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Maintenance of stemness is tightly linked to cell cycle regulation through protein phosphorylation by cyclin-dependent kinases (CDKs). However, how this process is reversed during differentiation is unknown. We report here that exit from stemness and differentiation of pluripotent cells along the neural lineage are controlled by CDC14, a CDK-counteracting phosphatase whose function in mammals remains obscure. Lack of the two CDC14 family members, CDC14A and CDC14B, results in deficient development of the neural system in the mouse and impairs neural differentiation from embryonic stem cells (ESCs). Mechanistically, CDC14 directly dephosphorylates specific proline-directed Ser/Thr residues of undifferentiated embryonic transcription Factor 1 (UTF1) during the exit from stemness, triggering its proteasome-dependent degradation. Multiomic single-cell analysis of transcription and chromatin accessibility in differentiating ESCs suggests that increased UTF1 levels in the absence of CDC14 prevent the proper firing of bivalent promoters required for differentiation. CDC14 phosphatases are dispensable for mitotic exit, suggesting that CDC14 phosphatases have evolved to control stemness rather than cell cycle exit and establish the CDK-CDC14 axis as a critical molecular switch for linking cell cycle regulation and self-renewal.

Background We evaluated a new chemoimmunotherapy combination based on the anti-PD1 monoclonal antibody pembrolizumab and the pyrimidine antimetabolite gemcitabine in HER2- advanced breast cancer (ABC) patients previously treated in the advanced setting, in order to explore a potential synergism that could eventually obtain long term benefit in these patients. Methods HER2-negative ABC patients received 21-day cycles of pembrolizumab 200 mg (day 1) and gemcitabine (days 1 and 8). A run-in-phase (6 + 6 design) was planned with two dose levels (DL) of gemcitabine (1,250 mg/m2 [DL0]; 1,000 mg/m2 [DL1]) to determine the recommended phase II dose (RP2D). The primary objective was objective response rate (ORR). Tumor infiltrating lymphocytes (TILs) density and PD-L1 expression in tumors and myeloid-derived suppressor cells (MDSCs) levels in peripheral blood were analyzed. Results Fourteen patients were treated with DL0, resulting in RP2D. Thirty-six patients were evaluated during the first stage of Simon’s design. Recruitment was stopped as statistical assumptions were not met. The median age was 52; 21 (58%) patients had triple-negative disease, 28 (78%) visceral involvement, and 27 (75%) ≥ 2 metastatic locations. Progression disease was observed in 29 patients. ORR was 15% (95% CI, 5–32). Eight patients were treated ≥ 6 months before progression. Fourteen patients reported grade ≥ 3 treatment-related adverse events. Due to the small sample size, we did not find any clear association between immune tumor biomarkers and treatment efficacy that could identify a subgroup with higher probability of response or better survival. However, patients that experienced a clinical benefit showed decreased MDSCs levels in peripheral blood along the treatment. Conclusion Pembrolizumab 200 mg and gemcitabine 1,250 mg/m2 were considered as RP2D. The objective of ORR was not met; however, 22% patients were on treatment for ≥ 6 months. ABC patients that could benefit of chemoimmunotherapy strategies must be carefully selected by robust and validated biomarkers. In our heavily pretreated population, TILs, PD-L1 expression and MDSCs levels could not identify a subgroup of patients for whom the combination of gemcitabine and pembrolizumab would induce long term benefit. Trial registration ClinicalTrials.gov and EudraCT (NCT03025880 and 2016–001,779-54, respectively). Registration dates: 20/01/2017 and 18/11/2016, respectively.

