Investigating Acquired Resistance To Targeted Anti Cancer Agents Biology Essay

Approximately 25 % of chest malignant neoplastic diseases overexpress the ErbB2 ( HER2 ) receptor, and this receptor is targeted for intervention, e.g. by Trastuzumab, an anti-HER2 monoclonal antibody and/or by Lapatinib a tyrosine kinase inhibitor of EGFR ( HER1 ) and HER2. Over clip some tumors that ab initio respond to these interventions develop opposition ; this may be a manifestation of hardiness, i.e. the cells accommodating to disturbances in their environment. Three HER2-positive malignant neoplastic disease cell lines, HCC1954, SKBR3 and BT474 and their several Lapatinib resistant discrepancies ( developed in the School of Pharmacy and Pharmaceutical Sciences, Trinity College Dublin ) as HCC1954 RL ( immune to Lapatinib ) , SKBR3 RL ( immune to Lapatinib ) and BT474 RL ( immune to Lapatinib ) were studied for this undertaking.

Word picture of three malignant neoplastic disease cell lines braces, Control and RL was performed. Invasion and migration checks were performed on HCC1954 and SKBR3 sensitive and immune braces. Additions of 25.7 % in invasion and 84.

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4 % in migration of SKBR3 RL cells compared to SKBR3 parent cells were observed ; whereas the HCC1954 cell line braces were seeded excessively dumbly to observe any differences.RNA was isolated from all three cell lines braces and later quantified utilizing NanoDrop. The degrees of look of a figure of cistrons were measured in both Control and Lapatinib resistant cell lines.

The cistron transcripts selected for analysis were AXL, EGFR, ERBB3, FOXO3, IGF1R, PTEN, Sample A* and Sample B* , and the degrees of look for the Lapatinib-resistant compared to the control cells. ( *Sample A and Sample B cistron transcripts and their checks are in the procedure of being patented, so for IP protection their existent names can non be listed in this study ) . This was to find if these cistrons were up- or down- regulated in the Lapatinib resistant cell lines. Overall, EGFR and Sample B messenger RNA were most well up-regulated and AXL most well down-regulated.Abbreviations: PBS – phosphate-buffered saline, EGFR – cuticular growing factor receptor, EGFRl – cuticular growing factor receptor 1, HER – human cuticular growing factor receptor, HER2 – human cuticular growing factor receptor 2, FBS – fetal bovine serum, qRT-PCR – quantitative existent clip polymerase concatenation reaction, DNA – Deoxyribonucleic acid, cDNA – complementary Deoxyribonucleic acid, RNA – Ribonucleic acid, mRNA – courier RNA, miRNA – micro RNA, DMSO – Dimethyl sulfoxide, EDTA – Ethylenediaminetetraacetic acid, RL – Resistant to Lapatinib, ECM – Extra-cellular matrix, PBS – Phosphate buffered solution, RPMI – Roswell Park Memorial Institute, erbB – erythroblastic leukaemia viral transforming gene homolog, TKI – Tyrosine Kinase Inhibitor, MMLV – Moloney Murine Leukaemia Virus


The Epidermal Growth Factor Receptor ( EGFR ) or ErbB household of receptors consists of four structurally-related receptor proteins, EGFR1 ( HER1 or erbB1 ) , HER2 ( neu or erbB2 ) , HER3 ( erbB3 ) and HER-4 ( erbB4 ) , with each holding an extracellular ligand adhering sphere ; a individual transmembrane sphere ; and a cytoplasmatic tyrosine kinase sphere ( Browne et al 2009 ) . These four receptors are involved in many cellular responses, HER2 can adhere with itself ( homodimerise ) or the other three proteins within the household to organize heterodimers, and has the strongest kinase activity. Thus aberrances in HER signalling, peculiarly HER-2, have been implicated in the patterned advance of chest malignant neoplastic disease. Harmonizing to the American Cancer Society about 180,000 new instances of chest malignant neoplastic disease are diagnosed each twelvemonth.

Approximately 8,000 to 10,000 adult females die from metastatic HER2 positive chest malignant neoplastic disease each twelvemonth.When cuticular growing factor and its relations bind the ErbB household of receptors, they trigger a rich web of signalling tracts, climaxing in responses runing from cell division and growing to apoptosis, motility or migration to adhesion ( Yarden & A ; Sliwkowski, 2001 ) . Ligands bind to the extracellular sphere advancing dimerisation, ensuing in the intracellular tyrosine kinase sphere going activated. Jones et Al ( 2006 ) studied the four receptors, but had to except HER4 due to miss of informations. They noted that at higher look degrees, EGFR and HER2 go much more promiscuous than when their look degrees are low ; whereas HER3 does non. Furthermore, the enlisting sites on HER2 are much more promiscuous than those on the other receptors. Amplification of EGFR and HER2 is often observed in human malignant neoplastic diseases and they propose that the elevated oncogenic belongingss of EGFR and HER2 are due, in portion, to their ability to trip different tracts when overexpressed, and non merely by increasing their primary tract signalling.Brown et Al ( 2009 ) noted that HER receptors are widely expressed and functionally of import in multiple tissues, peculiarly in mammalian development, with a function identified for EGFR in modulating epithelial development.

