Tumor Therapy Response Research Articles

Quantitative MRI assessment of mucinous rectal adenocarcinoma to predict tumour response after neoadjuvant therapy

To evaluate the association between volume ratio of the mucus pool and tumour response to neoadjuvant therapy in patients with mucinous rectal adenocarcinoma (MC). The volume of the mucus pool and whole tumour on pre-therapeutic T2-weighted magnetic resonance imaging (MRI) of 79 patients was measured using semi-automated software. Mucus pool volume, whole tumour volume, and volume ratio of the mucus pool were compared to tumour response and tumour and lymph node downstaging after neoadjuvant therapy using receiver operating characteristic curve (ROC) and multivariate logistic regression analysis. After preoperative neoadjuvant therapy of rectal MC, the rate of pathological complete response, tumour downstaging, tumour response, and lymph node downstaging were 9%, 48%, 39% and 58%, respectively. Tumour downstaging more frequently occurred in patients with a mucus pool volume ratio of at least 68.3% (area under the ROC curve [AUC], 0.793 with 95% confidence interval [CI]: 0.693-0.893), and at least 62.1% for identifying those with a higher tumour response with an AUC of 0.739 (95% CI: 0.630-0.847). A higher volume ratio of mucus pool in patients with MC may be related to more tumour downstaging and therapy response, and therefore, could serve as an independent imaging biomarker for predicting tumour response to neoadjuvant therapy.

Recent Progress on Liquid Biopsy Analysis using Surface-Enhanced Raman Spectroscopy.

Traditional tissue biopsy is limited in understanding heterogeneity and dynamic evolution of tumors. Instead, analyzing circulating cancer markers in various body fluids, commonly referred to as “liquid biopsy”, has recently attracted remarkable interest for their great potential to be applied in non-invasive early cancer screening, tumor progression monitoring and therapy response assessment. Among the various approaches developed for liquid biopsy analysis, surface-enhanced Raman spectroscopy (SERS) has emerged as one of the most powerful techniques based on its high sensitivity, specificity, tremendous spectral multiplexing capacity for simultaneous target detection, as well as its unique capability for obtaining intrinsic fingerprint spectra of biomolecules. In this review, we will first briefly explain the mechanism of SERS, and then introduce recently reported SERS-based techniques for detection of circulating cancer markers including circulating tumor cells, exosomes, circulating tumor DNAs, microRNAs and cancer-related proteins. Cancer diagnosis based on SERS analysis of bulk body fluids will also be included. In the end, we will summarize the “state of the art” technologies of SERS-based platforms and discuss the challenges of translating them into clinical settings.

Stem cell functionality is microenvironmentally defined during tumour expansion and therapy response in colon cancer.

Solid malignancies have been speculated to depend on cancer stem cells (CSCs) for expansion and relapse after therapy. Here we report on quantitative analyses of lineage tracing data from primary colon cancer xenograft tissue to assess CSC functionality in a human solid malignancy. The temporally obtained clone size distribution data support a model in which stem cell function in established cancers is not intrinsically but entirely spatiotemporally orchestrated. Functional stem cells that drive tumour expansion predominantly reside at the tumour edge, close to cancer-associated fibroblasts (CAFs). Hence, stem cell properties change in time depending on the cell location. Furthermore, although chemotherapy enriches for cells with a CSC phenotype, also in this context functional stem cell properties are fully defined by the microenvironment. To conclude, we identified osteopontin (OPN) as a key CAF-produced factor that drives in situ clonogenicity in colon cancer.

Cancer cell plasticity: Impact on tumor progression and therapy response.