Background Immune cells (ICs) infiltration and immune checkpoints have been shown to be important for BC patients’ (pts) prognosis and response to immunotherapy. We aimed to analyze the relation between TILs prevalence and PD-L1 expression with efficacy to an immunostimulatory combination with P and Gem in ABC HER2-negative pts previously treated with ≤4 chemotherapy and/or ≥2 hormone therapy lines from the PANGEA-Breast trial (NCT03025880). Methods Pre-treatment (ttm) metastatic BC samples were assessed for TILs density [% of occupied stromal area upon H&E staining] and for PD-L1 immunohistochemistry expression using monoclonal anti-PD-L1 antibody clone 22C3 (Merck) by calculating ICs score (% of positive infiltrated ICs) and combined positive score [CPS; PD-L1 stained cells (tumor cells, lymphocytes, macrophages) divided by total viable tumor cells, multiplied by 100]. Cut-offs ≥5%, ≥10%, ≥30% were explored for TILs. PD-L1 scores were considered positive if ≥1%. Cut-offs (≥5%, ≥20%, ≥50%) were additionally assessed for PD-L1 as CPS. Logistic regression models were used to evaluate association between TILs density and PD-L1 expression with ttm efficacy in terms of Objective Response Rate [ORR; Complete + Partial Response (CR + PR)], Clinical Benefit Rate [CBR; CR + PR + Stable Disease ≥24 weeks] and Progression Free Survival (PFS), according to RECIST v1.1. Results Thirty-six pts were included, 58% had triple negative BC and 98% ECOG score ≤1. Median number of prior ttm lines was 4. ORR and CBR were 15.2% and 17%, respectively; median PFS was 3.1 months. TILs and PD-L1 were evaluated in 30 and 29 pts, respectively. No association was found between TILs density and ttm efficacy in terms of ORR, CBR and PFS. Analysis of PD-L1 ICs score did not reveal any significant association with ORR, CBR or PFS. However, pts with negative PD-L1 expression by CPS ( Citation Format: Luis De la Cruz, María Gion, Josefina Cruz, Jose Luis Alonso, Vanesa Quiroga, Fernando Moreno, Marta Santisteban, Raquel Andrés, Esther Holgado, Natalia Palazón, Luz Milva Rodríguez, Asunción Soto, Javier Cortés, Alfonso Cortés, Manuel Ramos, Maribel Casas, Massimo Chiesa, Susana Bezares, Rosalía Caballero, Federico Rojo. Association of tumor infiltrating lymphocytes (TILs) density and PD-L1 expression with pembrolizumab (P) plus gemcitabine (Gem) efficacy in patients with HER2-negative advanced breast cancer (ABC) from the GEICAM/2015-04 (PANGEA-Breast) study [abstract]. In: Proceedings of the 2020 San Antonio Breast Cancer Virtual Symposium; 2020 Dec 8-11; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2021;81(4 Suppl):Abstract nr PS4-38.

BACKGROUND The appearance of secondary hypertension (HTN) is one of the most common side effects of anti-angiogenic agents since it emerges in over 50% of the patients with these therapies. Independently of tumor type, in most clinical trials it was possible to observe a positive association between secondary HTN and better clinical outcome, including Progression Free Survival (PFS) and Overall Survival (OS). Preeclampsia is one of the biological models that better resembles the anti-VEGF/VEGFR action of these therapies. DNA methylation is one of the epigenetic mechanisms potentially related to variation in susceptibility to gestational HTN. The objective of our study is to define a specific epigenetic signature that could predict secondary HTN to anti-angiogenic treatment in patients that received bevacizumab in combination with chemotherapy (CT) from the BRECOL study. METHODS Patients (n=113) from BRECOL study (NCT01733628) received bevacizumab in combination with oxaliplatin or irinotecan + fluoropyrimidines for metastatic colorectal cancer (n=49), and with paclitaxel or capecitabine for metastatic breast cancer (n=64). Blood pressure (BP) was recorded with a Holter measurement (24 hours registration starting 2 hours after treatment administration). A methylation analysis was carried out on DNA obtained from pretreatment peripheral blood samples in 32 patients (28%) distributed in 4 experimental groups (8 patients / each) and classified according to their HTN history and to their BP variation upon bevacizumab plus CT: • Group A: patients with HTN history and with BP increase • Group B: patients with HTN history and with no BP increase • Group C: patients without HTN history and with BP increase • Group D: patients without HTN history and with no BP increase Analysis was realized with the “Infinium Human Methylation EPIC BeadChip” array (Illumina®) on bisulfite-converted DNA and differentially methylated sites were identified with the LIMMA (“Linear Models for Microarray Analysis”) bioinformatics tool (Bioconductor®). RESULTS Upon analysis of 850000 different methylation sites distributed all over the genome, we identified 27 (18 localized in the coding regions of the genes: FMNL2, METTL3, ACOT6, SCARNA20, PREX1, DNAI2, RAET1G, KCNJ8, GDF7, SYNPO2, CUGBP1, FRMD8, MKL2, HIF1A, TMEM177, UTP23, PXK and TNPO1; 9 localized in intergenic regions) that are differentially methylated in patients that showed secondary HTN to bevacizumab plus CT, independently of HTN history (Groups A + C vs. B + D). Based on Principal Components (PC) analysis, we defined a methylation score predictive of elevated BP. First PC (PC1) explains the 83.2% of the variability of the 27 identified methylation sites and allows to distinguish between patients that do and do not show secondary HTN. CONCLUSIONS High BP upon anti-angiogenic treatment is associated to specific DNA methylation profiles. We identified an epigenetic methylation signature putative predictive of secondary HTN to bevacizumab treatment in metastatic breast and colorectal cancer. Citation Format: Juan de la Haba, Teresa Morales-Ruiz, Pilar García-Alfonso, Jose Ponce Lorenzo, Lourdes Calvo, Antonio Antón, Raul Marquez, Pedro Sánchez-Rovira, Ana Santaballa, Eva Ciruelos, María Victoria García-Ortiz, Teresa Roldán-Arjona, Jesús Herranz, Massimo Chiesa, Rosalía Caballero, Javier Gallego, Álvaro Rodríguez-Lescure. Identification of a specific epigenetic signature in patients showing secondary hypertension upon anti-VEGF treatment from the GEICAM/2011-04 (BRECOL) study [abstract]. In: Proceedings of the 2019 San Antonio Breast Cancer Symposium; 2019 Dec 10-14; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2020;80(4 Suppl):Abstract nr P4-10-28.

