The conflicting roles of tumor stroma in pancreatic cancer and their contribution to the failure of clinical trials: a systematic review and critical appraisal

• Published in: Cancer and metastasis reviews Vol. 34; no. 1; pp. 97 - 114
• Main Authors: Bijlsma, Maarten F., van Laarhoven, Hanneke W. M.
• Format: Journal Article
• Language: English
• Published: New York Springer US 01.03.2015; Springer; Springer Nature B.V
• Subjects: Animals; Antineoplastic Combined Chemotherapy Protocols - therapeutic use; Biomarkers, Tumor - metabolism; Biomedical and Life Sciences; Biomedicine; Cancer Research; Carcinoma, Pancreatic Ductal - drug therapy; Carcinoma, Pancreatic Ductal - metabolism; Carcinoma, Pancreatic Ductal - pathology; Clinical; Clinical trials; Humans; Oncology; Pancreas - drug effects; Pancreas - metabolism; Pancreas - pathology; Pancreatic cancer; Pancreatic Neoplasms - drug therapy; Pancreatic Neoplasms - metabolism; Pancreatic Neoplasms - pathology; Stromal Cells - drug effects; Stromal Cells - metabolism; Stromal Cells - pathology; Treatment Outcome; Tumor Microenvironment - drug effects; Stroma; Smooth muscle actin; Hedgehog; Desmoplasia; Pancreatic cancer
• ISSN: 0167-7659; 1573-7233
• DOI: 10.1007/s10555-014-9541-1

A nearly universal feature of pancreatic ductal adenocarcinoma (PDAC) is an extensive presence of activated stroma. This stroma is thought to aid in various tumor-promoting processes and hampers response to therapy. Here, we aim to evaluate the evidence that supports this role of the stroma in PDAC with functional experiments in relevant models, discuss the clinical trials that have aimed to target the stroma in this disease, and examine recent work that explains why these clinical trials based on stroma-targeting strategies have thus far not achieved the expected success. We systematically searched PubMed through August 2014 with no restrictions to identify published peer-reviewed research articles assessing the effect of targeting the stroma on tumor growth or metastases in preclinical animal models. Five hundred and thirty articles were extracted of which 31 were included in the analysis. Unfortunately, due to the large variety in models and outcome measures, we could not perform a meta-analysis of our data. We find that despite an abundance of positive outcomes reported in previous studies on stroma targeting, a strong discrepancy exists with the outcomes of clinical trials and the more recent preclinical work that is in line with these trials. We explain the incongruities by the duration of stroma targeting and propose that chronic stroma targeting treatment is possibly detrimental in the treatment of this disease.