Very little is known about receptor tyrosine kinases (RTK) expression on peripheral blood mononuclear cells (PBMC) in humans including renal cell carcinoma (RCC) patients. The primary objective of study was to evaluate expression levels of major RTKs on PBMC and tumor infiltrating lymphocytes (TIL) isolated from RCC patients. The secondary aim was to compare levels of RTK expression in RCC patients before surgery and on the 180th day after surgery (lymphocyte lifetime) and to compare with expression in healthy donors (HD). In addition, we compared RTK and PD-L1 expression in TIL.
Tumor and blood samples were obtained from 20 patients with primary RCC immediately after surgical resection. Blood samples were collected from 10 HD. Tumors were harvested into RPMI1640 medium (Gibco) and processed within 4 h. TIL isolation was performed under modified protocol [Baldan 2015]. Isolated TIL and PBMC were prepared for flow cytometry. Cells were double stained with anti-CD45 FITC-conjugated mouse antibody and with PE-conjugated mouse antibodies to VEGFR1-2, PDGFRα-β, FGFR2 (all Sony Biotech) and were analyzed on NovoCyte 2000R flow cytometer (ACEA Biosciences). Expression of RTK was evaluated with NovoExpress Software. 20 tumors from same patients were stained with PD-L1 IHC assay (clone SP142 (Ventana).
PBMC/TIL express RTKs (Table). In HD PBMC express all RTKs in 2-3 times higher than PBMC of RCC patients (all P < 0.05). TIL also had lower expression of RTK (all P < 0.05). There was no significant recovery of RTK expression on 180th day except of VEGFR2. Level of FGFR2 was lower on TIL (P = 0.03). 50% of patients had PD-L1 expression (1-11% of positive TIL). We found negative correlation of PDGFRα, β and PD-L1 expression (P = 0.04).Table: 27P
|Expression of RTK, %, mean||PBMC, HD||PBMC, RCC, before surgery||PBMC, RCC, 180 days after surgery||TIL, RCC|
PBMC and TIL had similar low RTK expression levels in RCC patients. Lymphocytes of healthy humans had significantly higher expression of RTK. PD-L1 and PDGFRa-b expression could correlate.
Clinical trial identification
Legal entity responsible for the study
Ministry of Health.
Kidney Cancer Research Bureau.
All authors have declared no conflicts of interest.