Open Access

Distinct expression pattern and prognostic values of pituitary tumor transforming gene family genes in non‑small cell lung cancer

  • Authors:
    • Shaolong Yang
    • Xiaodi Wang
    • Jingxing Liu
    • Bisha Ding
    • Kairi Shi
    • Jing Chen
    • Weiyang Lou
  • View Affiliations

  • Published online on: September 10, 2019     https://doi.org/10.3892/ol.2019.10844
  • Pages: 4481-4494
  • Copyright: © Yang et al. This is an open access article distributed under the terms of Creative Commons Attribution License.

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Abstract

Members of the pituitary tumor transforming gene (PTTG) family, including PTTG1, PTTG2 and PTTG3P, exhibit pivotal roles in the onset and progression of certain types of human cancer. However, to the best of our knowledge, a systematic study regarding the expression pattern and the prognostic values of PTTG family genes in non‑small cell lung cancer (NSCLC) remains to be performed. The expression levels of PTTG family genes in NSCLC were successively determined using the Gene Expression Profiling Interactive Analysis, UALCAN and Oncomine databases. Subsequently, the Kaplan‑Meier plotter database was used to assess the prognostic value of the PTTG family genes in patients with NSCLC, and to determine the associations between PTTG expression levels and the prognosis of patients based on different clinicopathological features, including cancer stage, grade, chemotherapy, radiotherapy, lymph node status, smoking history, and sex. PTTG1 was identified to be significantly upregulated in NSCLC in all three databases, whereas PTTG2 and PTTG3P were significantly upregulated in NSCLC in only the UALCAN database. Patients with NSCLC with higher expression levels of the three PTTG genes demonstrated shorter overall survival times. In summary, the results of the present study suggested that increased expression of PTTG family genes may serve as promising prognostic biomarkers for patients with NSCLC.

Introduction

Lung cancer is the leading cause of cancer-associated mortality worldwide in men and women, and its prognosis remains dismal with a five-year survival rate of <15% (1). Non-small cell lung cancer (NSCLC), including lung adenocarcinoma (LUAD) and lung squamous cell carcinoma (LUSC), accounts for ~75–80% of all lung cancer cases (2). In addition, although there are several treatment methods for patients with early-stage NSCLC, including surgery, chemotherapy, radiotherapy and molecular targeted therapy, the number of NSCLC cases is still increasing. In addition, treatment options for patients with advanced disease are limited (3), and almost 80% of patients with NSCLC are first diagnosed at an advanced stage (4). Therefore, there is an urgent requirement to conduct further investigations to study the mechanisms of the onset and progression of NSCLC, as well as to identify potential prognostic biomarkers. The development of prognostic biomarkers may improve the therapeutic choice for patients with NSCLC, and ultimately improve their prognosis.

The pituitary tumor transforming gene (PTTG) family is a novel class of homologous genes, which consists of three genes: PTTG1, PTTG2 and PTTG3P (5). The expression of PTTG1 is significantly upregulated in numerous endocrine-associated tumors, including pituitary, thyroid, breast and ovarian tumors (6). The dysregulation of PTTG1 enhances tumor cell proliferation, invasion and metastasis, and suppresses apoptosis (79). A number of studies have demonstrated that PTTG1 is an oncogene, and is overexpressed in human lung cancer. For example, Li et al (10) have reported that PPTG1 promotes the migration and invasion of NSCLC. In addition, Li et al (11) have demonstrated that knockdown of PTTG1 suppresses growth and invasion of LUAD. PTTG2 and PTTG3P, which are homologous genes of PTTG1, have recently been identified (5). Although little is understood regarding their biological functions, PTTG2 and PTTG3P have been revealed to be closely associated with the development of human cancer types. For example, Guo et al (12) have demonstrated that PTTG2 expression is significantly upregulated in glioblastoma, and its overexpression promoted glioblastoma cell proliferation and invasion. Weng et al (13) have demonstrated that PTTG3P enhances the in vitro proliferation and invasion of gastric cancer, and is an indicator of poor prognosis. However, to date, systematic analyses have not been performed for the mRNA expression pattern and prognostic roles of the PTTG family in NSCLC.