The PANGEA-Breast trial evaluated a new chemo-immunotherapeutic combination that would synergistically induce long-term clinical benefit in HER2-negative advanced breast cancer patients. Treatment consisted of 21-day cycles of 200 mg of pembrolizumab (day 1) plus gemcitabine (days 1 and 8). The primary objective was the objective response rate (ORR). The tumor infiltrating lymphocytes (TILs) density and PD-L1 expression in tumor, and the myeloid-derived suppressor cells (MDSCs) level in peripheral blood, were analyzed to explore associations with treatment efficacy. Considering a two-stage Simon’s design, the study recruitment was stopped after its first stage as statistical assumptions were not met. A subset of 21 triple-negative breast cancer (TNBC) patients was enrolled. Their median age was 49 years, 15 patients had visceral involvement, and 16 had ≤3 metastatic locations. Treatment discontinuation due to progressive disease (PD) was reported in 16 patients. ORR was 15% (95% CI 3.2–37.9). Four patients were on treatment &gt, 6 months before PD. Grade ≥3 treatment-related adverse events were observed in 8 patients, where neutropenia was the most common. No association was found between TILs density, PD-L1 expression or MDSCs levels and treatment efficacy. ORR in TNBC patients also did not meet the assumptions, but 20% were on treatment &gt, 6 months.

Background Copy Number Alterations (CNAs) represent changes in the copy number of genomic segments of somatic cells due to chromosomal instability. CNAs include gene amplifications or deletions and can be involved in tumorigenesis. We analyzed CNAs data in pre- and post-treatment (ttm) tumors from patients (pts) with early breast cancer (BC) in the neoadjuvant trials GEICAM/2006-03 and GEICAM/2006-14, with the aim to identify CNAs in particular genomic regions (genetic entropy) associated with treatment response. Methods GEICAM/2006-03 (NCT00432172) HER2-negative pts were selectively treated according to clinical subtypes: triple negative (TN) pts were treated with standard anthracycline/taxane -based chemotherapy (AT-CT) +/- carboplatin, while luminal patients were randomized to AT-CT vs. hormonotherapy; GEICAM/2006-14 (NCT00841828) HER2+ pts received AT-CT plus anti-HER2 therapy.Shallow-whole genome Illumina sequencing DNA data from 204 paraffin-embedded tumors (100 pre- and 104 post-ttm) were segmented to obtain CNAs and recurrent altered genomic regions were defined. We used Wilcoxon test to analyze the frequency of altered regions and logistic regression analyses to explore their association with tumor response, in terms of pathological complete response (pCR) in breast and axilla. Validation of altered genes associated with therapy response was performed in the microarray gene expression-based Hatzis dataset (GSE25066) from pts receiving neoadjuvant AT-CT (1). Results A total of 672 regions covering the whole genome were identified upon analysis of CNAs data. Regions were categorized according to their alteration status as amplified, normal and lost. Comparative analysis of alterations revealed 11 regions significantly different (p Conclusions According to our results, neoadjuvant therapy can modulate genomic aberrations landscape in BC. Our data suggest that amplification of specific genes in the genomic locus (21q22.12) is involved in the neoadjuvant therapy response in early BC. (1): Hatzis et al., JAMA 2011, 305(18) 1873-81 Citation Format: Alba E, Rueda OM, Lluch A, Albanell J, Chin S-F, Chacón JI, Calvo L, De la Haba-Rodriguez J, Bermejo B, Ribelles N, Sánchez-Rovira P, Plazaola A, Barnadas A, Cirauqul B, Ramos M, Arcusa A, Carrasco E, Herranz J, Chiesa M, Caballero R, Santonja A, Rojo F, Caldas C. Genome copy number entropy as predictor of response for neoadjuvant therapy in early breast cancer [abstract]. In: Proceedings of the 2018 San Antonio Breast Cancer Symposium; 2018 Dec 4-8; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2019;79(4 Suppl):Abstract nr P5-12-03.

