## 5 Discussion
Various experimental studies, in vitro and in vivo, have shown, by targeting this sub-unit, its downstream signaling mediator is able to prevent the transition of the dormant tumor cells to function into metastatic cells and attenuate cell proliferation [58; 60]. Further, by inhibiting its ability to cease apoptosis caused by various drugs such as paclitaxel could aid in reducing the chemoresistance via deactivation of AKT and MAPK pathways and effector molecules such as B-cell lymphoma-2 (Bd-2) [45]. In Figure 13 we have elucidated how this integrin sub-unit could involve in signaling pathways, and introduction of an antagonistic could help in hampering the pathways at various sites. Integrin \(\beta\)3 (ITG\(\beta\)3) a critical sub-unit which plays role in tumor invasion, neoangiogenesis, and inflammation, makes it one of the promising cancer targets. Tumor cells which  
Figure 13: A schematic representation of targeting ITG\(\beta\)1 in the cells, and possible ways of hampering essential tumorigenic pathways. show high expression of ITG\(\beta\)3 exhibit enhancement in their proliferation and metastasis, especially to bones [61, 62]. The role of this integrin in breast cancer has been studied in various experiments, in vitro as well as in vivo, suggesting its knockdown or deletion can play significant role in decreasing the metastasis. In our MTT assay, delivery of \(\beta\)3 siRNA loaded CA reduced the cell viability to \(\sim\)60% in MCF-7 (Figure 4a), with cytotoxicity of \(\sim\)14% (Table 2), while in MDA-MB-231 and 4T1 cell lines no reduction in cell viability was seen (Figure 4b,c respectively). However, in vivo model showed contrary results compared to cell line. Significant tumor reduction was observed from Day 10 (Figure 11), with highest of 4.9-fold decrease on Day 12 compared to CA control (Table 6) and reduced tumor size at the end of tumor excision (Figure 12d). Protein expression study showed the transfection of CA loaded \(\beta\)3 integrin siRNA caused reduction of total and phosphorylated MAPK and AKT proteins in MCF-7, MDA-MB-23, and 4T1 cells (Figure 8a-c respectively). One reason for high cell viability despite reduced AKT and MAPK pathways may be due to cross talks with signaling molecules such as that of signal transducer and activator of transcription (STAT)-6/STAT1. These cross talks could have resulted in controlling the balance between anti-tumor and pro-tumor immune cells [61] in the in vitro model. In several biological contexts, the locus of \(ITGB3\) is regulated epigenetically, which in turn is responsible for regulating its function and expression. This regulation is seen to control tumor senescence as well. For example, increased levels of endogenous \(\beta\)3 via transcriptional regulation of polycomb protein chromobox 7 (CBX7) is observed during oncogene-induced senescence (OIS) with concomitant increase in \(\beta\)3 mRNA expression [62]. Therefore, by hampering expression of this integrin along with other transcriptional proteins via an efficient vehicle may provide improved efficacy in tumor regulation. Integrin \(\beta\)4 (ITG\(\beta\)4) overexpression, chemoresistance to drugs such as tamoxifen, and its related aggressiveness has been found especially in basal-like breast cancers. Cell migration and invasion takes place with the aid of actin binding proteins, which help in stabilization of actin protrusions [31]. Targeting this subtype of integrin has shown reduction in tumors in aggressive cancers such as TNBC. Based on our results, ITG\(\beta\)4 siRNA-CA delivery did not caused visible reduction in cell viability in MCF-7 and 4T1 cells (Figure 5a,c respectively), while in MDA-MB-231, cell viability of \(\sim\)88% (Figure 5b), with cytotoxicity of \(\sim\)11% (Table 3) was observed. Presence of integrin \(\beta\)4 has been observed in TNBC patients. Inter and intra tumoral heterogeneity and presence of cancer stem like cells (CSC) being critical feature of this breast cancer [63].