Inflammatory state of lymphatic vessels and miRNA profiles associated with relapse in ovarian cancer patients

Abstract

25 Lymphogenic spread is associated with poor prognosis in epithelial ovarian cancer (EOC), 26 yet little is known regarding roles of non-peri-tumoural lymphatic vessels (LVs) outside the 27 tumour microenvironment that may impact relapse. We hypothesize that inflammatory status 28 of the LVs and/or changes in the miRNA profile of the LVs, could potentially have a 29 prognostic and predictive value for overall outcome and risk of relapse. Samples of 30 macroscopically normal human lymph LVs (n=10) were isolated from the external iliac 31 vessels draining the pelvic region of patients undergoing debulking surgery. This was 32 followed by quantification of the inflammatory state (low, medium and high) and presence of 33 cancer-infiltration of each LV using immunohistochemistry. LV miRNA expression profiling 34 was also performed, and analysed in the context of high versus low inflammation, and 35 cancer-infiltrated versus non-cancer-infiltrated. Results were correlated with clinical 36 outcome data including relapse with an average follow-up time of 13.3 months. The presence 37 of high inflammation correlated significantly with patient relapse (p=0.033). Cancer-38 infiltrated LVs showed a moderate but non-significant association with relapse (p=0.07).39 Differential miRNA profiles were identified in cancer-infiltrated LVs and LVs with high 40 versus low inflammation. In particular, the let-7 family was consistently downregulated < 41 1.8-fold in highly inflamed LVs (p<0.05) as opposed to the less inflamed ones. Down-42 regulation of the let-7 family appears to be associated with inflammation, but whether 43 inflammation contributes to or is an effect of cancer-infiltration requires further investigation. 44 45 Introduction 46 Epithelial Ovarian cancer (EOC) accounts for over 4000 deaths in the UK every year [1]. 47 Lymph nodes metastases are very common in EOC-patients and also associated with a more 48 dismal overall prognosis [2-3]. Total macroscopic tumour clearance, is one of the most 49 important prognostic factors for survival post-surgery in EOC, including also the removal of 50 bulky lymph nodes [3-4]. There is no therapeutic value in the systematic removal of clinically 51 normal appearing LN in the advanced disease setting, as shown in prospective randomised 52 trials [5]. The involvement and changes in the connecting lymphatic vessels (LVs) and how 53 they are related to the future risk of metastasis and relapse have never been investigated, to 54 our knowledge. 55 56 LVs are specialised in the uptake and transport of macromolecules from tissue fluid, 57 consequently permitting lymphogenic spread of cancer cells. Within the tumour 58 microenvironment, intra-tumoural LVs are present, however functional tests in mice have 59 indicated that intra-tumoural lymphatics are non-functional [6,7]. The collapse of intra-60 tumoural LVs is potentially due to the high interstitial pressure observed in multiple types of 61 tumours, a lack of lymphatic valves, or induced mechanical pressure of growing tumour cells 62 ...