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REVIEW ARTICLE
Year : 2004  |  Volume : 20  |  Issue : 2  |  Page : 75-78
 

Molecular biology in urology


Department of Urology, AIIMS, New Delhi, India

Correspondence Address:
Rajeev Kumar
Department of Urology, All India Institute of Medical Sciences, New Delhi - 110 029
India
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Source of Support: None, Conflict of Interest: None


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   Abstract 

Introduction: Molecular biologic techniques form the cornerstone of progress in the field of medicine in the next millennium. These techniques are useful in diagnosis, prog­nosis, management and follow-up of patients.
Methods: Recent publications in the field of molecular biology and its use in urology were reviewed. The mate­rial was then edited to produce this article.
Results: There has been a tremendous interest in this field in the last decade. Over 50 articles in indexed jour­nals and edited text books were found. Literature relating to its use in urology is less common but seems to be in­creasing in the last few years.
Conclusions: Molecular diagnosis is the identification of presence of disease or susceptibility to disease based on the presence of abnormal genes or their products. Mo­lecular therapy is the development of rational therapeutic strategies aimed at correcting the basic genomic abnor­mality using molecular biologic techniques. These two applications of molecular biology shall be the focus of advance in urology in the next millennium.


Keywords: Gene therapy, nucleotides, genetic engineering, FISH.


How to cite this article:
Kumar R. Molecular biology in urology. Indian J Urol 2004;20:75-8

How to cite this URL:
Kumar R. Molecular biology in urology. Indian J Urol [serial online] 2004 [cited 2019 Nov 17];20:75-8. Available from: http://www.indianjurol.com/text.asp?2004/20/2/75/20726



   Introduction Top


Molecular biology is a field that aims to find the mo­lecular basis for all processes that occur in the body-both physiologic and pathologic. After defining these molecular changes, it helps develop clinical tools to make early diagnosis of pathologic changes and also ways to reverse them. In this review, the role of molecular biology role in clinical urology will be discussed.

Molecular diagnostics involves the detection of a DNA, protein or gene sequence specific to a neoplasm or dis­ease. Neoplastic cells often acquire genetic sequences dif­ferent from the host cell. These sequences may be responsible for conferring immortality to neoplastic cells. The detection of these specific genetic abnormalities may help not only identify but also prognosticate the course of the disease. Manipulation of the genetic make up of ex­perimental animals or cell lines using genetic engineering can help understand the effect of natural mutations in dis­ease causation and termination. The most important thera­peutic use of molecular biology techniques lies in gene therapy whereby defective genes may be removed and tumor suppressor or drug susceptibility inducing genes may be selectively introduced into diseased cells.


   Methods Top


A literature search on the Pubmed was done using the key words molecular biology, urology, techniques, genetic engineering, FISH, PCR and blotting. Relevant articles were accessed and reviewed. Current textbooks on urol­ogy were also reviewed for relevant topics and the mate­rial was edited to suit the requirements.


   Detection of Genetic Disorders Top


Prostate cancer: Heredity and polvmorphisms: Up to 10% of prostate cancer may be linked to heredity and some of the high-risk alleles have been located on chromosome 1 and X chromosome. Genetic polymorphism at the Xgl1­Xg12 locus is the most common abnormality localized in carcinoma prostate cells. This gene codes for the andro­gen receptor and the length of the CAG nucleotide repeat sequences at this locus correlates with the risk for can­cer [1] . Races such as Asians with longer repeat sequences have been shown to have a lower cancer risk. Another important polymorphism identified is a single nucleotide polymorphism (SNP) at the Glutathione Transferase (GST) pi gene which may be associated with an increased cancer risk. [1]

Growth factors: A large number of growth factors such as epidermal growth factor (EGF), transforming growth factor (TGF) and insulin like growth factors (IGF) have been identified whose receptors may be over expressed in certain certain high-grade prostate cancers, indicating their dependence on these factors. [2] This may help decipher the stimulus necessary for cancer progression.

