Perception of breast cancer risk factors: Dysregulation of TGF-β/miRNA axis in Pakistani females

Unraveling the Role of BRCA1 variants in Dysregulation of Transcriptional and Post-Transcriptional Mechanisms in Breast Cancer

Objective

To screen BRCA1 gene variants and predict potential role of the identified variants in breast cancer.

Method

This case-control study included two hundred and fifty breast cancer patients and equal healthy individuals from the Federal Breast Cancer Screening Centre, Pakistan Institute of Medical Sciences, Islamabad from March 2021- January 2023. Demographic data was collected through questionnaires and clinical data was assessed using mammograms, ultrasound, histopathology and immunohistochemistry reports. Polymerase chain reaction and Sanger sequencing approach were used to detect variants in BRCA1 gene. In-silico analyses were carried out to predict mutation effect, miRNA binding site alterations and change in mRNA structure and stability.

Results

Invasive ductal carcinoma was the most prevalent type of breast cancer. Old age [OR: 2.8149 (1.5995 to 4.9538) p value = 0.0003] and family history [OR: 4.3186 (1.7336 to 10.7581) p value = 0.001] were significant breast cancer risk. Six variants were identified. Two novel missense variants, Chr17:43082553A>T and Chr17:43093710A>T were predicted deleterious as these disrupted interaction with PALB2 and importin alpha's NLS2 site, respectively. In silico analysis predicted the loss of hsa-miR-1179 binding site due to variant Chr17:43093220T>C. Moreover, four variants were predicted to affect the mRNA structure and stability.

Conclusion

Two novel variants were predicted to be pathogenic. In-silico analysis predicted the loss of miRNA binding site along with change in mRNA secondary structure plus stability, possible mechanisms for oncogenesis. Further, expressional studies are required to confirm BRCA1 gene dysregulation in breast cancer due to these variants.

A Senescence-Associated Secretory Phenotype of Bone Marrow Mesenchymal Stem Cells Inhibits the Viability of Breast Cancer Cells

Breast cancer, the most prevalent malignancy in women, often progresses to bone metastases, especially in older individuals. Dormancy, a critical aspect of bone-metastasized breast cancer cells (BCCs), enables them to evade treatment and recur. This dormant state is regulated by bone marrow mesenchymal stem cells (BMMSCs) through the secretion of various factors, including those associated with senescence. However, the specific mechanisms by which BMMSCs induce dormancy in BCCs remain unclear. To address this gap, a bone-specific senescence-accelerated murine model, SAMP6, was utilized to minimize confounding systemic age-related factors. Confirming senescence-accelerated osteoporosis, distinct BMMSC phenotypes were observed in SAMP6 mice compared to SAMR1 counterparts. Notably, SAMP6-BMMSCs exhibited premature senescence primarily due to telomerase activity loss and activation of the p21 signaling pathway. Furthermore, the effects of conditioned medium (CM) derived from SAMP6-BMMSCs versus SAMR1-BMMSCs on BCC proliferation were examined. Intriguingly, only CM from SAMP6-BMMSCs inhibited BCC proliferation by upregulating p21 expression in both MCF-7 and MDA-MB-231 cells. These findings suggest that the senescence-associated secretory phenotype (SASP) of BMMSCs suppresses BCC viability by inducing p21, a pivotal cell cycle inhibitor and tumor suppressor. This highlights a heightened susceptibility of BCCs to dormancy in a senescent microenvironment, potentially contributing to the increased incidence of breast cancer bone metastasis and recurrence observed with aging.

miRNAs in Cancer (Review of Literature)

MicroRNAs (miRNAs) are short, noncoding, single-stranded RNA molecules that regulate gene expression at the post-transcriptional level by binding to mRNAs. miRNAs affect the course of processes of fundamental importance for the proper functioning of the organism. These processes include cell division, proliferation, differentiation, cell apoptosis and the formation of blood vessels. Altered expression of individual miRNAs has been shown in numerous cancers, which may indicate the oncogenic or suppressor potential of the molecules in question. This paper discusses the current knowledge about the possibility of using miRNA as a diagnostic marker and a potential target in modern anticancer therapies.