Most tumors exhibit intra-tumor heterogeneity, which is associated with disease progression and an impaired response to therapy. Cancer cell plasticity has been proposed as being an important mechanism that, along with genetic and epigenetic alterations, promotes cancer cell diversity and contributes to intra-tumor heterogeneity. Plasticity endows cancer cells with the capacity to shift dynamically between a differentiated state, with limited tumorigenic potential, and an undifferentiated or cancer stem-like cell (CSC) state, which is responsible for long-term tumor growth. In addition, it confers the ability to transit into distinct CSC states with different competence to invade, disseminate and seed metastasis. Cancer cell plasticity has been linked to the epithelial-to-mesenchymal transition program and relies not only on cell-autonomous mechanisms, but also on signals provided by the tumor microenvironment and/or induced in response to therapy. We provide an overview of the dynamic transition for cancer cell states, the mechanisms governing cell plasticity and their impact on tumor progression, metastasis and therapy response. Understanding the mechanisms involved in cancer cell plasticity will provide insights for establishing new therapeutic interventions.

PO-205 Functional characterisation of BRIP1/FANCJ in tumour suppression and therapy response

Introduction The helicase BRIP1 is critically required for genomic maintenance, and BRIP1 helicase deficient germline variants are associated with Fanconi Anaemia (bi-allelic) and various cancers (mono-allelic), in particular ovarian and breast cancer. Cellular based assays and biochemical studies have elucidated the function of BRIP1 in replication stress responses, including interaction partners and enzymatic substrate specificity. However, functional characterisation of BRIP1 for these processes in vivo are largely unexplored, including the importance of BRIP1 as a tumour suppressor for breast cancer, and therapy responses. This project aims to elucidate the functional roles of BRIP1 as a tumour suppressor for breast cancer and in therapy responses. Material and methods We have developed breast tissue-specific knockout mice for BRIP1, and will monitor the development of breast tumours. In addition, we have developed mice deficient for BRIP1 helicase activity (K52R) to further investigate the functional role of BRIP1 as a tumour suppressor. In addition, we will use the mouse models for intervention studies, testing known and novel therapies for BRIP1 deficient breast cancer. Moreover, we will investigate BRIP1 germline variants identified in high-risk breast cancer families by large scale sequencing efforts. This comprehensive list of patient derived mutations will be introduced endogenously in a primary epithelial cell line using a CRISPR-CAS9 approach. To monitor the effect on BRIP1 activity, these cell lines will be tested in cancer relevant functional assays for which BRIP1 deficient cells are known to have a phenotype. Results and discussions This project is at an early stage, and we will present our preliminary data from our BRIP1 mouse models, and from our in vitro CRISPR assay for testing BRIP1 gene variants of uncertain significance (VUS). Conclusion This project is expected to yield novel insight into the regulation of critical genomic stability pathways and provide important knowledge for developing improved germ line variant risk prediction and treatment opportunities for patients.

Serial analysis of mutant KRAS in circulation cell-free DNA (cfDNA) of patients with KRAS mutant metastatic colorectal cancer: A translational study of the KRK0207 trial.

e15599Background: Circulating tumor DNA (ctDNA) is a promising marker for monitoring tumor burden and therapy response in metastatic colorectal cancer (mCRC). The AIO KRK 0207 trial investigated di...

RADIOPHARMACEUTICALS BASED ON THE GLUCOSE DERIVATIVES FOR TUMOR DIAGNOSIS

The purpose of the study was to review available literature on the efficacy of radiopharmaceuticals based on glucose derivatives labeled with radioactive isotopes for detection of various cancers. Material and methods. A systematic literature review was performed using the Scopus, Web of Science, MedLine, Cochrane Library, EMBASE, and Global Health databases from 2000 to 2016. Out of 900 papers in the field of nuclear medicine, 58 were included into the review. Results. 18F-fluoro-2-deoxy-D-glucose (18F-FDG) has been approved to be a powerful imaging tool for the detection of various cancers as well as for the assessment of tumor extent and therapy response. There is a continuous search for new more specific and effective radiopharmaceuticals for visualization of tumor tissue. Many studies are devoted to the development of radiopharmaceuticals based on technetium-99m labeled glucose derivatives for tumor visualization. Russian researches have made a significant progress in the development of imaging agents for single-photon emission computed tomography. Conclusion. Despite the widespread use of positron emission tomography technologies, which have proved to be effective, the specialists still have a great interest in radiopharmaceuticals based on technetium-99m. The literature review suggests that the emergence of a diagnostic radiopharmaceutical based on technetium-99m labeled glucose derivative will help to improve the availability of nuclear medicine methods and their effectiveness.