Apoptosis: Normal cells undergo programmed cell death known as apoptosis. One of the major mechanisms of car­cinogenesis is loss of this apoptosis leading to an immor­tal cell. Certain proteins within cells may act as inhibitors of apoptosis. Levels of anti-apoptosis proteins bcl-2 and mcl-1 are raised in cancers of the prostate. [3] These raised protein levels also predict a poorer outcome of therapy and is associated with a higher growth in artificial tumor cell lines such as LnCAP. Insertion of antisense bcl-2 oligonucleotides that block the natural bcl-2 protein can inhibit the growth of LnCAP and increase tumor sensitiv­ity to Taxol and Mitoxantrone. [4] Phase 1 clinical trials are underway with the use of bcl-2 oligonucleotides with or without mitoxantrone in treatment of clinical cancer pros­tate highlighting the most important role of molecular bi­ology in urology. [5]

Tumor suppressor genes: Two oncogenes are currently under investigation in prostate cancer. PTEN is inactivated by mutation in certain prostate cancers especially high grade metastatic ones. [6] It may be an apoptosis promoting gene similar to p53, the other important oncogene. The product of the p53 gene is essential in diverting the cell towards apoptosis. [7] Mutated p53 gene is found in high-grade meta­static prostate cancer and its presence is associated with poorer results following surgery or chemotherapy.

Other molecular abnormalities: The most commonly described molecular abnormality in prostate cancer is the aberrant expression of the cell adhesion molecule E­Cadherin coded by the GSTP1 gene that is over expressed. Prostate cancer cells can be detected in the peripheral blood using a PCR technique for PSA within these cells. [8] This is one of the most sensitive staging methods for prostate can­cer and can be used to predict failure in patients undergo­ing radical prostatectomy.

Renal Cancer: 4% of renal cell cancer has been shown to be hereditary and in Von-Hippel Lindau (VHL) disease, upto 45% of the affected individuals may develop renal cancer. The gene causing VHL has been identified on chro­mosome 3 (3p25). This allows antenatal diagnosis and ge­netic counselling. Genetic changes responsible for the development of different histologic subtypes of renal can­cer include 3p LOH and VHL gene in RCC-clear cell type; 9p-, 17p-, 21p- and 17p+ in papillary RCC; C-erb-1 oncogene expression in Bellini's Ductal carcinoma and l lp13 mutation in Wilms' tumor. This knowledge may be useful in diagnosis of the primary or the metastasis and allow gene therapy.

The presence of lAl allele of the cytochrome p450 (CYP) gene along with the TT1 or TPI allele of GST or the NAT-2 polymorphism (N acetyl transferase) is associ­ated with an increase in risk for developing renal cancer. Loss of the mul allele of GST (null polymorphism) and the presence of the pil GST polymorphism indicate a higher risk if the CYP lA 1 allele of NAT-2 allele is also present. [1]

Urothelial cancer: Induction of oncogenes is one of the potential mechanisms responsible for urothelial can­cers. The ras oncogene on chromosome p 21 has been found to be present in upto 10% cancers with single strand conformation polymorphism analysis and restricted frag­ment length polymorphisms showing some correlation with the grade of the tumor. [9],[10] Abnormality in another oncogene, c-myc, is also commonly seen in bladder can­cers and c jun may also serve as a marker for bladder can­cer as its abnormal expression may indicate aggressive growth and increased expression of EGF receptor, which in itself has a poor prognosis. [11]

The p53 gene is one of the most commonly altered sup­pressor oncogene in human cancers. However, despite this frequency, it is not essential that every mutation in the gene will be significant. It is now possible using crystallo­graphy to predict how the genetic mutation will affect the structure of p53 gene product and thus identify which mutation is likely to have functional consequences. [12] In a study of 243 patients, organ confined bladder cancer with p53 positivity had a significantly worse 5 year survival and relapse free rate compared to p53 negative tumors.'' However, this data, and that similar to it, cannot still be used to guide therapy. Studies are currently underway to help establish the specific role for p53 as a prognostic in­dicator to dictate therapy especially in cases of high-grade superficial tumors where it may guide the choice between bladder salvage and more aggressive therapy.

Another tumor suppressor gene, Rb, also codes for pro­teins responsible for diverting the cell into an apoptotic cycle. This was demonstrated by the non-random dele­tions of chromosomes 13q and 9 in bladder cancers. [14] Sev­eral groups have also demonstrated chromosome 9 deletions as the primary event in superficial bladder can­cer and have shown that in these cases, p53 may be nor­mal. This separation of effects of chromosome 9 and p53 would be invaluable in predicting the outcome of clinically superficial bladder cancer and choosing aggressive therapy for p53 positive superficial tumors. [14]