Identification of the different elements intervening at the immunoedition process, in each body compartment, seems key to explain clinical evolution in several tumor types. In this study, a set of immune biomarkers (myeloid derived suppressor cells, regulatory T cells, and OX40+ and PD-1+ T lymphocytes counts) in peripheral blood of patients diagnosed with advanced breast cancer, were analyzed prior to and along the implementation of first line antineoplastic therapy. Subsequently, a formal comparison between groups with clinical benefit versus progression of disease and with a healthy women cohort was executed. Results reflected that patients basally showed higher levels of myeloid derived suppressor cells (35.43, IR=180.73 vs 17.53, IR=16.96 cells/μl; p=0.001) and regulatory T cells (32.05, IR=29.84 vs 22.61, IR=13.57 cells/μl; p=0.001) in comparison with healthy women. Furthermore, after therapy, an increase in the number of activated T lymphocytes (expressing OX40), and a decrease of immune inhibitory cells (MDSCs, and Tregs), and the number of inhibited (or exhausted) T lymphocytes (expressing PD-1), could be ascertained in patients with clinical benefit (p≤0.001). The opposite trend was observed in the case of disease progression. These findings suggest that some critical immune elements can be easily detected and measured in peripheral blood, which open a new opportunity for translational research, as they seem to be clearly correlated with clinical evolution, at least in ABC.

Immunology and immunotherapy of cancer is an expanding field in oncology, with recent great achievements obtained through the new successful approaches implemented to circumvent immune evasion, which is undoubtedly considered a novel hallmark of cancer. Translational research in this topic has revealed targets that can be modulated in the clinical setting with new compounds and strategies. Like most of the tumors, breast cancer is considered a complex and heterogeneous disease in which host immune responses have been also recently demonstrated of critical relevance. T infiltrating lymphocyte measurement is suggested as a powerful new tool necessary to predict early breast cancer evolution, especially for the her2-positive and triple-negative subtypes. Other biomarkers in tissue and peripheral blood are under intense scrutiny to ascertain their eventual role as prognostic and/or predictive factors. This background has fueled the interest in developing clinical research strategies to test activity of modern immunotherapy in breast cancer, which constitutes the main focus of this review.