Conventional and advanced magnetic resonance imaging in patients with high-grade glioma.

Magnetic resonance imaging is integral to the care of patients with high-grade gliomas. Anatomic detail can be acquired with conventional structural imaging, but newer approaches also add capabilities to interrogate image-derived physiologic and molecular characteristics of central nervous system neoplasms. These advanced imaging techniques are increasingly employed to generate biomarkers that better reflect tumor burden and therapy response. The following is an overview of current strategies based on advanced magnetic resonance imaging that are used in the assessment of high-grade glioma patients with an emphasis on how novel imaging biomarkers can potentially advance patient care.

Epigenetic Modifications as Biomarkers of Tumor Development, Therapy Response, and Recurrence across the Cancer Care Continuum.

Aberrant epigenetic modifications are an early event in carcinogenesis, with the epigenetic landscape continuing to change during tumor progression and metastasis—these observations suggest that specific epigenetic modifications could be used as diagnostic and prognostic biomarkers for many cancer types. DNA methylation, post-translational histone modifications, and non-coding RNAs are all dysregulated in cancer and are detectable to various degrees in liquid biopsies such as sputum, urine, stool, and blood. Here, we will focus on the application of liquid biopsies, as opposed to tissue biopsies, because of their potential as non-invasive diagnostic tools and possible use in monitoring therapy response and progression to metastatic disease. This includes a discussion of septin-9 (SEPT9) DNA hypermethylation for detecting colorectal cancer, which is by far the most developed epigenetic biomarker assay. Despite their potential as prognostic and diagnostic biomarkers, technical issues such as inconsistent methodology between studies, overall low yield of epigenetic material in samples, and the need for improved histone and non-coding RNA purification methods are limiting the use of epigenetic biomarkers. Once these technical limitations are overcome, epigenetic biomarkers could be used to monitor cancer development, disease progression, therapeutic response, and recurrence across the entire cancer care continuum.

Thymidine Metabolism as a Confounding Factor for 3'-Deoxy-3'-18F-Fluorothymidine Uptake After Therapy in a Colorectal Cancer Model.

Noninvasive monitoring of tumor therapy response helps in developing personalized treatment strategies. Here, we performed sequential PET and diffusion-weighted MRI to evaluate changes induced by a FOLFOX-like combination chemotherapy in colorectal cancer xenografts, to identify the cellular and molecular determinants of these imaging biomarkers. Methods: Tumor-bearing CD1 nude mice, engrafted with FOLFOX-sensitive Colo205 colorectal cancer xenografts, were treated with FOLFOX (5-fluorouracil, leucovorin, and oxaliplatin) weekly. On days 1, 2, 6, 9, and 13 of therapy, tumors were assessed by in vivo imaging and ex vivo analyses. In addition, HCT116 xenografts, which did not respond to the FOLFOX treatment, were imaged on day 1 of therapy. Results: In Colo205 xenografts, FOLFOX induced a profound increase in uptake of the proliferation PET tracer 3'-deoxy-3'-18F-fluorothymidine (18F-FLT) accompanied by increases in markers for proliferation (Ki-67, thymidine kinase 1) and for activated DNA damage response (γH2AX), whereas the effect on cell death was minimal. Because tracer uptake was unaltered in the HCT116 model, these changes appear to be specific for tumor response. Conclusion: We demonstrated that 18F-FLT PET can noninvasively monitor cancer treatment-induced molecular alterations, including thymidine metabolism and DNA damage response. The cellular or imaging changes may not, however, be directly related to therapy response as assessed by volumetric measurements.

