rescue cells from the CDK4/6i palbociclib or the DNA-damaging agent doxorubicin, demonstrating pathway selectivity in the rescue phenotype. FGF2 rescued cells from anti-estrogen-, PI3Ki-, and mTORC1i-induced apoptosis and cell cycle arrest via activation of FGFR signaling through FRS2a, MEK1/2, ERK1/2, and downstream upregulation of cyclin D1 and degradation of Bim. FGF2-mediated anti-cancer effects were abrogated by co-treatment with the FGF2-neutralizing antibody GAL-F2, the pan-FGFR inhibitor PD-173074, the MEK inhibitor trametinib, or palbociclib. Cell cycle- and apoptosis-specific effects of FGF2 were abrogated by RNAi targeting cyclin D1 and Bim, respectively.

We generated a transcriptional signature of FGF2 response by RNA-seq of fulvestrant-treated MCF-7 and T47D cells treated +/- FGF2. In 3 cohorts of patients with ER+ breast cancer, a signature of FGF2 signaling was significantly associated with poor prognosis and predictive of anti-estrogen resistance, including in a multivariate analysis including age, tumor grade, tumor stage, and FGFR amplification status. Finally, the therapeutic potential of targeting FGF2 was confirmed in 3 mouse models of ER+ breast cancer: 1) FGF2 rescue MCF-7 xenografts from fulvestrant; 2) GAL-F2 synergized with fulvestrant to suppress growth of 59-2-HI murine mammary adenocarcinomas that recruit FGF2-secreting stroma; 3) GAL-F2 synergized with fulvestrant to induce regression of HCI-003 patient-derived xenografts. Therapeutic effects coincided with increased tumor cell apoptosis and decreased proliferation, but not changes in tumor vasculature. These findings warrant consideration of FGF2 as a novel therapeutic target in ER+ breast cancer.

Citation Format: Shee K, Hinds JW, Yang W, Hampsch RA, Patel K, Varn FS, Cheng C, Jenkins NP, Kettenbach AN, Demidenko E, Owens P, Lanari C, Faber AC, Golub TR, Straussman R, Miller TW. A microenvironment secretome screen reveals FGF2 as a mediator of resistance to anti-estrogens and PI3K/mTOR pathway inhibitors in ER+ breast cancer [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 PD4-08.

Therapeutically targeting tumor microenvironment-mediated drug resistance in estrogen receptor-positive breast cancer

Tumor microenvironment (TME) cytokine screening revealed FGF2 as a clinically relevant mechanism of resistance to anti-estrogens, mTORC1 inhibition, and PI3K inhibition in ER+ breast cancer. Shee et al. highlight an underdeveloped aspect of precision oncology: treating patients according to their TME constitution.

Drug resistance to approved systemic therapies in estrogen receptor–positive (ER+) breast cancer remains common. We hypothesized that factors present in the human tumor microenvironment (TME) drive drug resistance. Screening of a library of recombinant secreted microenvironmental proteins revealed fibroblast growth factor 2 (FGF2) as a potent mediator of resistance to anti-estrogens, mTORC1 inhibition, and phosphatidylinositol 3-kinase inhibition in ER+ breast cancer. Phosphoproteomic analyses identified ERK1/2 as a major output of FGF2 signaling via FGF receptors (FGFRs), with consequent up-regulation of Cyclin D1 and down-regulation of Bim as mediators of drug resistance. FGF2-driven drug resistance in anti-estrogen–sensitive and –resistant models, including patient-derived xenografts, was reverted by neutralizing FGF2 or FGFRs. A transcriptomic signature of FGF2 signaling in primary tumors predicted shorter recurrence-free survival independently of age, grade, stage, and FGFR amplification status. These findings delineate FGF2 signaling as a ligand-based drug resistance mechanism and highlights an underdeveloped aspect of precision oncology: characterizing and treating patients according to their TME constitution.

