**3.9 MYC**

68 Biomedicine

induce their apoptosis and death, but it had no effect on normal ovarian cells (Zeng *et al,*  2005). Super-expression of epithelial growth factor receptor HER2/neu was detected in many breast cancers, but its expression in patients with good prognosis was low. Transfection of HER2/neu siRNA led to an antiproliferative and apoptosis-inducing effect in breast cancer cells with high expression of HER2, and this effect was not observed in cells without HER2 expression, suggesting that interference with HER2 could be used as an effective strategy for the treatment of breast cancer with high expression of

Osteopontin (OPN) is a secretory extracellular matrix protein and a cytokine as well. It can promote cell chemotaxis, adhesion and migration. More studies (Wai&Kou, 2008; Wise & King, 2008;Ramaiah&Rittling,2008) have demonstrated that OPN can interact with αVβ3 and CD44 to participate in cell inflammatory response, promote cell migration, adhesion and transduction of related signals, regulate the expression of genes related to tumor development and progression, promote degradation of extracellular matrix, suppress the immune function of the body against tumors, and accelerate tumor progression. Studies(Coppola *et al,* 2004; Cui *et al,* 2007;Tang *et al,* 2007)have found that the level of OPN expression is generally increased in lung, gastrointestinal, urogenital and gynecological tumors. Zhang (Zhang *et al,* 2010) used plasmid-mediated OPN-target siRNA to transfect lung cancer A549 cells and found that the invasion and proliferation abilities of A549 cell decreased. Gong (Gong *et al,* 2010) used PEI as the carrier of OPNsiRNA and injected it between tumor tissues in nude mice bearing transplanted gastric cancer tumors. It was found that the tumor size of the experiment group was only onethird of the control group, and survival of the mice was also prolonged (animals in the control group survived 40 days, and 50% of the animals in the experiment group

β-catenin is a multi-functional adapter protein encoded by human CTNNB1 gene. Its function is expressed in two aspects: One is acting as an important component of the Wnt signaling pathway to mediate signal movement from the membrane to the cytoplasm and to the nucleus, regulating transcription of target genes (such as c-myc,cyclin D1, MMP-7 and cyclooxygenase-2). The other is participating in E-cadherin-mediated intercellular adhesion. β-catenin participates in cell growth, proliferation, invasion and metastasis in malignant tumor tissues. It was found that β-catenin expression was extraordinarily high in many tumors, especially in esophageal cancer. Wang (Wang *et al,* 2009,2010) used β-catenintargeted RNA to interfere with plasmid pGen-3-CTNNB1 and found that pGen-3-CTNNB1 could lower the expression level of β-catenin in esophageal cancer tissue, and reduce the invasion and metastasis abilities of cancer cells. The result of the experiment with nude mice bearing transplanted esophageal cancer showed that the mean volume of tumors in βcatenin RNAi plasmid group was 909.3mm3 versus 2684.4mm3 in the negative control group and 2722.6mm3 in the non-intervention group, indicating that β-catenin-target RNAi could

HER2(Faltus *et al,* 2004).

remained surviving at 60 days).

inhibit the growth of esophageal cancer tumors.

**3.8 β-catenin** 

**3.7 Osteopontin** 

Myc gene is a group of cancer genes discovered earlier, including C-myc, N-myc and L-myc, belonging to nucleoprotein-coding cancer gene. All the three genes encode a nuclear DNAbinding protein related to cell cycle regulation. The Myc gene family and its products can promote cell proliferation, immortalization, dedifferentiation and transformation, and play an important role in the formation of various tumors. Super-expression of Myc gene has been detected in gastric cancer, breast cancer, colon cancer, cervical cancer, Hodgkin's disease and head tumors. Zhang (Zhang *et al,* 2009)injected Myc-target siRNA between transplanted colon cancer tissues in nude mice, and found that the expression level of Myc decreased by 40%; large patches of necrosed cells were seen in tumor tissues; the proliferation of tumor cells was inhibited; and the mean tumor size was about 50% of the control group.

### **3.10 Epithelial cellular adhesion molecule**

Epithelial cellular adhesion molecule (EpCAM) is a recognized tumor-related protein encoded by TACSTDl gene. EpCAM is more than an adhesion molecule, and also has many other functions including participation in regulating cell migration, metastasis, differentiation, signal transduction, cell cycle and metabolism. Studies have demonstrated that EpCAM presents high expression in most solid tumors. In addition, the level of EpCAM expression is positively correlated with lymphatic metastasis. Du (Du *et al,* 2009) transfected lipofectamine 2000 with EpCAM-target siRNA to treat two gastric cell lines (AGS and SGC7901) in transplanted tumor-bearing nude mice, and found that the size of both tumors was about 50% smaller than that of the control group. They also found that the level of CCND1 expression in tumor tissues was decreased, and cell division was blocked at G1.

