Methods of Cancer Diagnosis, Therapy, and Prognosis (eBook)

Methods of Cancer Diagnosis, Therapy, and Prognosis 2
Contributors 8
Preface 16
Contents of Volumes 1, 2, 3, 4, 5 and 6 18
Contents 34
Part IGeneral Methods and Overviews 50
1Role of RNA Interference in Understanding the Molecular Basis of Cancer 52
Mechanism of RNA Interference 52
RNAi as a Cell Based Screening Tool 54
RNAi to Understand Compound Mechanism of Action 57
Compound Sensitization, Combination Strategies and Synthetic Lethal RNAi Screens 60
Problems Associated with RNAi Based Approaches 63
References 65
2Cancer Biomarkers (An Overview) 68
Introduction 68
Emerging Technologies for Cancer Biomarker Discovery 68
DNA Microarray 69
Serial Analysis of Gene Expression 70
MicroRNA Microarray 70
Two Dimensional Polyacrylamide Gel Electrophoresis 70
Free Flow Electrophoresis 70
Capillary Electrophoresis 71
Matrix-Assisted Laser Desorption/Ionization Time-of-Flight Mass Spectrometry 71
Surface-Enhanced Laser Desorption/Ionization Time-of-Flight Mass Spectrometry 72
Liquid Chromatography Coupled with Tandem Mass Spectrometry 72
Linear Ion Trap Quadrupole-Orbitrap 72
Imaging Mass Spectrometry 73
Isotope-Coded Affinity Tags 73
Multiple Reaction Monitoring 73
Absolute Quantification of Proteins 74
Protein Microarray 74
Tissue Array 74
Bioinformatics 75
Currently Used Cancer Biomarkers (Table 2.2) 75
Biomarkers for the Diagnosis of Cancers (Table 2.3) 77
Genomic-Based Biomarkers in Cancer 77
Transcriptomic-Based Biomarkers in Cancer 78
Proteomic-Based Biomarkers in Cancer 78
Biomarkers for the Treatment and Progression of Cancers (Table 2.3) 79
Genomic-Based Biomarkers in Cancer 79
Transcriptomic-Based Biomarkers in Cancer 79
Proteomic-Based Biomarkers in Cancer 80
Biomarkers for the Prognosis of Cancers (Table 2.3) 80
Genomic-Based Biomarkers in Cancer 80
Transcriptomic-Based Biomarkers in Cancer 81
Proteomic-Based Biomarkers in Cancer 81
Challenges and Perspectives 82
References 83
3Tumor Angiogenesis in Cancers: Expression of CD105 Marker 88
Introduction 88
Morphological Features of Tumor Angiogenesis 88
Detection of the Endothelium by Immunohistology 90
Antigenecity Retrieval 90
Immunohistology 90
Simultaneous Mass and Comparative Study: Tissue Array 91
Specific Markers for Vascular Endothelium in Tumor 91
Angiogenesis 91
CD105/Endoglin Endothelial Marker Specific for Newly Formed Blood Vessels 92
CD105 and Vasculogenesis 92
Organ Specificity of CD105 Positive Tumor Angiogenesis 93
Application of CD105 for Anti-angiogenic Cancer Therapy 93
References 95
4pindle Cell Oncocytoma of the Adenohypophysis: Integrated Clinicopathologic Diagnosis by Imaging, Histology, and Immunohistoch 98
Introduction 98
Clinical Presentation 98
Imaging Aspects 99
Histology and Immunophenotype 99
Differential Diagnosis 101
Therapeutic and Prognostic Implications 102
Discussion and Perspectives 103
References 103
5Disseminated Carcinoma of Unknown Primary Site: Detection with F-Fluorodeoxyglucose-Positron Emission Tomography 105
Introduction 105
Material and Methods 106
Results 108
Discussion 111
References 115
6Unknown Lymphadenopathy: Diagnosing Using an Endoscopic Ultrasound-Guided Fine-Needle Aspiration Biopsy 118
Introduction 118
Application 118
Equipment 118
Echoendoscopes and Endoscopic Ultrasound Processors 118
Needles 119
Procedure 120
Preparations 120
Fine Needle Apiration Biopsy 120
Treatment of Sampled Material 120
Management After the Procedure 122
Diagnostic Yield 122
Complications 123
References 123