ErbB3 drives mammary epithelial survival and differentiation during pregnancy and lactation

Background

During pregnancy, as the mammary gland prepares for synthesis and delivery of milk to newborns, a luminal mammary epithelial cell (MEC) subpopulation proliferates rapidly in response to systemic hormonal cues that activate STAT5A. While the receptor tyrosine kinase ErbB4 is required for STAT5A activation in MECs during pregnancy, it is unclear how ErbB3, a heterodimeric partner of ErbB4 and activator of phosphatidyl inositol-3 kinase (PI3K) signaling, contributes to lactogenic expansion of the mammary gland.

Methods

We assessed mRNA expression levels by expression microarray of mouse mammary glands harvested throughout pregnancy and lactation. To study the role of ErbB3 in mammary gland lactogenesis, we used transgenic mice expressing WAP-driven Cre recombinase to generate a mouse model in which conditional ErbB3 ablation occurred specifically in alveolar mammary epithelial cells (aMECs).

Results

Profiling of RNA from mouse MECs isolated throughout pregnancy revealed robust Erbb3 induction during mid-to-late pregnancy, a time point when aMECs proliferate rapidly and undergo differentiation to support milk production. Litters nursed by ErbB3^KO dams weighed significantly less when compared to litters nursed by ErbB3^WT dams. Further analysis revealed substantially reduced epithelial content, decreased aMEC proliferation, and increased aMEC cell death during late pregnancy. Consistent with the potent ability of ErbB3 to activate cell survival through the PI3K/Akt pathway, we found impaired Akt phosphorylation in ErbB3^KO samples, as well as impaired expression of STAT5A, a master regulator of lactogenesis. Constitutively active Akt rescued cell survival in ErbB3-depleted aMECs, but failed to restore STAT5A expression or activity. Interestingly, defects in growth and survival of ErbB3^KO aMECs as well as Akt phosphorylation, STAT5A activity, and expression of milk-encoding genes observed in ErbB3^KO MECs progressively improved between late pregnancy and lactation day 5. We found a compensatory upregulation of ErbB4 activity in ErbB3^KO mammary glands. Enforced ErbB4 expression alleviated the consequences of ErbB3 ablation in aMECs, while combined ablation of both ErbB3 and ErbB4 exaggerated the phenotype.

Conclusions

These studies demonstrate that ErbB3, like ErbB4, enhances lactogenic expansion and differentiation of the mammary gland during pregnancy, through activation of Akt and STAT5A, two targets crucial for lactation.

Electronic supplementary material

The online version of this article (doi:10.1186/s13058-017-0893-7) contains supplementary material, which is available to authorized users.

Development of Aggressive Pancreatic Ductal Adenocarcinomas Depends on Granulocyte Colony Stimulating Factor Secretion in Carcinoma Cells

The survival rate for pancreatic ductal adenocarcinoma (PDAC) remains low. More therapeutic options to treat this disease are needed, for the current standard of care is ineffective. Using an animal model of aggressive PDAC (Kras/p48^TGFβRIIKO), we discovered an effect of TGFβ signaling in regulation of G-CSF secretion in pancreatic epithelium. Elevated concentrations of G-CSF in PDAC promoted differentiation of Ly6G⁺ cells from progenitors, stimulated IL10 secretion from myeloid cells, and decreased T-cell proliferation via upregulation of Arg, iNOS, VEGF, IL6, and IL1b from CD11b⁺ cells. Deletion of csf3 in PDAC cells or use of a G-CSF-blocking antibody decreased tumor growth. Anti-G-CSF treatment in combination with the DNA synthesis inhibitor gemcitabine reduced tumor size, increased the number of infiltrating T cells, and decreased the number of Ly6G⁺ cells more effectively than gemcitabine alone. Human analysis of human datasets from The Cancer Genome Atlas and tissue microarrays correlated with observations from our mouse model experiments, especially in patients with grade 1, stage II disease. We propose that in aggressive PDAC, elevated G-CSF contributes to tumor progression through promoting increases in infiltration of neutrophil-like cells with high immunosuppressive activity. Such a mechanism provides an avenue for a neoadjuvant therapeutic approach for this devastating disease. Cancer Immunol Res; 5(9); 718-29. ©2017 AACR.

