Correlation of ERK/MAPK signaling pathway with proliferation and apoptosis of colon cancer cells

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1 ONCOLOGY LETTERS Correltion of ERK/MAPK signling pthwy with prolifertion nd poptosis of colon cncer cells GANG ZHOU, JING YANG nd PENG SONG Deprtment of Medicl Oncology, The Second Medicl Centre, Chinese PLA Generl Hospitl, Beijing , P.R. Chin Received April 9, 2018; Accepted October 26, 2018 DOI: /ol Abstrct. The role of extrcellulr signl regulted kinse/mito gen ctivted protein kinse (ERK/MAPK) signling pthwy in the prolifertion nd poptosis of humn colon cncer cells ws studied. The trnsduction process of ERK/MAPK signling pthwy ws inhibited using methyl ethyl ketone (MEK) inhibitor U0126. Promoting effect of heptocyte growth fctor (HGF) on prolifertion of humn colon cncer cells ws detected vi Cell Counting Kit 8 (CCK8), the cycle nd poptosis of humn colon cncer cells were detected vi flow cytometry, nd the migrtion of humn colon cncer cells ws detected vi wound heling ssy. The results reveled tht fter drug tretment for 48 h, there were sttisticlly significnt differences in 4 nd 8 µmol/l U0126 experimentl group compred with control group (P<0.05). Compred with those in control group, G1 phse, S phse, G2 phse nd prolifertion index (PI) in 2, 4 nd 8 µmol/l U0126 group hd sttisticlly significnt differences (P<0.05). There were sttisticlly significnt differences in comprison of G1 phse, S phse, G2 phse nd PI between control nd 8 µmol/l U0126 group (P<0.05). Compred with tht in control group, the cell migrtion distnce in 8 µmol/l U0126 group hd sttisticlly significnt difference fter drug tretment for 24 h (P<0.05). After drug tretment for 48 nd 72 h, the cell migrtion distnce in 4 nd 8 µmol/l U0126 group ws significntly reduced, nd the differences were sttisticlly significnt compred with tht in control group (P<0.05). In conclusion, ERK/MAPK signling pthwy is involved in the effects of HGF of promoting prolifertion nd regulting cell cycle nd poptosis of humn colon cncer cells, providing new pproch for the tretment of colon cncer. Introduction Colon cncer is common mlignnt tumor in the digestive system. In recent yers, the incidence rte of colon cncer hs grdully incresed nd the 5 yer survivl rte is still not high. Ptients with colon cncer often die of tumor recurrence nd metstsis (1). At present, the mechnisms of occurrence nd development of colon cncerre not completely understood. Heptocyte growth fctor (HGF) is fctor in vivo with multiple biologicl functions, which strongly promotes cell division, inducing epithelil cell migrtion, invsion nd ngiogenesis in vivo (2,3). Seti et l (4) found tht the HGF expression is significntly incresed in ptients with colon cncer, nd it is even higher in ptients complicted with metstsis, so it is believed tht HGF is involved in growth nd metstsis processes of colon cncer. HGF cn bind to c methionine (c Met) receptor nd ctivtes its ctivity, thus resulting in tyrosine phosphoryltion of vrious substrte proteins, including phospholipse C γ (PLC γ), phosphtidylinositol 3 kinse serine/threonine kinse/protein kinse B (PI3K AKT/PKB), mitogen ctivted protein kinse (MAPK) nd Grb2 ssocited binder 1 (Gb1) (5,6). MAPK prticiptes in the physiologicl functions of vrious cells in vivo, including in prolifertion, poptosis nd differentition (7). In this study, methyl ethyl ketone (MEK) inhibitor U0126 ws used to inhibit the extrcellulr signl regulted kinse (ERK)/MAPK signl trnsduction pthwy, so s to explore the roles of ERK/MAPK signling pthwy in the effects of HGF on promoting prolifertion, nd regulting cycle nd poptosis of humn colon cncer cells to find new therpeutic pproches of colon cncer. Mterils nd methods Correspondence to: Dr Gng Zhou, Deprtment of Medicl Oncology, The Second Medicl Centre, Chinese PLA Generl Hospitl, 28 Fuxing Rod, Beijing , P.R. Chin E mil: kungbu139@163.com Key words: extrcellulr signl regulted kinse/mitogen ctivted protein kinse, colon cncer, cell prolifertion, poptosis Mterils. Humn colon cncer SW620 cells were purchsed from Beijing Bein Chunglin Biotechnology Reserch Institute (ct. no. BNCC337664, Beijing, Chin). Cells were cultured using Roswell Prk Memoril Institute (RPMI) 1640 medium nd 15% fetl bovine serum (FBS) in n incubtor with 5% CO 2 t 37 C. Cells were cryopreserved using bsl medium, 5% dimethyl sulfoxide (DMSO) nd 15% FBS, nd those in logrithmic growth phse were used for subsequent experiments. Regents: Roswell Prk Memoril Institute (RPMI)-1640 (Hyclone; GE Helthcre Life Sciences; Logn, UT, USA),

