Epidermal growth factor receptor tyrosine kinase inhibitors for non-small cell lung cancer

First-generation epidermal growth factor receptor tyrosine kinase inhibitors(EGFR-TKIs), including gefitinib and erlotinib, have proven to be highly effective agents for advanced non-small cell lung cancer(NSCLC) in patients harboring an activating EGFR mutation such as the exon 19 deletion mutation and L858 R. Although those reversible small molecular targeted agents provide a significant response and survival benefit, all responders eventually acquire resistance. Secondgeneration EGFR-targeting agents, such as irreversible EGFR/HER2 tyrosine kinase inhibitors and pan-HER TKIs, may improve survival further and be useful for patients who acquired resistance to first-generation EGFR-TKIs. This review discusses novel therapeutic strategies for EGFR-mutated advanced NSCLC using first- and second-generation EGFR-TKIs.

Therapeutic Effect of First-line Epidermal Growth Factor Receptor Tyrosine Kinase Inhibitor (EGFR-TKI)Combined with Whole Brain Radiotherapy on Patients with EGFR Mutation-positive Lung Adenocarcinoma and Brain Metastases

This study compared the therapeutic effect of first-line epidermal growth factor receptor tyrosine kinase inhibitor(EGFR-TKI)with that of EGFR-TKI plus whole brain radiotherapy(WBRT)on patients with EGFR mutation-positive lung adenocarcinoma and brain metastases.A total of 139 patients with lung adenocarcinoma and brain metastases treated with first-line EGFR-TK1therapy from September 2008 to December 2017 were enrolled in this study.The study endpoints were intracranial time to progression(TTP)and overall survival(OS).The effects of clinical pathological parameters and EGFR gene status on the study endpoints were compared.The results showed that the intracranial TTP was significantly longer in EGFR-TKI plus WBRT group than in EGFR-TKI group (median 30.0 vs.18.2 months,χ2=10.824,P=0.001),but no significant difference in the OS was noted between the two groups (median 48.0 vs.41.1 months,χ2=0.012, P=0.912).Also,there was no statistically significant difference in the OS between patients treated with early and late radiotherapy (P=0.849)and between those with asymptomatic and those with symptomatic intracranial metastases (P=0.189).The OS and intracranial TTP of patients with intracranial oligometastases (≤3metastatic sites)were not significantly different from those of patients with multiple intracranial metastases (P=0.104 and P=0.357,respectively),and exon 19 and exon 21 mutations didn't show significant effects on the OS and intracranial TTP of patients (P=0.418 and P=0.386,respectively).In conclusion,there was no statistically significant difference in the OS between the EGFR-TKI alone group and EGFR-TK1 plus WBRT group.However, simultaneous use of WBRT was found to significantly prolong intracranial TTP and improve cerebral symptoms,and thus EGFR-TKI and WBRT combined may be clinically beneficial for patients with EGFR mutation-positive lung adenocarcinoma and brain metastases.

Review of epidermal growth factor receptor-tyrosine kinase inhibitors administration to non-small-cell lung cancer patients undergoing hemodialysis

Non-small-cell lung cancer(NSCLC)causes significant mortality worldwide.Patients with chronic renal failure have an increased risk of developing lungcancer.NSCLC Patients with chronic renal failure undergoing hemodialysis(HD)often exhibit poor performance,and chemotherapy is generally contraindicated.Oral epidermal growth factor receptor(EGFR)-tyrosine kinase inhibitors(TKIs)are effective treatment agents for NSCLC patients.However,the benefits andadverse effects of EGFR-TKIs in NSCLC undergoing HD are known.There are noclinical studies on the effects of EGFR-TKIs on NSCLC patients undergoing HD.We reviewed all previous case reports about EGFR-TKIs in NSCLC patientsundergoing HD.It is difficult to design studies about the effects of EGFR-TKIs inpatients undergoing HD,and this review is quite important.EGFR-TKIs are welltolerated in patients undergoing HD.The main routes of elimination of EGFRTKIsare metabolism via the liver,and renal elimination is minor.Therecommended doses and pharmacokinetics of these EGFR-TKIs for patientsundergoing HD are similar to those for patients with normal renal function.Theplasma protein binding of EGFR-TKIs is very high,and it is not necessary toadjust the dose after HD.In conclusion,EGFR-TKIs are effective and welltolerated in patients undergoing HD.