EGFR-deficient mice have shown impaired epithelial development in several variety meats including tegument, lung, and GI piece of land ; with encephalon, kidney and liver abnormalcies ensuing in decease within hebdomads of birth. Mutants in HER2, HER3 or neuregulin-1 proteins resulted in a deficiency of nervous crest precursor cells and mouse embryos missing HER2, HER3, HER4 or neuregulins died during embryogenesis, due to terrible cardiac abnormalcies and encephalon defects. HER2 is besides expressed in grownup cardiomyocytes, and loss of cardiac HER2 can do myocardiopathy in grownup mice – which has of import clinical deductions for HER2 targeted therapies. Overexpression of HER2 and subsequent dimerisation and phosphorylation activates Akt, MAPK and PKC signalling tracts, which finally promote proliferation and cell endurance ( see Figure 1A ) .



Figure 1A – HER 2 signalling tract ( Brown, et Al, 2009 )

Figure 1B – Inhibition of HER-2 signalling:

Trastuzumab binds extracellular sphere of HER-2 dimers cut downing HER-2 signalling ;

Lapatinib inhibits tyrosine kinase sphere of HER-2 and EGFR

A cosmopolitan trait of complex biological ( and non-biological ) systems is their capacity to keep map despite external and internal disturbances, a characteristic referred to as hardiness ( Bublil and Yarden, 2007 ) .

In this reappraisal the writers mention that disturbance of the ErbB map is implicated in some human diseases, runing from reduced look and signalling in some neurodegenerative diseases to overexpression and increased signalling in many malignant neoplastic diseases. High degrees of EGFR look were found in the bulk of carcinomas, and elaboration of the HER 2 cistron can be found in 20-30 % of metastatic chest lesions. Therefore, the ErbB receptors are attractive campaigners for targeted therapy and, to day of the month, several anti-ErbB monoclonal antibodies ( e.g. Trastuzumab or HerceptinA® ) and small-molecule tyrosine kinase inhibitors ( TKIs e.g. Lapatinib or TykerbA® ) have been licensed.

The exact mechanism ( s ) -of-action of these therapies is non to the full understood, nor is the method by which the malignant neoplastic disease cells develop opposition to them. Bublil and Yarden ( 2007 ) , nevertheless, propose that opposition to ErbB-targeted therapeutics could be viewed as manifestations of hardiness.Trastuzumab is a humanised monoclonal antibody that targets HER2, and was approved by the FDA in 1998 for the intervention of patients with metastatic chest malignant neoplastic disease whose tumors overexpress the HER2 protein and who had received one or more chemotherapy regimens for their metastatic disease. Trastuzumab ( in combination with paclitaxel ) was indicated for intervention of patients with metastatic chest malignant neoplastic disease whose tumors overexpress HER2 protein and who have non received chemotherapy for their metastatic disease. Trastuzumab is a big protein molecule that targets the portion of the HER2 protein on the exterior of the cell ( see Figure 1B ) .

In 2007 the FDA approved Lapatinib a Tyrosine Kinase Inhibitor ( TKI ) , to be used in combination with capectabine ( XelodaA® ) , another malignant neoplastic disease drug, for patients with advanced metastatic chest malignant neoplastic disease that is HER2 positive. The combination intervention was indicated for adult females who had received anterior therapy with other malignant neoplastic disease drugs, including an anthracycline, a taxane, and Trastuzumab ( HerceptinA® ) . Lapatinib is a little molecule that enters the cell and blocks the map of this and other proteins and works through multiple tracts to strip tumour cells of signals needed to turn ( see Figure 1B ) . An advantage of Lapatinib is that it is in tablet signifier that the patient can take in their place, while Trastuzumab must be administered by extract in a clinical scene.

Materials & A ; Methods

Safety Precautions

A category II down-flow re-circulating laminar flow cabinet was used for cell civilization work and sterile techniques were employed at all times. 70 % ethyl alcohol was used to swob the laminar flow cabinet before and after usage and any points to be used in it. Air was allowed to go around in the cabinet for 15 proceedingss between cell lines, and merely one cell line was worked on at a clip.