Abstract P5-10-01: Cellular senescence within HER2-amplified breast cancer: Potential implications for breast cancer immune surveillance and HER2-targeted therapy resistance

Abstract Background:Oncogene-induced senescence is considered as a barrier to tumor progression that arrests cells at risk for malignant transformation. Nevertheless, numerous findings demonstrate that senescent cells may also have the opposite function and promote tumor progression through the release of multiple factors called the senescence-associated secretory phenotype or senescence secretome. It is likely that the composition and the physiological consequences mediated by the senescence secretome are dependent on the oncogenes that trigger the senescence program. Breast cancer represents a heterogenous disease that can be divided into breast cancer subtypes caused by different subsets of genetic and epigenetic abnormalities. Therefore, tumor initiation and progression of breast cancer subtypes is triggered by variable oncogenic stimuli, and differences in the senescence secretomes within breast tumors might be responsible for tumor initiation, progression, metastasis and therapeutic response. Beside many studies concerning the role of senescence as a barrier to tumor progression using murine xenograft models very few investigations have been performed to elucidate how often senescent tumor cells appear within untreated human tumors, and if present whether these senescent tumor cells may play a role in disease progression, cancer immunosurveillance and therapy resistance. Methode: In the present study we analysed the appearance of senescent cells within invasive human breast cancers from 129 untreated patients. Cellular senescence was detected by the use of SAβ-gal staining and by immunohistochemical detection of p16, p21, p53, Ki67 and lamin B1. Results: Detection of cellular senescence by the use of SAβ-gal staining and detection of p16, p53, Ki67 and lamin B1 within invasive breast carcinomas indicate that senescent tumor cells varies strongly according to the breast cancer subtype. The highest percentages of senescent tumor cells exist within in the HER2-positive and luminal A breast carcinomas whereas no or very few senescent tumor cells were found in triple negative breast tumors. Based on these findings we suggest that the composition of secretomes released by senescent tumor cells from different breast cancer subtypes might be very distinct in respect to their ability to recruit immune cells, which can eliminate senescent tumor cells on one hand and regulate tumor growth, immune surveillance and therapy resistance on the other. Conclusion: Further characterization of senescent secretomes from HER2 and other breast cancer subtypes and their potential role in tumor progression, immune surveillance and therapy response might be warranted for the understanding of cancer biology as well as prognostic and therapeutic applications. Citation Format: Thaler S, Schad A, Kirkpatrick CJ, Sleeman JP, Springer E, Schmidt M, Cotarelo CL. Cellular senescence within HER2-amplified breast cancer: Potential implications for breast cancer immune surveillance and HER2-targeted therapy resistance [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 P5-10-01.

Inhibition of ATG12-mediated autophagy by miR-214 enhances radiosensitivity in colorectal cancer

Radioresistance hampers success in the treatment of patients with advanced colorectal cancer (CRC). Improving our understanding of the underlying mechanisms of radioresistance could increase patients’ response to irradiation (IR). MicroRNAs are a class of small RNAs involved in tumor therapy response to radiation. Here we found that miR-214 was markedly decreased in CRC cell lines and blood of CRC patients after IR exposure. Meanwhile, autophagy was enhanced in irradiated CRC cells. Mechanically, ATG12 was predicted and identified as a direct target of miR-214 by dual luciferase assay, qPCR, and Western blot. In vitro and in vivo experiments showed that miR-214 promoted radiosensitivity by inhibiting IR-induced autophagy. Restoration of ATG12 attenuated miR-214-mediated inhibition of cell growth and survival in response to IR. Importantly, miR-214 was highly expressed in radiosensitive CRC specimens and negatively correlated with plasma level of CEA. Moreover, ATG12 and LC3 expressions were increased in radioresistant CRC specimens. Our study elucidates that miR-214 promotes radiosensitivity by inhibition of ATG12-mediated autophagy in CRC. Importantly, miR-214 is a determinant of CRC irradiation response and may serve as a potential therapeutic target in CRC treatment.

High-Speed Live-Cell Interferometry: A New Method for Quantifying Tumor Drug Resistance and Heterogeneity.