2 2 ZHOU et l: CORRELATION OF ERK/MAPK WITH COLON CANCER CELLS Tble I. Inhibition rte of U0126 on colon cncer cell prolifertion. Inhibition Vribles OD rte (%) Control ± DMSO ± µmol/l U ± µmol/l U ± µmol/l U ± µmol/l U ± b µmol/l U ± b,c 28.9 P>0.05, b P<0.05 vs. control group. c P>0.05 vs. 4 µmol/l U0126 group. OD, opticl density; DMSO, dimethyl sulfoxide. Dimethyl sulfoxide (DMSO) (Beyotime, Shnghi, Chin), FBS, 0.25% trypsin (both from Thermo Fisher Scientific, Inc., Wlthm, MA, USA), Cell Counting Kit 8 (CCK8; Shnghi Yubo Biologicl Technology Co., Ltd., Shnghi, Chin), Annexin V fluorescein isothiocynte (FITC) poptosis detection kits, polyclonl ntibodies (ll from BD Phrmingen; BD Biosciences, Frnklin Lkes, NJ, USA), nd MAPK MEK1/2 efficient selective inhibitor U0126 (Shnghi Yesen Biologicl Technology Co., Ltd., Shnghi, Chin). The study ws pproved by the Ethics Committee of Chinese PLA Generl Hospitl (Beijing, Chin). Methods Detection of effect of U0126 on SW620 cell prolifertion vi CCK8. In this experiment, cells were divided into seven groups, including five experimentl groups (U0126: 0.5, 1, 2, 4 nd 8 µmol/l, respectively + HGF), the control group (+ HGF) nd the DMSO group. Ech group hd five repeted wells, nd HGF ws dded into ech group fter cell culture for 30 min nd fter culture for nother 48 h, 10 µl CCK8 regent ws dropwise dded into ech well, followed by incubtion in the drk for 2 h. The opticl density (OD) vlue of ech well ws detected using Sunrise microplte reder (Tecn Group, Ltd., Mnnedorf, Switzerlnd) t wvelength of 570 nm. Inhibition rte = (OD control group OD U0126 group )/OD control group x100%. Detection of cell cycle nd poptosis vi flow cytometry. Cells were cultured, collected, nd fixed t 4 C for t lest 24 h. The fixing solution ws removed before use, nd cells were wshed with phosphte buffered sline (PBS). The cell density ws djusted to 1.0x10 6 /ml. A totl of 0.1 ml cell suspension ws tken, dded with 1 ml propidium iodide dye liquor for stining in the drk t 4 C for hlf n hour nd filtered. The cell cycle nd poptosis were detected on the flow cytometer (Thermo Fisher Scientific, Inc., Wlthm, MA, USA). Multicycle AV softwre (De Novo Softwre, Glendle, CA, USA) ws used to nlyze the DNA cell cycle, nd the distribution percentge of ech time phse in DNA histogrm ws clculted. The cell prolifertive ctivity ws presented s prolifertion index (PI): PI = (S + G2/M)/(G0/G1 + S + G2/M) x100%. Figure 1. Inhibition rte of U0126 on colon cncer cell prolifertion. * P>0.05 nd # P<0.05, compred to control group; ** P>0.05, compred with 4 µmol/l U0126 group. Detection of cell migrtion vi wound heling ssy. Cells were inoculted nd cultured t density of 2x10 6 /well. After 8 h, the culture plte ws scrtched verticlly using sperhed, 6 scrtches/well. After the plte ws wshed with PBS, complete medium ws dded into control group, 0.1% DMSO ws dded into DMSO group, nd 4 nd 8 µmol/l U0126 ws dded into experimentl group. After hlf n hour, 20 ng/l HGF ws dded, nd cell growth (0 h) ws observed under light microscope (x100) (Nikon Instrument Inc., NY, USA). The width of 3 scrtches ws mesured using Imge-Pro Plus (Medi Cybernetics, Inc., Rockville, MD, USA), nd cells continued to be cultured. After 24 h, the complete medium ws replced, ech group ws dded with the bove mentioned corresponding regents, nd cell migrtion distnce ws observed nd mesured under the light microscope: Migrtion distnce (d) = (scrtch width t 0 h scrtch width t 24 h)/2. Cells continued to be cultured, the complete medium ws replced fter 48 h, nd cell migrtion distnce ws observed nd mesured under the light microscope: Migrtion distnce (d) = (scrtch width t 0 h scrtch width t 48 h)/2. Cells continued to be cultured until 72 h. Inhibition rte of migrtion distnce = (d control group d U0126 group )/d control group x100%. Sttisticl nlysis. Sttisticl Product nd Service Solu tions (SPSS) 20.0 softwre (SPSS, Inc., Chicgo, IL, USA) ws used for sttisticl nlysis. Mesurement dt were presented s men ± stndrd devition (SD), one wy nlysis of vrince (ANOVA) ws used for quntittive dt, nd Student Newmn Keuls (SNK) q test ws used for multiple comprisons s post hoc test. α=0.05 indicted the inspection level. Results Detection of colon cncer cell prolifertion vi CCK8. After drug tretment for 48 h, there were sttisticlly significnt differences in 4 nd 8 µmol/l U0126 experimentl group compred with control group (P<0.05). The inhibition rte hd no significnt difference between 4 nd 8 µmol/l U0126 in experimentl group (P>0.05) (Tble I nd Fig. 1).