Is there a role for epidermal growth factor receptor tyrosine kinase inhibitors in epidermal growth factor receptor wildtype non-small cell lung cancer?

Non-small cell lung cancer(NSCLC) is the most common type of lung cancer with a world-wide annual incidence of around 1.3 million. The majority of patients arediagnosed with advanced disease and survival remains poor. However, relevant advances have occurred in recent years through the identification of biomarkers that predict for benefit of therapeutic agents. This is exemplified by the efficacy of epidermal growth factor receptor(EGFR) tyrosine kinase inhibitors for the treatment of EGFR mutant patients. These drugs have also shown efficacy in unselected populations but this point remains controversial. Here we have reviewed the clinical data that demonstrate a small but consistent subgroup of EGFR wild-type patients with NSCLC that obtain a clinical benefit from these drugs. Moreover, we review the biological rationale that may explain this benefit observed in the clinical setting.

Tyrosine kinase inhibitors and human epidermal growth factor receptor-2 positive breast cancer

The body of evidence investigating human epidermal growth factor receptor-2(HER2)directed therapy in patients with breast cancer(BC)has been growing within the last decade.Recently,the use of tyrosine kinase inhibitors(TKIs)has been of particular interest in the treatment of human malignancies.This literature commentary is intended to highlight the most recent findings associated with the widely-studied TKI agents and their clinical significance in improving the outcomes of HER2 positive BC.

New era of epidermal growth factor receptor-tyrosine kinase inhibitors for lung cancer

Lung cancer is the leading cause of death globally, besides recent advances in its management; it maintains a low 5-year survival rate of 15%. The discovery of epidermal growth factor receptor(EGFR) activating mutations and the introduction of its tyrosine kinase inhibitors(TKIs) have expanded the treatment options for patients with non-small cell lung cancer. Nowadays, EGFR mutation testing is now a common routine for newly diagnosed lung cancer. First generation TKIs developed, erlotinib and gefitinib, were reversible ones. After a median of 14 mo, eventually all EGFR mutated patients develop resistance to reversible TKIs. Afatinib, dacomitinib and neratinib, second generation inhibitors, are selective and irreversible TKIs. Finally, third generation phase Ⅰclinical trials were performed, with lower toxicity profiles, and targeting with more precision the driving clone of this heterogeneous disease.

Research progress in the use of combinations of platinum-based chemotherapy and epidermal growth factor receptor-tyrosine kinase inhibitors

In the past decade,the advent of the epidermal growth factor receptor-tyrosine kinase inhibitors(EGFR-TKIs)has dramatically influenced the therapeutic strategies for treating lung cancer,but with tumor progression and drug resistance,patients will ultimately develop reduced sensitivity to EGFR-TKIs.How can we delay the emergence of drug resistance? What is the next strategy after drug resistance? How to reasonably combine platinum-based chemotherapy and EGFR-TKIs? These questions are currently the focus of lung cancer research.Clinical studies have reported that platinum-based chemotherapy can increase the sensitivity to EGFR-TKIs.However,results of pre-clinical and clinical studies have been inconsistent.The mechanisms of platinum chemotherapy and EGFR-TKIs are still unknown due to the lack of systematic research.Therefore,systematic studies are required to show the mechanisms of EGFR-TKIs and chemotherapy agents and define the markers sensitive to their combinations when given concurrently or sequentially.

Coexistence of anaplastic lymphoma kinase rearrangement in lung adenocarcinoma harbouring epidermal growth factor receptor mutation:A single-center study

BACKGROUND Accumulating evidences confirm that epidermal growth factor receptor(EGFR)mutation and anaplastic lymphoma kinase(ALK)rearrangement have coexisted in lung adenocarcinoma(LUAD).However,Its biological mechanism,clinicopathological features,and optimization of targeted drugs have not yet been completely elucidated.AIM To explore the clinical profile of LUAD patients with co-mutations of EGFR and ALK genes,with hopes of scientifically guiding similar patients towards selected,targeted drugs.METHODS Two hundred and thirty-seven LUAD patients were enrolled.EGFR mutations were detected by the amplification refractory mutation system-peptide nucleic acid technique,while the expression of ALK rearrangement was screened by the 5′/3′imbalance strategy for reverse transcription followed by quantitative polymerase chain reaction analysis.The clinicopathological features of these patients were analysed retrospectively,and the follow-up data were collected.RESULTS There were six cases with co-mutations of EGFR and ALK genes,which were more common in women,non-smoking and stage IV LUAD patients with bone metastasis,hence a positive rate of 2.53%(6/237).EGFR-tyrosine kinase inhibitors(EGFR-TKIs)were their preferred drugs for targeted therapy in these patients,with progression-free survival ranging from two months to six months.CONCLUSION In Gannan region,the positive rate of co-mutations of EGFR and ALK genes in LUAD patients is relatively high,and the co-mutations are more common in women,non-smoking and stage IV patients with bone metastasis.These patients prefer EGFR-TKIs as their preferred targeted drugs,but the therapeutic effect is not good.EGFR/ALK dual-TKIs may be more effective targeted drugs,which needs further study.