TGF-β, Bone Morphogenetic Protein, and Activin Signaling and the Tumor Microenvironment

The cellular and noncellular components surrounding the tumor cells influence many aspects of tumor progression. Transforming growth factor β (TGF-β), bone morphogenetic proteins (BMPs), and activins have been shown to regulate the phenotype and functions of the microenvironment and are attractive targets to attenuate protumorigenic microenvironmental changes. Given the pleiotropic nature of the cytokines involved, a full understanding of their effects on numerous cell types in many contexts is necessary for proper clinical intervention. In this review, we will explore the various effects of TGF-β, BMP, and activin signaling on stromal phenotypes known to associate with cancer progression. We will summarize these findings in the context of their tumor suppressive or promoting effects, as well as the molecular changes that these cytokines induce to influence stromal phenotypes.

HER2-Overexpressing Breast Cancers Amplify FGFR Signaling upon Acquisition of Resistance to Dual Therapeutic Blockade of HER2

Purpose: Dual blockade of HER2 with trastuzumab and lapatinib or pertuzumab has been shown to be superior to single-agent trastuzumab. However, a significant fraction of HER2-overexpressing (HER2⁺) breast cancers escape from these drug combinations. In this study, we sought to discover the mechanisms of acquired resistance to the combination of lapatinib + trastuzumab.Experimental Design: HER2⁺ BT474 xenografts were treated with lapatinib + trastuzumab long-term until resistance developed. Potential mechanisms of acquired resistance were evaluated in lapatinib + trastuzumab-resistant (LTR) tumors by targeted capture next-generation sequencing. In vitro experiments were performed to corroborate these findings, and a novel drug combination was tested against LTR xenografts. Gene expression and copy-number analyses were performed to corroborate our findings in clinical samples.Results: LTR tumors exhibited an increase in FGF3/4/19 copy number, together with an increase in FGFR phosphorylation, marked stromal changes in the tumor microenvironment, and reduced tumor uptake of lapatinib. Stimulation of BT474 cells with FGF4 promoted resistance to lapatinib + trastuzumab in vitro Treatment with FGFR tyrosine kinase inhibitors reversed these changes and overcame resistance to lapatinib + trastuzumab. High expression of FGFR1 correlated with a statistically shorter progression-free survival in patients with HER2⁺ early breast cancer treated with adjuvant trastuzumab. Finally, FGFR1 and/or FGF3 gene amplification correlated with a lower pathologic complete response in patients with HER2⁺ early breast cancer treated with neoadjuvant anti-HER2 therapy.Conclusions: Amplification of FGFR signaling promotes resistance to HER2 inhibition, which can be diminished by the combination of HER2 and FGFR inhibitors. Clin Cancer Res; 23(15); 4323-34. ©2017 AACR.

The Yin/Yan of CCL2: a minor role in neutrophil anti-tumor activity in vitro but a major role on the outgrowth of metastatic breast cancer lesions in the lung in vivo

Background

The role of the chemokine CCL2 in breast cancer is controversial. While CCL2 recruits and activates pro-tumor macrophages, it is also reported to enhance neutrophil-mediated anti-tumor activity. Moreover, loss of CCL2 in early development enhances breast cancer progression.

Methods

To clarify these conflicting findings, we examined the ability of CCL2 to alter naïve and tumor entrained neutrophil production of ROS, release of granzyme-B, and killing of tumor cells in multiple mouse models of breast cancer. CCL2 was delivered intranasally in mice to elevate CCL2 levels in the lung and effects on seeding and growth of breast tumor cells were evaluated. The TCGA data base was queried for relationship between CCL2 expression and relapse free survival of breast cancer patients and compared to subsets of breast cancer patients.