7Pretargeted Radioimmunotherapy in Cancer: An Overview 125
Introduction 125
Therapeutic Radioisotopes 126
Limitations of Classical Radioimmunotherapy in Solid Tumours 128
Pre-targeting Approach 129
Avidin–Biotin System 131
Avidin–Biotin Pretargeting in Glioma 133
Other Developments 139
Conclusion 140
References 140
8Chemotherapy-Induced Neurotoxicity 143
Introduction 143
Clinical Presentations of Neurotoxicity 144
Incidence of Neurotoxicity 145
Pathophysiology of Neurotoxicity 145
Clinical Evaluation and Assessment 146
Neurophysiological Assessment 147
Characteristics of Neurotoxic Chemotherapies 149
Taxanes 149
Cisplatin 150
Vinca Alkaloids 151
Other Neurotoxic Chemotherapies 151
Oxaliplatin-Induced Neurotoxicity 152
Pathophysiological Mechanisms of Oxaliplatin Neuropathy 154
Assessment of Oxaliplatin-Induced Neurotoxicity 154
Nerve Excitability Studies in Oxaliplatin-Induced Neuropathy 156
Future Directions and Neuroprotection 159
References 161
9Multidrug Resistance 164
Influence of Pharmacological and Physiological Factors 164
Molecular Mechanisms of Resistance to Traditional Chemotherapy 165
Intracellular Drug Activation 165
Detoxifying Systems 165
DNA Repair 165
Cell Death Regulation 166
Membrane Proteins 166
Cellular Models to Study Drug Resistance 166
Leukemic K562 Cells as a Model to Study Multi-drug Resistance 168
Animal Models to Study Drug Resistance 171
Cancer Stem Cells and Drug Resistance 172
Drug Resistance in the Clinic 172
Reversal of Drug Resistance in the Clinical Setting 173
References 174
10Role of Antibodies in Cancer Treatment (An Overview) 177
Introduction 177
Structure of an Antibody 177
Recombinant Antibodies 179
Chimeric and Humanized Monoclonal Antibodies 179
Human Monoclonal Antibodies 179
Antibody Fragments 179
Antibody Fragments Combinatorial Libraries 179
Pharmacokinetics of Antibodies 180
Tumor Antigens 181
Manufacturing of Therapeutic Monoclonal Antibodies 181
Mechanisms of Action of Therapeutic Monoclonal Antibodies (Pharmacodynamics) 182
Toxicities Associated with Therapeutic Monoclonal Antibodies 185
Therapeutic Monoclonal Antibodies Currently Licensed 185
Anti-CD20 Monoclonal Antibodies 186
Anti-CD33 Monoclonal Antibody 187
Anti-CD52 Monoclonal Antibody 187
Anti-HER-2 Monoclonal Antibody 187
Anti-EGFR Monoclonal Antibodies 188
Anti-VEGF Monoclonal Antibody 189
Therapeutic Monoclonal Antibodies and Antibody Targeted Therapeutics Under Investigation 190
Clinical Evaluation 190
Variation on a Clinically Proven Target 190
Building on Characterized Murine Monoclonal Antibodies 190
Human Monoclonal Antibodies Against New Targets and with Innovative Mechanisms of Action 190
Preclinical Evaluation 191
References 192
11Incorporating Pharmacogenomics into Cancer Therapy 195
Introduction 195
Current Use of Pharmacogenomics in Clinical Oncology 196
Thiopurine Methyltransferase (TPMT) 196
UDP-Glucuronosyltransferase 1A1 (UGT1A1) 197
Other Pharmacogenomic Markers in Clinical Investigation 199
Drug-Metabolizing Enzymes 199
Dihydropyrimidine Dehydrogenase (DPD, Gene Name: DPYD) 199
Cytochrome P450 2D6 (CYP2D6) 199
Glutathione S-Transferase P1 (GSTP1) 200
Transporter Proteins 200
Multidrug Resistance Protein 1 (MDR1,P-Glycoprotein, ABCB1) 200
Multidrug Resistance Protein 1 (MRP1, ABCC1) 201
Multidrug Resistance Protein 2 (MRP2, cMOAT, ABCC2) 201
Breast Cancer Resistance Protein (BCRP, ABCP, MXR, ABCG2) 201
Solute Carrier (SLC) Transporters 201
Drug Target, Pathway Genes 202
Methylenetetrahydrofolate Reductase (MTHFR) 202
Thymidylate Synthase (TS, TYMS) 202