We report the development of high-speed live-cell interferometry (HSLCI), a new multisample, multidrug testing platform for directly measuring tumor therapy response via real-time optical cell biomass measurements. As a proof of concept, we show that HSLCI rapidly profiles changes in biomass in BRAF inhibitor (BRAFi)-sensitive parental melanoma cell lines and in their isogenic BRAFi-resistant sublines. We show reproducible results from two different HSLCI platforms at two institutions that generate biomass kinetic signatures capable of discriminating between BRAFi-sensitive and -resistant melanoma cells within 24 h. Like other quantitative phase imaging (QPI) modalities, HSLCI is well-suited to noninvasive measurements of single cells and cell clusters, requiring no fluorescence or dye labeling. HSLCI is substantially faster and more sensitive than field-standard growth inhibition assays, and in terms of the number of cells measured simultaneously, the number of drugs tested in parallel, and temporal measurement range, it exceeds the state of the art by more than 10-fold. The accuracy and speed of HSLCI in profiling tumor cell heterogeneity and therapy resistance are promising features of potential tools to guide patient therapeutic selections.

Identification of Potential MR-Derived Biomarkers for Tumor Tissue Response to 177Lu-Octreotate Therapy in an Animal Model of Small Intestine Neuroendocrine Tumor

Magnetic resonance (MR) methods enable noninvasive, regional tumor therapy response assessment, but associations between MR parameters, underlying biology, and therapeutic effects must be investigated. The aim of this study was to investigate response assessment efficacy and biological associations of MR parameters in a neuroendocrine tumor (NET) model subjected to radionuclide treatment. Twenty-one mice with NETs received 177Lu-octreotate at day 0. MR experiments (day −1, 1, 3, 8, and 13) included T2-weighted, dynamic contrast-enhanced (DCE) and diffusion-weighted imaging (DWI) and relaxation measurements (T1/T2*). Tumor tissue was analyzed using proteomics. MR-derived parameters were evaluated for each examination day and for different radial distances from the tumor center. Response assessment efficacy and biological associations were evaluated using feature selection and protein expression correlations, respectively. Reduced tumor growth rate or shrinkage was observed until day 8, followed by reestablished growth in most tumors. The most important MR parameter for response prediction was DCE-MRI–derived pretreatment signal enhancement ratio (SER) at 40% to 60% radial distance, where it correlated significantly also with centrally sampled protein CCD89 (association: DNA damage and repair, proliferation, cell cycle arrest). The second most important was changed diffusion (D) between day −1 and day 3, at 60% to 80% radial distance, where it correlated significantly also with peripherally sampled protein CATA (association: oxidative stress, proliferation, cell cycle arrest, apoptotic cell death). Important information regarding tumor biology in response to radionuclide therapy is reflected in several MR parameters, SER and D in particular. The spatial and temporal information provided by MR methods increases the sensitivity for tumor therapy response.

Abstract A184: Clinical application of whole genome and transcriptome sequencing in cancer care

