The high mortality rate due to chemoresistance in patients with high-grade ovarian cancer (HGSOC) emphasizes the urgent need to determine optimal treatment strategies for advanced and recurrent cases. Our study investigates the interplay between estrogens and chemoresistance in HGSOC and shows clear differences between platinum-sensitive and -resistant tumors. Through comprehensive transcriptome analyzes, we uncover differences in the expression of genes of estrogen biosynthesis, metabolism, transport and action underlying platinum resistance in different tissues of HGSOC subtypes and in six HGSOC cell lines. Furthermore, we identify genes involved in estrogen biosynthesis and metabolism as prognostic biomarkers for HGSOC. Additionally, our study elucidates different patterns of estrogen formation/metabolism and their effects on cell proliferation between six HGSOC cell lines with different platinum sensitivity. These results emphasize the dynamic interplay between estrogens and HGSOC chemoresistance. In particular, targeting the activity of steroid sulfatase (STS) proves to be a promising therapeutic approach with potential efficacy in limiting estrogen-driven cell proliferation. Our study reveals potential prognostic markers as well as identifies novel therapeutic targets that show promise for overcoming resistance and improving treatment outcomes in HGSOC.

The liver is a central metabolic organ with pronounced sex-specific differences shaped by sex hormones, sex chromosome-linked gene expression, ageing, and circadian rhythm. These factors influence disease susceptibility, progression, and treatment response, with notable differences between females and males in the prevalence, severity, and clinical outcomes of metabolic dysfunction-associated steatotic liver disease. This condition represents a growing global health burden that can progress to hepatocellular carcinoma, the second leading cause of cancer-related death worldwide. Despite this impact, sex remains an underexplored variable in liver research, and the molecular mechanisms by which sex influences disease development remain poorly understood. In this review, we examine the key determinants of sex differences in liver pathogenesis. We highlight the protective role of estrogen signaling in female liver metabolism, the increased vulnerability to disease progression after menopause, and the contribution of circadian regulation to sex-specific outcomes. We further discuss how the lack of systematic inclusion of both sexes in preclinical and clinical studies limits the identification of biomarkers and the development of effective therapeutic interventions. Incorporating sex as a biological variable is therefore essential to improve mechanistic understanding, translational relevance, and the personalization of treatment approaches. Particular emphasis is placed on animal models that reflect sex-specific liver physiology and pathophysiology, as these provide valuable frameworks for studying disease progression and testing targeted interventions. In summary, recognizing and integrating sexual dimorphism in liver metabolism is crucial to advancing prevention, diagnosis, and treatment strategies. Addressing sex differences is critical for developing accurate diagnostic tools and personalized therapeutic approaches, ultimately improving outcomes for both women and men with liver disease.

Circadian rhythm disruptions are increasingly recognized in disorders such as obstructive sleep apnea (OSA), yet analysis of 24 h gene expression patterns remains challenging due to the lack of reliable reference genes for normalization. Even commonly used housekeeping genes may exhibit circadian oscillations, which can confound rhythmic gene expression analyses and hinder biomarker identification. To address this limitation, we evaluated the gene expression stability of 11 commonly used housekeeping genes in blood collected every 6 h over 24 h period from 40 adults with varying OSA severity and controls. Stability ranking by analytical tools RefFinder and EndoGeneAnalyzer identified ACTB (β-actin) and RPL13A (ribosomal protein L13a) as the most consistent reference genes, with minimal intra- and inter-individual variability across sampling times and disease groups. Their suitability was assessed by personalized cosinor analysis of core clock genes (BMAL1, PER2, CRY1), demonstrating that appropriate normalization enables detection of circadian oscillations in clinical samples. Using the optimal normalization, CosinorPy analysis of the core clock genes revealed significant circadian oscillations of at least one clock gene in the studied participants. These findings establish ACTB and RPL13A as robust reference genes for blood-based circadian studies of OSA and provide an important methodological framework for future circadian biomarker research.

