The clinical and radiological presentations of GLM often resemble those of BC. Both GLM and BC typically present as breast masses with indistinct borders and firm consistency, and may be accompanied by enlarged ipsilateral axillary lymph nodes. Although modern research has improved the non-invasive differential diagnosis of GLM and BC through various radiological techniques, such as sonogram radiomics model22, contrast-enhanced ultrasound23, ultrasound elastography24, deep-learning based AI automatic classification system25, and ARFI elastography26, the gold standard for diagnosing GLM still requires tissue biopsy. In some cases, multiple biopsies may be necessary for clinical differential diagnosis. Furthermore, a comprehensive analysis of the tissue proteome in GLM patients has identified 16 immune-related proteins and 17 proteins associated with cancer metabolism, highlighting the complex molecular relationship between GLM and BC27.Similarly, based on the literature review, Aksan et al. have identified serum miR-21 and PTEN levels as potential non-invasive biomarkers for distinguishing between GLM and BC28. No other studies have investigated serum biomarkers specific to GLM. Additionally, this study is the first to compare the expression levels of miR-451a, miR-5571-3p, CLN6, HSD11B1, and PDE4 in GLM, BC, and breast fibroadenoma, confirming the diagnostic significance of miR-451a, miR-5571-3p, and CLN6 in differentiating between GLM, BC and fibroma.
miR-451a is known to be involved in various cancers, including medullary thyroid carcinoma29, bladder cancer30, pancreatic cancer31, colorectal cancer32, and inflammatory diseases33. In a study conducted by Abdul et al., the relative expression levels of miRNAs in tumorous and normal adjacent tissues of Triple-negative breast cancer (TNBC) patients were determined using qRT-PCR. Their results revealed that miR-451a expression was significantly lower in the cancerous tissues compared to the normal adjacent tissues of TNBC patients34. Plasma expression of small non-coding RNAs, primarily microRNAs, in BC and control groups was analyzed using qPCR in a multicenter biomarker discovery study. The findings indicate that miR-451a is significantly down-regulated in the breast cancer group. There is an association between high miR-451a expression and low-risk factors for breast cancer. It is suggested that miR-451a may exert a tumor suppressive function in breast cancer35. Additional research has also supported the finding that miR-451 expression is reduced in cases of invasive breast cancer (IBC) compared to ductal carcinoma in situ (DCIS). In DCIS cases with high-risk characteristics for progression, the expression levels of miR-451 were consistently low. These findings indicate that miR-451 may play a significant role in the development of invasive carcinoma from DCIS as a tumor suppressor13. Furthermore, studies have reported that miR-451a can improve tamoxifen sensitivity and suppress cell proliferation in breast cancer36,37. It should be noted that the correlation between miR-451a and GLM is primarily indirect. Autoimmune inflammatory have been strongly associated with GLM, and individuals with granulomatous mastitis are susceptible to various autoimmune diseases38. Several conditions, including sarcoidosis, systemic lupus erythematosus (SLE), polyvasculitis granulomatous, psoriatic arthritis/psoriasis, familial Mediterranean fever, ankylosing spondylitis, Sjogren's syndrome, rheumatoid arthritis (RA), and erythema nodosum, have been associated with GLM. A systematic review of 3060 GLM patients revealed that 34% of them had an underlying immune disease39. While direct studies linking miR-451a to GLM are lacking, increased expression of miR-451a has been observed in various autoimmune diseases. For example, it has been found to be upregulated in the spleen and thymus of mouse models with SLE40. Furthermore, miR-451a has been closely linked to the progression of SLE and can serve as an indicator of disease severity. Other studies have also shown a correlation between circulating levels of miR-451a and the severity of autoimmune encephalomyelitis41. Our study's findings align with previous research. Despite the incomplete understanding of the specific mechanisms connecting miR-451a and autoimmune diseases, current research indicates that miR-451a may play a role in regulating immune responses. It is likely involved in modulating inflammatory pathways and influencing the expression of genes related to immune function. Additional studies are essential to explore the precise relationship and molecular mechanisms linking miR-451a with GLM and autoimmune diseases. Understanding these connections could potentially offer valuable insights into the development of targeted therapies for these conditions.
The research on miR-5571-3p is currently limited, but preliminary studies suggest its potential involvement in biological processes and inflammatory diseases. Associations have been observed between miR-5571-3p and the development of autoimmune thyroid disease42. Furthermore, an miRNA profiling analysis revealed elevated expression of miR-5571-3p, linked to increased risk and severity of rheumatoid arthritis15. Additionally, high expression of miR-5571-3p has been found in granulomatous mastitis14. It's important to note that our current understanding of miR-5571-3p's specific functions and mechanisms remains limited. Further research is anticipated to yield more significant discoveries regarding miR-5571-3p.
