Pancreatic ductal adenocarcinoma (PDAC) is an inherently chemoresistant tumor. Chemotherapy leads to apoptosis of cancer cells, and in previous studies we have shown that tumor-associated macrophage (TAM) infiltration increases following chemotherapy in PDAC. Since one of the main functions of macrophages is to eliminate apoptotic cells, we hypothesized that TAMs phagocytose chemotherapy-induced apoptotic cells and secrete factors, which favor PDAC chemoresistance. To test this hypothesis, primary human PDAC cultures were treated with conditioned media (CM) from monocyte-derived macrophage cultures incubated with apoptotic PDAC cells (MØApopCM). MØApopCM pretreatment rendered naïve PDAC cells resistant to Gemcitabine- or Abraxane-induced apoptosis. Proteomic analysis of MØApopCM identified YWHAZ/14-3-3 protein zeta/delta (14-3-3ζ), a major regulator of apoptotic cellular pathways, as a potential mediator of chemoresistance, which was subsequently validated in patient transcriptional datasets, serum samples from PDAC patients and using recombinant 14-3-3ζ and inhibitors thereof. Moreover, in mice bearing orthotopic PDAC tumors, the antitumor potential of Gemcitabine was significantly enhanced by elimination of TAMs using clodronate liposomes or by pharmacological inhibition of the Axl receptor tyrosine kinase, a 14-3-3ζ interacting partner. These data highlight a unique regulatory mechanism by which chemotherapy-induced apoptosis acts as a switch to initiate a protumor/antiapoptotic mechanism in PDAC via 14-3-3ζ/Axl signaling, leading to phosphorylation of Akt and activation of cellular prosurvival mechanisms. The data presented therefore challenge the idea that apoptosis of tumor cells is therapeutically beneficial, at least when immune sensor cells, such as macrophages, are present.

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We are indebted to José Germán Casas for CD14-enriched monocyte preparations, Carmen Sánchez Palomo and Esperanza Macarena Rodriguez Serrano for IHC and histological assistance, and María González Dionis for in vitro technical assistance. The research was supported by a Rámon y Cajal Merit Award (RYC-2012-12104) from the Ministerio de Economía y Competitividad, Spain (BS, Jr.), a Clinic and Laboratory Integration Program (CLIP) grant from the Cancer Research Institute (CRI), NY (BS, Jr.), a Coordinated grant (GC16173694BARB) from the Fundación Asociación Española Contra el Cáncer (AECC) (AC and BS, Jr.), Fondo de Investigaciones Sanitarias (FIS) grants PI15/01507 (BS, Jr.), PI15/01715 (LGB) and PI15/02101 (AC) (co-financed through Fondo Europeo de Desarrollo Regional (FEDER) “Una manera de hacer Europa”) from the Instituto de Salud Carlos III (ISCIII), Spain, funding from the Biomedical Research Network in Cancer (CIBERONC:CB16/12/00446) for clinical sample and data collection (AC), funding from the Austrian Science Fund (FWF-B27361) and Ingrid Shaker-Nessmann Foundation for Cancer Research (PM), a Max Eder Fellowship of the German Cancer Aid (111746) (PCH), and by the German Research Foundation (DFG, CRC 1279 “Exploiting the human peptidome for Novel Antimicrobial and Anticancer Agents”) (PCH).

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Author notes

  1. These authors contributed equally: Gabriele D’Errico, Marta Alonso-Nocelo


  1. Department of Biochemistry, Universidad Autónoma de Madrid (UAM), Madrid, Spain

    • Gabriele D’Errico
    • , Marta Alonso-Nocelo
    • , Mireia Vallespinos
    • , Sonia Alcalá
    • , Coral Pedrero García
    • , Laura Martin-Hijano
    • , Sandra Valle
    •  & Bruno Sainz Jr.
  2. Department of Medical Oncology, La Paz University Hospital, Madrid, Spain

    • Gabriele D’Errico
    •  & Jaime Feliu
  3. Department of Cancer Biology, Instituto de Investigaciones Biomédicas “Alberto Sols” (IIBM), CSIC-UAM, Madrid, Spain

    • Marta Alonso-Nocelo
    • , Mireia Vallespinos
    • , Sonia Alcalá
    • , Coral Pedrero García
    • , Laura Martin-Hijano
    • , Sandra Valle
    •  & Bruno Sainz Jr.
  4. Chronic Diseases and Cancer Area 3—Instituto Ramón y Cajal de Investigación Sanitaria (IRYCIS), Madrid, Spain

    • Marta Alonso-Nocelo
    • , Mireia Vallespinos
    • , Sonia Alcalá
    • , Coral Pedrero García
    • , Laura Martin-Hijano
    • , Sandra Valle
    • , Julie Earl
    • , Alfredo Carrato
    •  & Bruno Sainz Jr.
  5. Department of Internal Medicine I, Ulm University, Ulm, Germany

    • Patrick C. Hermann
    •  & Thomas Seufferlein
  6. Biomedical Research Network in Cancer (CIBERONC, CB16/12/00446 and CB16/12/00398), Madrid, Spain

    • Julie Earl
    • , Jaime Feliu
    •  & Alfredo Carrato
  7. Medical Oncology Department, Ramón y Cajal University Hospital, Alcala University, Madrid, Spain

    • Julie Earl
    •  & Alfredo Carrato
  8. Department of Pharmacy, University of Salerno, Fisciano, Salerno, Italy

    • Chiara Cassiano
    •  & Maria Chiara Monti
  9. Molecular Diagnostics Unit—Clinical Research Programme, Spanish National Cancer Research Centre (CNIO), Madrid, Spain

    • Luis Lombardia
  10. Biomarkers and Therapeutic Targets Group—IRYCIS, Madrid, Spain

    • Laura García-Bermejo
  11. Institute for Cancer Research, Comprehensive Cancer Center, Medical University Wien, Vienna, Austria

    • Paola Martinelli


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