3 ONCOLOGY LETTERS 3 Tble Ⅱ. Cell cycle nd poptosis (men ±SD). Vribles G1 S G2 PI Apoptosis Control 51.05± ± ± ± ± µmol/l U ±7.02 b 31.98±5.38 b 10.35±10.48 b 44.32±7.41 b 1.17±0.36 b 1 µmol/l U ±3.84 b 28.13±3.06 b 9.04±2.14 b 37.46±3.77 b 1.03±0.11 b 2 µmol/l U ± ± ± ± ±0.19 b 4 µmol/l U ± ± ± ± ±0.13 b 8 µmol/l U ± ± ± ± ±0.35 b P<0.05, b P>0.05 vs. control group. PI, prolifertion index. Tble Ⅲ. Effect of drug on inhibition rte of cell migrtion (men ±SD). 24 h 48 h 72 h Migrtion Migrtion Migrtion Vribles d (µm) inhibition rte (%) d (µm) inhibition rte (%) d (µm) inhibition rte (%) Control 34.9± ± ± DMSO 31.5±11.7 b ±9.9 b ±18.2 b - 4 µmol/l U ±7.2 b ± ± µmol/l U ± ±6.1,c ±10.7,c 54.1 P<0.05, b P>0.05 vs. control group. c P>0.05 vs. 4 µmol/l U0126 group. d, migrtion distnce; DMSO, dimethyl sulfoxide. Figure 2. Effects of drugs on colon cncer cell cycle nd poptosis. Compred to control group, * P<0.05; # P>0.05. Detection of cell cycle nd poptosis vi flow cytometry. Compred with those in control group, G1 phse, S phse, G2 phse nd PI in 2, 4 nd 8 µmol/l U0126 group hd sttisticlly significnt differences (P<0.05). G1 phse, S phse, G2 phse nd PI in control nd 8 µmol/l U0126 group were 51.05±8.59 vs ±5.27%, 36.28±9.42 vs ±4.26%, 12.39±15.37 vs. 7.15±2.74%, nd 48.03±8.21 vs ±5.07%, respectively, nd differences were sttisticlly significnt (P<0.05) (Tble Ⅱ, Fig. 2). Figure 3. Detection of cell migrtion vi wound heling ssy. Detection of cell migrtion vi wound heling ssy. After drug tretment for 24 h, compred with tht in control group, the cell migrtion distnce in 8 µmol/l U0126 group hd sttisticlly significnt difference (P<0.05), but it hd no significnt

4 4 ZHOU et l: CORRELATION OF ERK/MAPK WITH COLON CANCER CELLS difference between DMSO nd 4 µmol/l U0126 group (P>0.05). After drug tretment for 48 nd 72 h, the cell migrtion distnce in 4 nd 8 µmol/l U0126 group ws significntly reduced, nd the differences were sttisticlly significnt compred with those in control group (P<0.05). However, the cell migrtion distnce hd no sttisticlly significnt difference between 4 nd 8 µmol/l U0126 group (P>0.05) (Fig. 3, Tble III). Discussion The incidence rte of colon cncer is incresing yer by yer, seriously thretening humn helth. The widely-used tretment mens is surgery, nd the postopertive 5 yer survivl rte of ptients is lso different due to different stging of colon cncer. The 5 yer survivl rte of ptients in Dukes A stge is >90%, but tht of ptients in Dukes C stge is only 50% (8). Although the 5 yer survivl rte of ptients cn be incresed to some extent through vious comprehensive tretments, the prognosis is still unstisfctory. Tumor recurrence nd metstsis re still primry cuses of ptients' deth (9), nd these fctors re closely relted to the prolifertion nd invsion cpcities of tumor cells. In vriety of tissues in the humn body, there is n extrcellulr signl fctor, nmely HGF, nd it is essentilly polypeptide growth fctor (10). HGF cn be expressed nd secreted in norml humn nd tumor cells. Some scholrs found vi experiments tht HGF cn effectively promote the prolifertion nd invsion processes of SW620 cells in vitro (11). ERK/MAPK signling pthwy is involved in vriety of physiologicl cell functions, such s prolifertion, differentition nd poptosis. These functions of tumor cells re lso ssocited with the ERK/MAPK signl trnsduction pthwy (12). Rdziwon-Blick et l (13) found tht MEK phosphoryltion level is overexpressed in villous denom tissues, nd its expression is significntly incresed compred with tht in pr crcinom tissues nd norml tissues. Lee et l (14) lso found similr results in