At present, the primary focus of CLN6 research is on elucidating its pathogenesis and identifying therapeutic approaches. Neuronal Ceroid Lipofuscinoses (NCLs) constitute a group of fatal neurodegenerative lysosomal storage disorders characterized by the intracellular accumulation of lipoprotein aggregates in neurons and other tissues. Studies have revealed43 that KCTD7 derived from NCL patients leads to excessive accumulation of CLN5 in the endoplasmic reticulum. This accumulated CLN5 disrupts the interaction between CLN6-CLN8 and lysosomal enzymes, impairing ER-to-Golgi trafficking of lysosomal enzymes. These two NCL disease-causing genes exhibit biochemical connections and functions in a common neurodegenerative pathway. Furthermore, experimental studies have provided valuable insights into this disease. Gene therapy is being explored as a potential treatment for this condition. Research has demonstrated that delivering viral genes via cerebrospinal fluid transfer to the brains of CLN6-Batten disease mice effectively mitigates pathology in brain tissue and retinal neurons, partially alleviating vision deterioration44. Moreover, a separate study employed adeno-associated virus (AAV)-mediated gene therapy to address neurodegeneration in a mouse model of CLN6 disease. Neonatal bilateral intracerebroventricular injections with AAV9 carrying CLN6 led to a more than 90% increase in lifespan, sustained motor skills and coordination, and diminished neuropathological hallmarks of Cln6-deficient mice for up to 23 months following vector administration. Additionally, enhancements in motor performance, learning, and memory deficits were observed45,46. This investigation revealed a significant increase in the expression levels of the CLN6 gene in the serum of the GLM group and the BC group (P<0.01), suggesting a potential link between elevated CLN6 expression and the disease status of GLM and BC. However, further exploration is necessary to determine whether abnormal expression of the CLN6 gene also exists in GLM and BC patients.
HSD11B1 has been the subject of extensive discussion in tumor-related research, particularly regarding its potential role in certain types of tumors. Notably, a study revealed significantly elevated expression of HSD11B1 in 786-O cell lines and Clear cell renal cell carcinoma clinical tissues compared to the control group47. Furthermore, investigations into the mechanism of action of HSD11B1 have indicated potential associations with breast cancer among postmenopausal women. Specifically, a study suggested that common genetic variations in HSD11B1 and IRS2 may be linked to an increased risk of breast cancer, with the minor allele of HSD11B1 rs932335 demonstrating nearly twofold higher risk (P = 0.0002)48. A separate study involved the cloning and sequencing of the HSD11B1 gene, designating it as HSD11B1L-181. The overexpression of this variant was shown to notably enhance the proliferation, migration, and invasion of Glioblastoma (GBM) cells. Conversely, the suppression of HSD11B1L-181 expression resulted in the inhibition of the oncogenic potential of GBM cells49. These discoveries indicate the potential for targeting 11β-HSD1 as a valuable adjunct in cancer therapy. Additionally, there is evidence supporting a drug repurposing strategy that combines HSD11B1 inhibitors with immune checkpoint inhibitors to enhance melanoma immunotherapy19. The exact role of HSD11B1 in the immune system remains incompletely understood. HSD11B1 has the ability to regulate the biological activity of adrenal corticosteroids, which play a critical role in immune system regulation. Consequently, HSD11B1 may impact the function and immune response of immune cells through the modulation of adrenal corticosteroid metabolism. Research has indicated that HSD11B1, an enzyme involved in corticosteroid metabolism, exhibits high expression in autoimmune diseases. In individuals with atopic dermatitis, the expression of 11β-HSD1 in lesional epidermis was found to be elevated compared to healthy controls50. Similarly, in patients with anti-MDA5+ dermatomyositis, notable alterations in the immune response-related protein profile were observed, with a significant increase in HSD11B1 levels compared to the control group51. Notably, a clinical trial focusing on Crohn's disease revealed an association between low serum levels of the anti-inflammatory mediator HSD11B1 and the risk of mid-term/long-term clinical relapse52. Nevertheless, controversies and uncertainties persist regarding the relationship between HSD11B1 and both tumors and immunity. Further research and validation are necessary to clarify its specific mechanisms and its role in tumor development and immune regulation.
Regarding cancer, the exploration of PDE4 is still at an early stage. Evidence has demonstrated that the expression level of PDE4 is elevated in breast cancer stem cells in comparison to normal stem cells53. While studies have indicated no significant variances in the positive rates of PDE4 expression between breast cancer and para-carcinoma tissues (P > 0.05), associations among Epac1 and cyclin D2, PDE4 and cyclin D2, AKAP95 and PKC, Cx43 and PKC, and cyclin D2 and PKC proteins were observed (P < 0.05). These findings suggest potential synergistic effects among these proteins in the progression of breast cancer54. In the context of inflammation, elevated expression of PDE4 subtypes has been observed in tissue samples from patients with chronic ulcerative colitis. Clinically, PDE4 inhibitors are established pharmaceuticals used in the treatment of immune-related diseases. Several drugs have been authorized for the treatment of various immune-related conditions or have entered clinical trials. For example, apremilast, a selective PDE4 inhibitor, has been approved for the treatment of psoriasis. Selective PDE4 inhibitors are also under investigation in clinical trials for the treatment of ankylosing spondylitis, RA, ulcerative colitis, SLE, allergic rhinitis, multiple sclerosis, Alzheimer's disease, and other diseases21555657.
The main mechanisms through which PDE4 inhibitors exert their effects include58: inhibiting the activity of various inflammatory mediators, suppressing the up-regulation and expression of cell adhesion molecules, impeding the activation of blood leukocytes, inducing cell apoptosis, prompting the generation of cytokines with inhibitory activity such as IL-6, and triggering the release of catecholamines and endogenous hormones.Given the established use of PDE4 inhibitors in the clinical management of immune-related diseases, it is worthwhile to explore whether these inhibitors may have specific therapeutic effects on breast cancer and GLM drugs.
In recent years, non-invasive biomarkers, miRNA chips, and other technologies have emerged, potentially aiding in the diagnosis of GLM diseases. It is conceivable that these advanced technologies will continue to develop, potentially evolving into a new gold standard diagnostic tool, thereby reducing the reliance on invasive biopsies.