Lapatinib Tosylate was obtained in pulverization signifier from Sequoia Research Products Ltd. ( SRP01211l ) . The Lapatinib pulverization was made up as stock solution in DMSO at a concentration of 10mM. A on the job concentration of 1:1000 was made up fresh weekly and kept at 4°C. The working concentration was used for checks and intervention of cell lines.

Cell Culture

Three chest malignant neoplastic disease cell lines were used ; HCC1954, SKBR3 and BT474. The isolation and culturing of human HCC1954 ( Gazdar AF, et Al, 1998 ) , SKBR3 ( Trempe, 1976 ) and BT474 ( Lasfargues EY, et al. , 1978 ) cells have been detailed in old surveies.

Each cell line was grown as a monolayer in 25cm3 civilization flasks in an brooder at a temperature of 37°C and 5 % CO2. Cells were cultured in RPMI medium incorporating 10 % Foetal Bovine Serum ( FBS ) and 1 % L-Glutamine. Cells were subcultured and their medium renewed every two to three yearss. The cells were monitored for taint prior to cell civilization. To trypsinise/passage, civilization medium was removed from the flasks and discarded. 2ml of Trypsin/EDTA solution was added and the flask was so incubated at 37°C for about 2 proceedingss until all the cells were seen to hold detached.

2ml of growing medium was so added to neutralize the trypsin. This solution was transferred to a 30ml unfertile cosmopolitan tubing and centrifuged at 900rpm for 5 proceedingss. The cell pellet was re-suspended in 4ml fresh growing medium and cells were counted utilizing a haemocytometer to re-seed at the right denseness into a fresh flask for subsequent RNA isolation.Lapatinib-resistant cell lines were established in the research lab ( the School of Pharmacy and Pharmaceutical Sciences ) over a period of five months, by stepwise exposing to increased concentrations of Lapatinib, from 10nM to 250nM ; which finally became the care dosage. Three new Lapatinib -resistant cells lines were therefore established ; HCC1954 RL ( Resistant to Lapatinib ) , SKBR3 RL ( Resistant to Lapatinib ) and BT474 RL ( Resistant to Lapatinib ) . Parent cell lines were “ aged ” as controls for the several RL cell discrepancies, by culturing in analogue, but without exposing to Lapatinib.

In Vitro Invasion Assay

The invasive capacity of the HCC1954 Control, HCC1954 RL, SKBR3 Control and SKBR3 RL cell lines was investigated utilizing a somewhat modified invasion check protocol ( O’Driscoll et al, 2002 ) .

This check was carried out one time ( with two samples ) , at the same time for each of the two cell lines ( control and RL ) . This was performed by surfacing the transwell inserts with an ECM ( Sigma ) 24 hours prior to utilize. The cell suspension ( 5×105 cells/insert ) with 1 % FBS medium was placed inside the insert and 10 % FBS medium in the well. Cells were incubated at 37°C for 48 hours for HCC1954 and 72 hours for SKBR3 ( due to HCC1954 holding a higher proliferation rate ) .

After this clip had elapsed, the interior side of the insert was wiped with a PBS-soaked swab in order to take any cells which had non migrated through the insert. The inserts were gently rinsed with PBS three times and were stained, for 10 proceedingss, utilizing 25 % crystal violet. This was so rinsed with PBS and allowed to air-dry.Inserts were so viewed utilizing light microscopy and cells, at four- and ten-magnification, were examined and photographed. In order to quantify the cells stained with crystal violet, 200I?l of 33 % glacial acetic acid was added to solubilise the crystal violet. 50I?l of the eluted discoloration was transferred from each well into single Wellss of a 96 good home base and the optical density was read at 570nm utilizing a home base reader ( FLUOstar OPTIMA-Fluorescence Microplate Reader ) .

In Vitro Migration Assay

The migration ability of the HCC1954 Control, HCC1954 RL, SKBR3 Control and SKBR3 RL cell lines was investigated.

The protocol for the motility check was indistinguishable to that outlined above for the invasion check, with the exclusion that the inserts were non coated with ECM. This check was carried out one time ( 5×105 cells/insert ) at the same time for the cell lines. Again HCC1954 cells were incubated at 37°C for 48 hours, and SKBR3 cells for 72 hours.

messenger RNA Analysis

RNA Isolation from Cells

Isolation of RNA from cells was performed utilizing an ‘RNeasy Mini Kit ( 50 ) ‘ ( Qiagen Cat. No. 74104 ) utilizing the maker ‘s protocol.