Epidermal Growth Factor Receptor (EGFR) 203
DNA Repair Genes 203
Excision Repair Complementation Group 1 (ERCC1) 203
Xeroderma Pigmentosum Group D (XPD)/ERCC2 203
X-Ray Cross Complementation Group 1 (XRCC1) 204
Methodology 204
Genotyping Assays 204
Typical Genotyping Protocols 204
Comparison of Different Methods 205
Different Approaches in Pharmacogenomics 205
Candidate Gene Association Strategies 205
Whole-Genome Association Approaches 206
Integrative In Vitro/In Vivo Pharmacogenomic Approaches 206
Implementation of Pharmacogenomics in Drug Discovery and Development 207
Early Stage Clinical Development (Phase I and II Clinical Trials) 207
Candidate Gene Association Studies 207
Whole Genome Association Studies 209
Late-Stage Clinical Development (Phase III Clinical Trials) 209
Incorporating Pharmacogenomics into Clinical Trials: Technical and Legal Issues 210
Future Directions 211
References 211
12Cancer Stem Cells: An Overview 215
Introduction 215
Cancer Stem Cells: Concept 215
Isolation of Cancer Stem Cells 216
Origin of Cancer Stem Cells 217
Epigenetics and Cancer Stem Cells 219
Future Perspectives 220
References 222
13Translating In Vitro Cell Lines Result into Clinical Practice 224
Introduction 224
How Cell Lines Are Generated 225
Types of Cell Culture 225
Selection Bias 225
Selection Pressure 226
Cell Line Preference and Availability 227
Cross-Contamination 228
Microbial Contamination 228
Handling Errors 229
New Insights: Microarray Gene-Expression Profiling of Tumours and Cell Lines 229
Conclusions 230
References 231
14Classification of Cancer Stage Using Patient’s Immune System 234
Introduction 234
Classification System for Cancer Stage 234
TH1/TH2/TH3/TH17 Cytokine Physiological Network in Peripheral Blood Samples 235
TH1/TH2/TH3/HT17 Cytokine Network: Immuno System 235
TH1/ TH2-Type Immune Responses and the Regulating Role of the TH3-Type 235
Importance of a New Population Named TH17 236
Method to Study the TH1/TH2/TH3/HT17 Cytokine Network 237
Immune System Through Mathematical Modelling 238
Peripheral Blood Cytokine Network 238
Methods 239
Serum Samples 239
Peripheral Blood Mononuclear Cell Separation and Generation of Dendritic Cells from Monocytes Using Dynabeads 239
Whole Blood Cell Cultures 240
Cytokine Detection 240
Data Analysis 241
Physiological Evaluation of the Immune System 242
The TH1/TH2/TH3/TH17 Cytokine Network in Healthy Subjects 242
Cytokine Network Relationships in Men and Women 243
How to Define Immunological Parameters for Stage Classification 244
Comparative Study with Groups of Healthy Subjects and Cancer Patients 244
Disease Stage Indices in Colorectal Cancer 244
Prognostic Significance of Immunological Parameters 245
Normal Mucosa to Adenoma and Colon Cancer 245
Cytokines, sIL2R and sICAM Serum Levels 245
sCD30 Mechanisms Regulating TH1/TH2 Cell Functions 247
Accuracy of Prognostic Indices 247
Characterization of Disease Stage 247
Identifying Ranges for Immunological Markers 249
Preinvasive to Invasive Colorectal Cancer 249
Simultaneous Measurement of sCEA and TIMP1 249
Simultaneous Measurement of sIL2R, sIL6R, and Cytokine Serum Levels 250
References 250
15Late Relapse of Germ Cell Malignancies: Incidence, Management, and Prognosis 253
introduction 253
Incidence 253
Seminoma Clinical Stage I 254
Seminoma Clinical Stage > I
Nonseminoma Clinical Stage I 256
Nonseminoma Clinical Stage > I
Detection and Differential Diagnosis 258
Treatment and Survival 260
Seminoma 262
Non-seminoma 262
References 263
Part IIHead and Neck Cancer 265