Background dNLR is a novel biomarker associated with clinical outcome in solid tumors including early stage breast cancer (BC). Here we report the association of dNLR with pCR in triple-negative (TN) and luminal BC patients (pts) treated with neoadjuvant CT. Methods This was a retrospective analysis of two randomized studies (GEICAM/2006-03 - NCT00432172 and ETNA - NCT01822314) involving 821 pts with early stage (>2cm) or locally advanced TN or luminal BC receiving anthracycline/taxane-based CT +/- carboplatin (GEICAM/2006-03) or nab-paclitaxel/paclitaxel followed by anthracycline regimen (ETNA). dNLR was calculated as the ratio of neutrophils and the difference between total leukocytes and neutrophils in peripheral blood before CT (baseline) and at the end of treatment (EOT). Logistic regression analyses were used to explore dNLR association with pCR at the two time points by molecular subtype. Results 684 and 137 pts were from ETNA and GEICAM/2006-03 study respectively (TN n = 308; Luminal n = 513). In TN subgroup median baseline dNLR was 1.61 [interquartile range (IQR): 1.25-2.04] and at EOT 1.65 (IQR: 0.96-2.22). In luminal BC median baseline dNLR was 1.68 (IQR: 1.22-1.96) and at EOT 1.48 (IQR: 0.86-1.93). No association with pCR was found in luminal BC. Baseline dNLR was associated with pCR in TNBC in univariate analysis (OR: 0.709, CI: 0.5-1.006, p = 0.0406). At EOT significant association of dNLR as continuous variable with pCR was observed in TNBC both in univariate and multivariate analysis (OR: 0.665, CI: 0.501-0.884, p = 0.0034, n = 255 and OR: 0.62, CI: 0.406-0.946, p = 0.0231, n = 228 respectively). Quartiles distribution of EOT dNLR was also associated with pCR in univariate and multivariate analysis (Q1 vs combined Q2/Q3/Q4 group: OR: 0.32, CI: 0.17-0.64, p = 5e-04 and OR: 0.26, CI: 0.1-0.63, p = 0.002 respectively). Also a ROC curve - based optimal cut off method revealed significant association of EOT dNLR with pCR in TNBC (>2.231, OR: 0.43, CI: 0.25-0.74, p = 0.0035). Conclusions No association was found between dNLR and pCR in luminal BC. High dNLR levels at baseline and especially EOT seem to be associated with worse clinical outcome in TN tumors after neoadjuvant CT. Clinical trial identification GEICAM/2006-03 - NCT00432172: 07 Feb 2007 ETNA - NCT01822314: 02 Abr 2013. Legal entity responsible for the study GEICAM Spanish Breast Cancer Group. Funding Has not received any funding. Disclosure M. Mansutti: Advisory / Consultancy: Celgene; Advisory / Consultancy: Novartis; Advisory / Consultancy: Pfizer; Travel / Accommodation / Expenses: Roche; Travel / Accommodation / Expenses: AstraZeneca. A. Lluch: Research grant / Funding (self), Research grant / Funding (institution): Amgen; Research grant / Funding (self), Research grant / Funding (institution): AstraZeneca; Research grant / Funding (self), Research grant / Funding (institution): Boehringer-Ingelheim; Research grant / Funding (self), Research grant / Funding (institution): GSK; Advisory / Consultancy, Research grant / Funding (self), Research grant / Funding (institution): Novartis; Advisory / Consultancy, Research grant / Funding (self), Research grant / Funding (institution): Pfizer; Advisory / Consultancy, Research grant / Funding (self), Research grant / Funding (institution): Roche/Genentech; Advisory / Consultancy, Research grant / Funding (self), Research grant / Funding (institution): Eisai; Advisory / Consultancy, Research grant / Funding (self), Research grant / Funding (institution): Celgene; Research grant / Funding (self), Research grant / Funding (institution): Pierre-Fabre. M. Thill: Honoraria (self), Advisory / Consultancy, Research grant / Funding (institution), Travel / Accommodation / Expenses: Genomic Health; Honoraria (self), Advisory / Consultancy, Travel / Accommodation / Expenses: Amgen; Honoraria (self), Advisory / Consultancy, Travel / Accommodation / Expenses: AstraZeneca; Honoraria (self), Advisory / Consultancy, Travel / Accommodation / Expenses: Celgene; Honoraria (self), Advisory / Consultancy, Travel / Accommodation / Expenses: Eisai; Honoraria (self): Hexal; Honoraria (self), Travel / Accommodation / Expenses: Medtronic; Honoraria (self), Advisory / Consultancy, Travel / Accommodation / Expenses: MSD; Honoraria (self), Advisory / Consultancy, Travel / Accommodation / Expenses: Myriad; Honoraria (self), Advisory / Consultancy, Travel / Accommodation / Expenses: Novartis; Honoraria (self), Advisory / Consultancy, Travel / Accommodation / Expenses: Pfizer; Honoraria (self), Advisory / Consultancy, Travel / Accommodation / Expenses: PFM Medical; Honoraria (self), Advisory / Consultancy, Travel / Accommodation / Expenses: Roche; Honoraria (self), Advisory / Consultancy, Travel / Accommodation / Expenses: RTI Surgical; Honoraria (self), Advisory / Consultancy, Travel / Accommodation / Expenses: Teva; Advisory / Consultancy, Travel / Accommodation / Expenses: Biom-up; Advisory / Consultancy, Travel / Accommodation / Expenses: Lilly; Advisory / Consultancy, Travel / Accommodation / Expenses: Neodynamics; Advisory / Consultancy, Travel / Accommodation / Expenses: Norgine; Advisory / Consultancy, Travel / Accommodation / Expenses: Tesaro. L. Gianni: Advisory / Consultancy, MetIS, Novartis, Odonate Therapeutics, Revolution Medicine, Synaffix, Zymeworks: CONSULTANCY: ADC Therapeutics,; Advisory / Consultancy, RESEARCH FUNDING (institution): Zymeworks, Daiichi SankyoZymeworks, Daiichi Sankyo: AstraZeneca; Advisory / Consultancy, PATENTS, ROYALTIES: European Patent Application N. 12195182.6 and 12196177.5’, Roche: Celgene; Advisory / Consultancy: Lilly; Advisory / Consultancy: G1 Therapeutics; Advisory / Consultancy: Genentech; Advisory / Consultancy: Genomic Health; Advisory / Consultancy: MSD; Advisory / Consultancy: Oncolytics Biotech; Advisory / Consultancy: Odonate Therapeutics; Advisory / Consultancy: Onkaido; Advisory / Consultancy: Roche; Advisory / Consultancy: Pfizer; Advisory / Consultancy: Tahio Pharmaceutical; Advisory / Consultancy: Sandoz; Advisory / Consultancy: SeaGen,; Advisory / Consultancy: Synthon; Advisory / Consultancy: Zymeworks,; Advisory / Consultancy: CD47; Advisory / Consultancy: GENENTA. All other authors have declared no conflicts of interest.

Cancer immunology has gained renewed interest in the past few years due to emerging findings on mechanisms involved in tumoral immune evasion. Indisputably, immune edition is currently considered a critical hallmark of cancer. Basic research has revealed new targets which can be modulated in the clinical setting with new compounds and strategies. As recent evidence confirms, breast cancer (BC) is a complex and heterogeneous disease in which host immune responses play a substantial role. T-infiltrating lymphocytes measurement is suggested as a powerful new tool necessary to predict early BC evolution, especially in HER2-positive and triple negative subtypes. However, T-infiltrating lymphocytes, genomic platforms, and many other biomarkers in tissue and peripheral blood (e.g., regulatory T cells and myeloid-derived suppressor cells) are not the only factors being evaluated regarding their potential role as prognostic and/or predictive factors. Many ongoing clinical trials are exploring the activity of immune checkpoint modulators in BC treatment, both in the advanced and neoadjuvant setting. Although this field is expanding with exciting new discoveries and promising clinical results-and creating great expectations-there remain many uncertainties yet to be addressed satisfactorily before this long awaited therapeutic promise can come to fruition.

