Introduction

Gastric cancer is one of the most common malignancies worldwide, and the second most common cause of cancer death [1]. Surgery combined with chemotherapy remains the most effective method for treating resectable gastric adenocarcinoma (RGA), although the prognosis is still poor in advanced stage patients. Clinical trial data show that the survival of patients with RGA who received postoperative chemotherapy in adjuvant or neoadjuvant settings or both has improved over the past decade [2, 3]. Although a standard chemotherapy regimen for gastric adenocarcinoma chemotherapy has not been adopted, most first-line chemotherapeutic regimens contain fluoropyrimidine or a platinum agent or both in most countries worldwide.

Molecular biomarkers that possess prognostic value are of great value clinically, especially at early disease stages, and can help guide treatment [4]. Cyclin D (CCND) is essential regulator of the cell cycle. CCND plays an essential role in the activation of G1/S transition through forming complexes with CDK4 or 6 (cyclin D–Cdk4/6 complexes), which increase cell proliferation and growth [5]. CCND is induced by the activation of Ras/Raf/ERK signaling and is regarded as an oncogene due to its involvement in the growth factor signaling pathway and because it promotes cell cycle progression resulting cell overgrowth [6]. There are three CCND homologs, CCND1, CCND2 and CCND3. CCND1 is closely associated with cancer development and is frequently over-expressed in various human cancer cells and tissues [7, 8]. Aberrant expression of CCND1 in multiple cancer cells and tissues has been shown; however, the relationship between CCND1 expression levels and the prognosis of patients with RGA treated with fluoropyrimidine and or a platinum agent after resection remains to be determined.

In this study, we first detected the expression levels of CCND1 in RGA tissue by immunohistochemistry (IHC) and then explored the potential value of it as biomarker for patients with RGA.

Materials and methods

Patients and samples

A total of 211 specimens of paraffin-embedded tissue samples from patients with RGA who underwent surgery and postoperative chemotherapy (fluoropyrimidine or fluoropyrimidine plus platinum) between 2003 and 2008 at Fuzhou General Hospital, Fujian, China, were retrospectively examined in this study. Patient follow-up was performed every 6 months, beginning 3 months after surgery and ended March, 2013. Clinical information was obtained from detailed medical records. Survival data were collected by telephone, in person interviews, and social security death index data. All patients had provided informed consent for the research use of their tissue samples. This study was approved by the Ethical Committee of Fuzhou General Hospital.

Immunohistochemistry

IHC analysis for the expression level of CCND1 in RGA tissue samples was performed based on the methods described by us previously [9–11], except specific anti-CCND1 antibody (Abcam Company, Cambridge, MA, USA) was used. IHC results were determined by two pathologists who were blinded to patient data. The IHC staining results were graded 0, 1, 2, and 3 based on staining intensity [12]. Samples with a grade of 0 or 1 were regarded as low expression, and those with a grade of 2 or 3 regarded as high expression [12].

Statistical analysis

All statistical analyses were performed with SPSS 17.0 software (SPSS Inc., Chicago, IL). Chi-square test (or Fisher’s exact test when required) was used to analyze the relationship between the CCND1 expression level and clinicopathological features and patient survival. The association of CCND1 with prognosis (overall survival) was further analyzed by univariate and multivariate Cox regression analyses, Kaplan–Meier curves, and log-rank test. The multivariate Cox regression model was adjusted for factors including gross findings, age, gender, histologic grade, tumor site, lymph node involvement, and T stage. All P values were two-sided, and a value of P < 0.05 was defined as statistically significant.

Results

Patient characteristics

Patient demographic, clinical, and pathological characteristics, overall survival rate, and CCND1 expression are shown in Table 1. All 211 patients had adenocarcinoma and received a mean of four cycles of postoperative chemotherapy consisting of fluoropyrimidine plus platinum or fluoropyrimidine only. The median follow-up duration was 51 months (range 3–103 months), and 107 patients (50.7 %) died during the follow-up period. The median overall survival time was 54 months (range 3–106 months). Patients were divided into two groups based on postoperative chemotherapeutic regimen after resection: fluoropyrimidine plus platinum and fluoropyrimidine only.

Table 1 Patients’ characteristics
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CCND1 expression

A total of 110 (52.1 %) specimens displayed high CCND1 expression (Table 1). CCND1 expression exhibited a significant association with patient age (<60 vs. ≥60 years, P = 0.028) and survival (alive vs. dead, P = 0.011) (Table 2); patients with a shorter survival time had higher CCND1 expression. Additionally, the CCND1 expression was also associated with the postoperative chemotherapy agent: More cases in patients treated with fluoropyrimidine only exhibited higher CCND1 expression (61.9 %) than those treated with fluoropyrimidine plus platinum (47.1 %) (P = 0.042). No other significant association between CCND1 expression and other clinicopathological factors was detected. Representative images of tissue that exhibited low and high CCND1 expression by IHC are shown in Fig. 1.