Repurposed anti-cancer epidermal growth factor receptor inhibitors: mechanisms of neuroprotective effects in Alzheimer’s disease

Numerous molecular mechanisms are being examined in an attempt to discover disease-modifying drugs to slow down the underlying neurodegeneration in Alzheimer’s disease.Recent studies have shown the beneficial effects of epidermal growth factor receptor inhibitors on the enhancement of behavioral and pathological sequelae in Alzheimer’s disease.Despite the promising effects of epidermal growth factor receptor inhibitors in Alzheimer’s disease,there is no irrefutable neuroprotective evidence in well-established animal models using epidermal growth factor receptor inhibitors due to many un-explored downstream signaling pathways.This caused controversy about the potential involvement of epidermal growth factor receptor inhibitors in any prospective clinical trial.In this review,the mystery beyond the under-investigation of epidermal growth factor receptor in Alzheimer’s disease will be discussed.Furthermore,their molecular mechanisms in neurodegeneration will be explained.Also,we will shed light on SARS-COVID-19 induced neurological manifestations mediated by epidermal growth factor modulation.Finally,we will discuss future perspectives and under-examined epidermal growth factor receptor downstream signaling pathways that warrant more exploration.We conclude that epidermal growth factor receptor inhibitors are novel effective therapeutic approaches that require further research in attempts to be repositioned in the delay of Alzheimer’s disease progression.

JAK3 inhibitor Ⅵ is a mutant specific inhibitor for epidermal growth factor receptor with the gatekeeper mutation T790M

AIM:To identify non-quinazoline kinase inhibitors effective against drug resistant mutants of epidermal growth factor receptor(EGFR).METHODS:A kinase inhibitor library was subjected to screening for specific inhibition pertaining to the in vitro kinase activation of EGFR with the gatekeeper mutation T790 M,which is resistant to small molecular weight tyrosine kinase inhibitors(TKIs) for EGFR in nonsmall cell lung cancers(NSCLCs). This inhibitory effect was confirmed by measuring autophosphorylation of EGFR T790M/L858 R in NCI-H1975 cells,an NSCLC cell line harboring the gatekeeper mutation. The effects of a candidate compound,Janus kinase 3(JAK3) inhibitor Ⅵ,on cell proliferation were evaluated using the MTT assay and were compared between T790M-positive and-negative lung cancer cell lines. JAK3 inhibitor Ⅵ was modeled into the ATP-binding pocket of EGFR T790M/L858 R. Potential physical interactions between the compound and kinase domains of wild-type(WT) or mutant EGFRs or JAK3 were estimated by calculating binding energy. The gatekeeper residues of EGFRs and JAKs were aligned to discuss the similarities among EGFR T790 M and JAKs. RESULTS:We found that JAK3 inhibitor Ⅵ,a known inhibitor for JAK3 tyrosine kinase,selectively inhibits EGFR T790M/L858 R,but has weaker inhibitory effects on the WT EGFR in vitro. JAK3 inhibitor Ⅵ also specifically reduced autophosphorylation of EGFR T790M/L858 R in NCI-H1975 cells upon EGF stimulation,but did not show the inhibitory effect on WT EGFR in A431 cells. Furthermore,JAK3 inhibitor Ⅵ suppressed the proliferationof NCI-H1975 cells,but showed limited inhibitory effects on the WT EGFR-expressing cell lines A431 and A549.A docking simulation between JAK3 inhibitor Ⅵ and the ATP-binding pocket of EGFR T790M/L858 R predicted a potential binding status with hydrogen bonds. Estimated binding energy of JAK3 inhibitor Ⅵ to EGFR T790M/L858 R was more stable than its binding energy to the WT EGFR. Amino acid sequence alignments revealed that the gatekeeper residues of JAK family kinases are methionine in WT,similar to EGFR T790 M,suggesting that TKIs for JAKs may also be effective for EGFR T790 M. CONCLUSION:Our findings demonstrate that JAK3 inhibitor Ⅵ is a gatekeeper mutant selective TKI and offer a strategy to search for new EGFR T790 M inhibitors.

