Lentivirus-mediated short-hairpin RNA targeting IGF-1R inhibits growth and lymphangiogenesis in breast cancer

Radio-immunotherapy by 188Re-antiCD20 and stable silencing of IGF-IR in Raji cells, new insight in treatment of lymphoma

Hematologic malignancies such as Non-Hodgkin's lymphoma (NHL), remain a serious threat to human health due to their heterogeneity and complexity. The inherent genetic heterogeneity of NHL B-cells, as well as the instability of lymphoma cancer cells, results in drug resistance in lymphoma, posing a fundamental challenge to NHL treatment. Burkitt lymphoma (including Raji cell line) is a rare and highly aggressive form of B-cell NHL. Since overexpression of the insulin-like growth factor-1 receptor (IGF-1R) playing a prominent role in the development and transformation of different malignancies, especially lymphoma malignancies, we have explored the role of IGF-1R in the development and progression of Raji cells and the stable silencing of IGF-1R by lentivirus-mediated RNA interference (RNAi). We have shown that stable silencing of the IGF-1R gene in Raji cells using lentivirus-mediated-RNAi have resulted in a significant reduction in Raji cell proliferation. Moreover, the results of the cell viability assays indicatedhigh resistance of Raji cells to rituximab. However, coupling rituximab to 188Re potentially leads to specific targeting of Raji cells by 188Re, improving the therapeutic efficacy. We found that the synergistic effect of using a gene therapy-based system in combination with radioimmunotherapy could be a promising therapeutic strategy in the future. To the best of our knowledge, this is the first study that reports the knock down of IGF-1R via lentiviral-mediated shRNA in Raji cells.

Insulin-like growth factor-1 receptor knockdown enhances radiosensitivity via the HIF-1α pathway and attenuates ATM/H2AX/53BP1 DNA repair activation in human lung squamous carcinoma cells

Insulin-like growth factor-1 receptor (IGF-1R) is a cell membrane receptor involved in cell proliferation and apoptosis, which is highly expressed in lung squamous cell carcinoma (SCC). The present study aimed to observe the influence of IGF-1R silencing on the radiosensitivity of SCC and investigate the potential mechanisms involved. Human lung SCC H520 cells with relatively high expression of IGF-1R were used. IGF-1R expression was silenced using short hairpin RNA. The influence of IGF-1R silencing on radiosensitivity and apoptosis was assessed using a clone formation assay and flow cytometry. The expression levels of proteins relevant in DNA damage repair and hypoxic signaling pathways were analyzed using western blotting. Decreased expression of IGF-1R led to an increase in the sensitivity of H520 cells to irradiation. Molecular analysis showed that the reduced expression of IGF-1R decreased the protein expression of ataxia-telangiectasia mutated (ATM), H2A histone family member X (H2AX) and p53 binding protein 1 (53BP1), which are associated with the DNA repair pathway. Furthermore, 53BP1 is also known to be involved in apoptosis. Proteins involved in the hypoxic pathway, including hypoxia inducible factor 1 α (HIF-1α), matrix metallopeptidase 9 (MMP-9) and vascular endothelial growth factor A (VEGFA) were also involved in the radiosensitivity. In conclusion, decreased expression of IGF-1R leads to improved radiosensitivity of SCC cells, and the underlying mechanism may be associated with the decreased expression of proteins involved in ATM/H2AX/53BP1 DNA damage repair and the HIF-1α/MMP-9 hypoxic pathway, which results in the induction of apoptosis and increased radiosensitivity. These findings suggest that targeting of IGF-1R may represent a novel approach for lung SCC radiation treatment.

MicroRNA-503 inhibits the proliferation and invasion of breast cancer cells via targeting insulin-like growth factor 1 receptor

MicroRNAs (miRs), a class of non-coding RNAs that are 18–25 nucleotides in length, serve as key regulators in the development and progression of human cancers. Previously, miR-503 has been implicated in breast cancer. However, the underlying mechanism of miR-503 in regulating the proliferation and invasion of breast cancer cells remains largely unknown. In the present study, reverse transcription-quantitative polymerase chain reaction analysis indicated that the expression of miR-503 was significantly reduced in breast cancer tissues compared with their matched adjacent normal tissues. Furthermore, miR-503 expression levels were markedly reduced in T2-T4 stage breast cancer, compared with T1 stage. Insulin-like growth factor 1 receptor (IGF-1R) was further identified as a novel target of miR-503. Overexpression of miR-503 significantly suppressed the protein expression levels of IGF-1R. Furthermore, it inhibited the proliferation and invasion of human breast cancer MCF-7 cells, as assessed by MTT and Transwell assays, respectively. However, restoration of IGF-1R expression markedly ameliorated the suppressive effects of miR-503 overexpression on MCF-7 cell proliferation and invasion, indicating that miR-503 inhibits breast cancer cell proliferation and invasion at least partially via directly targeting IGF-1R. Furthermore, the mRNA and protein expression levels of IGF-1R were demonstrated to be significantly increased in breast cancer tissues compared with their matched adjacent normal tissues. In addition, IGF-1R mRNA expression levels were reversely correlated with miR-503 expression levels in breast tumors, suggesting that the upregulation of IGF-1R may be due to downregulation of miR-503 in breast cancer. In conclusion, the present study expanded the understanding of the regulatory mechanism of miR-503 in breast cancer, and implicates the miR-503/IGF-1R axis as a potential therapeutic target for breast cancer.