The third important genetic mechanism for tumorigen­esis in bladder cancer is over expression of growth factors and their receptors. The gene for EGF receptor is located on chromosome 7 and trisomy 7 is associated with a par­ticularly aggressive bladder cancer. In fact, this is the only other molecular marker that has approached the point of clinical usefulness. [14] Positive tumors have a significantly poorer prognosis but identification techniques are currently not standardised. Erb-2 oncogene that codes for a growth factor similar to EGF is also a potential marker for ag­gressive bladder cancer. [15]


   Genetic Engineering and Gene Therapy Top


An important development in molecular biologic tech­niques is the ability to introduce selected DNA fragments into recipient cells. DNA fragments can be obtained from endonuclease action on pre-existing DNA or through labo­ratory synthesis by using a known RNA template. Intro­duction of this selected fragment into cells can be done through the use of vectors such as viruses, plasmids, microinjection, liposomes or electric gradient. An animal which gains this new genetic information is termed transgenic. This technology forms the backbone of devel­opment of monoclonal antibodies and gene therapy.

Gene therapy is one of the prime goals of all molecular biologic techniques. There are over twelve trials currently underway in the USA on the role of gene therapy in urologic malignancies. [16] Gene therapy is defined as the introduction of normal or modified genetic code into hu­man cells to reverse a genetic or acquired disease. This therapy is based on the knowledge that most diseases, particularly cancer, result from aberration in normal ge­netic sequences. Once these abnormalities have been iden­tified, it may be possible to correct them using genetic engineering. There are two basic mechanisms of perform­ing gene therapy. These are corrective gene therapy and cytoreductive gene therapy. Corrective gene therapy in­volves replacement of a defective gene in the cancer cells while cytoreductive therapy involves the addition of a gene that promotes apoptosis in the cancer cells. Another strat­egy in the cytoreductive model is the introduction of cer­tain genes that will potentiate the action of chemotherapeutic drugs or prevent the normal cells such as the bone marrow from the adverse effects of these drugs, allowing higher doses to be used.

Corrective gene therapy is used to introduce the nor­mal or wild type gene into deficient cells. The correct iden­tification of defective genes in certain urologic cancers (p53 and 9p in bladder cancer; GST-pi and p53 in pros­tate cancer; VHL gene in RCC and WT1 gene in Wilm's tumor) has opened the potential for corrective gene therapy. p53 gene replacement has been attempted using viral vec­tors in vitro in bladder cancer biopsies. [16] Reintroduction of the GST-pi gene in prostate cancer hasa similar thera­peutic potential. Another corrective option is the preven­tion of emergence of metastatic clones through over expression of oncogenes. Antisense sequences to onco­genes such as c-myc can be developed to prevent their protein synthesis. The KAI-1 gene is an anti metastasis gene that is lost in prostate cancer. [17] This may be replaced using gene therapy.

There is a potential to develop PCR based diagnostic kits for p53, GST-pi and VHL mutations in urine or ex­pressed prostatic secretions. In bladder cancer, there is further therapeutic potential for delivering gene therapy vectors through bladder instillations. Corrective wild type VHL gene may be delivered into renal epithelium through renal artery catheterization.

The most thoroughly evaluated form of cytoreductive gene the rap, is the development of tumor vaccines which contain genetically engineered cells that provide immuno­stimulatory signals against tumor antigens. Tumor cells are removed during surgery and, in tissue culture, are trans­duced genetically with a cytokine-producing gene that stimulates the immune response to antigens present on the tumor cells. This modified cell is irradiated to prevent its neoplastic growth and reintroduced into the patient. There are trials already underway using this modality for renal cancers. [16]


   Conclusions Top


Disease diagnosis has evolved through symptom iden­tification, evaluation of signs, basic laboratory tests and microscopy to the current molecular levels. Therapy has also progressed from symptomatic, empirical and specific to gene therapy. Identification of basic cellular codes for the normal and abnormal cell function promises to be the cornerstone for all rational therapy in the future. This also has the potential for primary prophylaxis and early inter­vention, preventing any significant morbidity. The chal­lenge lies in the ability to make these tools fool proof and cost effective.