The present study determined the mRNA expression pattern of PTTG family genes in NSCLC, including LUAD and LUSC, using the Gene Expression Profiling Interactive Analysis (GEPIA), UALCAN and Oncomine databases. Subsequently, the prognostic values of PTTG family genes in NSCLC were assessed using the Kaplan-Meier plotter database. The Kaplan-Meier plotter database was also used to analyze the associations of PTTG1, PTTG2 and PTTG3P expression with the prognosis of patients based on clinicopathological features, including subtype, clinical stage, pathological grade, chemotherapy, radiotherapy, lymph node status, smoking history and sex. The in silico analysis performed in the present study may assist with the development of effective therapeutic targets and contribute to the improvement of the prognosis of patients with NSCLC.

Materials and methods

GEPIA database (http://gepia.cancer-pku.cn/detail.php)

The expression levels of PTTG family genes in patients with LUAD and LUSC were evaluated using the GEPIA database, which is a newly developed interactive web server for analyzing the RNA sequencing expression data of 9,736 tumors and 8,587 normal samples from The Cancer Genome Atlas (TCGA) and Genotype-Tissue Expression projects (14). The results of differential expression analyses (PTTG1, PTTG2 and PTTG3P in LUAD/LUSC) are available on the website (GEPIA). Fold-change (FC)>2 and P<0.05 were set as the thresholds of gene upregulation.

UALCAN database (http://ualcan.path.uab.edu/index.html)

The expression levels of PTTG family genes in patients with LUAD and LUSC were further analyzed using the UALCAN database. UALCAN is a user-friendly, interactive web resource for analyzing TCGA transcriptome data (15). The analytical results were presented on the webpage (UALCAN). P<0.05 was considered to indicate a statistically significant result.

Oncomine database (https://www.oncomine.org)

Oncomine, which is a cancer microarray database and a web-based data-mining platform, was used to analyze the expression levels of PTTG family genes in LUAD and LUSC samples compared with normal lung samples using the differential expression analysis provided by the database (16,17). FC>1.5, P<0.05 and a gene rank in the top 10% were set as the thresholds for selecting the datasets.

Kaplan-Meier plotter database (http://kmplot.com/analysis)

The prognostic value of the mRNA expression levels of PTTG family genes in patients with NSCLC was assessed using the online database Kaplan-Meier plotter, as previously described (1820). Kaplan-Meier plotter was established using gene expression data and the survival information of patients with cancer downloaded from the Gene Expression Omnibus database (21). In the present study, the associations between PTTG1, PTTG2 and PTTG3P expression levels and the overall survival (OS) of patients with NSCLC were evaluated. Briefly, the three genes were first put into the database to obtain Kaplan-Meier survival plots. According to the median expression level, the cases were generally classified into low- and high-expression groups. A log-rank P-value, hazard ratio (HR) and 95% confidence interval (CI) were automatically calculated and presented on the webpage (Kaplan-Meier plotter). A log-rank P<0.05 was considered to indicate a statistically significant difference.

Results

Expression levels of the PTTG family genes in patients with NSCLC

To investigate the mRNA expression levels of PTTG family genes in human NSCLC, three online databases, including GEPIA, UALCAN and Oncomine, were successively used. The GEPIA database was used to compare the mRNA expression levels of PTTG family genes in NSCLC samples with those in normal lung samples. PTTG1 expression was significantly upregulated in NSCLC subtypes LUAD and LUSC compared with normal lung samples (Fig. 1A). However, no significant differences were identified between PTTG2 or PTTG3P expression in cancer tissues and normal tissues (Fig. 1B and C). PTTG3P expression levels in LUAD, LUSC and corresponding normal controls were extremely low. Similar results of the expression levels of PTTG family genes in NSCLC were obtained using the UALCAN database (Fig. 1D-I). The UALCAN database demonstrated that the expression levels of PTTG2 and PTTG3P were low (transcripts per million <1), which may lead to inaccurate statistical differences of PTTG2 and PTTG3P.