RNA Quantification utilizing NanoDrop Spectrophotometer

The sum of RNA in each sample cell line was quantified utilizing the NanoDrop Spectrophotometer.

The ND-1000 package automatically calculated the measure of RNA in the samples utilizing the OD260 reading. RNA has its soaking up upper limit at 260nm, i.e. OD260 x 40 ten Dilution Factor/1000 = RNA content ( Aµg/Aµl ) .

The package at the same time measured the OD280 of the samples, leting the pureness of the sample to be estimated: Purity = OD260/OD280, and a ratio of ~2.0 is by and large accepted as “ pure ” for RNA. If the ratio is appreciably lower, it may bespeak the presence of protein, phenol or other contaminations that absorb strongly at or near 280 nanometers.The OD260/OD230 ratio was besides assessed, giving an indicant of the unity of the RNA sample. The 260/230 values for “ pure ” nucleic acid are frequently higher than the several 260/280 values. Expected 260/230 values are normally in the scope of 2.0-2.2.

If the ratio is appreciably lower than expected, it may bespeak the presence of contaminations which absorb at 230 nanometers.

Reverse-Transcription Polymerase Chain Reaction Analysis

Reverse Transcription of RNA from cells ( cDNA Synthesis )

messenger RNA was transcribed to cDNA by a 2 measure rearward written text procedure. 800ng of RNA was used to fix the complementary DNA, as summarised in Table 1.Once the RNA mixture had cooled ( ~2 min.

) , 10Aµl of the maestro mix was added and mixed by flicking. The mixture was centrifuged to roll up the stuff in the underside of the tubing and so incubated at 37A°C for 1 hour. 1:10 dilutions in RNase-free H2O were prepared for the cell complementary DNA and these were stored at -20A°C.

Quantitative Real Time Polymerase Chain Reaction ( qRT-PCR )

The complementary DNA was analysed for the look of cistrons of involvement by qRT-PCR ( as summarised in Table 3 ) . The cistrons of involvement were selected from a whole genome microarray survey performed, in this research lab, on SKBR3 Control and RL cells.

TaqMan investigations are oligonucleotides that are designed, based on nucleotide makeup, to be specific for the transcript of involvement, have fluorescent reporter dyes attached to the 5 ‘ terminal and a quencher mediety coupled to the complementary DNA part to be amplified by these primers. These investigations are designed to crossbreed to an internal part of a PCR merchandise. In the unhybridised province, the propinquity of the fluor and the quench molecules prevents the sensing of fluorescent signal from the investigation.

During PCR, when the polymerase replicates a templet on which a TaqMan investigation is bound, the 5′- nuclease activity of the polymerase cleaves the investigation. This decouples the fluorescent dye, therefore increasing the fluorescence in each rhythm, relative to the sum of investigation cleavage. In order to except any elaboration merchandise derived from genomic DNA or any other contamination that could pollute the RNA readying, entire RNA without rearward written text was used as a negative control.

Water, on its ain, replaces RNA as a negative control to govern out presence of any polluting RNA or DNA in the other constituents of the reaction mix. The PCR rhythm was performed, as summarised in Table 3.



10mM dNTP10I?lOligo dT1I?lRNA and RNase and DNase-free H208I?lEntire18I?lThe mix was incubated at 70A°C for 10 mins.

Table 1: Components of the complementary DNA Reaction Mixture



MMLV Buffer2I?lMMLV1I?lRNase Inhibitor0.5I?lRNase and DNase-free H206.

5mlEntire10I?l10 I?l was added to each well and incubated for 37A°C for 50 mins.

Table 2: Components of the qRT-PCR Reaction Mixture




CYCLE ( 40 rhythms )



10 min.15 sec.95A°C95A°C

Table 3: Thermal cycling conditions used in this survey


Statistical Analysis of Datas

Comparative statistical analysis was non carried out on the quantitative informations generated in this survey as all checks were non carried out in triplicate ( due to clip restrictions ) and, hence, statistical analysis would non be meaningful and may be misdirecting.

RNA Quantification utilizing NanoDrop Spectrophotometer

RNA was quantified to find the right sum for complementary DNA written text.

Sample ID






SKBR3 CON R-11093.3827.342.091.5940SKBR3 LAP 250 R-1405.0510.132.

040.9640HCC1954 CON R-1331. LAP 250 R-1228.675.

722.040.6640SKBR3 CON R-2442.3111.062.030.

9440SKBR3 250 LAP R-2372.789.312.051.0840BT474 CON R-1130.873.272.040.

3440BT474 LAP 250 R-1101.062.522.040.3440HCC1954 CON R-2263.656.592.

