Clinicopathologic and prognostic values of apolipoprotein D alterations in hepatocellular carcinoma

Abstract

We previously identified apolipoprotein D (Apo D) as a novel tumor suppressor gene based on the pharmacological unmasking of epigenetic silencing. We analyzed Apo D expression using realtime reverse transcription-PCR and evaluated its expression status based on the clinicopathological parameters of 70 patients with hepatocellular carcinoma (HCC). Immunohistochemical staining was also performed. We determined the methylation status of Apo D gene promoter by methylation-specific PCR (MSP). The Apo D gene-expression in tumor tissue was significantly lower than that in nontumor tissue (p = 0.011). A low Apo D expression significantly correlated with less-differentiated HCC ( p = 0.019). Immunohistochemical studies confirmed a decreased Apo D expression in poorly differentiated tumors. The prognosis of patients with a lower Apo D gene-expression was significantly worse than that in those with a higher expression (p = 0.028). The Apo D gene-expression was an independent prognostic factor (relative risk: 2.36, p = 0.018). An MSP assay showed a low-level of methylation in well differentiated HCC and a high-level of methylation in less differentiated tumors. Apo D may be a novel tumor suppressor gene of HCC, and its expression status may be a useful biomarker for predicting the patient outcome. ' 2005 Wiley-Liss, Inc.Key words: apolipoprotein D; hepatocellular carcinoma; histological grade; prognostic factor; methylationWe recently performed a comprehensive survey of commonly inactivated tumor suppressor genes in esophageal cancer cell lines based on functional reactivation by a demethylating agent. 1 A total of 58 silenced genes were thus identified using this approach, and one of those genes was Apolipoprotein D (Apo D). In our report, we detected the promoter hypermethylation of Apo D gene using bisulfite DNA sequencing. The methylation status of Apo D correlated closely with the Apo D expression status. Moreover, the growth suppressive activity of Apo D was also demonstrated by a colony focus assay. 1 These findings thus prompted us to analyze the clinical significance of the Apo D expression status in human cancers.Apo D, belonging to the lipocalin superfamily, is a glycoprotein of about 30 kDa found in the high-density lipoprotein fraction of human plasma. 2 The functional role of Apo D remains unclear, but the observation that this protein forms complexes with lecithin-cholesterol acyltransferase suggests that Apo D may be involved in cholesterol esterification. 3 More recently, the Apo D gene-expression was reported to be induced by retinoic acid in breast cancer cell lines. The induction of the Apo D expression was accompanied by an inhibition of cell proliferation and a progression through a more differentiated phenotype. These finding suggest that the mechanisms controlling retinoic acid-induced growth arrest, cell differentiation and Apo D synthesis may be directly coordinated in human breast cancer cells. 4 Furthermore, a low expression of Apo D determined by an immunohistochemical study was significantly as...

Expression and potential role of apolipoprotein D on the death–survival balance of human colorectal cancer cells under oxidative stress conditions

“…An extensive literature supports the notion that tumor cells maintain low levels of ApoD in their surroundings, and a decreased mRNA and/or protein expression has been reported in breast [22], ovary [23], prostate [24], hepatic [25,26], neural [27,28], esophageal cancer [29], and colorectal cancer [30]. Our data show a prominent decrease in mRNA and protein levels in the initial stages of CRC.…”

“…Many reports document low levels of ApoD in different forms of cancer [22][23][24][25][26][27][28][29]. In primary colorectal cancer, Ogawa et al [30] corroborated a similar downregulation of ApoD messenger RNA (mRNA), and by establishing two categories of mRNA expression, they found a positive correlation between ApoD levels and CRC patient survival.…”

An integrative strategy for quantitative analysis of the N-glycoproteome in complex biological samples

“…Therefore, these glycan changes on specific glycoproteins may be sensitive potential biomarkers for disease diagnosis, which are worthy of further investigation. Among these proteins, apolipoprotein D (APOD) was down-regulated in HCC patient serum in all three lectin subgroups, and CLUS was up-regulated in all three lectin subgroups, consistent with previous data [47,48]. To further validate the quantitative results obtained by our strategy, we determined the expression levels of glycoprotein LG3BP by western blot in the ConA and LCH lectin subgroups from HCC patient and healthy individual serum.…”

Apolipoprotein D is down-regulated during malignant transformation of neurofibromas

“…In breast and prostate carcinoma cell lines, apoD expression is inversely proportional to proliferation when modulated by androgens, estrogens, and other steroid hormones [9,11,12]. ApoD expression has also been documented to correlate inversely with aggressive behavior of several different types of malignant tumor [30][31][32]. The mechanistic link between cell cycle inhibition and apoD expression remains to be elucidated.…”