Oncomine analysis was used to further evaluate the mRNA expression of PTTG family genes in NSCLC. Similar to the previous results, PTTG1 expression was significantly increased in both LUAD (Fig. 2) and LUSC (Fig. 3) compared with normal lung tissues. No significant differences were identified in the PTTG2 and PTTG3P expression levels between NSCLC and normal samples. The detailed information of the datasets with statistical significance information is presented in Table I. These data suggested that PTTG1 may be upregulated in NSCLC compared with normal lungs, whereas PTTG2 and PTTG3P are not dysregulated in NSCLC.

Table I.

Expression levels of PTTG1 in patients with non-small cell lung cancer from Oncomine database.

Table I.

Expression levels of PTTG1 in patients with non-small cell lung cancer from Oncomine database.

A, LUAD vs. normal

Normal samplesCancer samplesReporterGene rank (%)P-valuetFold change
17132Bhattacharjee lung198 (top 3) 2.0×10−33.3613.729
1920Stearman lung24 (top 1) 4.4×10−108.2266.638
6545Hou lung154 (top 1) 1.8×10−149.3382.984
440Garber lung390 (top 4) 2.0×10−46.4423.212
4958Landi lung65 (top 1) 3.6×10−2011.5191.968
3027Su lung178 (top 2) 1.4×10−76.5312.174
20226Okayama lung379 (top 2) 1.2×10−1410.8452.460
5858Selamat lung629 (top 4) 3.5×10−149.0962.492

B, LUSC vs. normal

Normal samplesCancer samples ReporterGene rank (%)P-valuetFold change

1721Bhattacharjee lung46 (top 1) 3.5×10−87.02826.568
6527Hou lung27 (top 1) 1.4×10−2718.5605.665
413Garber lung241 (top 3) 4.7×10−58.9124.863
55Wachi lung53 (top 1) 2.0×10−510.7633.275
2834Talbot lung817 (top 10) 1.1×10−65.2871.643

[i] PTTG, pituitary tumor transforming gene; LUAD, lung adenocarcinoma; LUSC, lung squamous cell carcinoma.

Prognostic values of PTTG family gene mRNA expression levels in patients with NSCLC

Kaplan-Meier plotter database was used to assess the effects of the mRNA expression levels of PTTG family genes on the survival of patients with NSCLC. The prognostic value of PTTG1 in all patients with NSCLC, patients with LUAD and patients with LUSC is presented in Fig. 4. Patients with NSCLC with high expression of PTTG1 exhibited significantly shorter OS time compared with patients with a low expression of PTTG1 (HR, 1.66; 95% CI, 1.46–1.89; log-rank P=5.7×10−15; Fig. 4A). High expression of PTTG1 in patients with LUAD indicated a poor prognosis (HR, 2.36; 95% CI, 1.85–3.02; log-rank P=1.9×10−12; Fig. 4B). However, in patients with LUSC, high PTTG1 expression was not associated with OS (Fig. 4C).

The associations between PTTG2 mRNA expression levels and the overall survival of all patients with NSCLC, patients with LUAD and patients with LUSC were also analyzed. High PTTG2 expression levels were only significantly associated with a worse prognosis for all patients with NSCLC (HR, 1.21; 95% CI, 1.07–1.37; log-rank P=2.9×10−2; Fig. 5A). For patients with LUAD (HR, 1.16; 95% CI, 0.92–1.46; log-rank P=2.0×10−1) and patients with LUSC (HR, 1.06; 95% CI, 0.83–1.33; log-rank P=7.0×10−1), PTTG2 expression was not significantly associated with the prognosis of patients (Fig. 5B and C).