Results

Even though each of the tumor cell lines studied produced approximately equal amounts of CCL2, exogenous delivery of CCL2 to co-cultures of breast tumor cells and neutrophils enhanced the ability of tumor-entrained neutrophils (TEN) to kill the less aggressive 67NR variant of 4T1 breast cancer cells. However, exogenous CCL2 did not enhance naïve or TEN neutrophil killing of more aggressive 4T1 or PyMT breast tumor cells. Moreover, this anti-tumor activity was not observed in vivo. Intranasal delivery of CCL2 to BALB/c mice markedly enhanced seeding and outgrowth of 67NR cells in the lung and increased the recruitment of CD4+ T cells and CD8+ central memory T cells into lungs of tumor bearing mice. There was no significant increase in the recruitment of CD19+ B cells, or F4/80+, Ly6G+ and CD11c + myeloid cells. CCL2 had an equal effect on CD206+ and MHCII+ populations of macrophages, thus balancing the pro- and anti-tumor macrophage cell population. Analysis of the relationship between CCL2 levels and relapse free survival in humans revealed that overall survival is not significantly different between high CCL2 expressing and low CCL2 expressing breast cancer patients grouped together. However, examination of the relationship between high CCL2 expressing basal-like, HER2+ and luminal B breast cancer patients revealed that higher CCL2 expressing tumors in these subgroups have a significantly higher probability of surviving longer than those expressing low CCL2.

Conclusions

While our in vitro data support a potential anti-tumor role for CCL2 in TEN neutrophil- mediated tumor killing in poorly aggressive tumors, intranasal delivery of CCL2 increased CD4+ T cell recruitment to the pre-metastatic niche of the lung and this correlated with enhanced seeding and growth of tumor cells. These data indicate that effects of CCL2/CCR2 antagonists on the intratumoral leukocyte content should be monitored in ongoing clinical trials using these agents.

Electronic supplementary material

The online version of this article (doi:10.1186/s12885-017-3074-2) contains supplementary material, which is available to authorized users.

PI3K Inhibition Reduces Mammary Tumor Growth and Facilitates Antitumor Immunity and Anti-PD1 Responses

Purpose: Metastatic breast cancers continue to elude current therapeutic strategies, including those utilizing PI3K inhibitors. Given the prominent role of PI3Kα,β in tumor growth and PI3Kγ,δ in immune cell function, we sought to determine whether PI3K inhibition altered antitumor immunity.Experimental Design: The effect of PI3K inhibition on tumor growth, metastasis, and antitumor immune response was characterized in mouse models utilizing orthotopic implants of 4T1 or PyMT mammary tumors into syngeneic or PI3Kγ-null mice, and patient-derived breast cancer xenografts in humanized mice. Tumor-infiltrating leukocytes were characterized by IHC and FACS analysis in BKM120 (30 mg/kg, every day) or vehicle-treated mice and PI3Kγ^null versus PI3Kγ^WT mice. On the basis of the finding that PI3K inhibition resulted in a more inflammatory tumor leukocyte infiltrate, the therapeutic efficacy of BKM120 (30 mg/kg, every day) and anti-PD1 (100 μg, twice weekly) was evaluated in PyMT tumor-bearing mice.Results: Our findings show that PI3K activity facilitates tumor growth and surprisingly restrains tumor immune surveillance. These activities could be partially suppressed by BKM120 or by genetic deletion of PI3Kγ in the host. The antitumor effect of PI3Kγ loss in host, but not tumor, was partially reversed by CD8⁺ T-cell depletion. Treatment with therapeutic doses of both BKM120 and antibody to PD-1 resulted in consistent inhibition of tumor growth compared with either agent alone.Conclusions: PI3K inhibition slows tumor growth, enhances antitumor immunity, and heightens susceptibility to immune checkpoint inhibitors. We propose that combining PI3K inhibition with anti-PD1 may be a viable therapeutic approach for triple-negative breast cancer. Clin Cancer Res; 23(13); 3371-84. ©2016 AACR.