16Head and Neck Squamous Cell Carcinoma: Therapy with Fusaric Acid/Paclitaxel 266
Introduction 266
A New Class of Agents for Head and Neck Cancer? 266
A New Target in the Head and Neck Cancer Cell? 267
Evidence for Furaic Acid as a New Head and Neck Cancer Therapy 268
References 270
17Early Stage Oral Squamous Cell Carcinoma: Use of Signal Transducer and Activator of Transcription 3 as a Risk Factor for Poor 273
Introduction 273
Signal Transducers and Activators of Transcription 274
Activation of Signal Transducers and Activators of Transcription Signaling 275
Signal Transducer and Activator of Transcription 3 276
Physiological Role of Signal Transducer and Activator of Transcription 3 276
Signal Transducer and Activator of Transcription 3 in Oncogenesis 277
Signal Transducer and Activator of Transcription 3 in Oral Squamous Cell Carcinoma 277
Electrophoretic Mobility Shift Assay 277
Competition Mobility Shift Assay 278
Super Shift Assay 278
Method 278
DNA Binding Affinity Purification 279
Results 280
In Vitro Studies 280
In Vivo Studies 280
In Situ Hybridization 280
Method 280
Results 281
In Vivo Studies 281
Immunoblotting 281
Method 281
Results 282
In Vitro Studies 282
In Vivo Studies 282
Immunohistochemical Localization 282
Method 282
Results 283
In Vivo Studies 283
Reverse Transcription–Polymerase Chain Reaction 286
Method 286
Results 286
In Vivo Studies 286
References 288
18Salivary Gland Tumors: Preoperative Tissue Characterization with Apparent Diffusion Coefficient Mapping 290
Introduction 290
Diffusion-Weighted Imaging 290
Measurement of Diffusion-Weighted Imaging 291
Clinical Use of Diffusion Weighted Imaging 293
Salivary Gland Tumors 295
2D ADC Color Mapping of Salivary Gland Tumors 296
ADCs of Healthy Major Salivary Glands 298
ADCs of Benign Salivary Gland Tumors 301
ADCs of Malignant Salivary Gland Tumors 301
Tissue Characterization with Apparent Diffusion Coefficient Mapping 302
Applications of Apparent Diffusion Coefficient Mapping to the Diagnosis of Malignant Lesions 302
High-Resolution Imaging of Malignant Lesions 303
References 303
19Role of Human Papillomavirus in Tonsillar Cancer 305
Introduction 305
Tonsillar Cancer 305
Human Papillomavirus (HPV) 305
Epidemiology 306
Evidence of HPV Role in Carcinogenesis 307
Sexual Behaviour and Oropharyngeal Cancer 309
HPV and Prognosis in Tonsillar Cancer 309
Impact of Viral Load on Prognosis 310
P16INK4a – a Surrogate Marker for HPV 16 310
HPV in Other Oropharyngeal Cancer 311
Future Perspectives 311
Methods of HPV Detection and Genotyping 312
Polymerase Chain Reaction (PCR) 312
Hybrid Capture 312
DNA In Situ Hybridization (ISH) 312
HPV Genotyping 313
HPV mRNA Amplification and Detection 313
HPV Serology 314
HPV DNA Load 314
References 315
20Quantitative Reverse Transcription–Polymerase Chain Reaction Based Assessment of the Candidate Biomarkers for Tongue Cancer Me 318
Introduction 318
Quantitative Polymerase Chain Reaction 318
QPCR Chemistries 319
TaqMan Probes 319
Molecular Beacons 320
Self Fluorescing Amplicons 320
SYBR Green 321
Quantification of Results 321
Standard Curve Method 322
Comparative CT Method 323
Oral Tongue Cancer 323
Oral Tongue Squamous Cell Carcinoma (OTSCC), A Major Subset of Oral Cancer 323
Metastasis – A Major Clinical Problem of Oral Cancer 324
The Quantitative Polymerase Chain Reaction Based Evaluation of Candidate Tongue Cancer Metastasis Markers 326
Cancer Biomarkers 326
QRT-PCR Based Assessments of CTTN and MMP9 in Tongue Cancer 327
Cortactin (CTTN) 327
Matrix Metallopeptidase-9 (MMP9) 331