Abstract Aim: To investigate feasibility and utility of whole genome and RNA sequencing in cancer care. The use of comprehensive personal genomic information to guide cancer treatment decisions has gained momentum in recent years. Here we present the Personalized Oncogenomics (POG) project launched at British Columbia Cancer Agency in 2012. This project uses paired tumor/normal whole genome and transcriptome sequencing to characterize a patient's tumor and inform treatment options within a clinically relevant time frame. In the past 5 years, around 600 patients with metastatic cancers (including 49 pediatric cases) have been sequenced and analyzed, representing over 50 cancer types. The breadth and depth of data in POG enable the detection of multiple types of alterations, from simple mutations, indels, and copy number changes, to more complex alterations such as gene fusion, mutation signatures, and homologous recombination deficiency score. Incorporation of gene expression data through transcriptome sequencing informs on the impact of observed genomic alterations, and provides information regarding specific diagnosis via expression comparison to other cancer subtypes. All genomic and transcriptomic variants are integrated to build a personalized tumor-specific molecular profile, identify actionable items supported by an in-house knowledgebase and publically available molecular oncology, and characterize each individual tumor by intensive pathway analysis and literature search. Such multidimensional data also impose challenges in interpretation and communication. We developed a pipeline to translate complex genomic data into clinically actionable and hypothetical recommendations for the treatment of individual patients. The pipeline produces two reports: a panel-like report that contains known SNVs and fusions with therapeutic relevance from a collection of more than 4000 events, and a second comprehensive and manually curated report to fully characterize the tumor using the whole genome and transcriptome datasets. Genomic data are presented and discussed at a multidisciplinary molecular tumor board consisting of medical oncologists, pathologists, bioinformaticians, geneticists, and biologists. This approach has enabled clinicians to make informed clinical decisions based on the genomic data integrated with other clinical features, as well as to form new treatment-related hypothesis. POG has shown that use of both whole genome and transcriptome sequencing allows identification of therapeutic targets in a significant proportion of patients. Almost 80% cases were found to have one or more actionable alterations (100% in pediatric cases), and almost one-third of these are defined only using RNA data. Based on molecular tumor board discussion, patients are directed to clinical trials, positioned to genomically informed standard-of-care options, or treated with off-label drugs. With demonstrated effectiveness, the integrative approach developed by POG not only provides molecular insight and treatment options into individual tumors, but also provides a rich resource of molecular data with matched clinical information that will aid our understanding of tumor biology and therapy response mechanisms to inform treatment strategies in the future. Citation Format: Yaoqing Shen, Martin R. Jones, Erin Pleasance, Melika Bonakdar, Carolyn Ch'ng, Caralyn Reisle, Laura Williamson, Elisa Majounie, Greg Taylor, Simon Chan, Brandon Pierce, Wei Zhang, Amir Muhammadzadeh, Eric Y. Zhao, Dustin Bleile, Karen Mungall, Nina Thiessen, Eric Chuah, Tina Wong, Richard Corbett, Yussanne Ma, Richard A. Moore, Andrew J. Mungall, Yongjun Zhao, Stephen Yip, Anna F. Lee, Rod Rassekh, Rebecca Deyell, Howard Lim, Daniel Renouf, Robyn Roscoe, Steven J.M Jones, Janessa Laskin, Marco A. Marra. Clinical application of whole genome and transcriptome sequencing in cancer care [abstract]. In: Proceedings of the AACR-NCI-EORTC International Conference: Molecular Targets and Cancer Therapeutics; 2017 Oct 26-30; Philadelphia, PA. Philadelphia (PA): AACR; Mol Cancer Ther 2018;17(1 Suppl):Abstract nr A184.

Abstract 1981: Tissue-engineered bone for longitudinal intravital microscopy of solid tumor growth and therapy response

Abstract Bone metastases are the initial site of progression and account for many of the complications experienced by men with metastatic prostate cancer (PCa), including therapy resistance. Besides cell intrinsic mechanisms, the interaction between PCa cells and the bone microenvironment critically contributes to lesion expansion and drug sensitivity. We here developed a mouse model amenable to intravital multiphoton microscopy (iMPM) to longitudinally study PCa-stromal cell interactions and therapy response in a partially humanized neobone, established in the dermis of the mouse. Tissue engineered bone constructs, TEBCs, were generated by functionalizing polymeric polycaprolactone scaffolds with human mesenchymal stem cells (hMSCs) differentiated to osteoblasts followed by cell-derived calcification of the inter-scaffold space. 30 days after implantation of functionalized scaffolds under the skin of the mouse, bone and bone marrow maturation resulted in a 30mm3 cavity surrounded by optically transparent cortical bone of 50-60 μm thickness, as monitored by microCT and iMPM. Intra-bone tumor growth and osteolysis dynamics caused by human fluorescent PCa cells (PC3) were three-dimensionally reconstructed by multi-parameter detection through a body window, including collagen and bone matrix (SHG), calcified bone (fluorescent bisphosphonates), osteoclasts (cathepsin K), bone surface (THG), blood vessels and stromal phagocytes (fluorescent dextran), and PC3 cells (nuclear H2B/eGFP, cytoplasmatic DsRed2). As a proof of concept, the efficacy to halt bone remodeling during bisphosphonate therapy was detected, revealing the composition and kinetics of the bone-tumor interface. Combining engineered neobone with an optical window is suited to detail the 3D organization and dynamics of cancer lesions in bone and provides mechanistic insight and efficacy predictions for therapy response. Thus, this strategy will be implied to dissect the therapeutic effect of radium 223, a radioisotope with bone seeking properties, and the first agent that improves the duration and quality of life of advanced metastatic PCa patients. By using this model we will test the hypothesis that 223Ra alters stromal niches, structurally and molecularly, in a manner that accounts for the clinical observations in established macroscopic lesions. Citation Format: Eleonora Dondossola, Stephanie Alexander, Boris Holzapfel, Christopher J. Logothetis, Dietmar W. Hutmacher, Peter Friedl. Tissue-engineered bone for longitudinal intravital microscopy of solid tumor growth and therapy response [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 1981. doi:10.1158/1538-7445.AM2017-1981

