Oral Presentation ESA-SRB-APEG-NZSE 2022

From trash to treasure: InhaKO testis tumours produce growth factors that support SSC renewal (#38)

Penny A F Whiley 1 2 , Benedict Nathaniel 1 , Robin M Hobbs 1 2 , Kate L Loveland 1 2
  1. Centre for Reproductive Health, Hudson Institute of Medical Research, Clayton, Vic, Australia
  2. Department of Molecular and Translational Sciences, School of Clinical Sciences, Monash University, Clayton, VIC, Australia

Testicular somatic cell tumours represent ~5% of tumours in human adults and ~40% in children (1). Adult InhaKO mouse testes feature elevated (>10-fold) activin A bioactivity and develop focally invasive tumours thought to be derived from Sertoli cells (2, 3). I have used this model to study how elevated activin affects spermatogonial stem cells (SSCs) in newborn and adult testes. Unexpectedly, I discovered increased numbers of SSCs (GFRA1+/SALL4+) in InhaKO ‘normal’ tubules, with SSCs clusters (GFRA1+/EOMES+/LIN28-) present in tubules adjacent to tumours. Additionally, immunofluorescence (IF) staining of InhaKO tumours in adult testes revealed they are predominantly negative for the Sertoli cell marker, SOX9. These intriguing results formed the basis of this study which aims to identify (1) growth factors produced by InhaKO tumours important for SSC renewal, and (2) delineate the cellular origin of InhaKO tumours.

Adult testes (PND53-55) from InhaWT and KO mice (n=3/genotype) were decapsulated.  Tubules with ‘normal’ spermatogenesis, tumour regions, and tumour-associated tubules were microdissected for RNA extraction. RNA integrity was confirmed prior to whole transcriptomic RNAseq (MHTP Medical Genomics Facility) and bioinformatic analysis.

Proximity to tumours was associated with increased DEGs compared to WT (‘normal’, 38; tumour associated tubules, 4939; tumours, 12,983 DEGs). Transcripts encoding growth factors important for SSC self-renewal (Gdnf, Lif, Fgf2) were elevated in tumour-associated tubules and in tumour regions. Tumour regions exhibited reduced germ (Ddx4) and Leydig (Insl3), and increased immune (Cx3cr1, Csf1r) cell transcripts. Some Sertoli cell transcripts were decreased (Sox9, Wt1) reflective of IF data, while others were increased (Gja1, Clu, Vim), indicating these tumours comprise Sertoli cells with a modified transcriptomic state.

This demonstrates the InhaKO mice are an elegant model with which to identify new factors important to SSC biology, while offering new insights into the origins and transcriptomic landscape of these somatic cell tumours.

  1. Ewa Rajpert-De Meyts et al. Endotext (2018)
  2. Matzuk et al. Proc Natl Acad (1994)
  3. Kumar et al. Endocrinology (1996)