Quantification and Statistical Evaluation of the Markers 331
Future Developments 333
References 334
21Nasopharyngeal Carcinoma (Retropharyngeal Lymph Node Metastasis): Spread Pattern, Prognosis, and Staging 336
Introduction 336
Materials and Methods 337
Patient Characteristics 337
Imaging Protocol and Criteria for RLN Metastasis and Other Cervical Lymph Node 338
Treatment 338
Follow-Up and Statistical Analysis 339
Incidence and Distribution of RLNs Demonstrated by MRI 340
Relationship Between Metastatic RLNs and Tumor Involvement 340
Results 340
Prognosis and Staging of RLN Metastasis Based on CT Data 341
Incidence of RLN Metastasis Demonstrated by CT 341
Prognosis 342
Hazard Consistency and Hazard Discrimination 342
Comparing Staging Categories of RLN Metastasis 343
Discussion 343
Imaging Criteria for Metastatic RLNs 343
Incidence of RLNs Metastasis 344
Spread Patterns of RLNs Metastasis 345
Prognostic Significance and Staging of RLNs Metastasis 346
References 348
22Retinoblastoma: Diagnosis, Treatment and Prognosis 351
Introduction 351
Diagnosis 351
Epidemiology 351
Genetics 352
Semeiology 352
Clinical Features 353
Clinical Investigation (Balmer and Munier 2002) 356
Tumor Growth 357
Extraocular Retinoblastoma 357
Histopathologic Risk Factors 358
Second or Multiple Nonocular Tumors 358
Classification 359
Differential Diagnosis 359
Treatment 360
Treatment Methods 361
Chemotherapy 361
Focal Consolidation Treatment 362
Chemothermotherapy 362
Thermotherapy 363
Brachytherapy 363
External Beam Radiotherapy (EBR) 363
Proton Therapy 363
Enucleation 364
Future Advances 364
Prognosis 365
References 366
Part IIIThyroid Carcinoma 369
23Molecular Genetics of Thyroid Cancer 371
Introduction 371
Papillary 371
RET Oncogene 373
RAS Oncogene 374
BRAF 374
APC 374
Follicular 375
RAS Oncogene 375
PAX8/PPARg 375
PTEN 375
Hürthle Cell Carcinomas 376
Medullary 376
RET Oncogene 376
Anaplastic 377
P53 Mutations 377
MRP-1 378
Molecular Profiling 378
Fine Needle Aspirations (FNA) Reports 378
References 379
24Thyroid Cancer: Identification of Gene Expression Markers for Diagnosis 383
Introduction 383
Gene Expression Technologies 384
cDNA Microarrays 384
Oligonucleotide Arrays 385
Serial Analysis of Gene Expression 386
Future Tag-Sequence Methods 386
Experimental Issues 387
Array Design 387
Sample Preparation 387
Replicates 388
Data Analysis Issues 388
Quality Assessment 388
Normalization and Background Correction 389
Probe/Tag Mapping 389
Differential Expression Analysis 390
Expression Profiling Software and Databases 391
Validation Methods 391
Clustering and Classification Analysis 393
Cancer Diagnosis Using Tumor Gene Expression Signatures 393
Defining New Molecular Subtypes with Gene Expression Data 393
Developing Biomarkers or Panels from Microarray Class Predictors 394
Expression Profiling Studies in Thyroid Cancer 394
Cross-Platform Integration and Meta-Analysis 397
Molecular Markers for Thyroid Cancer 399
References 402
25Papillary Thyroid Carcinoma: Use of HBME1 and CK19 as Diagnostic Markers 408
Introduction 408
Protocol 409
Materials 409
Methods 410
Interpretation of Staining 410
HBME1 in Papillary Thyroid Carcinoma and Benign Thyroid Lesions 410
CK19 in Papillary Thyroid Carcinoma and Benign Thyroid Lesions 412
References 413
26Papillary Thyroid Carcinoma: Detection of Copy Gain of Platelet Derived Growth Factor B Using Array Comparative Genomic Hybrid 415
Introduction 415
Comparative Genomic Hybridization 415
Vysis GenoSensor Array CGH 417
Methodology 418
Tumors and Cell Lines 418