Silencing HS6ST3 inhibits growth and progression of breast cancer cells through suppressing IGF1R and inducing XAF1

Heparan sulfate 6-O-sulfation is biologically edited by 6-O-sulfotransferases (HS6STs) within heparan sulfate chains. Three isoforms of HS6ST have been identified. These enzymes are found to be differentially expressed in a variety of tissues. Recently, several studies have shown that dysregulation of 6-O-sulfotransferases could be involved in tumorigenesis of several cancers. This study aimed to analyze the expression and function of HS6ST3 in breast cancer. HS6ST3 was found up-regulated in T47D, MCF7 and MDA-MB231 breast cancer cell lines. HS6ST3 was then silenced in T47D and MCF7 using siRNA. Silencing HS6ST3 diminished tumor cell growth, migration and invasion, but enhanced cell adhesion and apoptosis in breast cancer. Gene microarray analysis revealed that silencing HS6ST3 significantly changed the expression of IGF1R and XAF1 in breast cancer cells. Further functional studies showed that the cellular processes were mediated by IGF1R and XAF1 after silencing HS6ST3 in breast cancer cells. Together these results indicate that HS6ST3 might be involved in the tumorigenesis of breast cancer and it could be a promising target in breast cancer therapy.

An active IGF-1R-AKT signaling imparts functional heterogeneity in ovarian CSC population

Deregulated IGF-1R-AKT signaling influences multiple nodes of cancer cell physiology and assists in migration, metastasis and acquirement of radio/chemoresistance. Enrichment of cancer stem cells (CSC) positively correlates with radio/chemoresistance development in various malignancies. It is unclear though, how IGF-1R-AKT signalling shapes CSC functionality especially in ovarian cancer. Previously we showed that upregulated IGF-1R expression is essential to initiate platinum-taxol resistance at early stage which declines with elevated levels of activated AKT at late resistant stage in ovarian cancer cells. Here, we investigated the effect of this oscillatory IGF-1R-AKT signalling upon CSC functionality during generation of chemoresistance. While gradual increase in CSC properties from early (ER) to late (LR) resistant stages was observed in three different (cisplatin/paclitaxel/cisplatin-paclitaxel) cellular models created in two ovarian cancer cell lines, the stemness gene expressions (oct4/sox2/nanog) reached a plateau at early resistant stages. Inhibition of IGF-1R only at ER and AKT inhibition only at LR stages significantly abrogated the CSC phenotype. Interestingly, real time bioluminescence imaging showed CSCs of ER stages possessed faster tumorigenic potential than CSCs belonging to LR stages. Together, our data suggest that IGF-1R-AKT signalling imparts functional heterogeneity in CSCs during acquirement of chemoresistance in ovarian carcinoma.

HIF-2α attenuates lymphangiogenesis by up-regulating IGFBP1 in hepatocellular carcinoma

BACKGROUND INFORMATION

Tumour-associated lymphangiogenesis was identified as an important clinical determinant for the prognosis of hepatocellular carcinoma (HCC) and significantly influences patient survival. However, in this context, little is known about regulation of lymphangiogenesis by hypoxia-inducible factors (HIF). In HCC, mainly HIF-1α was positively correlated with lymphatic invasion and metastasis, whereas a defined role of HIF-2α is missing.

RESULTS

We created a stable knockdown (k/d) of HIF-1α and HIF-2α in HepG2 cells and generated co-cultures of HepG2 spheroids with embryonic bodies. This constitutes an in vitro tumour model mimicking the cancer microenvironment and allows addressing the role of distinct HIF isoforms in regulating HCC lymphangiogenesis. In co-cultures with a HIF-2α k/d, lymphangiogenesis was significantly increased, whereas the k/d of HIF-1α showed no effect. The HIF-2α-dependent lymphangiogenic phenotype was confirmed in vivo using matrigel plug assays with supernatants of HIF-2α k/d HepG2 cells. We identified and verified insulin-like growth factor binding protein 1 (IGFBP1) as a HIF-2α target gene. The potential of HepG2 cells to induce lymphangiogenesis in two independent functional assays was significantly enhanced either by a k/d of HIF-2α or by silencing IGFBP1. Moreover, we confirmed IGF as a potent pro-lymphatic growth factor with IGFBP1 being its negative modulator.

CONCLUSIONS

We propose that HIF-2α acts as an important negative regulator of hepatic lymphangiogenesis in vitro and in vivo by inducing IGFBP1 and thus, interfering with IGF signalling. Therefore, HIF-2α may constitute a critical target in HCC therapy.