Abstract IA07: Genetic determinants of tumor development, therapy response and resistance in mouse models of BRCA-deficient breast cancer

Abstract Heterozygous germline mutations in BRCA1 or BRCA2 strongly predispose to development of breast and ovarian cancer (as well as other cancer types) via loss of the remaining wildtype allele. BRCA1/2-deficient cancers are defective in DNA double-strand break (DSB) repair via homologous recombination (HR) and therefore hypersensitive to DNA-damaging agents, including platinum drugs and poly(ADP-ribose) polymerase (PARP) inhibitors. However, these treatments do not result in tumor eradication and eventually resistance develops. To maximize therapeutic efficacy of these drugs and achieve durable remissions, it is important to unravel the mechanisms by which these tumors acquire resistance to platinum drugs and PARP inhibitors, in order to develop combination therapies that prevent development of resistance or re-sensitize resistant tumors. To study therapy response and resistance in a realistic in vivo setting, we have established several genetically engineered mouse models (GEMMs) and patient-derived tumor xenograft (PDX) models for BRCA-deficient breast cancer. These mice develop mammary tumors that are characterized by genomic instability and hypersensitivity to DNA-damaging agents, including platinum drugs and PARP inhibitors. Using cross-species oncogenomics and reverse genetics, we have identified several cancer genes including p53, MYC and RB as critical drivers in BRCA1-associated breast cancer. In addition, we have used these mammary tumor models for preclinical evaluation of therapy response and elucidation of mechanisms of acquired drug resistance. Using functional genetic screens, reverse genetics and genomic analysis of therapy-resistant tumors, we found that therapy response and resistance of BRCA1-deficient mammary tumors to cisplatin and the clinical PARP inhibitor olaparib is affected by several factors, including drug efflux transporter activity, type of BRCA1 founder mutation and restoration of HR repair via loss of 53BP1 or REV7. Also BRCA1 re-activation via genetic or epigenetic mechanisms contributes to therapy resistance in PDX models of BRCA1-deficient breast cancer. Importantly, pharmacokinetic or HR-related mechanisms underlie olaparib-resistance in only a fraction of BRCA1/2-deficient mammary tumors, indicating the existence of additional, unknown mechanisms. Citation Format: Jos Jonkers. Genetic determinants of tumor development, therapy response and resistance in mouse models of BRCA-deficient breast cancer [abstract]. In: Proceedings of the AACR Special Conference on DNA Repair: Tumor Development and Therapeutic Response; 2016 Nov 2-5; Montreal, QC, Canada. Philadelphia (PA): AACR; Mol Cancer Res 2017;15(4_Suppl):Abstract nr IA07.

Clinical impact of circulating tumor cells and therapy response in pancreatic cancer

BackgroundAmong gastrointestinal cancers, the prognosis of pancreatic cancer is one of the poorest, with a large number of patients being diagnosed with unresectable tumors at the first visit to a doctor. The aims of the present study were to investigate the circulating tumor cells (CTC) in peripheral blood in order to assess their clinical significance in patients with pancreatic cancer. MethodsSixty-five patients with advanced pancreatic cancer were enrolled. Borderline resectable pancreatic tumor patients were 9, and Unresectable patients were 56. The CellSearch system was used to isolate and enumerate CTCs. ResultsCTCs were identified in 21 out of 65 patients (32.3%) with only unresectable tumors. The overall survival rate was significantly lower in unresectable patients with than in those without CTCs (P = 0.0051). CTC positivity was significantly higher in patients with than in those without liver metastasis. A multivariate analysis identified the presence or absence of CTCs as an independent prognostic factor. Follow-up blood specimens were obtained from 40 patients treated with chemotherapy or chemoradiotherapy. The incidences of CTC positivity at three months after beginning of treatments in patients with progressive disease and stable disease or a partial response were 45.4% and 24.1%, respectively. The overall survival rate was significantly lower in patients with than in those without CTCs even after treatments (P = 0.045). ConclusionCTC numbers represents a useful tool for predicting prognoses and therapeutic responses to chemotherapy among patients with advanced pancreatic cancer.

