Hyaluronan heterogeneity in pancreatic ductal adenocarcinoma, primary tumors, and sites of metastasis.

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e16231 Background: Pancreatic ductal adenocarcinoma (PDAC) is one of the most aggressive cancers with an estimated five-year survival rate of 10%. The dense desmoplastic stroma in PDAC contributes to its aggressive nature and treatment resistance. Among the components comprising the stroma, hyaluronan (HA) has been demonstrated to play a critical role in tumor progression and survival. Previous preliminary studies have suggested differences in HA expression in primary and metastatic foci in PDAC. However, the effects of treatment and location of HA expression as well as the role of CD44, a known receptor for HA, on HA as a biomarker signature remain unknown. Thus, we investigated the potential of HA as a biomarker in primary PDAC and metastases. Methods: PDAC tissue from primary (n = 43) and metastatic (n = 66) sites were obtained from Cedars-Sinai Medical Center along with associated clinical data. Tissue slides were stained with H&E, HA using a histochemical assay, and CD44 by immunohistochemistry. HA staining was scored according to the proportion of stromal staining at an intensity greater than the background stroma. HA status was defined as ≥ 50% staining being HA high and < 50% as being HA low. CD44 staining was recorded as an H-score (percentage of tumor cells staining multiplied by intensity of staining on a scale from 0 to 3). Associations between HA levels and the requested variables were examined with t-test, Wilcoxon rank-sum test, Chi-squared test, Fisher’s exact test, or Cox regression model where appropriate. Kaplan-Meier curves were created to assess progression free survival and overall survival. Analyses were performed using SAS 9.4 with two-sided tests and a significance level of 0.05. Results: HA score was significantly higher in primary PDAC tissue compared to sites of metastases (p = 0.0148). Within the metastases, HA score was significantly higher in liver metastasis compared to other sites of metastasis (p = 0.0478). In the liver metastasis tissue, HA score trended lower in patients with previously treated tissue compared to treatment naïve tissue (p = 0.0622). In the treatment naive liver metastasis cohort, patients with HA high status had decreased progression free survival and overall survival compared to patients with HA low status (p = 0.0032 and p = 0.0478, respectively). Using HA score and CD44 in a Cox regression model demonstrated that for every one unit increase in HA score, the risk for recurrence/progression increased by 4.4% at any fixed point in time, adjusting for CD44 score (p = 0.0049). Conclusions: HA score is variable between primary PDAC, PDAC metastatic to the liver, and PDAC metastatic to other sites. Within liver metastases, patients with HA high status had decreased progression free survival and overall survival compared to patients with HA low status. HA levels can serve as a potential biomarker to guide pancreatic cancer treatments and trial design for agents targeting the stroma.