The associations between PTTG3P mRNA expression level and survival for all patients with NSCLC, patients with LUAD and patients with LUSC were evaluated. As presented in Fig. 6A and B, high expression of PTTG3P was significantly associated with unfavorable OS for all patients with NSCLC (HR, 1.57; 95% CI, 1.38–1.78; log-rank P=2.9×10−12) and patients with LUAD (HR, 1.81; 95% CI, 1.43–2.30; log-rank P=7.1×10−7). However, for patients with LUSC, PTTG3P was not significantly associated with OS (HR, 1.19; 95% CI, 0.94–1.50; log-rank P=1.6×10−1; Fig. 6C). Taken together, these results indicated that the three PTTG family genes may be promising biomarkers that predict a poor prognosis in all patients with NSCLC. Additionally, PTTG1 and PTTG3P may also be two prospective prognostic biomarkers for patients with LUAD.

Associations between the prognostic values of PTTG family mRNA expression and clinical stage

The associations between the prognostic values of the PTTG family mRNA expression levels and the clinical stage of patients with NSCLC were examined. Patients with clinical stage I NSCLC with high expression of PTTG1 (HR, 3.13; 95% CI, 2.32–4.21; log-rank P=3.2×10−15; Fig. 7A), PTTG2 (HR, 1.43; 95% CI, 1.09–1.87; log-rank P=9.7×10−3; Fig. 7B) and PTTG3P (HR, 2.73; 95% CI, 2.04–3.65; log-rank P=2.3×10−12; Fig. 7C) exhibited worse OS compared with patients with low PTTG1 expression. High expression of PTTG2 indicated a poor prognosis in patients with clinical stage II NSCLC compared with low PTTG2 expression (HR, 1.61; 95% CI, 1.12–2.33; log-rank P=1.0×10−2; Fig. 7E). PTTG1 (HR, 1.26; 95% CI, 0.87–1.82; log-rank P=2.2×10−1; Fig. 7D) and PTTG3P (HR, 1.18; 95% CI, 0.82–1.70; log-rank P=3.8×10−1; Fig. 7F) did not demonstrate any significant effects on the OS of patients with stage II NSCLC. For patients with clinical stage III NSCLC, PTTG1 (HR, 0.89; 95% CI, 0.51–1.53; log-rank P=6.6×10−1; Fig. 7G), PTTG2 (HR, 0.74; 95% CI, 0.42–1.27; log-rank P=2.7×10−1; Fig. 7H) and PTTG3P (HR, 1.29; 95% CI, 0.75–2.22; log-rank P=3.6×10−1; Fig. 7I) expression levels exhibited no significant associations with prognosis. These results suggested that PTTG family genes may be effective prognostic biomarkers for patients with clinical stage I NSCLC.

Associations between the prognostic values of PTTG family mRNA expression and chemotherapy or radiotherapy

Chemotherapy and radiotherapy are two major therapeutic strategies for treating different cancer types, including NSCLC, particularly for patients with advanced stage disease. The present study further investigated the associations between the prognostic roles of the mRNA expression levels of PTTG family genes and chemotherapy and radiotherapy in NSCLC. High expression levels of PTTG1 (HR, 1.58; 95% CI, 1.13–2.22; log-rank P=7.0×10−3) and PTTG3P (HR, 1.45; 95% CI, 1.03–2.03; log-rank P=3.0×10−2) were significantly associated with OS of patients with NSCLC without chemotherapy (Table II). However, none of the PTTG family gene expression levels were significantly associated with OS of patients with or without radiotherapy (Table III).

Table II.

Correlation of PTTG family with chemotherapy of patients with non-small cell lung cancer.

Table II.

Correlation of PTTG family with chemotherapy of patients with non-small cell lung cancer.

