We thank the members of the Institute of Molecular Oncology for their thoughtful comments and helpful advice, and Editage for their assistance with English language editing. This work was supported by the MEXT-supported Program for the Strategic Research Foundation at Private Universities (2012-2016) from the Ministry of Education, Culture, Sports, Science, and Technology of Japan. Tohru Ohmori received research funding (2015-2016) from Boehringer-Ingelheim (Ingelheim, Germany).

1. Establish Gefitinib-resistant Cells
<ol>
	<li>Determine the initial gefitinib concentration by 3-(4,5-dimethylthiazol-2-yl)-2,5- diphenyltetrazolium bromide (MTT) assay.
	<ol>
		<li>Culture PC-9 cells in growth medium (RPMI-1640 medium with 10% FBS and 1% antibiotics (penicillin: 100 U/mL and streptomycin: 100 &#181;g/mL)), in a 5% CO2 incubator at 37 &#176;C.</li>
		<li>Adjust the cells to 1.0 &#215; 105 cells/mL using an automated cell counter (see Table of materials<...

<ol>
	<li>Lynch, T. J., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Activating+mutations+in+the+epidermal+growth+factor+receptor+underlying+responsiveness+of+non-small-cell+lung+cancer+to+gefitinib.">Activating mutations in the epidermal growth factor receptor underlying responsiveness of non-small-cell lung cancer to gefitinib.</a> N Engl J Med. 350 (21), 2129-2139 (2004).</li><li>Paez, J. G., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=EGFR+mutations+in+lung+cancer:+correlation+with+clinical+response+to+gefitinib+therapy.">EGFR mutations in lung cancer: correlation with clinical response to gefitinib therapy.</a> Science. 304 (5676), 1497-1500 (2004).</li><li>Pao, W., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=EGF+receptor+gene+mutations+are+common+in+lung+cancers+from+"never+smokers"+and+are+associated+with+sensitivity+of+tumors+to+gefitinib+and+erlotinib.">EGF receptor gene mutations are common in lung cancers from "never smokers" and are associated with sensitivity of tumors to gefitinib and erlotinib.</a> Proc Natl Acad Sci U S A. 101 (36), 13306-13311 (2004).</li><li>Mitsudomi, T., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Mutations+of+the+epidermal+growth+factor+receptor+gene+predict+prolonged+survival+after+gefitinib+treatment+in+patients+with+non-small-cell+lung+cancer+with+postoperative+recurrence.">Mutations of the epidermal growth factor receptor gene predict prolonged survival after gefitinib treatment in patients with non-small-cell lung cancer with postoperative recurrence.</a> J Clin Oncol. 23 (11), 2513-2520 (2005).</li><li>Sequist, L. V., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Genotypic+and+histological+evolution+of+lung+cancers+acquiring+resistance+to+EGFR+inhibitors.">Genotypic and histological evolution of lung cancers acquiring resistance to EGFR inhibitors.</a> Sci Transl Med. 3 (75), 75ra26 (2011).</li><li>Engelman, J. A., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=MET+amplification+leads+to+gefitinib+resistance+in+lung+cancer+by+activating+ERBB3+signaling.">MET amplification leads to gefitinib resistance in lung cancer by activating ERBB3 signaling.</a> Science. 316 (5827), 1039-1043 (2007).</li><li>Schmidt, L., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Novel+mutations+of+the+MET+proto-oncogene+in+papillary+renal+carcinomas.">Novel mutations of the MET proto-oncogene in papillary renal carcinomas.</a> Oncogene. 18 (14), 2343-2350 (1999).</li><li>Olivero, M., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Novel+mutation+in+the+ATP-binding+site+of+the+MET+oncogene+tyrosine+kinase+in+a+HPRCC+family.">Novel mutation in the ATP-binding site of the MET oncogene tyrosine kinase in a HPRCC family.</a> Int J Cancer. 82 (5), 640-643 (1999).</li><li>Janne, P. A., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=AZD9291+in+EGFR+inhibitor-resistant+non-small-cell+lung+cancer.">AZD9291 in EGFR inhibitor-resistant non-small-cell lung cancer.</a> N Engl J Med. 372 (18), 1689-1699 (2015).</li><li>Bean, J., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=MET+amplification+occurs+with+or+without+T790M+mutations+in+EGFR+mutant+lung+tumors+with+acquired+resistance+to+gefitinib+or+erlotinib.">MET amplification occurs with or without T790M mutations in EGFR mutant lung tumors with acquired resistance to gefitinib or erlotinib.