Laser Capture Microdissection 418
DNA Extraction 419
Array Comparative Genomic Hybridization 419
Labelling Protocol 420
DNASE Digestion and Labelled Probe Purification 420
Checking the Labelled DNA 421
Hybridization Protocol 421
Preparing the Reagents 421
Preparing the Hybridization Solution 421
Hybridization 421
Washing the Microarrays 422
Image Analysis 423
Results 424
Analysis Cohort 424
Array CGH 424
Recurrent Gains and Losses 424
Discussion 424
References 425
27PET Imaging in Thyroid Carcinoma 427
Introduction 427
Positron Emission Tomography 428
Combined PET/CT 429
18fluorine-Fluorodeoxyglucose (18F-FDG) 429
Mechanism 429
Scan Method 430
Clinical Application 430
Thyroid Nodules 430
Differentiated Thyroid Cancer (DTC): Follow-Up 430
Medullary Thyroid Cancer (MTC) 431
18Fluorine-dihydroxypheny­lalanine (18F-DOPA) 432
Mechanism 432
Scan Method 433
Clinical Application 433
Medullary Thyroid Cancer 433
11C-Methionine (MET) PET 434
Mechanism 434
Scan Method 435
Clinical Application 435
Differentiated Thyroid Cancer 435
124I-PET 435
Mechanism 435
Scan Method 435
Clinical Application 436
Differentiated Thyroid Cancer 436
Conclusion 437
References 439
28Metastasized Medullary Thyroid Carcinoma: Detection and Therapy Using Radiolabeled Gastrin Analogs 443
Medullary Thyroid Carcinoma 443
Symptoms 443
Diagnostic Procedures 443
Pentagastrin Testing 443
Whiskey Stimulation Testing 444
Carcinoembrionic Antigen 444
Ultrasound 444
Computed Tomography 445
Magnetic Resonance Imaging 445
Positron Emission Tomography 445
Somatostatin Receptor Scintigraphy 445
Fine Needle Aspiration 445
Selective Venous Sampling 446
Localizing and Treating Metastatic Medullary Thyroid Carcinoma 446
Radiopeptide Scanning Versus Anatomical Imaging Modalities 447
Radiolabeled Peptides 448
Minigastrin for Detecting Metastasized Medullary Thyroid Carcinoma 449
Cholecystokinine 2 (CCK2) Receptor Expression 450
Labeling 450
Scanning Protocol 450
Biodistribution of Minigastrin 450
Clinical Studies 451
Peptide Receptor Radiotherapy of Metastasized Medullary Thyroid Carcinoma with Gastrin Analogs 453
Future Perspectives of DGlu1-Minigastrin 456
References 456
29Medullary Thyroid Carcinoma: Prognosis based on Stage of Disease and Age 460
Introduction 460
Epidemiolmogy 460
Pathology and Pathogenesis of Medullary Thyroid Cancer 460
Clinical Presentation 462
Diagnostic Testing 462
Genetic Screening 462
Genotype – Phenotype Correlations 463
Prognostic Factors 463
Treatment 466
Treatment of Patients with Clinically Evident MTC 466
Prophylactic Surgery for Patients with ret Proto-Oncogene Mutations 466
Non-Surgical Treatment Modalities 467
Surveillance 467
References 468
30Overexpression of the Components of the Plasminogen Activating System as Prognostic Factors in Human Thyroid Carcinoma 469
Plasminogen Activating System (PAS) 469
The Plasminogen Activating System in Pathophysiological Conditions 470
Role of Plasminogen Activating System in Human Cancers 471
Clinical Significance of the Expression of Plasminogen Activating System Components 472
The Plasminogen Activating System in Human Thyroid Carcinomas 473
Methods to Evaluate Expression of Plasminogen Activating System Components 475
Substrate Gel Electrophoresis (Zymograms) 475
Invasion Assay 477
Real Time RT-PCR 478
Immunohistochemistry 479
Enzyme-Linked Immunosorbent Assay (ELISA) 480
References 481
Index 483

"13 Translating In Vitro Cell Lines Result into Clinical Practice (p. 183-184)

Jai Prakash Mehta, Lorraine O’Driscoll, Niall Barron, Martin Clynes, and Padraig Doolan