Epidermal growth factor receptor inhibitors in colorectal cancer treatment: What's new?

Colorectal cancer constitutes one of the most common malignancies and the second leading cause of death from cancer in the western world representing one million new cases and half a million deaths annually worldwide. The treatment of patients with metastatic colon cancer comprises different regimens of chemotherapeutic compounds （fluoropyrimidines, irinotecan and oxaliplatin） and new targeted therapies. Interestingly, most recent trials that attempt to expose patients to all five-drug classes （fluoropyrimidines, irinotecan, oxaliplatin, bevacizumab and cetuximab） achieve an overall survival well over 2 years. In this review we will focus on the main epidermal growth factor receptor inhibitors demonstrating clinical benefit for colorectal cancer mainly cetuximab, panitumumab, erlotinib and gefltinib. We will also describe briefly the molecular steps that lie beneath them and the different clinical or molecular mechanisms that are reported for resistance and response.

Effect of Zhiyang Pingfu Liquid on epidermal growth factor receptor inhibitor-related skin lesion

Objective:To verify the efficacy of the Chinese medicine“Zhiyang Pingfu Liquid”on the lesion associated with Epidermal Growth Factor Receptor Inhibitors(EGFRIs).Methods:Female BN rats were divided into Control group and Gefitinib group randomly.The Gefitinib group was administered gefitinib for 21 days.After 21 days,the rats in the Gefitinib group were grouped again and randomly divided into Model group,Gefitinib+ZY group,and Gefitinib+NS group.Starting from day 22,rats in Gefitinib+ZY or NS were given different drugs for 7 days besides the other conditions are as the same as before.Observe the morphological changes and histopathological changes of the skin during the research.The changes of inflammatory factors such as TNF-αand IL-6 in the serum of were detected by ELISA.Results:The application of“Zhiyang Pingfu Liquid”for 7 days could significantly reduce the skin inflammation whether in gross or pathological view.The concentration of TNF-αand IL-6 in Gefitinib+ZY is significantly lower than those in the Model group(P=0.002,P=0.002)and there is no significant changes compared with the Control group(P=0.279,P=0.165).Conclusion:Chinese herbal“Zhiyang Pingfu Liquid”can reduce the lesion and inflammatory caused by EGFRIs.

Advanced Lung Adenocarcinoma with EGFR 19-del Mutation Transformed into SCC after EGFR-tyrosine Kinase inhibitors Treatment:A Case report

BACKGROUND Epidermal growth factor receptor tyrosine kinase inhibitors(EGFR-TKIs)significantly improve the survival of patients with Epidermal growth factor receptor(EGFR)sensitive mutations in non-small cell lung cancer(NSCLC).CASE SUMMARY A 67-year-old female patient in advanced lung adenocarcinoma suffered from drug resistance after EGFR-TKIs treatment.Secondary pathological tissue biopsy confirmed squamous cell carcinoma(SCC)transformation.Patients inevitably encountered drug resistance issues after receiving EGFR-TKIs treatment for a certain period of time,while EGFR-TKIs can significantly improve the survival of patients with EGFR-sensitive mutations in NSCLC.Notably,EGFR-TKIs resistance includes primary and acquired.Pathological transformation is one of the mechanisms of acquired resistance in EGFR-TKIs,with SCC transformation being relatively rare.Our results provide more detailed results of the patient’s diagnosis and treatment process on SCC transformation after EGFR-TKIs treatment for lung adenocarcinoma.CONCLUSION Squamous cell carcinoma transformation is one of the acquired resistance mechanisms of EGFR-TKIs in advanced lung adenocarcinoma with EGFR mutations.

Advanced lung adenocarcinoma with EGFR 19-del mutation transforms into squamous cell carcinoma after EGFR tyrosine kinase inhibitor treatment

In this editorial we comment on the article by Ji et al.We focus specifically on the EGFR tyrosine kinase inhibitor(EGFR-TKI)treatment and the development of drug resistance to EGFR-TKIs.

