Zoheir Khairy Ma, Abd-Rabou Ahmed A, Harisa Gamaleldin I, Kumar Ashok, Ahmad Sheikh Fayaz, Ansari Mushtaq Ahmad, Abd-Allah Adel R
Pharmacology and Toxicology Department, College of Pharmacy, King Saud University, Riyadh, Saudi Arabia.
Cell Biology Department, National Research Centre, Cairo, 12622, Egypt.
Tumour Biol. 2016 Oct;37(10):13927-13939. doi: 10.1007/s13277-016-5283-8. Epub 2016 Aug 3.
IQ motif-containing GTPase-activating proteins (IQGAPs) belong to a conserved family, and they are involved in various intracellular processes. IQGAP1 is expressed in all cells, while IQGAP2 and IQGAP3 are mainly expressed in hepatic cells. IQGAP1 has been suggested to be an oncogene, while IQGAP2 is considered a tumor-suppressor gene. However, the relationship between RAS family genes and IQGAP genes remains unclear. We recently demonstrated this interaction in a chemically induced mouse liver cancer. In this study, IQGAP1 expression was partially silenced in human hepatocellular carcinoma (HepG2) cells. We investigated the impact of IQGAP1 silencing on the interactions of IQGAP and RAS with several apoptotic proteins, including caspase-3 (CASP3), BCL2-associated X protein (BAX), and B-cell leukemia/lymphoma 2 (BCL2). Additionally, we investigated the effects of the interactions of these genes on cell viability, proliferation, apoptosis, and invasive capacity. IQGAP1 siRNA-treated HepG2 cells showed lower invasive capacity than the control cells, and this reduction was time- and vector concentration-dependent. In addition, IQGAP1 silencing resulted in significantly lower IQGAP1 level and subsequently higher IQGAP2 and IQGAP3 expression in HepG2 cells than in the control. Flow cytometry analyses indicated that the silencing of IQGAP1 can induce early and late apoptosis in HepG2 cells. Additionally, IQGAP2, IQGAP3, CASP3, and BAX were upregulated whereas IQGAP1 and BCL2 were downregulated in the siRNA-treated cells. Furthermore, we observed that the mRNA levels of HRAS, KRAS, NRAS, and MRAS decreased upon IQGAP1 silencing. These findings indicate that IQGAP1 potentially regulates the expression of IQGAP and RAS gene families and demonstrate its regulatory role in the apoptotic network. Taken together, our findings suggest that IQGAP1 silencing plays crucial roles in the apoptosis of HepG2 cells and lowers their proliferative and invasive capacities.
含IQ基序的GTP酶激活蛋白（IQGAPs）属于一个保守家族，参与多种细胞内过程。IQGAP1在所有细胞中均有表达，而IQGAP2和IQGAP3主要在肝细胞中表达。IQGAP1被认为是一种癌基因，而IQGAP2被视为肿瘤抑制基因。然而，RAS家族基因与IQGAP基因之间的关系仍不清楚。我们最近在化学诱导的小鼠肝癌中证实了这种相互作用。在本研究中，IQGAP1在人肝癌（HepG2）细胞中的表达被部分沉默。我们研究了IQGAP1沉默对IQGAP和RAS与几种凋亡蛋白相互作用的影响，这些凋亡蛋白包括半胱天冬酶-3（CASP3）、BCL2相关X蛋白（BAX）和B细胞淋巴瘤/白血病-2（BCL2）。此外，我们还研究了这些基因相互作用对细胞活力、增殖、凋亡和侵袭能力的影响。用IQGAP1 siRNA处理的HepG2细胞的侵袭能力低于对照细胞，且这种降低具有时间和载体浓度依赖性。此外，与对照相比，IQGAP1沉默导致HepG2细胞中IQGAP1水平显著降低，随后IQGAP2和IQGAP3表达升高。流式细胞术分析表明，IQGAP1沉默可诱导HepG2细胞早期和晚期凋亡。此外，在经siRNA处理的细胞中，IQGAP2、IQGAP3、CASP3和BAX上调，而IQGAP1和BCL2下调。此外，我们观察到IQGAP1沉默后，HRAS、KRAS、NRAS和MRAS的mRNA水平降低。这些发现表明，IQGAP1可能调节IQGAP和RAS基因家族的表达，并证明其在凋亡网络中的调节作用。综上所述，我们的研究结果表明，IQGAP1沉默在HepG2细胞凋亡中起关键作用，并降低其增殖和侵袭能力。
