1. Field of the Invention
The present invention relates to the identification of polynucleotide sequences that are differentially expressed in bladder cancer. More specifically, the present invention relates to the use of the sequences and gene products for diagnosis and as probes.
2. Description of Related Art
Bladder cancer is the second most-common genitourinary cancer in the United States, with only prostate cancer being more frequently diagnosed. Bladder cancer accounts for approximately two percent of all malignant tumors and approximately seven percent of all urinary tract malignancies in U.S. men. Over 54,000 new cases were estimated to be diagnosed in the United States in 1998, with approximately 12,500 deaths predicted [American Cancer Society, 19981]. The prevalence of bladder cancer is higher in industrialized nations, perhaps reflecting increased exposure to environmental carcinogens. Men are three times more frequently affected than women. The disease usually occurs between 60-70 years of age and the age-adjusted bladder cancer rate in white men is almost twice that of black men. Most bladder cancers (over 90%) are carcinomas of the transitional epithelium of the bladders mucosal lining (transitional cell carcinoma (TCC)). Although 90 percent of the cases are localized at diagnosis, up to 80 percent recur.
A number of etiological factors are associated with the development of bladder cancer, but in industrialized countries, cigarette smoking is the most significant. Specific chemicals have also been identified as causing bladder cancer, as have a number of occupational exposures to less well-defined specific agents. Treatment with cytostatic drugs, especially cyclophosphamide, is associated with increased risk of bladder cancer, as is treatment with radiotherapy for uterine cancer.
Bladder cancer is a potentially preventable disease, with a significant morbidity and mortality in many parts of the world.
Tumors are graded according to the degree of cellular abnormality, with the most atypical cells being designated as high-grade (i.e., G3 grade) tumors. The major prognostic factors in carcinoma of the bladder are the depth of invasion into the bladder wall and the degree of differentiation of the tumor. The higher the grade of the tumor at the diagnosis, the higher the incidence of death from the disease within two years.
The stage of development of the tumor is significant in estimating disease prognosis. Most superficial, non-invasive tumors are papillary tumors which do not invade the lamina propria, and are classified as non-invasive TCC, i.e., “Ta” tumors, and they can recur, but nearly 70% will not progress further. A tumor which does not invade the muscle but does enter the lamina propria presents in many cases a worse prognosis. Such tumors are also classified as non-invasive TCC but are termed T1 tumors. Most superficial tumors are well differentiated and classified as G1 grade tumors. Patients in whom superficial tumors are less differentiated, large, multiple, or associated with carcinoma in situ in other areas of the bladder mucosa, (classified as G2-G3 tumors) are at greatest risk for recurrence and the development of invasive cancer. Invasive bladder tumors tend to spread rapidly to the regional lymph nodes and then into adjacent structures. Overall, the five-year survival rate of TCC is 76 percent for whites and 55 percent for blacks.
One of the management problems is the fact that carcinoma of the bladder is frequently multifocal. The entire bladder epithelium and the lining of the entire urothelial cell tract can undergo malignant change. After apparently successful treatment of a bladder lesion, new tumors can occur at the same site (recurrence) or in other urothelial cells in the bladder. Approximately 30 percent of bladder carcinomas present as multiple lesions at the time of initial diagnosis. The early diagnosis of bladder cancer is central to the effective treatment of TCC. Presently, the detection of bladder tumors relies on intravenous pyelogram or other contrast studies to rule out urothelial involvement in the kidneys or ureters, and invariably cystoscopy which remains the accepted standard for diagnosis of mucosal abnormalities. There are no presently reliable methods available to easily and specifically identify the presence of bladder cancer cells. A variety of new technologies and potential tumor markers are being studied in bladder cancer and some are being translated into clinical use.
It is important to realize that all available results of the diagnostic value of tumor markers do not allow firm clinical recommendations, but tests based on biomarkers undoubtedly influence the management of bladder cancer in the near future. Several new markers have been already identified and even approved for use (e.g. bladder tumor antigen (BTA) markers, NMP22, FDP). However, their clinical use is limited [Grossman, 1983], due to sensitivity and specificity problems in conjunction with cystoscopic examination.
Furthermore, due to the high rate of disease recurrence, follow-up of TCC patients is obligatory. There is a need to eliminate the invasive cytoscopy method of diagnosis and of follow-up and replace it with a reliable and noninvasive method of diagnosis.
Approximately 70-80 percent of patients with ne diagnosed bladder cancer present with superficial, non-invasive bladder tumors. Those who do are often curable. Tumor patients with deeply invasive disease can sometimes be cured by complete surgical removal of the bladder, irradiation, or a combination of modalities that include chemotherapy, however the five-year survival rate is less likely for such tumors. It is therefore of major importance to detect new tools that aid in both the initial early diagnosis and in follow-up of non-invasive TCC tumors.
Adverse prognostic features associated with a greater risk of disease progression include the presence of multiple aneuploid cell lines, nuclear p53 overexpression, and expression of the Lewis-x blood group antigen [Hudson and Herr, 1995; Lacombe et al., 1996]. It has been postulated that p53 can be useful for predicting the level of aggression of the tumor and to identify patients who will not benefit from chemotherapy. However, only a very small, select group of patients with invasive disease can benefit from this approach [Ozen, 1981].
Several treatment methods (i.e., transurethral surgery, intravesical medications, and cystectomy) have been used in the management of patients with superficial tumors, and each method can be associated with five-year survival in 55-80 percent of patients treated [Hudson and Herr, 1995; Torti and Lum, 1984]. Invasive tumors that are confined to the bladder muscle on pathologic staging after radical cystectomy are associated with an approximately 75 percent, five-year progression-free rate of survival. Patients with more deeply invasive tumors (which are also usually less well differentiated) experience five-year survival rates of 2040 percent following radical cystectomy. When the patient presents with a locally extensive tumor that invades pelvic viscera or with metastases to lymph nodes or distant sites, a five-year survival rate: is uncommon, but considerable symptomatic palliation can still be achieved.
Surgery is the main treatment method. The extent of surgery is dependent on the pathological stage of the disease. Early disease is generally treated by intravesical chemotherapy and transurethral resection. Locally invasive disease can usually be managed only by radical cystectomy and urinary diversion. Definitive (curative) radiotherapy is generally reserved for bladder cancer patients who are not candidates for surgery. For superficial, low-grade disease, chemotherapy is applied intravesically (directly into the bladder) to concentrate the drug at the tumor site and eliminate any residual tumor mass after resection. Systemic chemotherapy can also be used to manage advanced bladder cancer; compete response rates of 30-50 percent have been reported. Single agent chemotherapy has demonstrated limited success
However, even following surgery and resection of non-invasive TCC tumors, frequent follow-up is required (every 3 months) in both non-invasive and invasive cases.
It would therefore be useful to be able to identify early stage TCC in bladder cancer which has a significantly higher cure rate and generally does not require surgery. In addition, it would be useful to identify markers that can be employed for early diagnosis and follow-up of both non-invasive and invasive TCC, as an efficient and non-invasive alternative to cytoscopy.