Deletion of the BMP receptor BMPR1a impairs mammary tumor formation and metastasis

Bone Morphogenetic Proteins (BMPs) are secreted cytokines/growth factors belonging to the Transforming Growth Factor β (TGFβ) family. BMP ligands have been shown to be overexpressed in human breast cancers. Normal and cancerous breast tissue display active BMP signaling as indicated by phosphorylated Smads 1, 5 and 9. We combined mice expressing the MMTV.PyMT oncogene with mice having conditional knockout (cKO) of BMP receptor type 1a (BMPR1a) using whey acidic protein (WAP)-Cre and found this deletion resulted in delayed tumor onset and significantly extended survival. Immunofluorescence staining revealed that cKO tumors co-expressed Keratin 5 and mesenchymal cell markers such as Vimentin. This indicates that epithelial-to-mesenchymal (EMT)-like transitions occurred in cKO tumors. We performed microarray analysis on these tumors and found changes that support EMT-like changes. We established primary tumor cell lines and found that BMPR1a cKO had slower growth in vitro and in vivo upon implantation. cKO tumor cells had reduced migration in vitro. We analyzed human databases from TCGA and survival data from microarrays to confirm BMPR1a tumor promoting functions, and found that high BMPR1a gene expression correlates with decreased survival regardless of molecular breast cancer subtype. In conclusion, the data indicate that BMP signaling through BMPR1a functions as a tumor promoter.

The Bone Microenvironment: a Fertile Soil for Tumor Growth

Bone metastatic disease remains a significant and frequent problem for cancer patients that can lead to increased morbidity and mortality. Unfortunately, despite decades of research, bone metastases remain incurable. Current studies have demonstrated that many properties and cell types within the bone and bone marrow microenvironment contribute to tumor-induced bone disease. Furthermore, they have pointed to the importance of understanding how tumor cells interact with their microenvironment in order to help improve both the development of new therapeutics and the prediction of response to therapy.

Abstract 629: The impact of BMP4 on breast cancer metastasis in an in vivo xenograft mouse model

Background. Breast cancer is the most common cancer in women worldwide. Bone morphogenetic proteins (BMPs), members of the transforming growth factor β superfamily, are known to regulate cell proliferation, differentiation and motility, and have also been shown to be involved in cancer pathogenesis, also in breast cancer. We have previously demonstrated that BMP4 is able to consistently reduce breast cancer cell proliferation through G1 cell cycle arrest and to simultaneously induce migration and invasion in a subset of breast cancer cell lines. Similarly, our clinical data revealed a correlation between elevated BMP4 expression in primary breast tumors and reduced proliferation as well as increased risk of recurrence. The growth inhibitory effects of BMP4 have also been demonstrated in vivo but its possible metastasis promoting functions are less well characterized. Here we set out to investigate this topic using a xenograft mouse model.

Methods. MDA-MB-231 breast cancer cells were transduced with a luciferase-expressing vector to allow monitoring of the metastasis formation using bioluminescence imaging. Cells (2 × 105) were injected into the mice intracardially and BMP4 (100 ng/g, 10 animals) or vehicle control (11 animals) was administered through tail vein three times a week. After seven weeks, the mice were sacrificed and metastases collected for histological analyses.

Results. The overall amount of metastases was similar in both groups (13 in BMP4-treatment group vs. 12 in control group). There was a slight but non-significant trend of metastases developing earlier in the BMP4 group compared to controls. Most of the metastases occurred in bone and adrenal glands. There were somewhat more metastases in bone in the BMP4-treated mice (10 vs. 7) and more adrenal gland metastases in vehicle-treated animals (5 vs. 1). To assess the contribution of BMP4 to the characteristics of the metastases, the tumors were stained for pSMAD1/5/9 (BMP signaling activation), Ki67 (proliferation), MECA32 (blood vessels), mesenchymal marker vimentin, α-SMA (cancer-associated fibroblasts) and basal markers K5 and K14. No major dissimilarities were observed between the BMP4 and vehicle tumor groups in the staining patterns. Interestingly, the osteoclast marker Tartrate-resistant acid phosphatase (TRAP) was expressed in both groups in the cancer cells whereas Toluidine Blue staining revealed that the bone morphology was not detrimentally affected by BMP4 treatment.

Conclusions. Despite its ability to enhance breast cancer cell migration and invasion in vitro, BMP4 does not seem to have a dramatic impact on in vivo metastasis formation, although a small acceleration in appearance of the metastases was observed. However, the limitations of the xenograft model do not allow us to exclude the possible long-term effects of BMP4 that might be more applicable to human situation.