Spanish Ministry of Health Spanish Ministry of Science and Innovation Fundacio Marato de TV3, Spain

The stromal vascular fraction (SVF) of adipose tissue is an easy to obtain source of adipose tissue-derived stem cells (ADSCs). We and others have achieved significant but suboptimal therapeutic effects with ADSCs in various settings, mainly due to low rates of differentiation into specific cell types and with the downside of undesired side effects as a consequence of the undifferentiated ADSCs. These data prompted us to find new stem cell-specific markers for ADSCs and/or subpopulations with higher differentiation potential to specific lineages. We found a subpopulation of human ADSCs, marked by c-Kit positiveness, resides in a perivascular location, and shows higher proliferative activity and self-renewal capacity, higher telomerase activity and expression, higher in vitro adipogenic efficiency, a higher capacity for the maintenance of cardiac progenitors, and higher pancreatogenic and hepatogenic efficiency independently of CD105 expression. Our data suggests that the isolation of ADSC subpopulations with anti-c-Kit antibodies allows for the selection of a more homogeneous subpopulation with increased cardioprotective properties and increased adipogenic and endodermal differentiation potential, providing a useful tool for specific therapies in regenerative medicine applications.

2543 Background: High levels of myeloid-derived suppressor cells (MDSCs) seem a negative prognostic factor in advanced breast cancer (ABC) patients (pts). Preclinical studies suggest an immunomodulatory effect of some classical anti-tumor agents through alteration of MDSCs homeostasis. We analyzed the association of MDSCs and clinical evolution of ABC pts, taking into account the systemic treatment (tx) modulation of MDSCs levels in pts from two studies (“A”: GEICAM/2015-04 PANGEA-BREAST, NCT03025880 “Efficacy and Safety of Pembrolizumab and Gemcitabine in HER2-negative ABC”, and “B”: PI-0502-2014 “Peripheral blood analyses of immune response induced by 1st line tx of ABC according to clinical guidelines”). Methods: MDSCs (CD33+ CD11b+) levels were determined by flow-cytometry in peripheral blood samples at three time points (basal, at cycles 3 and 6) from: 39 HER2-negative heavily pretreated pts from study “A”, 43 non-pretreated pts (all subtypes) from study “B” and 20 women from a healthy cohort (HC), with no cancer diagnosis. MDSCs levels from the different cohorts were compared and correlated with pts with Clinical Benefit (CB: partial/complete response + disease stabilization) vs pts with Progressive Disease (PD). Results: Tx response was assessed in 33 pts (85%) from study “A” and 39 pts (91%) from study “B”. CB was observed in 11 pts (28%) from study “A” and in 34 (79%) from study “B” while PD was observed in 22 pts (56%) from study “A” and in 5 (12%) from study “B”. Basal MDSCs levels were significantly higher in ABC pts (studies “A”+”B”) than in HC (15.95 vs 0.81 cells/µl, p = 0.009). At cycle 6, MDSCs were considerably lower in pts with CB vs DP (2.90 vs 13.75 cells/µl, p < 0.001). This decrease was more pronounced in study “B” than in study “A” pts (p < 0.001 vs p = 0.074, respectively), probably due to differences in number of events, tumor subtypes and tx between both studies. Conclusions: Our results suggest that ABC pts show alterations in MDSCs and that their decrease along tx may have a positive predictive value, highlighting the importance that immune-competent status may play in the evolution of ABC. MDSCs may represent a target for therapeutic purposes in ABC.

Cdc14 is a dual-specific phosphatase with relevant functions during mitotic exit in yeast. The relevance of vertebrate Cdc14 phosphatases is not well understood due to the presence of two paralogs, Cdc14A and Cdc14B, and their dispensability for cell cycle progression. Here, we report that overexpression of mammalian Cdc14B, but not Cdc14A, leads to dramatic changes in morphology and malignant transformation of normal murine fibroblasts. Cdc14B disrupts the cytoskeletal F-actin organization with loss of actin stress fibers and vinculin adhesions in a phosphatase-dependent manner. These morphological changes are associated to cellular transformation, as Cdc14B-overexpressing cells display anchorage-independent growth and are able to form tumors in vivo. These alterations are similar to those induced by Ras oncogenes ,and both Cdc14B and H-RasV12 lead to similar changes in the transcriptional profile of transformed cells. Pharmacologic inhibition of the Ras-Mek pathway rescues these defects. These data suggest that Cdc14B, but not Cdc14A, is one of the few phosphatases that display oncogenic activity in mammals and point to the Ras-MAP kinase pathway as a major effector pathway during oncogenic transformation by Cdc14B.

592Background: Genomic instability (GI) drives tumor development, generates selective clonal competence and enhances cancer aggressiveness. Copy Number Alterations (CNAs) data from a cohort of pre-...

