DLL3 Expression in Neuroendocrine Carcinomas and Neuroendocrine Tumours: Insights From a Multicentric Cohort of 1294 Pulmonary and Extrapulmonary Neuroendocrine Neoplasms

Abstract

Delta-like ligand 3 (DLL3) is frequently expressed in pulmonary small cell neuroendocrine carcinoma (SCNEC) and has emerged as a promising therapeutic target. However, limited data on DLL3 expression in other neuroendocrine neoplasms (NEN), such as extrapulmonary SCNEC, large cell neuroendocrine carcinomas (LCNEC), mixed neuroendocrine-non-neuroendocrine neoplasms (MiNEN), gastroenteropancreatic neuroendocrine tumours (GEP-NET), and pulmonary carcinoids, impedes an estimation if other types of NEN might be suitable candidates for anti-DLL3 therapies. We evaluated DLL3 expression in 1294 NEN and 479 non-neuroendocrine carcinomas, correlating the findings with histological subtypes, tumour localisation, and overall survival (OS). Furthermore, we explored the concordance of DLL3 expression during metastatic progression in 67 paired primary NEN and metastases. DLL3 expression was significantly higher in NEC (64.0%) compared to GEP-NET and pulmonary carcinoids (10.1%, p < 0.001), particularly in SCNEC (80.4%), followed by LCNEC (62.6%) and MiNEN (28.6%). DLL3 was common in pulmonary carcinoids (41.5%), but rare in GEP-NET (5.1%) and non-neuroendocrine carcinomas (1.3%). Overall DLL3 expression was highly concordant between metastases and corresponding primary NEN (92.5%, p < 0.001). In univariable analyses, DLL3-expressing pulmonary carcinoids (p = 0.005) and GEP-NET (p = 0.018) were associated with decreased OS, but this was not retained in multivariable analyses adjusting for stage and grade (p = n. s.). No prognostic impact was observed in pulmonary (p = 0.708) or GEP-NEC (p = 0.87). Our study highlights significant differences in DLL3 expression across NEN subtypes and localisations, with largely concordant expression in metastases. DLL3-based therapies may be effective in many NEC and pulmonary carcinoids, while DLL3 appears to be a minor therapeutic target for GEP-NET and non-neuroendocrine carcinomas.

Keywords: DLL3; Neuroendocrine carcinoma; Neuroendocrine neoplasms; Neuroendocrine tumour.

Fig. 1

Overview of the cohort and DLL3 expression in different NEN. A Frequency of NET (including AC/TC) and NEC (including MiNEN) in the overall cohort of 1294 NEN. B Frequency of different NET (G1/G2/G3, TC/AC) and NEC (SCNEC/LCNEC/MiNEN) subtypes in the overall cohort. C Detailed localisations of the investigated NEN in the overall cohort. D Frequency of DLL3 expression groups according to the IRS in the overall cohort (all NEN). E General comparison of DLL3 expression groups according to the IRS between NET and NEC. F Frequency of DLL3 expression groups according to the IRS in NEC between different simplified localisations (pulmonary, GEP-NEC, skin). G Frequency of DLL3 expression groups according to the IRS in pulmonary and gastroenteropancreatic SCNEC. H Frequency of DLL3 expression groups according to the IRS in pulmonary and gastroenteropancreatic LCNEC. I Frequency of DLL3 expression groups according to the IRS in gastroenteropancreatic NET and pulmonary TC/AC. J Frequency of DLL3 expression groups according to the IRS in pulmonary TC and AC. K Frequency of DLL3 expression groups according to the IRS in pulmonary and gastroenteropancreatic non-neuroendocrine carcinomas. DLL3, Delta-like-protein 3; NEN, neuroendocrine neoplasm; NET, neuroendocrine tumour; NEC, neuroendocrine carcinoma, LCNEC, large cell neuroendocrine carcinoma; SCNEC, small cell neuroendocrine carcinoma; MiNEN, mixed neuroendocrine-non-neuroendocrine carcinoma; TC, typical carcinoid; AC, atypical carcinoid; GEP, gastroenteropancreatic; MCC, Merkel cell carcinoma