Citation Format: Minna Ampuja, Emma L. Alarmo, Philip Owens, Riikka Havunen, Agnes E. Gorska, Harold L. Moses, Anne Kallioniemi. The impact of BMP4 on breast cancer metastasis in an in vivo xenograft mouse model. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 629.

Overexpression of PIK3CA in murine head and neck epithelium drives tumor invasion and metastasis through PDK1 and enhanced TGFβ signaling

Head and neck squamous cell carcinoma (HNSCC) patients have a poor prognosis, with invasion and metastasis as major causes of mortality. The phosphatidylinositol 3-kinase (PI3K) pathway regulates a wide range of cellular processes crucial for tumorigenesis, and PIK3CA amplification and mutation are among the most common genetic alterations in human HNSCC. Compared to the well-documented roles of the PI3K pathway in cell growth and survival, the roles of the PI3K pathway in tumor invasion and metastasis have not been well delineated. We generated a PIK3CA-genetically engineered mouse model (PIK3CA-GEMM) in which wildtype PIK3CA is overexpressed in head and neck epithelium. Although PIK3CA overexpression alone was not sufficient to initiate HNSCC formation, it significantly increased tumor susceptibility in an oral-carcinogenesis mouse model. PIK3CA overexpression in mouse oral epithelium increased tumor invasiveness and metastasis by increasing epithelial-mesenchymal transition and by enriching a cancer stem cell phenotype in tumor epithelial cells. In addition to these epithelial alterations, we also observed marked inflammation in tumor stroma. AKT is a central signaling mediator of the PI3K pathway. However, molecular analysis suggested that progression of PIK3CA-driven HNSCC is facilitated by PDK1 and enhanced TGFβ signaling rather than by AKT. Examination of human HNSCC clinical samples revealed that both PIK3CA and PDK1 protein levels correlated with tumor progression, highlighting the significance of this pathway. In summary, our results offer significant insight into how PIK3CA-overexpression drives HNSCC invasion and metastasis, providing a rationale for targeting PI3K/PDK1 and TGFβ signaling in advanced HNSCC patients with PIK3CA amplification.

Bone morphogenetic protein signaling promotes tumorigenesis in a murine model of high-grade glioma

BACKGROUND

Improved therapies for high-grade glioma (HGG) are urgently needed as the median survival for grade IV gliomas is only 15 months. Bone morphogenetic protein (BMP) signaling plays critical and complex roles in many types of cancer, including glioma, with most of the recently published work focusing on BMP-mediated regulation of glioma stem cells (GSCs). We hypothesized that BMP signaling may be an important modulator of tumorigenic properties in glioma cells outside of the GSC compartment.

METHODS

We used a human HGG tissue microarray and performed immunohistochemistry for phospho-Smads1,5,8. To examine the role of BMP signaling in tumorigenic astrocytes, transgenic mice were used to delete the BMP type IA receptor (Bmpr1a) and generate astrocytes transformed with oncogenic Ras and homozygous deletion of p53. The cells were transplanted orthotopically into immunocompetent adult host mice.

RESULTS

First we established that BMP signaling is active within the vast majority of HGG tumor cells. Mice implanted with BMPR1a-knockout transformed astrocytes showed an increase in median survival compared with mice that received BMPR1a-intact transformed astrocytes (52.5 vs 16 days). In vitro analysis showed that deletion of BMPR1a in oncogenic astrocytes resulted in decreased proliferation, decreased invasion, decreased migration, and increased expression of stemness markers. In addition, inhibition of BMP signaling in murine cells and astrocytoma cells with a small molecule BMP receptor kinase inhibitor resulted in similar tumor suppressive effects in vitro.

CONCLUSION

BMP inhibition may represent a viable therapeutic approach in adult HGG.

