Abstract 346: Trop-2 induces apoptosis via transcriptional activation of TRAIL, FAS-FASL, CD40-TNFRSF5

Abstract Trop-2 is a transmembrane signal transducer that activates cancer growth and metastatic diffusion (1). However, this does not occur in all tumor types, as Trop-2 is associated to better disease outcome in some cancers, e.g. breast and lung tumors. A prototypic pattern of Trop-2 expression in normal multistratified epithelia, e.g. epidermis, esophagus, is that of preferential expression in non-proliferating, terminally differentiated cells. The corresponding expression gradient parallels that of induction of programmed cell death, e.g. in the corneum layer of skin keratinocytes. This led us to explore Trop-2 function as a trigger of apoptosis. We thus assessed NS-0 myeloma Trop-2 transfectants for apoptosis induction by dynamic cell morphometry and quantification of membrane blebbing and cell fragmentation. This was shown to be preceded by phosphatidyl-serine membrane exposure, and was followed by nuclear pyknosis and karyorrhexis. DNA fragmentation was shown by TUNEL and DNA laddering, and was accompanied by a dramatic increase of apoptotic death of Trop-2-expressing cells. Transcriptomic analysis at early time points of apoptosis induction indicated overexpression of TRAIL, FAS/FASL and CD40/TNFRSF5 transmembrane death receptors. This paralleled upregulation of downstream death-inducing signaling complex components and of executioner Caspases 8 and 3, suggesting Trop-2 as a trigger of extrinsic apoptosis pathways. Apoptosis induction translated into diminished tumor growth in vivo, which was shown to be proportional to Trop-2 expression levels. However, apoptosis induction was found to parallel stimulation of NS-0 cell growth and of defence mechanisms from apoptosis, as increased levels of inhibitory transcription factors, Rb-binding protein, survivin, Myd-118. These findings suggest a previously unappreciated balance between stimulation of cell growth and triggering of cell death by Trop-2, and may pave the way for selective anticancer therapy approaches in Trop-2-expressing cancers.(1) Trerotola M. et al., Neoplasia 23: 415-428 (2021). Citation Format: Saverio Alberti, Emanuela Guerra, Antonino Moschella, Martina Ceci, Ludovica Pantalone, Roberta Di Pietro, Marco Trerotola. Trop-2 induces apoptosis via transcriptional activation of TRAIL, FAS-FASL, CD40-TNFRSF5 [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 346.