</a> Proc Natl Acad Sci U S A. 104 (52), 20932-20937 (2007).</li><li>. NCT02468661 - ClinicalTrials.gov Available from: <a target="_blank" href="https://clinicaltrials.gov/ct2/show/NCT02468661">https://clinicaltrials.gov/ct2/show/NCT02468661</a> (2017)</li><li>Yamaoka, T., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Acquired+Resistance+Mechanisms+to+Combination+Met-TKI/EGFR-TKI+Exposure+in+Met-Amplified+EGFR-TKI-Resistant+Lung+Adenocarcinoma+Harboring+an+Activating+EGFR+Mutation.">Acquired Resistance Mechanisms to Combination Met-TKI/EGFR-TKI Exposure in Met-Amplified EGFR-TKI-Resistant Lung Adenocarcinoma Harboring an Activating EGFR Mutation.</a> Mol Cancer Ther. 15 (12), 3040-3054 (2016).</li><li>Mosmann, T. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Rapid+colorimetric+assay+for+cellular+growth+and+survival:+application+to+proliferation+and+cytotoxicity+assays.">Rapid colorimetric assay for cellular growth and survival: application to proliferation and cytotoxicity assays.</a> J Immunol Methods. 65 (1-2), 55-63 (1983).</li><li>Cifone, M. A., Fidler, I. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Correlation+of+patterns+of+anchorage-independent+growth+with+in+vivo+behavior+of+cells+from+a+murine+fibrosarcoma.">Correlation of patterns of anchorage-independent growth with in vivo behavior of cells from a murine fibrosarcoma.</a> Proc Natl Acad Sci U S A. 77 (2), 1039-1043 (1980).</li><li>Ercan, D., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Amplification+of+EGFR+T790M+causes+resistance+to+an+irreversible+EGFR+inhibitor.">Amplification of EGFR T790M causes resistance to an irreversible EGFR inhibitor.</a> Oncogene. 29 (16), 2346-2356 (2010).</li><li>Ogino, A., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Emergence+of+epidermal+growth+factor+receptor+T790M+mutation+during+chronic+exposure+to+gefitinib+in+a+non+small+cell+lung+cancer+cell+line.">Emergence of epidermal growth factor receptor T790M mutation during chronic exposure to gefitinib in a non small cell lung cancer cell line.</a> Cancer Res. 67 (16), 7807-7814 (2007).</li><li>Ando, K., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Enhancement+of+sensitivity+to+tumor+necrosis+factor+alpha+in+non-small+cell+lung+cancer+cells+with+acquired+resistance+to+gefitinib.">Enhancement of sensitivity to tumor necrosis factor alpha in non-small cell lung cancer cells with acquired resistance to gefitinib.</a> Clin Cancer Res. 11 (24 Pt 1), 8872-8879 (2005).</li><li>Suda, K., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Reciprocal+and+complementary+role+of+MET+amplification+and+EGFR+T790M+mutation+in+acquired+resistance+to+kinase+inhibitors+in+lung+cancer.">Reciprocal and complementary role of MET amplification and EGFR T790M mutation in acquired resistance to kinase inhibitors in lung cancer.</a> Clin Cancer Res. 16 (22), 5489-5498 (2010).</li><li>Shien, K., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Acquired+resistance+to+EGFR+inhibitors+is+associated+with+a+manifestation+of+stem+cell-like+properties+in+cancer+cells.">Acquired resistance to EGFR inhibitors is associated with a manifestation of stem cell-like properties in cancer cells.</a> Cancer Res. 73 (10), 3051-3061 (2013).</li><li>Sagawa, Y., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Establishment+of+three+cisplatin-resistant+endometrial+cancer+cell+lines+using+two+methods+of+cisplatin+exposure.">Establishment of three cisplatin-resistant endometrial cancer cell lines using two methods of cisplatin exposure.</a> Tumour Biol. 32 (2), 399-408 (2011).</li><li>Ritter, C. A., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Human+breast+cancer+cells+selected+for+resistance+to+trastuzumab+in+vivo+overexpress+epidermal+growth+factor+receptor+and+ErbB+ligands+and+remain+dependent+on+the+ErbB+receptor+network.">Human breast cancer cells selected for resistance to trastuzumab in vivo overexpress epidermal growth factor receptor and ErbB ligands and remain dependent on the ErbB receptor network.</a> Clin Cancer Res. 13 (16), 4909-4919 (2007).</li></ol>