050.6040HCC1954 250 LAP R-2184.434.612.160.5240SKBR3 CON R-11256.7331.


Table 4: RNA Concentrations measured by NanoDrop Spectrophotometer

Invasion and Migration Assays

As outlined above, the SKBR3 cell line grew for 72 hours before being examined and photographed and the cells quantified by home base reader. There was a celebrated difference in both the invasion and migration checks between the Control and the RL discrepancies ( see Figure 2 ) .SKBR3 Inv CTRL2-1.

jpgSKBR3 Inv LAP 2-2.jpgSKBR3 Mig CTRL 1-1.jpgSKBR3 Mig LAP 1-1.jpg

SKBR3 Control Invasion

SKBR3 Lapatinib Resistant Invasion

SKBR3 Control Migration

SKBR3 Lapatinib Resistant Migration

Figure 2. Control and RL cells Invasion and Migration as apparent by microscopy ( above ) and following dye elution and quantification ( underside ) .

The HCC1954 cell line grows more quickly so, although these were seeded for merely 48 hours, the inserts were about merging with cells and there was small seeable or mensurable difference ( see Figure 3 ) .HCC1954 CTRL 1-2.

jpgHCC1954 LAPr 2-2.jpgHCC1954 Mig CTRL 1-2.jpgHCC1954 Mig LAPr 1-2.jpg

HCC1954 Control Invasion

HCC1954 Lapatinib Resistant Invasion

HCC1954 Control Migration

HCC1954 Lapatinib Resistant Migration

Figure 3. Control and RL Invasion and Migration as apparent by microscopy ( above ) and following dye elution and quantification ( underside ) .

Quantitative existent clip Polymerase Chain Reaction ( qRT-PCR )

Consequences for the assorted cistron transcripts are graphed below. The control lines were assigned an arbitrary value of 1, with the several RL discrepancies calculated as +fold addition or -fold lessening. Due to IP protection, Sample A* and Sample B* , cistrons whose checks are in the procedure of being patented, can non be listed under their existent names in this study.

Figure 4. Graphs Showing Expression of Genes of Interest in RL discrepancies compared to their Controls as measured by qRT-PCR ( y axis = fold alteration )

GAPDH was taken as endogenous control.HCC1954 was done on 2 replicates.SKBR3 was done on 2 replicates but 1 replicate gave really high Ct values for GAPDH so merely 1 replicate was used.BT474 was done on 1 replicate.

Discussion and Decisions

The migration and invasion analysis for SKBR3 was as expected, with its RL discrepancy demoing greater leaning for migration ( 84.4 % addition ) and invasion ( 25.

7 % addition ) compared to SKBR3 parent cells. The HCC1954 cell line braces were seeded excessively dumbly to observe any differences and should be repeated with fewer cells seeded ab initio. The addition in migration and invasion could mime increased mobility/motility and ability to metastasize, severally, in vivo.The sum of RNA in each sample cell line was quantified utilizing a NanoDrop Spectrophotometer. The OD260/OD280 ratio ranged from 2.03 to 2.

16 and was within the expected scope for a pure sample. The OD260/230 scope ( 0.34 to 1.59 ) was lower than expected ( 2.0 to 2.

2 ) for pure nucleic acid.As outlined above, the degrees of look of a figure of cistrons were measured in SKBR3, HCC1954, and BT474 Lapatinib — immune discrepancies compared to their sensitive parent/control cell lines. The cistrons analysed were AXL, EGFR, ERBB3, FOXO3, IGF1R, PTEN, Sample A* and Sample B* ( *Sample A and Sample B cistrons and their checks are in the procedure of being patented, so their existent names can non be listed in this study for IP protection. ) This was to find if these cistron transcripts were up- or down- regulated in the RL cell lines. Expression of EGFR, AXL and Sample B* were found to be most affected by geting opposition. As Jones et Al ( 2006 ) reported, elaboration of EGFR and HER2 is often observed in human malignant neoplastic diseases and, as the lines studied in this undertaking are HER2-positive cell lines, the elevated EGFR degrees ( 579x in SKBR3 RL and 201,441x in BT474 RL ) may back up this determination.

AXL is reported to hold higher look degrees in more invasive/metastatic cell lines. ( Chan et al 2001 ) , and at that place was a 302x addition in BT474 RL and a 53.40x lessening in SKBR3 RL. Sample B is still being investigated and there is small literature available for the cistron.

While collateral testing and farther analysis is required, the surveies performed here suggest that at least three of the cistrons assessed may hold a function in acquired opposition to Lapatinib in HER2-positive chest malignant neoplastic disease. More extended surveies of these cistrons are now warranted to look into their possible relevancy in this scene.


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