Biology subjects

Mitchell, R. T.

Publications and source records attributed to Mitchell, R. T..

4 recordsLinked to original sources

bioRxiv2026

Mitochondrial priming in human germ cell tumors is dependent on MCL1 and BCL2L1

Germ cell tumors (GCTs) are highly sensitized to cell death in response to DNA damaging agents, a property that underlies the success of current chemotherapeutic regimens. To address the molecular basis for this, known as apoptotic priming, we evaluated how different BCL2 family members modulate the heightened sensitivity of GCTs to therapy. Our analysis of human GCTs finds consistently high expression of the pro-survival factors MCL1 and BCL2L1 (BCLX) in a cohort of primary tumors and in their embryonic precursor cells, frequently accompanied by copy number gains of these loci and reciprocal losses of their pro-apoptotic interaction partners and inhibitors, PMAIP1 (NOXA) and BAD. We find that co-inhibition of MCL1 and BCLX using selective BH3 mimetics results in a potent synthetic lethality in multiple GCT embryonal carcinoma cell lines. When these cell lines were cultured with the DNA damaging agents cisplatin or etoposide, inhibition of MCL1 or BCLX potentiated their apoptotic effect in undifferentiated embryonal carcinoma cell lines, but not in retinoic acid-differentiated cells. The inhibition of MCL1 also heightened cisplatin sensitivity in p53-deficient or -mutant cell lines, which is associated with resistance to therapy. Employing an in ovo human xenograft model, we validate that the combination of cisplatin and MCL1 inhibition enhanced the therapeutic response by eliminating tumor cells. Our findings identify MCL1 and BCLX as critical factors to maintain GCT viability and as putative therapeutic targets to further augment GCT responsiveness to DNA damaging agents.

cancer biology↗

bioRxiv2026

Investigation into the effects of sodium valproate on prepubertal mouse gonads in vivo

Objective Sodium valproate (SV) is a widely used anti-epileptic drug with well-established reproductive and teratogenic effects, yet its impact on the developing prepubertal reproductive system remains poorly understood. This study investigated the effects of prepubertal SV exposure on gonadal development, including folliculogenesis, testicular architecture and steroidogenic gene expression in male and female mice in vivo. Methods CD1 mouse pups received intraperitoneal injections of saline (control), low or high dose SV (50 or 100 mg/kg, respectively) on postnatal days (PND) 6, 8, and 10. On PND17 the animals were culled and gonads dissected. Ovaries and testes were assessed histologically using haematoxylin and eosin staining. Ovarian follicle number, stage and health were quantified. Testicular tubule morphology and key testicular cell numbers (germ, Sertoli, spermatogonial stem cells, and interstitial/Leydig cells) were evaluated using immunofluorescence with automated image analysis. Expression of key steroidogenic genes (CYP11A1, STAR, CYP19A1 in ovaries; INSL3, STAR, CYP11A1 in testes) was measured by RT-qPCR. Results SV exposure did not significantly affect ovarian follicle number, distribution or health. Testicular morphology and the density of Sertoli, spermatogonial stem cells, and interstitial cells were likewise unaffected. However, a dose-dependent trend toward reduced germ cell density was observed in males at a high dose SV, though this did not reach statistical significance (P = 0.058). Steroidogenic gene expression was unaffected by SV exposure in both ovaries and testes across all treatment groups. Significance This study provides the first in vivo assessment of short-term prepubertal SV exposure on gonadal development in both sexes. The overall findings suggest that brief SV exposure during the prepubertal window does not cause overt gonadotoxicity. Nonetheless, the trend toward reduced testicular germ cell density warrants further investigation with longer exposure durations and functional fertility endpoints, to better inform clinical risk assessment in paediatric patients receiving SV.

pharmacology and toxicology↗

bioRxiv2026

Chemotherapy-induced transfer of apoptotic machinery in extracellular vesicles between somatic and germ cells of the testis: mechanistic insights into onco-fertility preservation in pre-pubertal boys

Extracellular vesicles (EVs) are increasingly recognized as critical mediators of intercellular communication, not least during cellular stress or therapy. While EV signalling is well-studied in various tissues, its role in the prepubertal testicular environment is not well understood. Chemotherapy, commonly used in paediatric oncology, poses a significant risk to spermatogonial stem cells (SSCs) and may affect long-term fertility in cancer survivors. The role of EVs in chemotherapy-induced testicular damage in these patients is unknown and may be important for developing new fertility preservation methods. Immortalised murine Sertoli (TM4) and spermatogonial (GC1-spg) cell lines were used to investigate cisplatin-induced changes in EV biogenesis, release, and function in an in vitro model of the prepubertal testicular microenvironment. Our findings indicate that cisplatin significantly increases EV secretion and internalisation by recipient cells. Notably, EVs from cisplatin-exposed Sertoli cells exhibit a novel pro-apoptotic phenotype when co-cultured with chemotherapy-naive Sertoli cells. Proteomic profiling of these EVs shows enrichment of apoptosis-regulatory proteins including caspases, activating Caspase-3/7 in recipient Sertoli cells. Conversely, germ cells exposed to Sertoli cell-derived EVs displayed reduced levels of apoptosis as well as a chemoprotective role to germ cells undergoing treatment with cisplatin. These findings indicate a dual role for Sertoli cell-derived EVs in mediating (1) apoptosis in Sertoli cells and (2) protection of germ cells following cisplatin exposure. The presence of pro-apoptotic molecules, especially caspases, in chemotherapy-induced Sertoli cell EVs provides mechanism for the induction of somatic cell apoptosis. Furthermore, their protective effects on germ cells demonstrate the complexity of EV-mediated signalling between testicular cell types. Manipulating EV biogenesis and cargo loading could be a promising approach to reduce chemotherapy-related gonadotoxicity and preserve fertility in childhood cancer patients.

cell biology↗

bioRxiv2020

Transcriptional comparison of Testicular Adrenal Rest Tumors with fetal and adult tissues

Testicular Adrenal Rest Tumors (TART) are a common complication of unknown origin in patients with Congenital Adrenal Hyperplasia. These benign tumors may derive from cells of adrenal origin or from pluripotent progenitor cells from the fetal adrenogonadal primordium. By comparing the transcriptome of TART with fetal- and adult-testis and adrenal tissues, this study aims to unravel the origin of TART. Targeted transcriptome sequencing was followed by unsupervised clustering-, differential expression-, functional enrichment- and pathway analyses. Immunohistochemistry demonstrated co-expression of adrenal-specific CYP11B1 and testis-specific HSD17B3 in TART, indicating the existence of a distinct TART cell exhibiting both adrenal- and testicular characteristics. Principal component analysis indicated that the TART transcriptome was distinct from either adrenal or testis fetal tissue, making a progenitor-like phenotype of TART unlikely. Rather, TART appears to originate from -or differentiate into-a mature cell type, with both adrenal- and testicular characteristics. The present study, the first to describe the TART transcriptome, expands knowledge about the identity and functional characteristics of TART and identifies clinically targetable pathways associated with fibrosis.

molecular biology↗