Worldwide, Breast Cancer (BC) constitutes the primary cause of cancer-derived fatalities between females. As highlighted in the 2018 Cancer Statistics, it ranks as the most prevalent neoplasm in women and the leading cause of cancerous demise, with over 2,100,000 new diagnoses annually and beyond Sixty-two thousand deceased [1]. Five intrinsic/molecular subgroups of BCs can be distinguished by the existence or lack of three hormone receptors, including human epidermal Growth Factor 2 (HER2), Progesterone Receptor (PR), Estrogen Receptor (ER), and along with the proliferation index marker Ki67[2, 3]. Breast cancer subtypes encompass HER2-positive, basal-like, and normal-like tumors, luminal A and luminal B [3, 4]. Despite enhancements in outcomes for Breast Cancer patients due to early diagnosis and the latest anti-cancer medications, including surgery confined to the region, standard chemotherapeutic treatments, targeted radiotherapy, hormone-based therapy, and monoclonal antibody administration, this disease still has a significant recurrence rate and threatens the lives of a great number of people around the world [5–8]. Thus, the analysis of gene expression associated with BC, comprehending gene expression patterns in various clinical and pathological circumstances related to it, and detecting diagnostic and prognostic biomarkers can yield significant awareness of the disease and assisting in its precaution [9].
Gastric Cancer (GC) is a substantial health crisis globally. Helicobacter pylori contamination and food intake habits play a major role in determining the epidemiology of this disease[10, 11]. With over 1 million cases and more than 768,000 casualties in 2020, GC is considered the fifth most widespread cancer diagnosis and the third predominant cause of cancer-associated deaths [1, 12]. Based on the molecular classification by the Asian Cancer Research Group (ACRG), four subtypes have been identified, including i) Microsatellite instability in gastric carcinomas (MSI GCs), ii) Gastric carcinomas demonstrating epithelial-to-mesenchymal transition (EMT GCs), iii) Microsatellite stable gastric cancers with preserved TP53 activity (MSS/TP53+) and iv) Microsatellite-stable gastric tumors exhibiting TP53 inactivity (MSS/TP53-)[13]. A distinguishing aspect of the ACRG Sorting, is its potential for relating each molecular category to therapeutic results and specific relapse models [14]. The latest advancements in genome analysis have revealed numerous biomarkers involving genes, lncRNAs, and miRNAs. The emergence of these biomarkers is expected to greatly influence cancer progression, effective treatment selection, and follow-up practices[15, 16].
Colorectal cancer (CRC) is excessive cell proliferation or abnormal cell growth in the colon, rectum, or appendix[17]. The incidence of this disease has increased worldwide and is now the third most prevalent tumorous malignancy in men and the second most prevalent in women. Furthermore, 10% of cancer fatalities are attributed to CRC[18]. Approximately nineteen million CRC occurrences and 10 million casualties due to this cancer were reported in 2020[19]. By 2030, the international incidence of CRC is anticipated to elevate by 60% leading to approximately two million two hundred thousand new diagnoses and 1,100,000 fatalities [20]. The majority of patients receive a diagnosis of colorectal cancer at an advanced stage, leading to a poor prognosis[21]. At this stage, malignant proliferation and significant metastasis have already taken root[22]. Statistics show that 50% of the patients with CRC lose their lives due to the spread of the disease to distant organs. Colorectal cancer initiation and progression is a multifaceted, multi-phase procedure involving various biological pathways and genetic changes. Consequently, it is crucial to seek pioneering biomarkers which are able to either stimulate or prohibit CRC progression[23].
lncRNAs (Long non-coding RNAs) are classified as a type of RNA that does not encode proteins. They are longer than 200 base pairs and do not possess open reading frames[24]. Compared to protein coding genes, lncRNAs usually contain reduced number of exons, are less conserved, and are present in lower quantities[25]. The importance of lncRNAs not only in transcriptional but also in post-transcriptional regulation of genes has been demonstrated[25]. They achieve this by interacting physically with various Surfaces, including proteins (transcriptional co-factors), RNAs (microRNA sponges), and DNA (chromatin interaction frameworks)[26]. Meanwhile, lncRNAs could be encapsulated within lipid vesicles, like exosomes and apoptotic bodies, or firmly attach to particular proteins. They are then emitted in to serum, urine, and various body fluids, facilitating their acquisition and detection. [27]. These molecules have a half-life of around 3.5 hours, surpassing that of many mRNAs[28]. lncRNAs are recognized as crucial regulators of the biological behavior of cells, playing essential roles in cancer initiation, development, and metastasis[29, 30]. Additionally, their stable expression and easy acquisition from body fluids make them viable candidates for tumor diagnosis and prognosis[31].
A sophisticated relationship between miRNAs and lncRNAs has been distinguished, suggesting that specific lncRNAs serve as host genes for miRNAs and are designed to generate miRNAs that inhibit intended genes [32, 33]. Findings indicate that lncRNA MIR497HG, positioned on chromosome 17p, is downregulated and acts as a tumor suppressor in bladder cancer[34, 35]. Progressive investigations reveal that the MIR497HG-derived miR-497/195 cluster is diminished and serves as a cancer-inhibiting factor in various human neoplastic diseases, such as hepatic malignancy, bladder cancer, lung cancer, glioma, colon cancer, ovarian cancer, acute lymphoblastic leukemia, and breast cancer[32].NORAD (LINC00675) is triggered by DNA damage and takes part in preserving genome steadiness and normal mitosis[36]. This lncRNA is extensively expressed and thoroughly preserved across mammalian species. In the human DNA sequence, the NORAD gene consists of a single exon, yielding a 5.3 kb transcript, and is found at Chr20q11.23. NORAD is primarily distributed within the cytoplasmic area of human cells[37, 38]. It ensures genomic stability by interacting with Pumilio proteins, restricting the inhibition of their aimed mRNAs. Thus, the deactivation of NORAD results in chromosomal instability and aneuploidy, contributing to the buildup of genetic mutations and cancer development. NORAD has been observed in multiple forms of cancers such as breast cancer[39].TRIM29 also referred to, as the ataxia-telangiectasia group D complementing gene (ATDC), is part of the TRIM protein family, locating on chromosome 11q[40]. Increased amounts of theTRIM29 expression have been detected in lung, bladder, pancreatic, gastric, prostate, and nasopharyngeal carcinomas[41–46]. TRIM29 has been shown to enhance malignant cell proliferation and invasiveness via the stabilization of β-catenin[47]. The mechanisms could involve suppressing p53 activity and enhancing cell vitality by downregulating apoptosis-promoting genes that are modulated through p53[48]. However, reduced expression of it has been reported in prostate cancers[49, 50]. Hence, its function is intricate, relying on the specific cancer subtype and the microenvironmental context[51].
Numerous efforts have been directed towards pinpointing lncRNAs as innovative active genetic sequences involved in cancerous tumorigenesis and understanding their potential as novel biomarkers for BC, GC, and CRC diagnosis and prognosis. In this study, we concentrated on two novel lncRNAs (MIR497HG, NORAD) and a gene (TRIM29) to investigate their expression levels in BC, GC, and CRC via laboratory experiments. Simultaneously, diverse bioinformatic analyses were employed to investigate the roles and significance of the three mentioned elements in BC, GC, and CRC.