Page 136 - SRPSKO DRUŠTVO ISTRAŽIVAČA RAKA

Serbian Association for Cancer Research SDIRSACR

P42

Circulating extracellular vesicles in liver and pancreatic cancer: an initial assessment of sialylation

Sanja Goč , Filip Janjić , Ninoslav Mitić , Tamara Janković , Milan Jovanović , Zoran Rujanovski , Miroslava Janković 1
1
1
2
1
1
2
1 Institute for the Application of Nuclear Energy – INEP, University of Belgrade, Belgrade, Serbia
2 Department of Abdominal Surgery, Military Medical Academy, Belgrade, Serbia
Keywords: Extracellular vesicles, hepatocellular carcinoma, nanoparticle tracking analysis, pancreatic cancer, sialic acid
Background: Extracellular vesicles (EVs) are cell-derived, membrane-surrounded vesicles that carry various bioactive
molecules and deliver them to recipient cells. They are considered mini-maps of their cells of origin. Altered tissue/cell
glycosylation is a hallmark of different cancers but little is known about how these changes affect circulating EVs. One
of the most prevalent changes is sialylation, the addition of sialic acid (Sia) to galactose or N-acetylgalactosamine at the
terminal position of glycan chains. Starting from data on the changes in sialylation of liver and pancreatic cancer tissues,
this study aimed to assess whether these changes are mirrored in related circulating EVs, specifically within large EV
populations, previously indicated to comprise cancer-derived vesicles. This is important issue regarding designation of
introductory studies of the functional and biomarker potential of these EVs.
Materials and Methods: Serum samples were collected from patients with hepatocellular carcinoma (HCC, n
= 5), pancreatic cancer (PC, n = 10), and healthy donors (HD, n = 10). Circulating EVs were isolated by differential
centrifugation and ultracentrifugation. Their size distribution was analyzed using nanoparticle tracking analysis (NTA).
Surface sialylation was assessed by fluorescent NTA (f-NTA) using Sambucus nigra agglutinin (SNA) and wheat germ
agglutinin (WGA), which have distinct requirements for binding Sia residues. Statistical analyses were performed
through GraphPad Prism 8.0 applying the Kruskal-Wallis test.
Results: Median (IQR) EV sizes from HCC (146 nm (144.5-150.8 nm)) and PC (155.5 nm (151.5-160.4 nm)) were
significantly higher than those from HD (126.4 nm (123.3-128.9 nm)) (P < 0.001). Large EVs (>200 nm) were more
abundant in cancers (~30%) compared to HD (~10%). There was no statistically significant difference (P > 0.05) in the
sizes of SNA- and WGA-reactive EVs between cancers and HD. The proportion of SNA-reactive large EVs was similar
between cancer patients and HD (~40%), whereas the proportion of WGA-reactive large EVs was similar between HCC
and HD (~30%), but reduced in PC (~20%).
Conclusions: The median EVs size and the ratio of large EVs were increased in both HCC and PC in comparison to
HD. This increase is accompanied by the changes in surface sialylation seen as decrease in sialic acid-binding lectins
reactivity, notably in PC. The changes in EVs sialylation were opposite to those detected in liver and pancreatic cancer
tissue.

Acknowledgments and funding: This work was supported by the Ministry of Science, Innovation and Technological
Development of the Republic of Serbia [Grant No. 451-03-136/2025-03/200019].

P43

The association of baseline concentrations of circulating tumor DNA with clinical course of advanced
melanoma

Bojana Cikota-Aleksić1, Branko Dujović2, Radmila Janković3, Viktorija Dragojević-Simić1, Lidija Kandolf2

1Center for Clinical Pharmacology, Military Medical Academy, Belgrade, Serbia
2Clinic of Dermatovenerology, Military Medical Academy, Belgrade, Serbia
3Institute of Oncology and Radiology of Serbia

Keywords: circulating tumor DNA, melanoma, prognosis

Background: Immune checkpoint inhibitors (ICI), applied as a monotherapy or in combination regimens, demonstrated
significant survival benefits in patients with advanced melanoma, However, a significant proportion of patients fail to
respond to ICI or experience relapse after an initially successful response. Detection and quantification of circulating
tumor DNA (ctDNA) has been considered a promising prognostic biomarker in melanoma patients treated with ICI.

121