The authors have no conflicts of interest to disclose.

The protocol described here can be used for the establishment of acquired dual-resistance in cancer cells using a 2-step dose-escalation method in vitro. Many research papers have reported that PC-9 cells developed EGFR-TKI (gefitinib or erlotinib) resistance through T790M EGFR mutations15,16. However, we did not detect T790M mutations in exon 20 of our PC-9MET1000 cells by direct sequencing (Figure 4C). Moreover, MET amplif...

Oncogenic mutations in the epidermal growth factor receptor (EGFR) are found in a subset of patients with non-small cell lung cancer (NSCLC) and are important predictive biomarkers of this disease1,2. These activating EGFR mutations most commonly occur as either an in-frame deletion in exon 19 (delE746-A750) or a point mutation replacing leucine with arginine at codon 858 of exon 21 (L858R) in the EGFR tyrosine kinase domain3,4. Treatment with EGFR-tyrosine kinase inhibitors (TKIs) is a clinically effective therapy for patients with NSCLC harboring EGFR mutations. However, this therapy is limited by the inevitable acquisition of resistance to EGFR-TKIs such as gefitinib and erlotinib. The most common acquired resistance occurs through a secondary T790M mutation in exon 20 of EGFR, which was detected in approximately 60% of patients who acquired EGFR-TKI (gefitinib or erlotinib) resistance. Other molecular mechanisms associated with acquired resistance to EGFR-TKIs are activation of bypass signaling caused by MET amplification, transformation of small-cell lung cancers, and epithelial-to-mesenchymal transition5,6. The receptor for the hepatocyte growth factor, encoded by the MET gene, which is dysregulatedin many tumors, has been reported to be an important candidate for targeted therapies7,8.
Strategies for overcoming the acquired resistance to EGFR-TKIs are now undergoing clinical evaluation. Preclinical and clinical studies have shown that third-generation EGFR inhibitors such as osimertinib are effective for patients with the T790M mutation9. In addition, the growth of EGFR-mutant cancers with MET amplification can be inhibited by combined treatment with EGFR- and MET-TKIs6,10. Clinical trials assessing a combination of MET and EGFR inhibitors in patients with acquired resistance to gefitinib and erlotinib are underway now11.
To study the molecular mechanism of acquired resistance to chemotherapeutic agents, cell lines that initially respond to inhibitors are treated continuously with these inhibitors. Two methods are available to establish acquired resistance in cell lines. One is stepwise dose-escalation, and the other is high-concentration exposure. The stepwise escalation method has been more commonly used, because it has a higher success rate. The cells are first exposed to low concentrations of the inhibitors, nearly a tenth of the half-maximal inhibitory concentration (IC50) value, and the concentration is then gradually increased by 10-30% until the target concentration is achieved. The high-concentration exposure method involves exposing the cells to the final dose of inhibitor in the culture medium, which is more than the IC50 value, so the parental cells are almost completely killed. This high-concentration exposure method has much a lower success rate than the stepwise escalation method.
In a previous study, combined treatment with EGFR-TKI and MET-TKI was shown to be effective in an in vitro system. Acquired resistance to an EFGR-TKI, gefitinib, was established through stepwise escalation for 12 months, along with MET-amplification, and thus, a gefitinib-resistant cell line called PC-9MET1000 was generated12.
The protocol presented here is a two-step dose-escalation procedure for obtaining EGFR-mutated NSCLC PC-9 cells with dual resistance to the EGFR-TKI, gefitinib, and a MET-TKI, PHA665752 (Figure 1). This method for establishing acquired resistant in cell lines is relatively easy to perform, with a high success rate. The described protocol can be modified for application with inhibitors of other molecular target drugs and cytotoxic agents as well.

