N-glycosylated Proteomic Detection of Serum Biomarkers for High-grade Serous Ovarian Carcinoma

High–grade serous ovarian carcinoma (HGSC) is the most common and lethal subtype of gynecological malignancy in women. The current standard of treatment is cytoreductive surgery and adjuvant chemotherapy. Despite the efficacy of initial standard treatment, most patients develop recurrent cancer, and 70% of patients die within the 5–years of initial diagnosis. Cancer antigen 125, or Mucin–16 (CA125) is the current FDA approved biomarker used in the clinic for monitoring response to treatment and cancer recurrence. Although increasing levels of CA125 precede clinical symptoms of cancer recurrence, often “second–look” surgeries reveal microscopic and macroscopic tumors that are beneath the detection limits of CA125. I describe a two–stage strategy for discovery of serum biomarkers for earlier detection of cancer recur- rence. In the first stage, I detected 3693 N–glycosylated sites from sera and tumors of patient–derived xenografts (PDX) mice made from recurrent tumors. Using label–free shotgun–proteomics, I showed that HGSC tumor–associated proteins (CA125, MSLN) can be quantified in PDX sera. Following species– assignment and bio–informatic prioritization; targeted–proteomics based screening in the second stage revealed the presence of 27 candidates in longitudinal sera from HGSC patients. The refined targeted– proteomics quantification of the 27 targets in a second independent cohort of longitudinal sera accurately quantified four N–glycosylated proteins with tumor burden profiles of CA125 and earlier rise of the sig- nal. Interestingly, the four proteins are associated with biological functions in the extracellular matrix, which have been linked to cancer progression. Together, the results demonstrate the discovery of novel markers for cancer recurrence using a rational serum–biomarker discovery strategy, where initial targets are discovered in PDX mouse models and subsequently verified in longitudinal patient sera.Ph.D.2020-03-21 00:00:0