Table 2 Association between CCND1 expression and characteristics of patients
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Fig. 1
figure 1

Representative images of immunohistochemistry for CCND1 staining. a Normal gastric tissue. b Low expression of CCND1 in resected gastric carcinoma (RGA) tissue. c High expression of CCND1 in RGA tissue

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Association of CCND1 expression with survival

The Kaplan–Meier survival analysis showed that high CCND1 expression was associated with a significantly decreased median overall survival time (MST) (43.0 vs. 62.0 months, P = 0.013) (Fig. 2). Similar results were observed when the data were stratified by differential expression of CCND1 and different postoperative chemotherapeutic regimens. As shown in Fig. 3a, high expression of CCND1 was associated with reduced MST in patients treated with fluoropyrimidine plus platinum (65.0 vs. 74.5 months, P = 0.032). The MST in these patients was longer than that of the whole group of 211 patients, indicating postoperative chemotherapy with fluoropyrimidine plus platinum is an effective treatment for patients with RGA. No significant survival difference between high and low CCND1 expression was observed in patients treated with fluoropyrimidine only (Fig. 3b). However, after controlling for age, gender, histologic grade, gross findings, and tumor site, and factors which were determined as significant on univariate analysis (lymph node metastasis and T stage), high expression of CCND1 persisted to be negative prognostic indicator (increased death risk) in the Cox multivariate regression analysis for patients treated with fluoropyrimidine plus platinum [adjusted hazard ratio (HR) 1.91, 95 % confidence interval (CI) 1.12–3.23; P = 0.017] (Table 3) and was also a negative prognostic indicator for patients treated with fluoropyrimidine only (adjusted HR 2.14, 95 % CI 1.08–4.25; P = 0.029) (Table 4).

Fig. 2
figure 2

Kaplan–Meier curves according to differential CCND1 expression levels for all patients. MST, median survival times in months. P values from log-rank test

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Fig. 3
figure 3

Kaplan–Meier curves according to differential CCND1 expression levels by chemotherapeutic regimen therapy. a Patients who received fluoropyrimidine plus platinum. b Patients who received fluoropyrimidine only

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Table 3 Univariate and multivariate Cox regression analyses for overall survival in patients receiving fluoropyrimidine plus platinum therapy
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Table 4 Univariate and multivariate Cox regression analyses for overall survival in patients receiving fluoropyrimidines therapy only
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The relationships between overall survival, postoperative chemotherapeutic regimen, and CCND1 expression were further analyzed. Within the group of 110 patients who displayed high CCND1 expression, patients who received fluoropyrimidine plus platinum (n = 66) showed an increased MST compared with those received fluoropyrimidine only (n = 44, 65.0 vs. 29.0 months; P = 0.041) (Table 2; Fig. 4a). Multivariate Cox regression analysis further confirmed that treatment with fluoropyrimidine plus platinum was closely associated with a decreased risk of death as compared to fluoropyrimidine only (adjusted HR 0.47, 95 % CI 0.28–0.78) (Table 5). Similar results were also demonstrated within the group of 101 patients who exhibited low CCND1 expression. As shown in Table 2 and Fig. 4b, patients with low CCND1 expression treated with fluoropyrimidine plus platinum (n = 74) had a longer MST than those treated with fluoropyrimidine only (n = 27, 74.5 vs. 33.0 months; P = 0.003). This finding was also demonstrated by the multivariate Cox regression analyses (adjusted HR 0.44, 95 % CI 0.23–0.82; P = 0.010) (Table 6).

Fig. 4
figure 4

Kaplan–Meier curves according to CCND1 expression in patients who received fluoropyrimidine plus platinum versus fluoropyrimidine only. a High CCND1 expression. b Low CCND1 expression

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Table 5 Univariate and multivariate Cox regression analyses for overall survival in patients with high CCND1 expression
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Table 6 Univariate and multivariate Cox regression analysis for overall survival in patients with low CCND1 expression
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Discussion

Patients with RGA have a poor prognosis, and as such identification of prognostic factors to guide treatment decisions is necessary. Molecular biomarker expression profiles may provide important prognostic information that is of more value than common clinicopathological data. In this study, we identified the potential prognostic value of CCND1 expression in patients with RGA.

Evidence has demonstrated that elevated CCND1 expression correlates with reduced survival in several different cancers [13–15]. Here, we have shown for the first time that high expression of CCND1 was associated with decreased overall survival of patients with RGA and was also associated with decreased overall survival in RGA patients treat with fluoropyrimidine plus platinum or fluoropyrimidine only after resection. Additionally, CCND1 expression was also a prognostic biomarker for the effect of chemotherapy. The overall survival of patients treated with fluoropyrimidine plus platinum after surgery was significantly longer than of those treated with fluoropyrimidine only when analyzed by both Kaplan–Meier survival curves and multivariate Cox regression analyses on the basis of low or high CCND1 expression. Patients treated with fluoropyrimidine plus platinum after resection exhibited a significantly greater overall survival time compared with those treated with fluoropyrimidine only in both high CCND1 and low CCND1 expression groups.

The correlation of biomarker expression with both survival and treatment modality has been demonstrated previously in RGA patients by Squires et al. [16]. The study found that excision repair cross-complementing gene-1 (ERCC1) expression was not related with decreased or increased overall survival of patients with RGA, but high ERCC1 expression was related with an increased overall survival in a subset of patients who underwent resection only, and reduced overall survival in a subset of patients who received additional chemotherapy [16].

Over-expression of CCND1 in tumor tissues is a frequent event. As an oncogene that promotes cell cycle progression, high CCND1 expression is related to increased cancer cell growth and proliferation and decreased cell apoptosis [17–20]. Therefore, the association of elevated expression of CCND1 and decreased overall survival is easy to understand.

The results of this study showed that CCND1 expression may be used as an indicator of chemotherapy effectiveness. In both the high and low CCND1 expression groups, patients treated with fluoropyrimidine plus platinum exhibited a longer survival than those treated with fluoropyrimidine only. The anti-cancer mechanisms of both fluoropyrimidine and platinum involve inhibition of cell cycle progression. The mechanisms by which patients treated with fluoropyrimidine plus platinum had increased overall survival compared with those treated with fluoropyrimidine only are still unclear and require further investigation. Due to relatively small size of this study, a study with a larger number of samples may be necessary to identify the true clinical value of the findings.

In summary, we have demonstrated for the first time that CCND1 expression may have prognostic value for patients with RGA, and CCND1 may be used as a new prognostic biomarker for the evaluation of survival of patients with RGA and the effect of chemotherapy for RGA after resection.