INTRODUCTION

Immortalized cell lines provide an easy and convenient option for analysis of biological systems compared to clinical specimens. Cell culture has gained wide popularity in the study of cancer, because of the innate continuously proliferating nature of these cell lines. Cancer cell lines are obtained by the enzymatic digestion or explant growth of tumour specimens. The main advantage of using cell lines for such research is the immortal nature of the cell lines, enabling them to be continuously cultured, distributed and studied in many labs and to act as a reliable platform for comparison of results, before advancing research to the next level.

Another advantage of performing research on cell lines is ease of handling and storage. Cell lines are cultured in flasks under well-controlled nutritional and environmentalal conditions and this ensures a greater degree of reproducibility in the results. Some assays require large amount of material; with cell line models, this is generally not a constraint. Cells can be stored indefinitely in liquid nitrogen and can be used when needed. Apart from the ease in maintenance and access, cell lines offer a convenient platform for genetic manipulation of cells. Many recent studies in cancer have centered on functional aspects of gene expression changes.

Cell lines offer a realistic platform to knockdown or over-express genes of interest. Due to the tremendous benefits of working on cell lines, they have dramatically contributed to basic research in cancer biology. Recent interest has focused on extrapolating the relevance of findings from cell line models to clinical models. There are obvious differences between cell line models and clinical specimens due to the difference in environments to which they have been exposed. These differences need to be accurately defined for the results arising from the cell line studies to be clinically relevant.

A detailed study on these differences will help researchers to decide on the applicability of cell line models for their particular study and will pave the way in making the results more accurate and relevant to that of clinical condition. This manuscript examines the differences between cell line models and clinical specimens, particularly focusing on breast cancer. HOw CeLL LINeS ARe GeNeRATeD enzymatic digestion: Tumour tissue is digested using enzymes such as collagenase, trypsin, or pronase.

These enzymes break down the extracellular matrix, thereby releasing the cells which are subsequently cultured in nutrient rich medium and in a controlled environment (Doyle et al. 1998). explant culture: Small pieces of tissue are placed in nutrient rich medium and the cells that grow out and migrate from the primary tissue are further cultured (Doyle et al. 1998). TyPeS Of CeLL CuLTuRe Primary cultures: Cells obtained directly from the tissue are termed primary cultures.

Primary cultures have a defined life span and undergo a process of senescence and stop dividing, while remaining viable for short time period. Studies done on primary cultures can be very useful as these cells have not been in culture for long time after procuring from the body/ in vivo condition. However, primary culture has its own limitations. Since primary cultures cannot be maintained in culture for extended periods, lengthy experiments may be challenging; these cells generally cannot be distributed to other labs; and the experiments performed cannot be repeated at a later date to determine reproducibility."