<table width="970">
	<tbody>
		<tr height="21">
			<td height="21" style="width:365px;height:21px;">RPMI-1640</td>
			<td style="width:177px;">Wako</td>
			<td style="width:119px;">189-02025</td>
			<td style="width:309px;">with L-Glutamine and Phenol Red</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">CellTiter 96</td>
			<td style="width:177px;">Promega</td>
			<td style="width:119px;">G4100</td>
			<td>Non-Radioactive Cell Proliferation Assay</td>
		</tr>
		<tr height="21">
			<td height="21" style="width:365px;height:21px;">FBS</td>
			<td style="width:177px;">gibco</td>
			<td style="width:119px;">26140-079</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="width:365px;height:21px;">Pen Strep</td>
			<td style="width:177px;">gibco</td>
			<td style="width:119px;">15140-163</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="width:365px;height:21px;">gefitinib</td>
			<td style="width:177px;">Selleck</td>
			<td style="width:119px;">S1025</td>
			<td>stocked 10 mM/EMSO at -20&#186;C</td>
		</tr>
		<tr height="21">
			<td height="21" style="width:365px;height:21px;">PHA665752</td>
			<td style="width:177px;">Selleck</td>
			<td style="width:119px;">S1070</td>
			<td>stocked 10 mM/EMSO at -20&#186;C</td>
		</tr>
		<tr height="21">
			<td height="21" style="width:365px;height:21px;">96-well plate</td>
			<td style="width:177px;">IWAKI</td>
			<td style="width:119px;">860-096</td>
			<td>flat bottom with lid, low evaporation type</td>
		</tr>
		<tr height="21">
			<td height="21" style="width:365px;height:21px;">TC10 Automated Cell Counter</td>
			<td style="width:177px;">BIO RAD</td>
			<td>#1450010</td>
			<td></td>
		</tr>
		<tr height="26">
			<td height="26" style="width:365px;height:26px;">CellTiter 96 Non-Radioactive Cell Proliferation Assay</td>
			<td style="width:177px;">Promega</td>
			<td style="width:119px;">G4100</td>
			<td style="width:309px;">Dye Solution and Solubilization/Stop Solution</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Powerscan HT microplate reader</td>
			<td>BioTek</td>
			<td style="width:119px;"></td>
			<td></td>
		</tr>
		<tr height="26">
			<td height="26" style="width:365px;height:26px;">GraphPad Prism v.5.0 software</td>
			<td style="width:177px;">GraphPad Inc.</td>
			<td style="width:119px;"></td>
			<td></td>
		</tr>
		<tr height="26">
			<td height="26" style="width:365px;height:26px;">PC-9</td>
			<td style="width:177px;">Riken BioResource Center</td>
			<td style="width:119px;">RCB4455</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="width:365px;height:21px;">P100 dish</td>
			<td style="width:177px;">FALCON</td>
			<td align="right" style="width:119px;">353003</td>
			<td></td>
		</tr>
	</tbody>
</table>

establishing dual resistance to egfr-tki and met-tki in lung adenocarcinoma cells in vitro with a 2-step dose-escalation procedure

