Leukemia is a range of highly malignant diseases that severely affect the hematopoietic system. During the process of hematopoiesis, cancerous changes in white blood cells lead to leukemia, which is characterized by impaired immune cell function and disruption of normal bone marrow function. Despite significantly advancements made in leukemia treatment in recent years, several challenges such as multidrug resistance, cellular heterogeneity, heterogeneous molecular abnormalities, karyotypic instability, and lack of selective action of antineoplastic agents still persist [1]. Due to the migratory and survival capabilities of malignant leukocytes within the bloodstream as well as their potential for uncontrolled cellular proliferation, leukemia exhibits a highly aggressive nature and poses considerable challenges for treatment [2]. Consequently, early identification of diagnostic markers for leukemia is of utmost importance.

Benzene, a crucial component of organic solvents, is commonly utilized in industry settings [3,4]. Long-term exposure to benzene is closely associated with various types of leukemia, including acute non-lymphocytic leukemia, acute lymphocytic leukemia (ALL), and non-Hodgkin's lymphoma [5]. The International Agency for Research on Cancer recognizes benzene as a human carcinogen [6]. Hydroquinone (HQ), one of the main metabolites of benzene, is frequently employed as a substitute for benzene in vitro experiment [7]. Our previous studies have revealed that HQ exposure induces DNA damage, cell cycle arrest, cell apoptosis, autophagy, and malignant transformation in TK6 cells [[8], [9], [10], [11]].

Exosomes, are extracellular vesicles with a diameter ranging from 40 to 150 nm. They are secreted by all cells with an intimate system and facilitate intercellular communication by transporting various nucleic acids and protein molecules [12]. Recent research has confirmed the notion that these exosomes carry and deliver microRNAs to recipient cells. In tumor microenvironment context, exosomes provide an effective means for information exchange between malignant transformed cells and normal cells to regulate tumor development [13]. Moreover, the content of exosomal miRNAs may serve as important diagnostic biomarker for early cancer detection [14]. There is urgent need for more effective biomarkers in the early diagnosis and treatment of occupational leukemia [4]. To comprehend changes in exosomal miRNA expression following long-term HQ exposure, we conducted RNA sequencing analysis on exosomal miRNAs derived from HQ-transformed cells (HQ19, exposed to HQ for 19 weeks), as well as phosphate buffered solution control cells (PBS19). Additionally, we also conducted a comprehensive biological analysis of these exosomal miRNAs in order to gain deeper insights into their functional role and underlying mechanism, thereby providing a more scientific foundation for the study of HQ-induced leukemia.

The proto-oncogene miR-1246 is significantly overexpressed in a various tumor tissues, including pancreatic cancer [15], lung cancer [16], and breast cancer [17]. Previous studies have revealed that exosomal miR-1246 derived from breast cancer MDA-MB-231 cells can be transferred to non-malignant HMLE cells via exosomes. This transfer promotes HMLE cell proliferation and enhances chemoresistance through the targeting of cyclin G2 (CCNG2). These findings highlight the potential application of miRNA-based therapeutics for breast cancer treatment [18]. CCNG2, an untypical cyclin that inhibits cell cycle progression, is often down-regulated in human cancers, including leukemia [19]. Although CCNG2 has been associated with leukemia development previously reported [20], the mechanism underlying CCNG2 expression regulation in HQ-transformed cells remains unclear. Based on exosome sequencing results, we hypothesize that abnormally high expression of exosomal miR-1246 derived from HQ-transformed cells may play a role in mediating communication between malignant and normal cells via exosomes. Furthermore, it may also contribution to TK6 malignant transformation induced by HQ through its targeting of the known target CCNG2.

In the present study, we employed RNA sequencing and qRT-PCR to validate differential expression and characteristic features of miRNA in exosomes derived from HQ-transformed cells compared to solvent control cells. We investigated the impact of miR-1246 in exosomes isolated from HQ-transformed cells on cell proliferation and cell cycle arrest, as well as explored the underlying mechanisms in recipient TK6 cells following exposure to HQ. Furthermore, we examined the association between miR-1246 and CCNG2 expression after HQ exposure. This study may provide a novel biomarker for HQ-induced cell malignant transformation.