tubulr denoms. HGF binds to c Met receptor in vivo nd ctivtes its kinse ctivity nd multiple downstrem signling pthwys, including ERK/MAPK (15), which provides new ide for inhibiting ERK/MAPK signling pthwy to block the effects of HGF on promoting prolifertion nd invsion of colon cncer cells. Enyt et l (16) showed tht inhibiting ERK/MAPK signl trnsduction pthwy cn produce more significnt inhibitory effects on prolifertion nd invsion of tumor cells. In this study, fter drug tretment for 48 h, there were sttisticlly significnt differences in 4 nd 8 µmol/l U0126 experimentl group compred with control group (P<0.05). The inhibition rte hd no significnt difference between the experimentl groups of 4 nd 8 µmol/l U0126 (P>0.05), nd the tumor cell prolifertion ws not inhibited in DMSO, 0.5, 1 nd 2 µmol/l U0126 groups. The bove results suggest tht inhibiting ERK/MAPK signling pthwy cn effectively block the bility of HGF to promote tumor cell prolifertion, but there is no concentrtion dependent effect. This is consistent with the results of Chen et l (17). It is speculted tht the possible reson is tht there re other downstrem signling pthwys in HGF, such s PLC γ nd PI3K/AKT, directly leding to no dose-dependence in inhibition effect. Results of flow cytometry showed tht U0126 inhibited the cell cycle from entering S phse, nd U0126 hd no obvious effect on poptosis of colon cncer cells. However, Bodur et l (18) found tht inhibiting ERK/MAPK signling pthwy cn promote poptosis. It is speculted tht the ppliction of U0126 cnnot completely ntgonize the effect of HGF of inhibiting tumor cell poptosis, nd ERK/MAPK signl trnsduction pthwy does not ply mjor role in regulting the poptosis of colon cncer SW620 cells. Wound heling ssy showed tht fter drug tretment for 24 h, compred with tht in control group, the cell migrtion distnce in 8 µmol/l U0126 group hd sttisticlly significnt difference (P<0.05), but it hd no significnt difference between DMSO nd 4 µmol/l U0126 group (P>0.05). After drug tretment for 48 nd 72 h, the cell migrtion distnce in 4 nd 8 µmol/l U0126 group ws significntly reduced, nd the differences were sttisticlly significnt compred with those in control group (P<0.05). However, the cell migrtion distnce hd no sttisticlly significnt difference between 4 nd 8 µmol/l U0126 group (P>0.05). These results indicte tht inhibiting ERK/MAPK signl trnsduction pthwy cn significntly inhibit SW620 cell migrtion, during which the number of cell processes is reduced, nd the length is shortened. ERK/MAPK signling pthwy my exert inhibition effect vi inhibiting the cytoskeleton nd cell processes. Zhng et l (19) lso found similr phenomenon. Njr et l (20) found tht ERK signl trnsduction regultes the expression of cell trnscription fctor, cusing cytoskeletl degenertion nd enhncing invsion nd metstsis cpcities of tumor cells. In conclusion, ERK/MAPK signling pthwy is involved in the effects of HGF on promoting prolifertion nd regulting cell cycle nd poptosis of humn colon cncer cells, providing new pproch for the tretment of colon cncer. Acknowledgements Not pplicble. Funding No funding ws received. Avilbility of dt nd mterils All dt generted or nlyzed during this study re included in this published rticle. Authors' contributions GZ nd JY were responsible for CCK-8 ssy. GZ nd PS contributed to flow cytometry. All uthors red nd pproved the finl mnuscript. Ethics pprovl nd consent to prticipte The study ws pproved by the Ethics Committee of Chinese PLA Generl Hospitl (Beijing, Chin). Ptient consent for publiction Not pplicble.

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