Minireview The RB2/p130 Gene: The Latest Weapon in the War against Lung Cancer? 1 Pier Paolo Claudio, Mario Caputi, and Antonio Giordano 2 Department of Pathology, Anatomy, and Cell Biology, Thomas Jefferson University, and Sbarro Institute for Cancer Research and Molecular Medicine, Philadelphia, Pennsylvania 19107 [P. P. C., A. G.]; Universita’ degli Studi di Napoli “Federico II,” Dipartimento di Scienze Odontostomatologiche e Maxillo Facciali, Napoli 80131, Italy [P. P. C.]; and Istituto di Malattie dell’Apparato Respiratorio, II Universita’ degli Studi di Napoli, Istituto di Ricerca Cardio- Pneumologica A. O. “Monaldi,” Napoli, Italy 80131 [M. C.] Abstract Lung cancer is the second cause of death after cardio- vascular diseases and is the major cause of cancer deaths in the Western world. Large scale screening trials conducted 15–20 years ago using chest X-rays and sputum cytology were able to detect stage I cancers but failed to impact on survival. This is because of the early metastatic potential of small primary tumors. It is important then to detect lung cancer at an earlier stage, studying and identifying genetic lesions that could indicate a new target(s) for gene therapy. The retinoblastoma-related gene pRb2/p130, a new tumor suppressor gene cloned in 1993, is emerging as one of the candidate markers and targets for gene therapeutic ap- proach. Effective genetic therapy requires both a genetic material to be used therapeutically and a means to deliver it. A scope for this review is to examine some of the gene delivery systems mostly used, discussing their weaknesses and strengths, and to discuss the role of pRb2/p130 in lung cancer. Introduction Lung cancer is one of the leading causes of cancer death in the world (1). The high mortality rate for lung cancer probably results from the absence of standard clinical procedures for diagnosis of early tumoral stages compared with breast, pros- tate, and colon cancers (2). Early studies indicated that several distinct chromosomal loci (3p, 9p, 13q, 17p, and others) are implicated, suggesting that maybe sequential genetic events occur during initiation and progression of lung carcinogenesis (2– 4). Recent studies indicated instead that allelic loss of sev- eral other chromosomal regions could be involved in the patho- genesis of lung cancer. These chromosomal regions include 1p, 1q, 2q, 5p, 6p, 8p, 8q, 10q, 14q, 17q, 18q, and 22q (5–12). The malignant transformation of pulmonary epithelial cells is the result of multistep accumulation of genetic and molecular alter- ations highly related to tobacco carcinogens, involving key regulatory elements of the cell cycle and mechanism of prolif- eration and apoptosis. Oncogene activation (ras, myc, and au- tocrine growth factors loops) or more importantly tumor sup- pressor gene inactivation (p53, pRb family, and cyclin- dependent kinase inhibitor p16) at a genetic, epigenetic, or posttranslational level removes crucial constraints on cell divi- sion at the G 1 checkpoint and apoptosis, accelerating cell divi- sion (Refs. 13 and 14; Fig. 1). p53 inactivation is one of the most common alterations in lung cancer (75% of genetic alterations). In fact, mutations of p53 have been reported with frequencies up to 50% in NSCLC 3 and 70 – 80% in SCLC (15, 16). On the other hand, some authors have reported mutations or deletions of the RB gene in NSCLCs in .90% of the cases (16). p53 missense mutation is highly concordant with p53 stabilization and immu- noreactivity; other gene products, like pRb and Ras, are either rapidly degraded or not detectable at the immunohistochemical level if mutated. By immunohistochemistry the expression of p53, pRb, Ras, and Bcl-2 have been investigated in a panel of 65 samples of preneoplastic lesions of the bronchial epithelium. The frequency of p53-positive and pRb-negative microscopic fields was directly related to the morphological grading of the lesions. One of the main patterns found to be correlated with the severity of histopathological features was characterized by com- bined p53 hyperexpression and pRb hypoexpression (17). Lung cancer arises from a series of morphological and molecular changes that take several years to progress from a normal epithelium to an invasive cancer. The molecular changes include activation of dominant oncogenes as well as loss of recessive growth regulatory genes or antioncogenes (18). Inter- estingly, some authors could correlate the prognostic signifi- cance of the loss of Rb protein either alone or combined with Ras or with p53 in patients with NSCLC. The individual with theoretically the best pattern of protein expression in their tumors versus those with theoretically the worst pattern of gene expression, i.e., Rb1/Ras2 versus Rb2/Ras1 and Rb1/p532 versus Rb2/p531, showed a longer period of survival. The correlation between Rb and Ras appeared to be a better prog- nostic factor compared with the Rb/p53 status in NSCLCs. In patients affected by squamous cell carcinoma, neither Rb/Ras nor Rb/p53 status was a significant prognostic factor in this cohort instead (19). Received 10/8/99; revised 12/13/99; accepted 12/14/99. The costs of publication of this article were defrayed in part by the payment of page charges. This article must therefore be hereby marked advertisement in accordance with 18 U.S.C. Section 1734 solely to indicate this fact. 1 Supported by NIH Grants RO1 CA 60999-01A1 and PO1 NS 36466 (to A. G.). P. P. C. is the recipient of a fellowship from the Associazione Leonardo di Capua, Napoli, Italy. 2 To whom requests for reprints should be addressed, at Pathology, Anatomy, and Cell Biology, Thomas Jefferson University, 1020 Locust Street, Room 226, Philadelphia, PA 19107. Phone: (215) 503-0781; Fax: (215) 923-9626; E-mail: agiordan@lac.jci.tju.edu. 3 The abbreviations used are: NSCLC, non-small cell lung cancer; AAV, adeno-associated virus; rAAV, recombinant AAV; wt, wild type; TAg, large T antigen; rSV40, recombinant SV40; Rb, retinoblastoma. 754 Vol. 6, 754 –764, March 2000 Clinical Cancer Research