Cap43/NDRG1/Drg-1 is a molecular target for angiogenesis and a prognostic indicator in cervical adenocarcinoma
Introduction
The Cap43 gene is a nickel- and calcium-inducible gene [1], identical to the previously described N-myc downstream-regulated gene 1 (NDRG1). It is one of the four closely related genes (NDRG1-4) whose expression is down-regulated by c-myc or the N-myc/Max complex [2], [3], [4], [5]. Cap43 is also identical to the homocysteine-inducible gene, whose expression is reduced in tumor cells (RTP/rit42) [6], and to the differentiation-related gene-1 (Drg-1) [7]. The protein encoded by Cap43 has a molecular weight of 43 kDa. It has three unique 10-amino acid tandem-repeat sequences at its carboxyl terminal and is phosphorylated by protein kinase A [8].
The functions of Cap43 remain poorly understood. Expression of the Cap43 gene has been strongly associated with nickel, cobalt, oxidative stress, hypoxia, phorbol esters, vitamins A and D, steroids, histone deacetylase-targeting drugs, homocysteine, β-mercaptoethanol, tunicamycin, and lysophosphatidylcholine, as well as with oncogenes (N-myc and c-myc) and the products of tumor-suppressor genes (p53 and VHL) [1], [2], [6], [9], [10]. Cap43 is expressed in most organs, most prominently in the prostate, ovary, colon, and kidney. Its expression in the kidney, brain, liver, and gut is actively modulated during postnatal development [2], [3], [11], [12], suggesting that Cap43 plays a key role in organ maturation.
Transfection studies by Kurdistani and colleagues demonstrated that Cap43 inhibits the primary growth of human breast, prostate, and bladder cancer cell lines and suppresses the anchorage-independent growth of these cell lines in soft agar [6]. Moreover, the overexpression of Cap43 markedly promotes the growth of human pancreatic cancer xenografts in mice, but not of pancreatic cancer cells in culture [13]. The survival rate of patients with pancreatic cancer whose tumors expressed high levels of Cap43 was found to be significantly higher than that of patients whose tumors expressed low levels of Cap43 [13]. In another study, low tumor Cap43 expression was strongly associated with poor outcomes in women with breast cancer [14]. Chua and colleagues recently reported that Cap43 overexpression significantly correlates with tumor differentiation, vascular invasion, and overall survival in patients with hepatocellular carcinoma, suggesting that increased Cap43 expression may be a useful indicator of tumor aggressiveness and prognosis [15]. Taken together, the above findings suggest that Cap43 may have tissue-of-origin-specific functions in human malignancies [16].
The incidence of invasive cervical cancer has decreased in developed countries, presumably because of intensive national screening programs. This declining incidence is attributed primarily to a decrease in squamous cell carcinoma, whereas the incidence of adenocarcinoma has remained stable or risen slightly [17], [18]. The prevalence of adenocarcinoma among women with cervical cancer has increased from 5% to 13% in the 1950s to 20% in the 1990s [19], [20]. Recent studies attribute this rise to an increased incidence of cervical adenocarcinoma among young women [21], [22]. Cervical adenocarcinoma is associated with unfavorable outcomes, attributed to late detection on Papanicolaou smears, a poorer response to radiotherapy than squamous cell carcinoma, or the inclusion of subtypes with particularly poor outcomes, such as clear cell carcinoma [23]. New tumor markers that can be used to predict outcomes predictors have been identified by numerous studies, including immunohistochemical analyses [24], [25], [26].
Angiogenesis is an important pathological aspect of tumor growth and chronic inflammatory diseases [27]. Of the various angiogenesis factors identified to date, vascular endothelial growth factor (VEGF)-A plays a key role in pathological angiogenesis, including that required for the rapid growth of solid tumors. Antiangiogenesis agents targeting VEGF-A and VEGF-receptor 2 have been developed and are currently used clinically [28], [29]. In a previous study, we demonstrated that higher tumor Cap43 expression is associated with higher tumor microvessel density (MVD) than lower tumor Cap43 expression in patients with pancreatic cancer [13]. Angiogenesis in cervical carcinoma has been shown to be inversely related to survival [30], [31]. Kaku and colleagues [32] demonstrated a significant correlation of MVD with both progression-free survival and overall survival in cervical adenocarcinoma.
In this study we immunohistochemically evaluated the intensity of Cap43 expression in patients with stage I or II cervical adenocarcinoma according to the staging system of the International Federation of Gynecology and Obstetrics (FIGO). We also examined correlations of Cap43 staining intensity with angiogenesis and other clinicopathological factors.
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Patients and treatment
Between 1990 and 2005, a total of 100 patients with stage I or II cervical adenocarcinoma underwent surgery at Kurume University Hospital and National Cancer Center Hospital. The procedure was radical hysterectomy in 93 patients and simple abdominal hysterectomy in the other seven. Pelvic lymphadenectomy and para-aortic lymph node biopsy were performed in all patients. Patients with deep stromal invasion, lymph node metastasis, or both were considered candidates for postoperative adjuvant
Patient characteristics
The patients’ characteristics are shown in Table 1. The median follow-up time was 51.3 months. At the time of the analysis, tumor recurrence had been diagnosed in 30 patients, and 25 patients had died. Table 2 shows the Cap43 expression, VEGF expression, and microvessel density.
Correlation between Cap43 expression and angiogenesis
High Cap43 expression correlated with high VEGF expression (Table 3). Immunohistochemical staining analysis showed that median MVD was 39.4 in the specimens with high Cap43 expression and 26.1 in the specimens with low
Discussion
Our study showed that the intensity of Cap43 expression was significantly associated with tumor angiogenesis and other poor prognostic factors in cervical adenocarcinoma. Survival analysis showed that high tumor expression of Cap43 was associated with poor progression-free survival and overall survival.
The controversy surrounding the relevance of Cap43 expression in cancer may be attributed in part to the fact that Cap43 expression is highly influenced by pleiotropic factors and stimuli,
Disclosure/conflict of interest
The authors declare no potential conflict of interest.
Acknowledgments
This work was supported in parts by the 21st Century Center of Excellence program in Japan and Grants-in-Aid for Scientific Research from the Ministry of Education, Science, Sports and Culture of Japan; and Fukuoka Obstetrics and Gynecology Researcher’s Charity Foundation Fund Japan.
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