CRC tissue samples and cell lines
101 cases of formalin-fixed paraffin-embedded human CRC and their paired normal tissue sections were purchased from Shanghai Outdo Biotech Company. None of the patients received radiotherapy or chemotherapy prior to biopsy sampling. This study was approved by the Research Ethics Committee of the First Affiliated Hospital of Sun Yat-sen University, and written informed consent was obtained from each participant.
The human CRC cell line HCT116 and RKO were purchased from Cell Bank of the Chinese Academy of Sciences (Shanghai, China). All of the cells were cultured at 37 °C in Dulbecco’s modified Eagle's medium (DMEM) and supplemented with 10% fetal bovine serum (FBS) in a 5% CO2 atmosphere. Notably, all CRC cell lines were tested for mycoplasma contamination.
Immunohistochemical (IHC) Staining
Briefly, the specimens were deparaffinized and blocked with citric acid antigen. Subsequently, antibody HSPA4 (1: 200, abcam, USA, # ab185962) was added at 4 °C overnight and elution with PBS, next antibody IgG (1: 400, abcam, USA, # ab6721) was added. Tissue slices were stained with DAB and hematoxylin. All tissues in the chip were observed with microscopic and all slides were viewed with ImageScope and CaseViewer. IHC scores were determined by staining percentage scores (classified as: 1 (1%-24%), 2 (25%-49%), 3 (50%-74%), 4 (75%-100%)) and staining intensity scores (scored as 0: signalless color, 1: brown, 2: light yellow, 3: dark brown). Pathological examination of tumor specimens was carried out by two independent pathologists.
Target gene RNA interferes with the preparation of lentiviral vector
Short hairpin RNAs (shRNA) of human HSPA4 and related control sequence were designed by Shanghai bioscienceres Co., Ltd. for knockdown experiments. The relevant sequence information was shown in the Table below. Afterwards, target sequences were inserted into BR-V-108 vector (Shanghai bioscienceres Co. Ltd., Shanghai, China) using the T4 DNA ligase enzyme (NEB). Plasmids were extracted by EndoFree Maxi Plasmid Kit (Tiangen) and qualified plasmid was packaged with 293T cells. HCT116 and RKO cells at a density of 2 × 105 cells/mL were seeded in a 6-well plate. 24 h later, cells were transfected with 100 µL lentiviral vectors (1 × 107 TU/mL) additive with ENI.S and polybrene (10 µg/mL, Sigma-Aldrich). After cultured for 72 h, the fluorescence was observed by microscope and then transfection efficiency detected via qRT-PCR and Western Blot.
Primer Name | Primer Sequence (5’-3’) |
Human-HSPA4 (RNAi-1) | AAAGTCAAAGTTCGAGTAAAT |
Human-HSPA4 (RNAi-2) | GGTGACATATATGGAGGAAGA |
Human-HSPA4 (RNAi-3) | AAGCAATGGAGTGGATGAATA |
Qrt-pcr
Total RNA was extracted from cell lines HCT116 and RKO with TRIzol reagent (Invitrogen, CA, USA) according to the manufacturer’s instructions. RNA (2.0 µg) was transcribed into cDNA with M-MLV RT kit (Promega). GAPDH was used as the internal controls for the quantification of HSPA4 (primer sequences were detailed in Table). The qRT-PCR was carried out on the Roche Light Cycler® 96 real-time PCR platform, and expression of HSPA4 was quantified using the 2−ΔΔCT method.
Primer | Upstream Sequence (5’-3’) | Downstream Sequence (5’-3’) |
HSPA4 | GCAGACACCAGCAGAAAATAAGG | TCGATTGGCAGGTCCACAGT |
GAPDH | TGACTTCAACAGCGACACCCA | CACCCTGTTGCTGTAGCCAAA |
Western Blot
HCT116 and RKO cells transfected with shCtrl and shHSPA4 were fully lysed in ice-cold RIPA buffer (Millipore). The protein concentration detection was performed by BCA Protein Assay Kit (#23225, HyClone-Pierce). 20 µg protein from each group was separated by 10% SDS-PAGE, transferred onto PVDF membranes, and analyzed with required antibodies (antibody information was detailed in Table). The blots were visualized by Amersham ECL plusTM Western Blotting system and the density of the protein band was analyzed.
Antibody Name | Protein Size (KDa) | Diluted Multiples | Antibody Source | Company | Number |
HSPA4 | 94 | 1:2000 | Rabbit | abcam | ab185962 |
Akt | 60 | 1:1000 | Rabbit | CST | 4685 |
p-Akt | 60 | 1:1000 | Rabbit | Bioss | BS-5193R |
CCND1 | 36 | 1:2000 | Rabbit | CST | 2978 |
CDK6 | 37 | 1:1000 | Rabbit | abcam | ab151247 |
PIK3CA | 110 | 1:1000 | Rabbit | abcam | ab40776 |
GAPDH | 37 | 1:3000 | Rabbit | Bioworld | AP0063 |
Celigo Cell Counting Assay
HCT116 and RKO cells transfected with shCtrl and shHSPA4 were seeded into a 96-well plate (500 cells/well) and cultured until cell clones formed. After that, cell clones were fixed with 4% paraformaldehyde and then stained with Giemsa. The visible colonies were photographed and counted for 5 consecutive days.
