Therapeutic implications of PD-L1 expression in bladder cancer with squamous differentiation

Abstract

Background: Immune checkpoint inhibitors (ICI) are an integral part of bladder cancer therapy, however, the relevance of ICI treatment for mixed and pure squamous cell carcinoma of the bladder remains poorly studied. Therefore, we analysed the expression of programmed death-ligand 1 (PD-L1) in urothelial carcinomas with squamous differentiation (UC/SCC) and pure squamous cell carcinoma (SCC) of the bladder and studied a UC/SCC patient with ICI therapy.

Methods: Tissue microarrays of 45 UC/SCC and 63 SCC samples were immunohistochemically stained with four anti-PD-L1 antibodies (28-8, 22C3, SP142 and SP263). PD-L1 expression was determined for tumour cells (TP-Score), immune cells (IC-Score) and combined (CPS, combined positive score). In addition, we present clinical and histological data of an UC/SCC patient with nivolumab therapy.

Results: Overall, positive PD-L1 staining ranged between 4.8 and 61.9% for IC and 0 and 51.2% for TC depending on the used antibody. There were no significant differences between UC/SCC and SCC. According to current FDA guidelines for example for first line therapy of urothelial cancer with pembrolizumab (CPS ≥ 10), a subset of SCC patients up to 20% would be eligible. Finally, our UC/SCC index patient revealed excellent therapy response regarding his lung metastasis.

Conclusions: Our data reveal a PD-L1 expression in squamous differentiated carcinomas comparable with current data shown for urothelial tumours. In accordance with the encouraging clinical data of the index patient we suggest ICI treatment also for mixed and pure SCC of the urinary bladder.

Keywords: Bladder cancer; Immunotherapy; PD-L1; Squamous cell carcinoma.

Fig. 1

PD-L1 protein expression in squamous differentiated bladder cancer (SD-BLCA). a Immunohistochemical PD-L1 staining is shown for representative tissue cores illustrating both immune cells (IC) and tumour cells (TC) by applying four different antibodies: DAKO 28–8, DAKO 22C3, Ventana SP263 and Ventana SP142. Squamous tumour components are histologically shown by H&E staining. CD68 staining highlights macrophages. Black scale bar: 100 μM. Please note: Due to tissue loss during the first immunohistochemical staining with the 22C3 antibody deeper tissue sections of the patient’s FFPE material were used which show slight differences in histology. b-c Scatter plot graphs show overall distribution of PD-L1 positive areas of IC and TC for mixed (UC/SCC) and pure squamous cancers (SCC). d-e Spearman correlation analysis demonstrating inter-assay heterogeneity for IC (d) and TC (e)

Fig. 2

Therapeutic implications of used PD-L1 antibodies in SD-BLCA according to FDA-approved guidelines for first line therapy in bladder cancer. Scatter plots represent CPS and IC for DAKO 22C3 and Ventana SP142, respectively. Red dotted line: drug-related cut-off values. Below: Percentages of patients with putative choice of first line therapy with pembrolizumab (a) and atezolizumab (b)

Fig. 3

SD-BLCA index patient treated with nivolumab in a second line therapy. aUpper: History time line of index patient illustrating the diagnostic and therapeutic management over 140 months since first diagnosis. Below: CT images of the index patient show pulmonary metastasis size (white arrow) at different therapy time points. b Immunohistochemical PD-L1 staining of primary tumour lesions of the index patients derived from tissues removed before and after nivolumab treatment is shown. Squamous components are histologically shown by H&E staining and highlighted by K5/6 staining. PD-L1 expression was determined in both tumour cells (TC) and immune cells (IC) by using four different antibodies: DAKO 28–8, DAKO 22C3, Ventana SP263 and Ventana SP142. Black scale bar: 100 μM.HG: high grade; pT: pathological tumour stage; L: invasion into lymphatic vessels; V: invasion into vein; R: the completeness of the operation; pN: pathological degree of spread to regional lymph nodes; cM: clinical metastasis; CR: complete response, PD: progressive disease; Cx: cystectomy; TUR-B: transurethral resection of the bladder; m: months