Activation of Rac1-PI3K/Akt is required for epidermal growth factorinduced PAK1 activation and cell migration in MDA-MB-231 breast cancer cells

Epidermal growth factor （EGF） may increase cell motility, an event implicated in cancer cell invasion and metastasis. However, the underlying mechanisms for EGF-induced cell motility remain elusive. In this study, we found that EGF treatment could activate Ras-related C3 botulinum toxin substrate 1 （Racl）, PI3K/Akt and p21- actived kinase （PAK1） along with cell migration. Ectopic expression of PAK1 K299R, a dominant negative PAK1 mutant, could largely abolish EGF-induced cell migration. Blocking PI3K/Akt signalling with LY294002 or Akt siRNA remarkably inhibited both EGF-induced PAK1 activation and cell migration. Furthermore, expression of dominant-negative Racl （T17N） could largely block EGF-induced PI3K/Akt-PAK1 activation and cell migration. Interestingly, EGF could induce a significant production of ROS, and N-acetyl-L-cysteine, a scavenger of ROS which abolished the EGF-induced ROS generation, cell migration, as well as activation of PI3K/Akt and PAK, but not Racl. Our study demonstrated that EGF-induced cell migration involves a cascade of signalling events, including activation of Racl, generation of ROS and subsequent activation of PI3K/Akt and PAK1.

Associations Between Epidermal Growth Factor Receptor Gene Mutation and Serum Tumor Markers in Advanced Lung Adenocarcinomas: A Retrospective Study

Objective To investigate the associations between epidermal growth factor receptor （EGFR） gene mutations and serum tumor markers in advanced lung adenocarcinomas. Methods We investigated the association between EGFR gene mutations and clinical features, including serum tumor marker levels, in 97 advanced lung adenocarcinomas patients who did not undergo the treatment of EGlaR tyrosine kinase inhibitors. EGFR gene mutation was detected by real-time PCR at exons 18, 19, 20, and 21. Serum tumor marker concentrations were analyzed by chemiluminescence assay kit at the same time. Results EGFR gene mutations were detected in 42 （43%） advanced lung adenocarcinoma patients. Gender （P=0.003）, smoking status （P=0.001）, and abnormal serum status of carcinoembryonic antigen （CEA, P=0.028） were significantly associated with EGFR gene mutation incidence. Multivariate analysis showed the abnormal CEA level in serum was independently associated with the incidence of EGFR gene mutation （P=0.046） with an odds ratio of 2.613 （95% Ch 1.018-6.710）. However, receiver operating characteristic （ROC） curve analysis revealed CEA was not an ideal predictive marker for EGFR gene mutation status in advanced lung adenocarcinoma （the area under the ROC curve was 0.608, P=0.069）. Conclusions EGFR gene mutation status is significantly associated with serum CEA status in advanced lung adenocarcinmoas. However, serum CEA is not an ideal predictor for EGFR mutation.

Recent advances and new insights in the management of early-stage epidermal growth factor receptor-mutated non-small-cell lung cancer

Patients with early-stage non-small-cell lung cancer(NSCLC)are candidates for curative surgery;however,despite multiple advances in lung cancer management,recurrence rates remain high.Adjuvant chemotherapy has been demonstrated to significantly prolong overall survival(OS),but this benefit is modest and there is an urgent need for effective new therapies to provide a cure for more patients.The high efficacy of tyrosine kinase inhibitors(TKIs)against epidermal growth factor receptor-mutated(EGFR)in patients with advanced EGFR-mutated NSCLC has led to the evaluation of these agents in early stages of the disease.Multiple clinical trials have evaluated the safety and efficacy of EGFR TKIs as an adjuvant treatment,in patients with resected EGFR-mutated NSCLC,and shown that they significantly prolong disease-free survival(DFS),but this benefit does not translate to OS.Recently,an interim analysis of the ADAURA trial demonstrated that,surprisingly,osimertinib improved DFS.This led to the study being stopped early,leaving many unanswered questions about its potential effect on OS and its incorporation as a standard adjuvant treatment in this patient subgroup.These targeted agents are also being evaluated in locally-advanced disease,with promising results,although prospective studies with larger sample sizes are needed to confirm these results.In this article,we review the most relevant studies on the role of EGFR TKIs in the management of early-stage EGFR-mutated NSCLC.