Flow Cytometry
HCT116 and RKO cells transfected with shCtrl and shHSPA4 were inoculated in a 96-well plate until cell density reached 85%. Cells were harvested, centrifuged (1200 × g), and resuspended. Apoptosis analyses and cell cycle distribution was detected Guava easyCyte HT FACS Calibur (Millipore).
In terms of cell apoptosis, 10 µL Annexin V-APC (eBioscience) was added and incubated at room temperature without light for 10 min. Cell apoptotic ratio was calculated based on the following formula: (number of positive cells/number of all counted cells) × 100%.
For cell cycle, cells were stained by PI staining solution (BD Biosciences). The ratio of cells in the G1, S and G2 stage of the HSPA4 knockdown group and the control group were detected and analyzed by flow cytometry.
Wound Healing Assay
Cell migration was measured by a scratch wound healing assay. HCT116 and RKO cells transfected with shCtrl and shHSPA4 were plated into a 96-well dish (5 × 104 cells/well) for culturing until the confluence reached 90%. Subsequently, cell scratches across the cell layer were made by a 96-wounding replicator (VP scientific). After cell layers were gently washed, photographs were taken by a fluorescence microscope at 24 h and 48 h post scratching and the migration rates were calculated.
Transwell Assay
8 × 104 HCT116 and RKO cells transfected with shCtrl and shHSPA4 were seeded in a 24-well Transwell cell culture plate, respectively, in the upper chamber. The lower chamber was filled with 600 µL medium and supplemented with 30% FBS. After 24 h culturing, the non-metastatic cells were washed away gently and metastatic cells were stained with 400 µL Giemsa for 5 min at room temperature. Cells were observed via a microscope (200 × magnification) and the migration ability of cells was analyzed.
Animal Xenograft Model
Animal research experiments were approved by the Ethics committee of the First Affiliated Hospital of Sun Yat-sen University and conducted in accordance with guidelines and protocols for animal care and protection. BALB/c nude mice (female, 4 weeks old) obtained from Shanghai Lingchang Laboratory Animal Technology Co., Ltd. 4 × 106 RKO cells transfected with shCtrl and shHSPA4 were subcutaneously injected into each mouse under the armpit of the right forearm (n = 10 per group). The tumor size and weight were monitored 2 times per week, and tumor volume = π/6 × L × W, where L represents the long diameter and W represents the short diameter. After 26 days of injection, all mice were anesthetized by intraperitoneal injection of 0.7% Pentobarbital Sodium (10 uL/g), and anesthetized mice were placed under the Berthold Technologies living imaging system and in vivo bioluminescence images was collected. Then anesthetized mice were sacrificed and the tumor tissues were harvested.
Ki67 Staining
Mice tumor tissues were fixed in 10% formalin and then were paraffin-embedded. 5 µm slides were cut and immersed in xylene and ethanol. Tissue slides were blocked with 3% PBS-H2O2 and were incubated with anti-Ki67 and HRP goat anti-rabbit IgG. Slides were stained by Hematoxylin (Baso, # BA4041) and Eosin (Baso, # BA4022). Stained slides were examined at 200 × and 400 × objective lens microscopic.
Human Apoptosis Antibody Array
For signal pathway gene detecting, Human Apoptosis Antibody Array (abcam, # ab134001) were applied following the manufacturer’s instructions. Briefly, RKO cells transfected with shCtrl and shHSPA4 were lysed in cold RIPA buffer (Millipore) and protein concentration was detected by BCA Protein Assay Kit (HyClone-Pierce). Proteins were incubated with blocked array antibody membrane overnight at 4 °C. After washing, 1:100 Detection Antibody Cocktail was added incubating for 1 h, followed by incubated with HRP linked streptavidin conjugate for 1 h. All spots were visualized by enhanced ECL and the signal densities were analyzed with ImageJ software (National Institute of Health).
Statistical Analysis
All experiments were performed in triplicate and data were shown as mean ± SDs. Statistical analyses and graphs were performed by GraphPad Prism 8.01 (Graphpad Software) and P value < 0.05 as statistically significant. The significance difference between groups were determined using the two-tailed Student’s t test or One-way ANOVA analysis. Mann-Whitney U analysis and Spearman rank correlation analysis were used while explaining the relationships between HSPA4 expression and tumor characteristics in patients with CRC.