Drug resistance is a major challenge in cancer therapy. The generation of resistant sublines in vitro is necessary for discovering novel mechanisms to overcome this challenge. Here, a 2-step dose-escalation method for establishing dual-resistance to an epidermal growth factor receptor (EGFR)-tyrosine kinase inhibitor (TKI), gefitinib, and a MET-TKI, PHA665752, is described. This method is based on simple stepwise dose-escalation of inhibitors for inducing acquired resistance in cell lines. The alternate method for generating resistant sublines involves exposing the cells to high concentrations of the inhibitor in one step. The stepwise dose-escalation method has a higher possibility of successfully inducing acquired resistance than this method. Activating EGFR mutations are biomarkers of a response to treatment with EGFR-TKI, which is an applied first-line treatment for non-small cell lung cancers (NSCLC) that harbor these mutations. However, despite reports of effective responses, the use of EGFR-TKI is limited because tumors inevitably acquire resistance. The major mechanisms behind EGFR-TKI resistance include a secondary mutation at the gatekeeper site, T790M in exon 20 of EGFR, and a bypass signal of MET. Thus, a potential solution for this issue would be a combination of EGFR-TKI and MET-TKI. This combined treatment has been shown to be effective in an in vitro study model. Acquired gefitinib-resistance was established through MET-amplification by stepwise dose-escalation of gefitinib for 12 months, and a cell line named PC-9MET1000 was generated in a previous study. To further investigate the mechanisms of acquired MET-TKI and EGFR-TKI resistance, a MET-TKI, PHA665752, was administered to these cells with stepwise dose-escalation in the presence of gefitinib for 12 months. This protocol has also been successfully applied for a number of combination therapies to establish acquired resistance to other inhibitor molecules.

The overview of the protocol presented in this manuscript is shown in Figure 1, including the induction of acquired dual-resistance to gefitinib and PHA665752 in PC-9 cells by a 2-step dose-escalation procedure. Figure 2 shows a decrease in the proliferation of parental PC-9 cells as the concentration of gefitinib increases. This indicates that the PC-9 cells became sensitive to gefitinib after the dose-escalation procedure was p...

Watch this Scientific Journal Video about Establishing Dual Resistance to EGFR-TKI and MET-TKI in Lung Adenocarcinoma Cells In Vitro with a 2-step Dose-escalation Procedure at JoVE.com

Establishing Dual Resistance to EGFR-TKI and MET-TKI in Lung Adenocarcinoma Cells In Vitro with a 2-step Dose-escalation Procedure

An in vitro method for establishing dual resistance to an EGFR-TKI and a MET-TKI in cancer cells is described. This method is useful for developing treatments for patients with EGFR-mutations, who exhibit disease progression despite EGFR-TKI treatment with MET-amplification. It can also be modified for inhibitors targeting other molecules.

Establishing Dual Resistance to EGFR-TKI and MET-TKI in Lung Adenocarcinoma Cells In Vitro with a 2-step Dose-escalation Procedure

Drug resistance is a major challenge in cancer therapy. The generation of resistant sublines in vitro is necessary for discovering novel mechanisms to ...