PTTG family memberAffymetrix IDChemotherapyLow expression (N)High expression (N)HR95% CILog-rank P-value
PTTG1203554_x_atNo1551551.581.13–2.22 7.0×10−3a
203554_x_atYes88880.950.63–1.45 8.3×10−1
PTTG2214557_atNo1581521.160.83–1.63 3.7×10−1
214557_atYes88880.930.62–1.4 7.3×10−1
PTTG3P208511_atNo1561541.451.03–2.03 3.0×10−2a
208511_atYes89870.810.54–1.22 3.1×10−1

a P<0.05. PTTG, pituitary tumor transforming gene.

Table III.

Correlation of PTTG family with radiotherapy of patients with non-small cell lung cancer.

Table III.

Correlation of PTTG family with radiotherapy of patients with non-small cell lung cancer.

PTTG family memberAffymetrix IDRadiotherapyLow expression (N)High expression (N)HR95% CILog-rank P-value
PTTG1203554_x_atNo1371341.220.86–1.75 2.6×10−1
203554_x_atYes35350.950.55–1.63 8.4×10−1
PTTG2214557_atNo1361351.040.73–1.49 8.2×10−1
214557_atYes36340.870.51–1.49 6.2×10−1
PTTG3P208511_atNo1361351.110.77–1.58 5.8×10−1
208511_atYes35351.150.68–1.96 6.0×10−1

[i] PTTG, pituitary tumor transforming gene.

Associations between the prognostic values of PTTG family mRNA expression levels and other clinicopathological features

The associations of individual PTTG family genes with other clinicopathological features, including pathological grade (Fig. 8), lymph node status (Table IV), smoking status (Table V) and sex (Table VI), were determined. Fig. 8 presents the prognostic values of PTTG family genes in NSCLC based on various pathological grades; none of the genes demonstrated a significant association with OS of patients with grade I, II or III NSCLC, which may have occurred partially due to the relatively limited sample size. The data presented in Table IV demonstrated the associations between the prognostic values of PTTG family mRNA expression levels and lymph node status of patients with NSCLC. A high expression of PTTG1 (HR, 1.39; 95% CI, 1.12–1.71; log-rank P=2.3×10−3) was significantly associated with poor OS for patients with NSCLC without invasive and/or metastatic lymph nodes (lymph node, 0). However, PTTG2 and PTTG3P were not associated with NSCLC lymph node status. Table V presents the associations of the PTTG family with the smoking history of patients with NSCLC. Compared with patients with NSCLC with low expression of PTTG1, high expression of PTTG1 indicated a worse prognosis in patients with NSCLC who had never smoked (HR, 3.03; 95% CI, 1.63–5.62; log-rank P=2.2×10−4) or smoked (HR, 1.32; 95% CI, 1.07–1.62; log-rank P=8.9×10−3). Patients with NSCLC with a high expression of PTTG2 who had smoked (HR, 1.47; 95% CI, 1.19–1.81; log-rank P=2.8×10−4) and never-smoked (HR, 2.10; 95% CI, 1.18–3.75; log-rank P=1.0×10−2) exhibited a shorter OS time compared with patients with NSCLC with low expression of PTTG2. Additionally, high expression of PTTG3P was also significantly associated with the OS or patients who had never-smoked (HR, 3.11; 95% CI, 1.70–5.71; log-rank P=1.1×10−4) and smoked (HR, 1.41; 95% CI, 1.15–1.74; log-rank P=1.1×10−3). High expression of PTTG1, PTTG2 and PTTG3P was significantly associated with OS of both female and male patients with NSCLC (PTTG1-female: HR, 1.87; 95% CI, 1.47–2.38; log-rank P=1.7×10−7; PTTG1-male: HR, 1.53; 95% CI, 1.31–1.79; log-rank P=1.2×10−7; PTTG2-female: HR, 1.34; 95% CI, 1.06–1.69; log-rank P=1.4×10−2; PTTG2-male: HR, 1.24; 95% CI, 1.06–1.46; log-rank P=6.9×10−3; PTTG3P-female: HR, 1.81; 95% CI, 1.43–2.29; log-rank P=6.6×10−7; PTTG3P-male: HR, 1.45; 95% CI, 1.24–1.70; log-rank P=4.2×01−6; Table VI).