Fig. 2

Expression of DLL3 in pulmonary NEN. A–E Pulmonary carcinoids (HE, A). B Example of pulmonary typical carcinoid with complete absence of DLL3 expression (IRS 0). C Example of weak DLL3 expression in pulmonary typical carcinoid showing a weak expression intensity in > 10% of tumour cells (IRS 2). D Moderate DLL3 expression in pulmonary typical carcinoid with up to strong cytoplasmatic staining intensity, which is restricted to > 10% of tumour cells (IRS 6). E Strong DLL3-expression in pulmonary atypical carcinoid with strong expression intensity in > 80% of carcinoid cells (IRS 12). F–J Examples of different pulmonary LCNEC (HE, F). G Example of negative DLL3 expression in pulmonary LCNEC without any cytoplasmatic DLL3 expression (IRS 0). H Pulmonary LCNEC with weak DLL3-expression demonstrating an up to strong staining intensity in < 10% of carcinoma cells (IRS 3). I Moderate DLL3 expression in pulmonary LCNEC with strong staining intensity in > 10% of tumour cells (IRS 6). J Example of pulmonary LCNEC with strong cytoplasmatic staining reaction in > 80% of carcinoma cells falling into strong DLL3 expression group (IRS 12). K–O Different pulmonary SCNEC (K, HE). L Pulmonary SCNEC with no expression of DLL3 at all (IRS 0). M Example of weak DLL3 expression demonstrating up to strong staining reaction in < 10% of tumour cells (IRS 3). N Moderate DLL3 expression in pulmonary SCNEC with up to strong cytoplasmatic staining reaction in > 10% of tumour cells (IRS 6). O Example of pulmonary SCNEC with strong staining reaction in almost all carcinoma cells meaning an overall strong DLL3 expression (IRS 12). Overview: × 20 magnification, Inlay: × 100 magnification. HE, hematoxylin and eosin; DLL3, Delta-like-protein 3; IRS, immunoreactive score; NEN, neuroendocrine neoplasm; LCNEC, large-cell neuroendocrine carcinoma; SCNEC, small-cell neuroendocrine carcinoma

Fig. 3

DLL3 expression in gastroenteropancreatic NEN. A–E Different pancreatic NET (HE, A). B Example of pancreatic NET with complete absence of DLL3 expression (IRS 0). C Weak DLL3 expression in pancreatic NET with an up to moderate cytoplasmatic staining reaction in < 10% of tumour cells (IRS 2). D Example of pancreatic NET with moderate expression intensity in > 10% of tumour cells meaning a moderate DLL3 expression (IRS 4). E Strong DLL3 expression in pancreatic NET with strong staining intensity in > 50% of tumour cells (IRS 9). F–J Examples of DLL3 expression in different GEP-LCNEC (HE, F). G Example of pancreatic LCNEC with complete absence of DLL3 expression (IRS 0). H Example of weak DLL3 expression in rectal LCNEC with an up to strong expression intensity in < 10% of carcinoma cells (IRS 3). I Moderate DLL3 expression in rectal LCNEC demonstrating an up to strong staining intensity in > 10% of tumour cells (IRS 6). J Example of pancreatic LCNEC with strong cytoplasmatic staining reaction in almost all tumour cells meaning a strong DLL3 expression (IRS 12). K–O SCNEC of different sides of the GEP (K, HE). L Example of SCNEC in colon with no expression of DLL3 at all (IRS 0). M SCNEC of the colon demonstrating a weak staining reaction in > 10% of tumour cells corresponding to an overall weak DLL3 expression (IRS 2). N Moderate DLL3 expression in rectal SCNEC showing a moderate staining reaction in > 50% of carcinoma cells (IRS 6). O Example of gastric SCNEC with strong DLL3 expression in almost all tumour cells (IRS 12). Overview: × 20 magnification, Inlay: × 100 magnification. HE, hematoxylin and eosin; DLL3, Delta-like-protein 3; IRS, immunoreactive score; NEN, neuroendocrine neoplasm; LCNEC, large-cell neuroendocrine carcinoma; SCNEC, small-cell neuroendocrine carcinoma; GEP, gastroenteropancreatic