## 1 Introduction  
Breast cancer is the second highest cancer-related illness worldwide, causing over 0.6 million deaths with around three-fold new cases annually [1]. It is caused through numerous genetic changes including gain of function mutations in proto-oncogenes and loss of function mutations in tumour suppressor genes. Among several intracellular signaling proteins, protein kinase C (PRKC) oncoprotein and PTEN tumour suppressor are examples of potential therapeutic targets for blocking the malignancy of breast cancer cells [2]. PRKC is a family of serine/threonine protein kinases involved in a number of signal transduction pathways which regulate several cellular functions including differentiation, proliferation, and apoptosis. Consequently, its inevitable implication in tumorigenesis and metastasis has led to extensive research to date [3]. Human PRKC isoforms encompass 15 members which are classified into three groups [4]. The protein kinase C alpha (PRKC\(\alpha\)) isoform, encoded by PRKCA gene, belongs to the 'classical' group which can be activated by phospholipids, Ca\({}^{2+}\), and diacylglycerolcerol (DAG), a lipid second messenger formed upon stimulation of membrane receptors, such as receptor tyrosine-kinases and G-protein coupled receptors [5; 6; 7]. Due to multifaceted and highly tissue-specific functions, PRKC\(\alpha\) was shown to be downregulated in colorectal and kidney cancer. The anti-tumorigenic role was inferred from spontaneous formation of intestinal tumour in PRKC\(\alpha\)-deficient mouse [8]. However, importantly, PRKC\(\alpha\) acts as a tumour promoter and is reported to be upregulated in breast, bladder, endometrial and brain cancers. For the tumorigenic role, it not only supports proliferation, but also resists apoptosis due to radiation and chemotherapy [7]. Because there are numerous studies linked PRKC\(\alpha\) to increased proliferation and anti-apoptotic signals [9; 10; 11], there is a growing interest in this kinase as a potential target for breast cancer therapy. This isozyme of PRKC is upregulated in breast cancer accompanied with endocrine resistance [12; 13]. [PERSON], [PERSON] et al. showed that expression of PRKC\(\alpha\) in primary breast tumours is predictive of tumour reappearance following tamoxifen treatment [13]. Likewise, expression of PRKC\(\alpha\) was elevated in Triple Negative Breast Cancer (TNBC) patients and shown to be responsible for chemotherapy resistance and metastasis [11]. In this study, we deployed RNA interference therapy using short interfering RNA (siRNA) against PRKCA gene to silence its expression with a view to reduce the proliferative signal resulting in diminished breast cancer cell growth. Another therapeutic target in this study was PTEN (phosphatase and tensin homolog), encoded by the PTEN gene on chromosome 10q23.31 [14]. PTEN, the first identified phosphatase tumour suppressor, has dual phosphatase activity on both lipid and protein and plays important roles in regulation of cell growth, migration and genomic stability [15; 16; 17]. Its lipid phosphatase activity dephosphorylates PIP3 to PIP2 and thus negatively regulates the phosphatidylinositol-3-kinase (PI3K)/protein kinase B (Akt) pathway [18]. PTEN, as a protein phosphatase, directly dephosphorylates and thus downregulates AKT, which leads to an upsurge of p27 levels and causes apoptosis [19]. However, its protein phosphatase activity is widely noticed in the nucleus where it works on centromere protein C1 (CENP-C1), DNA repair protein RAD51, anaphase-promoting complex (APC) and E-cadherin (encoded by CDH1) and thus contributes to DNA repair and cell-cycle arrest [18]. PTEN loss can be sporadic or hereditary. Loss of heterozygosity is common for PTEN. However, the gene can be silenced by missense or epigenetic mutations as well [14]. [PERSON]'s second hit theory that tumour suppressor genes need two mutations to manifest symptoms does not fit for PTEN.