579Background: Integrative Clustering (IntClust) is a breast cancer (BC) classification of 10 different subgroups with distinctive molecular profiles and clinical outcomes (Curtis et al., Nature 20...

Purpose: To evaluate the in vivo biocompatibility of grafts composed of sheets of decellularized human corneal stroma with or without the recellularization of human adipose derived adult stem cells (h-ADASC) into the rabbit cornea. Methods: Sheets of human corneal stroma of 90 gm thickness were decellularized, and their lack of cytotoxicity was assayed. The recellularization was achieved by the injection of 2 x 10(5) labeled h-ADASC in the graft followed by five days of cell culture. The grafts were implanted in vivo into a stromal pocket at 50% depth. After a triple-masked three-month follow-up, the animals were euthanized and the bio-integration of the graft, the viability of the stem cells and the expression of keratocan (human keratocyte-specific protein) were assessed. Results: The decellularized stromal sheets showed an intact extracellular matrix with a decellularization rate of 92.8% and an excellent recellularization capacity in vitro with h-ADASC. A complete and stable graft transparency was observed during the full follow-up, with absence of any clinical sign of rejection. The postmortem analysis demonstrated the survival of the transplanted human stem cells inside the graft and their differentiation into functional keratocytes, as assessed by the expression of human keratocan. Conclusions: We report a new model of lamellar keratoplasty that requires only a simple and safe procedure of liposuction and a donor allogeneic cornea to provide an optically transparent autologous stromal graft with excellent biocompatibility and integration into the host tissue in a rabbit model This work was supported in part by grants CEN-20091021 from the Spanish Ministry of Health, IAP-560610-2008-44 and SAF2010-19230 from the Spanish Ministry of Science and Innovation, and from Fundacio Marato de TV3, Spain.

Currently available keratoprosthesis models (nonbiological corneal substitutes) have a less than 75% graft survival rate at 2 years. We aimed at developing a model for keratoprosthesis based on the use of poly(ethyl acrylate) (PEA)-based copolymers, extracellular matrix-protein coating and colonization with adipose-derived mesenchymal stem cells. Human adipose tissue derived mesenchymal stem cells (h-ADASC) colonization efficiency of seven PEA-based copolymers in combination with four extracellular matrix coatings were evaluated in vitro. Then, macroporous membranes composed of the optimal PEA subtypes and coating proteins were implanted inside rabbit cornea. After a 3-month follow-up, the animals were euthanized, and the clinical and histological biointegration of the implanted material were assessed. h-ADASC adhered and survived when cultured in all PEA-based macroporous membranes. The addition of high hydrophilicity to PEA membranes decreased h-ADASC colonization in vitro. PEA-based copolymer containing 10% hydroxyethyl acrylate (PEA-HEA10) or 10% acrylic acid (PEA-AAc10) monomeric units showed the best cellular colonization rates. Collagen plus keratan sulfate-coated polymers demonstrated enhanced cellular colonization respect to fibronectin, collagen, or uncoated PEAs. In vivo implantation of membranes resulted in an extrusion rate of 72% for PEA, 50% for PEA-AAc10, but remarkably of 0% for PEA-HEA10. h-ADASC survival was demonstrated in all the membranes after 3 months follow-up. A slight reduction in the extrusion rate of h-ADASC colonized materials was observed. No significant differences between the groups with and without h-ADASC were detected respect to transparency or neovascularization. We propose PEA with low hydroxylation as a scaffold for the anchoring ring of future keratoprosthesis.

We have recently demonstrated that regulation of Cdc25A protein abundance during S phase and in response to DNA damage is mediated by SCF(betaTrCP) activity. Based on sequence homology of known betaTrCP substrates, we found that Cdc25A contains a conserved motif (DSG), phosphorylation of which is required for interaction with betaTrCP.1 Here, we show that phosphorylation at Ser 82 within the DSG motif anchors Cdc25A to betaTrCP and that Chk1-dependent phosphorylation at Ser 76 affects this interaction as well as betaTrCP-dependent degradation. We propose that a hierarchical order of phosphorylation events commits Cdc25A to betaTrCP-dependent degradation. According to our model, phosphorylation at Ser 76 is a "priming" step required for Ser 82 phosphorylation, which in turn allows recruitment of Cdc25A by betaTrCP and subsequent betaTrCP-dependent degradation.