Lanosterol 14α-demethylase (CYP51), a key enzyme in cholesterol synthesis, is essential for normal liver function. Reduced CYP51 activity leads to metabolism-associated liver disease and ultimately hepatocellular carcinoma, yet the hepatocellular processes most affected and their crosstalk with other liver cell types remain poorly defined. Here, we present a new inducible liver-specific Cyp51 KO mouse (iLKO) model designed to study how acute disruption of cholesterol synthesis is managed in the adult liver. Doxycycline-inducible deletion minimizes developmental confounders of albumin-Cre models and enables isolation of viable primary hepatocytes. iLKO hepatocytes and liver tissue showed efficient CYP51 depletion with marked accumulation of lanosterol and 24,25-dihydrolanosterol, whereas hepatic cholesterol levels remained unchanged or only mildly reduced, indicating compensatory uptake and/or pathway rerouting. Histology and transmission electron microscopy revealed hepatomegaly with mild portal inflammation, ductular reaction, endoplasmic reticulum dilation, mitochondrial swelling, and increased nuclear lipid droplets, consistent with adaptation to endoplasmic reticulum stress but without overt fibrosis at the studied time points. Notably, crystal-like inclusions-particularly in Kupffer cells-were observed. Although MALDI-TOF mass spectrometry imaging could not determine their exact composition, their presence in the context of toxic sterol overload strongly suggests noncholesterol sterol crystallization as a previously unrecognized trigger of inflammation. In summary, the iLKO model allows dissection of sterol toxicity independently of developmental effects and provides mechanistic insight into how disrupted cholesterol synthesis in adult hepatocytes initiates sterol-driven cellular stress and inflammation that predispose to metabolism-associated liver disease and hepatocellular carcinoma.

Lanosterol 14α-demethylase (CYP51) is an enzyme involved in cholesterol synthesis, crucial for the normal liver function. Diminished activity of CYP51 leads to metabolism associated liver disease, ending in hepatocellular carcinoma. It is still not clear which processes are most affected in the hepatocytes and how they communicate with other cells towards the progressive liver pathology. Herein we describe a new inducible, liver-specific Cyp51 knockout mouse model (iLKO), developed to study how acute disruption of cholesterol synthesis is managed in the adult liver. Doxycycline inducible deletion avoided developmental confounders of albumin-Cre models and enabled isolation of viable primary hepatocytes. iLKO hepatocytes and liver tissue showed CYP51 depletion with accumulation of lanosterol and 24,25-dihydrolanosterol, while hepatic cholesterol levels remained largely unchanged, indicating compensatory uptake and/or pathway rerouting. Histological examination and transmission electron microscopy (TEM) revealed hepatomegaly with mild portal inflammation and ductular reaction but no overt fibrosis at the studied time points. iLKO hepatocytes displayed increased nuclear lipid droplets (LD) that might be involved in adaptation to endoplasmic reticulum (ER) stress. Additionally, we discovered crystal-like inclusions, especially in Kupffer cells. MALDI-TOF MSI could not resolve their composition, but their occurrence alongside sterol overload implicates non-cholesterol sterol crystallization as a potential trigger of inflammation. In summary, iLKO is a suitable model for dissection of sterol toxicity, clearly separated from developmental effects of Cyp51 depletion. Future examinations could reveal how toxic sterol intermediates are buffered in adult liver and how they might be connected to inflammation driven pathologies, relevant also to human health.

Obstructive sleep apnea (OSA), one of the most common breathing disorders during sleep, is associated with circadian rhythm disruption, yet circadian genes expressed in blood remain largely unexplored as biomarkers. Reliable circadian gene expression analysis requires stable reference genes for qRT-PCR normalization, but no clear guidance exists for blood-based circadian studies in OSA. We evaluated the expression of 11 candidate reference genes ( GAPDH, ACTB, RPL13A, PPIB, TBP, HPRT1, PPIA, SDHA, TUBB2A, UBC ) in whole blood collected every 6 hours over 24 hours from 40 participants who underwent overnight respiratory polygraphy. Gene stability was assessed with RefFinder and EndoGeneAnalyzer across OSA severity levels, intra-individual variability, and time-point variability. ACTB and RPL13A consistently emerged as the most stable reference genes under all conditions. Their robustness was confirmed by personalized cosinor analysis of core clock genes ( BMAL1, PER2, CRY1 ), showing that reliable normalization enables detection of circadian oscillations in clinical samples. While population-level analysis revealed no significant rhythmicity, individual profiles showed oscillations in 25 participants, independent of OSA severity. These findings identify ACTB and RPL13A as strong candidates for circadian transcriptomic studies in blood and provide a methodological foundation for biomarker discovery in sleep medicine, molecular medicine, and translational chronobiology.