Date of Award

10-24-2025

Degree Type

Thesis

Degree Name

MPhil in Biological and Biomedical Sciences

First Advisor

Dr. Shagufta Khan

Second Advisor

Dr. Adnan Abdul Jabar Khan

Third Advisor

Dr. Imrana Mansoor

Department

Biological and Biomedical Sciences

Abstract

Introduction: Hormone receptor positive (HR+) Human epidermal growth factor receptor 2 negative (HER2-) breast cancer patients are well responsive to hormonal therapy. However, these patients gradually develop endocrine resistance, which leads to progression of the disease. PIK3CA gene encodes the catalytic subunit p110α of phosphatidylinositol 3-kinase (PI3K). The hotspot mutations in PIK3CA can constantly activate the PI3K/AKT/mTOR signaling pathway, promoting cell growth, preventing apoptosis, and resistance to therapy. To date, none of the studies have reported the PIK3CA mutation status and clinicopathological features of endocrine resistant, HR+ HER2- metastatic breast cancer patients in Pakistan, thus this study designed.
Methods: This study was conducted using formalin fixed paraffin embedded blocks and clinicopathological features that were noted from the Integrated Laboratory Management System. After nucleic acid extraction, the quantity and quality were assessed using both NanoDrop and gel electrophoresis. PIK3CA selected exons (10 and 21) were amplified and sent to Eurofins for Sanger sequencing. RNA was transcribed to cDNA for quantitative PCR analysis of PIK3CA gene expression.  Results :Our data showed that the metastatic breast cancer was significantly prevalent in 20-59 years women, 56% women were premenopausal, significantly high comorbidities (60%, p ≤ 0.001), and bone metastasis (p ≤ 0.01). Among these patients 92% received hormonal therapy. About 50% of patients received a combination of tamoxifen and letrozole. The left metastatic breast cancer (52%) and IDC (76%) were found to be the most common. Grade III (48%) and strong positive expression of ER (68%) were significantly high in our population. The PIK3CA hotspot mutations in exons 10 and 21 were found in 72% of the patients. The highest frequency of mutations E545K and E545G was found in exon 10, followed by exon 21 for H1047R. Whereas the v PIK3CA gene expression analysis showed highly significant (p = 0.005) upregulation of PIK3CA in the mutated samples. 
Conclusion: We found in the Pakistani population, higher frequency of the exon 10 hotspot SNV rs104886003 G>A (E545K). In contrast, the more prevalent SNV rs121913279 C>T (H1047R) in exon 21 is seen in other studies. The presence of the PIK3CA gene mutation is significantly associated with high upregulation of PIK3CA gene expression.

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1

Last Page

86

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