This work is licensed under a Creative Commons Attribution-NonCommercial., Cdc14 is an essential phosphatase in yeast but its role in the mammalian cell cycle remains obscure. We report here that Cdc14b-knockout cells display unscheduled induction of multiple cell cycle regulators resulting in early entry into DNA replication and mitosis from quiescence. Cdc14b dephosphorylates Ser5 at the C-terminal domain (CTD) of RNA polymerase II, a major substrate of cyclin-dependent kinases. Lack of Cdc14b results in increased CTD-Ser5 phosphorylation, epigenetic modifications that mark active chromatin, and transcriptional induction of cell cycle regulators. These data suggest a function for mammalian Cdc14 phosphatases in the control of transcription during the cell cycle., This work was funded by grants from the Association for International Cancer Research (AICR #08-0188), Foundation Ramón Areces, and the Spanish Ministry of Science and Innovation (MICINN; BFU2008-04293 to M.S.; SAF2009-07973 to M.M.). The Cell Division and Cancer Group of the CNIO is supported by the OncoCycle Programme (S-BIO-0283-2006) from the Comunidad de Madrid, the OncoBIO Consolider-Ingenio 2010 Programme (CSD2007- 00017) from the MICINN, Madrid, and the European Union Seventh Framework Programme (MitoSys project; HEALTH-F5-2010-241548).

In eukaryotic cells, control mechanisms of cell-cycle progression have evolved to accurately monitor the integrity of genetic information to be transferred to the progeny. Cdc25A phosphatase is an essential activator of cell-cycle progression and is targeted by checkpoint signals. Ubiquitylation regulates Cdc25A activity through fine tuning of its protein levels. Two different ubiquitin ligases (APC/C and SCF complex) are involved in Cdc25A turnover. While APC/C is involved in regulating Cdc25A at the exit of mitosis, SCF regulates the abundance of Cdc25A in S phase and G2. In response to DNA damage or to stalled replication, the activation of the ATM and ATR protein kinases leads to Chk1 and Chk2 activation and to Cdc25A hyperphosphorylation. These events stimulate SCF-mediated ubiquitylation of Cdc25A and its proteolysis. This contributes to delaying cell-cycle progression, thereby preventing genomic instability. Based on recent findings, we discuss the role of Cdc25A ubiquitylation and degradation in cell-cycle progression and in response to DNA damage. Moreover, we discuss the role of phosphorylation at multiple sites in triggering ubiquitylation signals.

We have recently demonstrated that regulation of Cdc25A protein abundance during S phase and in response to DNA damage is mediated by SCF(betaTrCP) activity. Based on sequence homology of known betaTrCP substrates, we found that Cdc25A contains a conserved motif (DSG), phosphorylation of which is required for interaction with betaTrCP.1 Here, we show that phosphorylation at Ser 82 within the DSG motif anchors Cdc25A to betaTrCP and that Chk1-dependent phosphorylation at Ser 76 affects this interaction as well as betaTrCP-dependent degradation. We propose that a hierarchical order of phosphorylation events commits Cdc25A to betaTrCP-dependent degradation. According to our model, phosphorylation at Ser 76 is a "priming" step required for Ser 82 phosphorylation, which in turn allows recruitment of Cdc25A by betaTrCP and subsequent betaTrCP-dependent degradation.

Several reports have shown that the ectopic expression of the human telomerase catalytic subunit gene (hTERT) leads to an indefinite extension of the life span of human fibroblasts cultured in vitro without the appearance of cancer-associated changes. We infected two fibroblast strains derived from centenarian individuals with an hTERT containing retrovirus and isolated transduced massive populations (cen2tel and cen3tel). In both populations, hTERT expression reconstituted telomerase activity and extended the life span. In cen2tel, a net telomere lengthening was observed while, in cen3tel, telomeres stabilized at a length lower than that detected in senescent parental cells. Interestingly, both cen2tel and cen3tel cells developed chromosome anomalies, numerical first and structural thereafter. Moreover, cen3tel cells acquired the ability to grow in the absence of solid support, a typical feature of transformed cells. The results we present here highlight an unexpected possible outcome of cellular immortalization driven by telomerase reactivation, and indicate that, in some cases, an artificial extension of cellular replicative capacity can increase the probability of occurrence of genomic alterations, which can lead to cellular transformation.

The Cdc25A phosphatase is essential for cell-cycle progression because of its function in dephosphorylating cyclin-dependent kinases. In response to DNA damage or stalled replication, the ATM and ATR protein kinases activate the checkpoint kinases Chk1 and Chk2, which leads to hyperphosphorylation of Cdc25A. These events stimulate the ubiquitin-mediated proteolysis of Cdc25A and contribute to delaying cell-cycle progression, thereby preventing genomic instability. Here we report that beta-TrCP is the F-box protein that targets phosphorylated Cdc25A for degradation by the Skp1/Cul1/F-box protein complex. Downregulation of beta-TrCP1 and beta-TrCP2 expression by short interfering RNAs causes an accumulation of Cdc25A in cells progressing through S phase and prevents the degradation of Cdc25A induced by ionizing radiation, indicating that beta-TrCP may function in the intra-S-phase checkpoint. Consistent with this hypothesis, suppression of beta-TrCP expression results in radioresistant DNA synthesis in response to DNA damage--a phenotype indicative of a defect in the intra-S-phase checkpoint that is associated with an inability to regulate Cdc25A properly. Our results show that beta-TrCP has a crucial role in mediating the response to DNA damage through Cdc25A degradation.