 
   References Top

1.Walther MM. Leach F. Ornstein DK. Zambrano N and Linehan WM. Genitourinary malignancy: Etiology and molecular genetics, natu­ral history and treatment. In: Gillenwater JY. Grayhack JT, Howards SS, Mitchell ME (eds.). Adult and Pediatric Urology. 4 th ed. Phila­delphia: Lippincott Williams and Wilkins. 2002, pp 319-362.  Back to cited text no. 1    
2.Seth D, Shaw K. Jazayeri J. Leedman PJ. Complex post-transcrip­tional regulation of EGF-receptor expression by EGF and TGF-al­pha in human prostate cancer cells. Br J Cancer 1999; 80(5-6):657-69.  Back to cited text no. 2    
3.Krajewska M. Krajewski S, Epstein JI, Shabaik A. Sauvageot J, Song K et al. Immunohistochemical analysis of bcl-2. bax, bcl-X, and mcl­I expression in prostate cancers. Am J Pathol 1996;148(5):1567-76.  Back to cited text no. 3    
4.Miyake H, Monia BP, Gleave ME. Inhibition of progression to androgen independence by combined adjuvant treatment with antisense bcl-xl and antisense bcl-2 oligonucleotides plus taxol af­ter castration in the Shionogi model. Int J Cancer 2000; 86: 855-62.  Back to cited text no. 4  [PUBMED]  [FULLTEXT]
5.Ornstein DK, Dahut WL, Liotta LA, Emmert-Buck MR. Review of AACR meeting: new research approaches in the prevention and cure of prostate cancer, 2-6 December 1998, Indian Wells, CA. Biochem Biophys Acta 1999; 1424(1): RI1-9.  Back to cited text no. 5    
6.Dong JT, Li CL, Sipe TW, Frierson HF Jr. Mutations of PTEN/ MMACI in primary prostate cancers from Chinese patients. Clin Cancer Res 200; 7(2): 304-8.  Back to cited text no. 6    
7.Howell SB. Resistance to apoptosis in prostate cancer cells. Mol Urol 2000; 4(3): 225-231  Back to cited text no. 7    
8.Shariat SF, Kattan MW, Song W, Bernard D, Gottenger E, Wheeler TM, Slawin KM. Early postoperative peripheral blood reverse tran­scription PCR assay for prostate-specific antigen is associated with prostate cancer progression in patients undergoing radical prosta­tectomy. Cancer Res 2003;63(18): 5874-8.  Back to cited text no. 8    
9.Knowles MA and Williamson M. Mutation of H-ras is infrequent in bladder cancer: confirmation by single-strand conformation poly­morphism analysis, designed restriction fragment length polymor­phisms, and direct sequencing. Cancer Res 1993; 53(1): 133-9.  Back to cited text no. 9    
10.Viola MV, Fromowitz F, Oravez S, Deb S, Schlom J. ras oncogene p2l expression is increased in premalignant lesions and high grade bladder carcinoma. J Exp Med 1985; 161(5): 1213-8.  Back to cited text no. 10    
11.Tiniakos DG, Mellon K, Anderson JJ, Robinson MC, Neal DE, Horne CH. c-jun oncogene expression in transitional cell carcinoma of the urinary bladder. Br J Urol 1994; 74(6): 757-61.  Back to cited text no. 11    
12.Cordon-Cardo C. Mutation of cell cycle regulators-biological and clinical implications for human neoplasia. Am J Pathol 1995; 147: 545-560.  Back to cited text no. 12  [PUBMED]  [FULLTEXT]
13.Esrig D, Elmajian D, Groshen S, Freeman JA, Stein JP, Chen SC, et al. Accumulation of nuclear p53 and tumor progression in bladder cancer. N Eng J Med 1994; 331: 1259-64.  Back to cited text no. 13    
14.Messing EM and Catalona W. Urothelial tumors of the urinary tract. In Walsh PC, Retik AB, Vaughan ED and Wein AJ (eds.). Campbell's Urology 7` h Ed. WB Saunders, Philadelphia, 1998, pp 2329-2391.  Back to cited text no. 14    
15.Tetu B, Fradet Y, Allard P, Veilleux C, Roberge N, Bernard P. Preva­lence and clinical significance of HER/2neu, p53 and Rb expres­sion in primary superficial bladder cancer. J Urol 1996; 55(5): 1784-8.  Back to cited text no. 15    
16.Simons JW and Marshall FF. The future of gene therapy in the treat­ment of urologic malignancies. Urol Clin North Am 1998; 25: 23-­38.  Back to cited text no. 16    
17.Gao AC, Lou W, Dong JT, Barrett JC, Danielpour D, Isaacs JT. Defining regulatory elements in the human KAII (CD 82) metasta­sis suppressor gene. Prostate 2003; 57(4): 256-60.  Back to cited text no. 17    




 

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    Abstract
    Introduction
    Methods
    Detection of Gen...
    Genetic Engineer...
    Conclusions
    References

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