GnRHa treatment of cryptorchidism alters testicular sumo gene expression

Faruk Hadziselimovic; Gilvydas Verkauskas; Michael Stadler

Introduction: Reversible post-translational modifications (PTMs) dynamically regulate the activities of numerous proteins. The Small Ubiquitin-related Modifier (SUMO) proteins are conjugated to lysines in their target proteins in a process termed SUMOylation. This PTM regulates, among others, transcription, gene silencing, chromatin structure and DNA repair. Here, we investigated the expression of five SUMO genes in testicular samples from patients with cryptorchidism before and after curative GnRH treatment.

Materials and Methods: During orchidopexy for bilateral cryptorchidism within the framework of a prospective study, biopsies are performed to histologically confirm the presence of type Ad spermatogonia and to study the transcriptome utilizing RNA sequencing. Cryptorchid boys (high infertility risk [HIR] lacking Ad spermatogonia) were randomized and assigned to one of two groups. The “surgery only” group underwent a second orchidopexy without hormonal treatment. The GnRHa group received therapy followed by a second orchidopexy. During orchidopexy a testis biopsy was conducted after six months of treatment or observation (5/5 boys).

Results: SUMO1, 2 and 3 are not significantly differentially expressed in HIR versus LIR (low infertility risk) samples. However, following curative GnRH treatment SUMO1, SUMO2 and SUMO3 are expressed at lower levels than before the treatment. In contrast, SUMO1P1 expression increases, while SUMO4 expression remains unaffected (Table 1).

**Table 1.** SUMO gene expression in HIR and LIR (control group) samples from cryptorchid boys before (GnRHa-) and after (GnRHa+) treatment. Expression signals are given in RPKM (Reads Per Kilobase per Million mapped reads). log2 fold changes (log2FC) and false discovery rates (FDRs) are shown
Gene Name	HIR/LIR	GnRH+	GnRH-	log2	FDR
SUMO1	35/36	21.7	41.6	-0.93	0.0002
SUMO2	114/195	57.3	131.6	-1.19	3.49E-05
SUMO3	22/24	14.3	29.4	-1.03	9.29E-05
SUMO4	5.9/4.7	5.9	6.4	-0.33	0.32
SUMO1P1	0.4/0.6	1.63	0.5	1.7	0.002

Conclusions: We report the first analysis of testicular SUMO gene expression following GnRHa treatment. We find that SUMO1, 2 and 3 are negatively regulated by GnRH, which indicates possible roles in germ cell proliferation rather than differentiation. It is interesting that the expression of SUMO1P1, which is known to be involved in the development and differentiation of promyelocytic leukemia (PML) bodies, increases after GnRHa treatment. PML is a tumor suppressor that belongs to the TRIM/RBCC family. Given that GnRHa possesses a yet poorly understood tumor suppressive activity, we hypothesize that SUMO1P1 may be involved in suppressing testicular tumors.

ESPE Abstracts

RFC9.6