Clinical patient tissues
Fresh primary GBM tissues and paired normal brain tissues were collected from 38 patients at the Affiliated Hospital of Southwest Medical University. Diagnosis of each primary GBM was confirmed by experienced pathologists. No patients received treatment prior to operation. Written informed consent was acquired from the patients for research purposes. This study was approved and supervised by The Ethics Committee of Southwest Medical University and all aspects of this study comply with the Declaration of Helsinki.
Cell culture
GBM cell lines LN229(CA NO.CRL-2611), U251(CA NO.TCHu-58), U87(CA NO.HTB-14), and T98G(CA NO.CRL-1690) were obtained from the Cell Bank of the Chinese Academy of Sciences (Shanghai, China) and ATCC, USA. LN229, U87, and T98G cells were cultured in Eagle’s Minimum Essential Medium (MEM; Hyclone, Logan, UT, USA) and U251 cells were cultured in Dulbecco’s modified Eagle’s medium (DMEM; Hyclone). All media were supplemented with 10% fetal bovine serum (Thermo Scientific, Waltham, MA, USA). The cells were cultured at 37 °C with a humidity of 90–95 and 5% CO2. All cells were propagated for less than 6 months after resuscitation.
siRNA and stable knockdown construction
After propagation, cells were transfected with 100 nM Lipofectamine 2000 reagent (Invitrogen, Carlsbad, CA, USA). LASP1-specific siRNA was purchased from GenePharma (Shanghai, China). The siRNA sequences were as follows:
siRNA1 5′-CGCGCGGUGUAUGACUAAdTdT-3′;
siRNA2 5′-GAAUCAACAAGACCCAGGAdTdT-3′;
siRNA3 5′-CGCGCGGUGUACUAGACUAdTdT-3′;
Negative control siRNA 5′-TTCTCCGAACGTGTCACGT-3′.
Based on their knockdown efficiencies, siRNA3 was selected to synthesized shRNA by GenePharma (Shanghai, China). Transfection of shRNA was performed according to the manufacturer’s instructions. After 1 week of transfection, cells were selected with 1 μg/mL puromycin. Knockdown efficiency was confirmed by western blotting.
cDNA synthesis and quantitative real-time PCR
Total RNA was extracted by using a Trizol kit according to the manufacturer’s instructions. After extraction, 1 μg total RNA was reverse-transcribed by using Takara RT reagent according to the manufacturer’s protocol. Each cDNA was subjected to quantitative real-time PCR in triplicate on a LightCycler 480 system (Roche, Basel, Switzerland). The following primers were used in this study: GAPDH (F: ACCCAGAAGACTGTGGATGG, R: TCTAGACGGCAGGTCAGGTC), LASP1 (F: ATGAACCCCAACTGCGCC, R: TCAGATGGCCTCCACGTAGTT).
MTT assays
For proliferation analysis, 1000 cells were plated in 5 replicates in 96-well plates after gene transfection. For TMZ sensitivity analysis, 5000 cells were seeded in 96-well plates. After culturing the cells for the indicated times, the media were replaced with 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) followed by co-culture for 4 h, and then 150 μL DMSO was added before measured at 570 nm in a multimode plate reader (Perkin Elmer, Waltham, MA, USA) according to the manufacturer’s instructions.
Western blotting (WB)
Cells were washed with 5% PBS 3 times and then lysed in RIPA lysis buffer for 1 h. Protein quantification was performed using BCA kits. Equal amounts of proteins were separated by SDS-PAGE and transferred onto polyvinylidene difluoride membranes (Amersham Pharmacia Biotech, Amersham, UK). The proteins were labeled with specific antibodies against LASP1 (1:1000; Chemicon, Temecula, CA, USA); cleaved poly (ADP-ribose) polymerase (PARP), cleaved caspase3, caspase3,p-PI3K, PI3K, p-Akt(Ser473), Akt (1:1000, Cell Signaling Technology, Danvers, MA, USA); and GAPDH (1:1000, Santa Cruz Biotechnology, Dallas, TX, USA). Autoradiography signals were quantified and analyzed using Quantity One software (Bio-Rad, Hercules, CA, USA).
Colony formation and EdU assays
For colony formation assays, 1000 cells were plated in 6-well plates at 2 mL/well and the medium was replaced every 3 days. After 2 weeks, colonies were fixed with 4% paraformaldehyde, stained with 0.1% crystal violet and analyzed.
For 5-ethynyl-2′-deoxyuridine (EdU) experiments, cells were transferred into a 96-well plate at 2000 cells/well; 24 h later, cells were dyed with EdU Cell Proliferation Assay Kit (RiboBio, Guangzhou, China) according to the standard protocol, and photographed with a fluorescence microscope (Olympus, Tokyo, Japan).
Xenograft tumor growth
Male nude mice were maintained in a barrier facility and this study was approved by the Ethical Committee of Southwest Medical University. All procedures were conducted according to approved protocols. Stable shRNA against LASP1 cells and control cells (1 × 106 cells in 150 μL PBS) were injected into the right subcutaneous space of nude mice. For the TMZ therapy group, at 1 week, mice were administered TMZ by oral gavage at a concentration of 100 μM per day for 5 days per week, with therapy continuing for 3 weeks. One month after injection, mice were sacrificed, tumors were dissected, and tumor volumes were measured as follows: length × width2 × ½. Tumor weight was measured using a scale.
Statistical analysis
Data were analyzed by SPSS version 19.0 software (SPSS, Chicago, IL, USA). Each experiment was performed at least three times independently and values are shown as the mean ± standard deviation (SD). Two-tailed Student’s t-tests were used to estimate the significance between two independent groups. For the quantitative reverse transcription (qRT)-PCR assay, if the distribution of the data was abnormal, the Wilcoxon rank-sum test and Kruskal–Wallis test were used, while the Student’s t-test was used for normally distributed data.