Effect of Calmodulin and Voltage-dependent Ca^(2+) Channel on the Proliferation of Heptoma Cells Induced by Epidermal Growth Factor

The effect of thyrosine kinase, calmodulin and voltage-dependent Ca 2+ channel on the proliferation of hepatoma cells induced by EGF was studied. Hepatoma cell line SMMC7721 was cultured in RPMI1640 serum-free medium. DNA synthesis rate of hepatoma cells was measured by 3H-TdR incorporation. 10 -9 mol/L EGF could significantly stimulate the proliferation of hepatoma cells (P<0.05), and this effect might be significantly inhibited by tyrosine kinase inhibitor (P<0.001). Calmodulin inhibitor W-7 had no effect on the basic phase of cultured hepatoma cells (P> 0.05), but it had very significantly inhibitory effect on the proliferation of hepatoma cells induced by EGF (P<0.001). Voltage-dependent Ca 2+ channel inhibitor Varapamil had no inhibition on the proliferation of hepatoma cells induced by EGF (P>0.05). It had no effect on the basic phase of cultured hepatoma cells (P>0.05). It is suggested that tyrosine kinase and Ca 2+-calmodulin-dependent pathway may play a critical role on the proliferation of heptoma cells induced by EGF, and voltage-dependent Ca 2+ channel is independent of the effect of EGF.

Epidermal Growth Factor Enhances Orthovanadate-Induced Contraction via Src and Myosin Phosphatase Target Subunit 1 in Rat Vascular Smooth Muscle

Inhibition of protein tyrosine phosphatase by orthovanadate induces vasoconstriction, which is mediated by the Rho kinase-dependent inactivation of myosin light chain phosphatase (MLCP) via signaling downstream of Src-induced activation of the epidermal growth factor (EGF) receptor. The present study investigated the potential role of EGF in orthovanadate (OVA)-dependent vaso-constriction. OVA-induced aortic contraction significantly increased in the presence of EGF, and was abolished by inhibitors of Rho kinase (Y27632), extracellular signal-regulated kinase 1 and 2 (Erk1/2) (FR180204), Erk1/2 kinase (PD98059), EGF receptor (AG1478), and Src (PP2). Treatment of the rat endothelium-denuded thoracic aorta with either EGF or OVA augmented the phosphorylation of myosin phosphatase target subunit 1 (MYPT1) at Thr-853 and of the EGF receptor at Tyr-1173. The phosphorylation of MYPT1 was further increased by co-stimulation with EGF and OVA. EGF receptor phosphorylation at Tyr-845 was also increased by EGF or OVA;this effect was augmented by co-stimulation with EGF and OVA, and was abolished by Src inhibition. In addition, Erk1/2 was phosphorylated by EGF or by co-treatment with EGF and OVA;this was abolished by an EGF receptor inhibitor, but not by Src inhibition. These results suggested that OVA-induced EGF-related contraction was mediated by the Rho kinase-dependent inactivation of MLCP via two different signaling cascades: Src-dependent phosphorylation of the EGF receptor at Tyr-845 and EGF-dependent phosphorylation of Erk1/2.

Effects of retinoic acid on proliferation,phenotype and expression of cyclin-dependent kinase inhibitors in TGF-β1-stimulated rat hepatic stellate cells

AIM To study the molecular mechanisms ofretinoic acid(RA)on proliferation andexpression of cyclin-dependent kinase inhibitors(CKI),i.e.p16,p21 and p27 in cultured rathepatic stellate cells(HSC)stimulated withtransforming growth factor beta 1(TGF-β1).METHODS HSC were isolated from healthy ratlivers and cultured.After stimulated with1 mg/L TGF-β1,subcultured HSC were treatedwith or without 1 nmol/L RA.MTT assay,immunocytochemistry(ICC)for p16,p21,p27and α-smooth muscle actin(α-SMA)protein,insitu hybridization(ISH)for retinoic acidreceptor beta 2(RAR-β2)and p16,p21 and p27mRNA and quantitative image analysis(partially)were performed.RESULTS RA inhibited HSC proliferation(41.50%,P【0.05),decreased the protein levelof α-SMA(55.09%,P【0.05),and induced HSCto express RAR-β2 mRNA.In addition,RAincreased the protein level of p16(218.75%,P【0.05)and induced p21 protein expression;meanwhile,p27 was undetectable by ICC in bothcontrol and RA-treated HSC.However,RA hadno influence on the mRNA levels of p16,p21 orp27 as determined by ISH.CONCLISION Up-regulation of p16 and p21 on post-transcriptional level may contribule, in part to RA inhibition of TGF-β1-initiated rat HSC activation in vitro.