The overall goal of this experiment is to discover novel mechanisms to overcome drug resistance. This method can help answer key questions in the cancer research field such as those about graft resistance. The main advantage of this technique is that the cells resistant to true inhibitors can be established.To begin, plate PC-9 cells in growth medium and culture the cells at 37 degrees Celsius in a 5%CO2 incubator. Use an automated cell counter to count the cells and adjust the concentration to 1.0 times 10 to the fifth cells per milliliter in growth medium. Then, seed 50 microliters of the cells into each well of a 96-well plate.Incubate the plate overnight at 37 degrees Celsius. The following day, add 50 microliters of Gefitinib at different concentrations so that the final volume in each well is 100 microliters. Incubate the plate at 37 degrees Celsius for 72 hours.Next, add 15 microliters of dye solution to each well and incubate the plate at 37 degrees Celsius for four hours. Add 100 microliters of the solubilization stop solution to each well for solubilizing the formazan produced by the dye solution and incubate the plate at 37 degrees Celsius overnight. Using a microplate reader, measure the optical density at 570 nanometers and use statistical software to generate a cell proliferation curve to obtain the IC50 value.Plate one milliliter of PC-9 cells in P100 dishes with 10 milliliters of growth medium and incubate the cells in a 5%CO2 incubator at 37 degrees Celsius. Add 1/10 the IC50 value of Gefitinib into the P100 dish. When the cells in the culture medium become subconfluent, use a one milliliter pipette to add one to two milliliters of cells to 10 milliliters of fresh growth medium with a 10 to 30%higher concentration of Gefitinib and culture the cells under the same conditions as just demonstrated.Increase the Gefitinib concentration progressively by 10 to 30%with each split until it reaches one micromolar. This may take about six to 12 months. After the cells have been cultured with one micromolar of Gefitinib, perform the MTT assay to confirm that the cells are Gefitinib resistant by the increased protein and RNA levels of MET.To determine the initial concentration of PHA-665752 using the MTT assay, plate the MET1000 cells in P100 dishes with 10 milliliters of growth medium and one micromolar Gefitinib and incubate the cultures in a 5%CO2 incubator at 37 degrees Celsius. After adjusting the final concentration of the cells to 1.0 times 10 to the fifth cells per milliliter, seed the cells in 50 microliters of the growth medium in a 96-well plate at 5.0 times 10 to the third cells per well. Incubate the plate overnight.After the incubation period, add 50 microliters of PHA-665752 at different concentrations in the presence or absence of two micromolar Gefitinib so that the final volume in each well is 100 microliters. Incubate the plate at 37 degrees Celsius for 72 hours. Next, add 15 microliters of the dye solution to each well and incubate the plate at 37 degrees Celsius for four hours.Add 100 microliters of the solubilization stop solution to each well for solubilizing the formazan produced by the dye and again incubate the plate at 37 degrees Celsius overnight. Measure the optical density of the cells at 570 nanometers and use statistical software to obtain the IC50 value of PHA-665752 in the presence of Gefitinib by generating a cell proliferation curve. To establish dual resistance in MET1000 cells to Gefitinib and PHA-665752, culture the MET1000 cells in P100 dishes with 10 milliliters of growth medium and one micromolar Gefitinib.Add 1/10 of the IC50 value of PHA-665752 into the growth medium in the presence of one micromolar of Gefitinib and culture the cells under the same conditions. Increase the PHA-665752 concentration progressively by 10 to 30%with each split until it reaches one micromolar. This might take about six to 12 months.Finally, perform the MTT assay to confirm that the cells are resistant to Gefitinib and PHA-665752 and that they are not sensitive to PHA-665752 in the presence of Gefitinib. These dual resistant cells are referred to as PC-9DR. This graph illustrates the results of an MTT assay where a decrease was seen in the proliferation of parental PC-9 cells as the concentration of Gefitinib increased, indicating that the PC-9 cells are sensitive to Gefitinib after the dose escalation procedure was performed.As seen here, PC-9MET1000 cells exhibit resistance to Gefitinib even at high concentrations, but are sensitive to a MET-TKI PHA-665752 in the presence of Gefitinib. PC-9 cell proliferation was suppressed at higher concentrations of Gefitinib, indicating that they were sensitive to Gefitinib. Amplified levels of MET protein and RNA in PC-9MET1000 and PC-9DR cells are demonstrated here and no acquired mutations are present in EGFR and MET.Therefore, the emergence of bypass signaling is highly suggested as the cause of the acquired resistance to EGFR-TKI and/or MET-TKI. In this experiment, the MTT assay was used to show resistance of PC-9DR cells to PHA-665752 in the presence of one micromolar Gefitinib. Although proliferation of PC-9MET1000 cells was inhibited by treatment with Gefitinib and PHA-665752, PC-9DR cells survived the treatment, indicating that they had acquired dual resistance to Gefitinib and PHA-665752.Once mastered, each procedure can be performed in 30 to 60 minutes. While attempting this procedure, it is important to remember to seed equal volumes of the viable cells into each well of the 96 plate for the MTT assay. After its development, this technique paved the way for the researchers in the field of cancer research to explore novel resistant mechanisms to cancer agent in all kinds of cancers.After watching this video, you should have a good understanding of how to obtain resistant cell rise to cancer agent in cancer therapy through the procedure. Don't forget that working with the solubilization stop solution in the MTT assay can be extremely hazardous and precautions such as wearing gloves should always be taken while performing this procedure.

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Cancer Research

8.7K visualizações.  Showa University. The overall goal of this experiment is to discover novel mechanisms to overcome drug resistance. This method can help answer key questions in the cancer research field such as those about graft resistance. The main advantage of this technique is that the cells resistant to true inhibitors can be established.To begin, plate PC-9 cells in growth medium and culture the cells at 37 degrees Celsius in a 5%CO2 incubator. Use an automated cell counter to count the cells and adjust the concent...