#### **3.11 CD147**

CD147 is a transmembrane glycoprotein extensively expressing in various tissues of the human body, belonging to the immunoglobulin super-family participating in various physilogical and pathological processes of the body. CD147 interacts with integrin, central avidin, monocarboxylate transporter 1 (MCT1), MCT3 and MCT4 proteins. It is also related to the expression of lactate transporters. These proteins may act as candidate ligands or receptors of CD147 molecule and mediate the biological function of epithelial cells via protein-protein interactions. High expression of CD147 is detected in multiple tumor tissues, especially in pancreatic cancer (Zhang *et al,* 2007), where it promotes invasion, metastasis and anchorage-independent growth of tumor cells, and induces tumor angiogenesis. Schneiderhan (Schneiderhan *et al,* 2009) used CD147-target RNAi to treat pancreatic cancer cells and found that MCT1 and MCT4 were inhibited in tumor cells, and the intracellular concentration of lactate was increased, thus inhibiting the growth of tumor cells. In vivo experiments using shRNA-target silencing of CD147 to treat transplanted pancreatic cancer tumors in nude mice showed that the tumor size of the experiment group was significantly smaller than that of the control group (39.7mm3 vs 89.7mm3), indicating that CD147 as a helper protein could also be used as the target for tumor treatment.

RNA Interference for Tumor Therapy 71

between CIAPIN1 and tumor formation showed that CIAPIN1 expression was increased significantly in HCC, gastric cancer and other malignant tumor tissues (Ida *et al,* 2007;Zhang *et al,* 2008). Li (Li *et al,* 2008) used adenovirus-mediated RNAi to knock out CIAPIN1 in HCC cells and found that CIAPIN1 gene expression in HCC cells was down-regulated, where cells were prevented from entering phase S and cell proliferation was inhibited. Eight weeks after injection of adenovirus/siRNA between transplanted tumor tissues, the tumor size was only one-sixth of the control group, and pathological sections showed apoptotic cells in

Available studies showed that any form of genetic variation should function at the protein level (Branhart&Simon, 2007). Therefore the relationship between eukaryotic cell (protein translation) initiation factor and tumors has aroused increasing attention, especially eukaryotic initiation factor 4E (eIF4E), which was believed to be more closely related to tumors (Sonenberg,2008). Data have shown that eIF4E can alter the amount of expression of some malignant tumor-related genes and is the determinant of malignant phenotype production. It promotes cells to surpass the limit of normal growth and undergo carcinogenesis through regulating the amount of translation of some specific malignancyrelated molecules (Culjkovic *et al,* 2006). Dong (Dong *et al,* 2009) used a vector carrying shRNA of survivin-targeted eIF4E to transfect human breast cancer cells, and found that not only the level of eIF4E mRNA and protein expression was decreased but tumor progressionrelated protein VEGF, FGF2 and CCND1 were also down-regulated markedly. The breast cancer tumor size of the intervention group using eIF4E-targeted shRNA was significantly smaller than that of the control group (233.5mm3 vs 397.7mm3, P<0.01). In addition, shRNA could also enhance the chemotherapy effect of cisplatin. The result showed that the tumor size of the cisplatin+shRNA plasmid combination group was significantly smaller than that

Erythropoietin (EPO) was initially found to play a main regulatory role in the proliferation and differentiation of erythroid cells. Studies have shown that t EPO and erythropoietin receptor (EPOR) are expressed in many different nonhematopoietic organs and tissues, playing a role in promoting angiogenesis and protecting tissues. Many recent studies have discovered extensive expressions of EPO and EPOR in many malignant tumors, the autocrine/paracrine pathways of which are associated with tumor microangiogenesis, stimulation of tumor cell proliferation and sensitivity to chemotherapy. In addition, Paragh(Paragh *et al,* 2009) found that EPOR had a function independent of EPO in tumors. It was found that EPOR was highly expressed in ovarian cancer A2780 cell line, but no expression of EPO was observed in normal or hypoxic conditions. Use of exogenous EPO to intervene 2780 cells did not alter their biological effect. Paragh(Paragh *et al,* 2009) transplanted ovarian cancer cells treated with EPORtarget shRNA and those with a negative control vector in mice subcutaneously for 7 weeks, and found that the mean tumor size of the negative control group was 10-fold larger than that of the intervention group. This difference in tumor size is mainly due to decreased cell proliferation in the intervention group. However, the apoptotic rate was

tumor tissues.

**3.17 Erythropoietin** 

**3.16 Eukaryotic initiation factor 4E** 

of the plasmid control group (134.5mm3 vs 208.9mm3, P<0.01).