Abstract A77: Differential recruitment of myeloid derived immune cells and fibroblasts to the thyroid tumor microenvironment in mouse models of papillary and follicular thyroid cancer

Thyroid cancer is the most common endocrine malignancy, and its incidence has steadily increased worldwide over the last 30 years. Genetic alterations leading to the activation of the MAPK signaling pathway are crucial for the initiation and progression of thyroid cancer, as evidenced by the high frequency of activating mutations in BRAF, HRAS, NRAS, RET and TRK. Mutations in BRAF are observed in ~45% of papillary thyroid cancers (PTCs), while follicular thyroid cancer (FTC) is often associated with mutations in RAS. We have shown that thyroid specific expression of HrasG12V and Pten inactivation leads to the development of FTCs and poorly differentiated thyroid cancer (PDTC) in HrasG12V/Ptenhom/TPO-cre mice while thyroid specific expression of BrafV600E and loss of Pten leads to the rapid development of PTC and PDTC in BrafV600E/Ptenhom/TPO-cre mice with complete lethality by weaning. We sought to determine whether activation of Braf or Hras resulted in the differential recruitment of stromal cells to the thyroid tumor microenvironment in HrasG12V/Ptenhom/TPO-cre and BrafV600E/Ptenhom/TPO-cre mice. FACS analysis revealed a significant increase in the overall amount of CD45+ cells in Hras (60.95±5.28%) versus Braf (18.35±1.3%) driven murine thyroid tumors. However, we found that the population of CD45+ cells in Braf driven tumors was comprised of a higher percentage of CD11b+ myeloid cells (62.1±1.3%) in comparison to Hras (37.0±5.5%) driven tumors. We next measured levels of cytokine expression in tumor cell lines derived from BrafV600E/Ptenhom/TPO-cre and HrasG12V/Ptenhom/TPO-cre mice. Braf driven tumor cells expressed higher levels of GM-CSF in comparison to Hras driven tumor cells, which we hypothesize contributes to the larger myeloid compartment observed in BrafV600E/Ptenhom/TPO-cre thyroid tumors. Studies are ongoing to further characterize the immune cell populations in these tumors. FACS analysis also revealed an increase in CD45-CD326-CD140α+ fibroblast infiltrate in Braf versus Hras driven thyroid tumors (68.4±0.424% versus 9.8±4.27%, p&lt;.0001). Fibroblasts are a major source of type I collagen (Col1a1), which has been linked to the immunosuppression of tumor infiltrating leukocytes via inhibition of Leukocyte-associated immunoglobulin-like receptor 1 (LAIR1). Therefore, we hypothesized that the increase in fibroblast infiltrate observed in Braf driven thyroid tumors would result in a subsequent increase in Col1a1 production, thus potentially leading to a more immunosuppressive thyroid tumor microenvironment in PTC. Indeed, levels of Col1a1 gene expression were significantly upregulated an average of 80 fold (p&lt;.0001) in Braf versus Hras driven thyroid tumors, with no significant difference in Col1a1 expression between Hras driven tumors and WT thyroid controls. Histopathological analysis via Picrosirius red staining confirmed higher levels of total and fibrillar collagen in Braf versus Hras driven tumors. In addition, microarray analysis of human thyroid tumors revealed that Col1a1 expression levels are highest in PTCs, particularly in those with mutations in BRAF, and lowest in FTCs and follicular variant PTC, which are both associated with a high RAS mutation rate. Because FTCs and PTCs have distinct pathological features and differ in prognosis and responses to therapy, we aim to translate these findings to the discovery of more personalized diagnostic and treatment strategies that are targeted toward the thyroid tumor microenvironment.

Citation Format: Lee Ann King, Sergey Novitsky, Julio Ricarte-Filho, Philip Owens, Aime T. Franco. Differential recruitment of myeloid derived immune cells and fibroblasts to the thyroid tumor microenvironment in mouse models of papillary and follicular thyroid cancer. [abstract]. In: Proceedings of the AACR Special Conference: Tumor Immunology and Immunotherapy: A New Chapter; December 1-4, 2014; Orlando, FL. Philadelphia (PA): AACR; Cancer Immunol Res 2015;3(10 Suppl):Abstract nr A77.