Can Shear Wave Elastography Variables Predict the Pathological Response to Neoadjuvant Chemotherapy in Patients with Invasive Breast Cancer?

This study was designed to evaluate the performance of shear wave elastography (SWE) parameters inin predicting the pathological response of invasive breast cancer to neoadjuvant chemotherapy (NAC). The prospective study recruited 25 eligible patients from August 2016 to August 2017. SWE was performed 1 d before biopsy (time point t0, elasticity E0), after the first and second, fourth cycles of anthracycline-based or anthracycline/taxane-based NAC, and compared to a pre-NAC baseline scan. Tumour stiffness was assessed by quantitative SWE velocity. SWE parameters measured included changes in bidimensional tumour size on SWE time, quantitative SWE velocity, the relative changes in them after the first and second, fourth NAC cycles were considered as the variables [Δt1, Δt2, Δt4]. The pathological response was classified according to the residual cancer burden (RCB) protocol, RCB-0 (pCR,0); RCB-I (minimal residual disease, 0-1.36); RCB-II(moderate residual disease, 1.36-3.28); and RCB-III(extensive residual disease, >3.28). The responsive group include RCB 0 and RCB-I, the unresponsive group included RCB II and RCBIII. Correlations between SWE variables and RCB scores were evaluated. The predictive diagnostic performances of SWE parameters, and the predictive RCB (predRCB) score determined by a linear regression model were compared. SWE variables were significantly different among the RCB 0/I and RCBII/III groups. The SWE variables of Δt2had significantly better diagnostic performance than other variables regarding predicting the pathological. Our results suggest that SWE can be potentially used as an early predictor of tumor therapy response during NAC for invasive breast cancer.

Gemcitabine Mechanism of Action Confounds Early Assessment of Treatment Response by 3'-Deoxy-3'-[18F]Fluorothymidine in Preclinical Models of Lung Cancer.

3'-Deoxy-3'-[18F]fluorothymidine positron emission tomography ([18F]FLT-PET) and diffusion-weighted MRI (DW-MRI) are promising approaches to monitor tumor therapy response. Here, we employed these two imaging modalities to evaluate the response of lung carcinoma xenografts in mice after gemcitabine therapy. Caliper measurements revealed that H1975 xenografts responded to gemcitabine treatment, whereas A549 growth was not affected. In both tumor models, uptake of [18F]FLT was significantly reduced 6 hours after drug administration. On the basis of the gemcitabine concentration and [18F]FLT excretion measured, this was presumably related to a direct competition of gemcitabine with the radiotracer for cellular uptake. On day 1 after therapy, [18F]FLT uptake was increased in both models, which was correlated with thymidine kinase 1 (TK1) expression. Two and 3 days after drug administration, [18F]FLT uptake as well as TK1 and Ki67 expression were unchanged. A reduction in [18F]FLT in the responsive H1975 xenografts could only be noted on day 5 of therapy. Changes in ADCmean in A549 xenografts 1 or 2 days after gemcitabine did not seem to be of therapy-related biological relevance as they were not related to cell death (assessed by caspase-3 IHC and cellular density) or tumor therapy response. Taken together, in these models, early changes of [18F]FLT uptake in tumors reflected mechanisms, such as competing gemcitabine uptake or gemcitabine-induced thymidylate synthase inhibition, and only reflected growth-inhibitory effects at a later time point. Hence, the time point for [18F]FLT-PET imaging of tumor response to gemcitabine is of crucial importance. Cancer Res; 76(24); 7096-105. ©2016 AACR.