Description

Biomarkers that are readily detectable in fluid biopsies are of outmost importance for diagnosis and prediction of therapeutic response in all cancer patients. Pancreatic ductal adenocarcinoma (PDAC) is an example of a deadly malignancy that is diagnosed very late due to lack of sensitive and reliable markers \[1\]. The incidence and mortality of PDAC will double in the next 15 years, which is unprecedented among all cancer types \[2\]. Secondary cancer prevention through early diagnosis of PDAC will therefore be an essential preparedness asset for facing the immense healthcare burden.

Discovery of diagnostic biomarkers depends essentially on the availability of patient material ideally collected at different time points during the disease progression (e.g. early lesion, before treatment and after recurrence). Unfortunately, it is very difficult to access fresh biopsies from pre-malignant lesions for research purposes. These are needed in their entirety for histo-pathological evaluation and diagnosis. The ability to use liquid biopsies (e.g. serum, urine, saliva) brought the promise to circumvent this problem, opening access to many different biomolecules such as circulating DNA and proteins. However, upon their release from the tumor, these molecules are diluted up to several billion-fold in blood with molecular species originating from healthy tissues \[3-4\]. This hampers de novo discovery of biomarkers for diagnosing and understanding the disease.

To circumvent these limitations, the investigators recently engineered a novel biomarker discovery approach that is non-destructive and fully compatible with OMICS profiling as well as routine clinical procedures (5). The latter approach - termed EXPEL - mines the interstitial tissue fluid that is the richest source of soluble, undiluted and uncontaminated biomarkers. The method notably gives access to proteins, metabolites, RNA, DNA and exosomes, thus enabling holistic biomarker discovery. Owing to its non-destructive nature, EXPEL provides for the first time both clinicians and researchers with the opportunity to analyze identical material, while having virtually no disadvantage in their respective tasks. The investigators have recently shown the ability of our methodology to find new markers in the context of precious human colorectal cancer samples. Thus, the investigators are convinced that EXPEL can be successfully applied to pancreatic cancer. In addition, knowing the important proportion of stroma in PDAC (usually 2/3 of tumor mass), the secretome of pancreatic cancer is expected to be much richer in soluble "communication factors" exchanged between cancer cells and host tissue.

In clinical practice, most of patients undergo endoscopic ultrasound with fine needle aspiration/biopsy of the pancreatic mass to confirm the diagnosis of PDAC. The needle is rinsed in a conservation liquid Cytolyt® (Methanol 30% et water 50%) and sent to the pathologists. Microbiopsy are fixed in paraffin then analyzed and liquid is cytofiltrated to keep potential tumor cells. The remnant Cytolyt® liquid is systematically trashed.

The present study is based on the hypothesis that this liquid, previously in contact with tumoral tissue, could contain the tissue secretome and permit a comprehensive OMICS analysis of PDAC (all stages confounded) by using a "modified EXPEL" procedure. These are ideal conditions for EXPEL approach that will additionally to finding novel biomarkers also shed light on complex network of cancer cell - stroma interactions.

For this purpose, the investigators aim to perform proteomic analysis on the conservation liquid (Cytolyt) in patients who underwent endoscopic ultrasound with fine needle aspiration/biopsy for suspicious pancreatic mass at the CHU de Montpellier between Jan 2018 and Jan 2019.