Table IV.

Correlation of PTTG family with lymph node status of patients with non-small cell lung cancer.

Table IV.

Correlation of PTTG family with lymph node status of patients with non-small cell lung cancer.

PTTG family memberAffymetrix IDLymph node statusLow expression (N)High expression (N)HR95% CILog-rank P-value
PTTG1203554_x_at03903911.391.12–1.71 2.3×10−3a
214775_at11261261.210.89–1.66 2.3×10−1
208511_at256551.010.67–1.51 9.7×10−1
PTTG2203554_x_at03913901.060.86–1.31 5.7×10−1
214775_at11291231.220.89–1.67 2.1×10−1
208511_at256551.230.82–1.84 3.2×10−1
PTTG3P203554_x_at03913901.120.9–1.38 3.1×10−1
214775_at11281241.240.91–1.69 1.8×10−1
208511_at256551.320.88–1.97 1.8×10−1

a P<0.05. PTTG, pituitary tumor transforming gene.

Table V.

Correlation of PTTG family with smoking history of patients with non-small cell lung cancer.

Table V.

Correlation of PTTG family with smoking history of patients with non-small cell lung cancer.

PTTG family memberAffymetrix IDSmoking statusLow expression (N)High expression (N)HR95% CILog-rank P-value
PTTG1203554_x_atNever smoked1021033.031.63–5.62 2.2×10−4a
203554_x_atSmoked4104101.321.07–1.62 8.9×10−3a
PTTG2214557_atNever smoked1021032.11.18–3.75 1.0×10−2a
214557_atSmoked4233971.471.19–1.81 2.8×10−4a
PTTG3P208511_atNever smoked1051003.111.70–5.71 1.1×10−4a
208511_atSmoked4134071.411.15–1.74 1.1×10−3a

a P<0.05. PTTG, pituitary tumor transforming gene.

Table VI.

Correlation of PTTG family with the sex of non-small cell lung cancer patients.

Table VI.

Correlation of PTTG family with the sex of non-small cell lung cancer patients.

PTTG family memberAffymetrix IDSexLow expression (N)High expression (N)HR95% CILog-rank P-value
PTTG1203554_x_atFemale3593561.871.47–2.38 1.7×10−7a
203554_x_atMale5505501.531.31–1.79 1.2×10−7a
PTTG2214557_atFemale3643511.341.06–1.69 1.4×10−2a
214557_atMale5805201.241.06–1.46 6.9×10−3a
PTTG3P208511_atFemale3593561.811.43–2.29 6.6×10−7a
208511_atMale5565441.451.24–1.70 4.2×10−6a

a P<0.05. PTTG, pituitary tumor transforming gene.

Discussion

Lung cancer is the leading cause of cancer-associated mortality worldwide, which is associated with significant health and financial burdens (1). As the most common type or lung cancer, rapid improvements in the diagnosis, treatment and prognosis of NSCLC is important. The PTTG family, which comprises PTTG1, PTTG2 and PTTG3P, is a newly identified gene class. Among the three homologous genes, PTTG1 has been the most extensively studied and has been identified to be closely associated with the onset and progression of multiple human cancer types, including pituitary tumor (22), malignant glioma (7), thyroid (23), breast (24), ovarian (25), bladder (8), prostate (9) and lung cancer (2630). Honda et al (30) have demonstrated that PTTG1 is significantly upregulated in NSCLC and its overexpression serves a role in the genesis and progression of NSCLC. However, to the best or our knowledge, a systematic analysis regarding the expression and prognostic role of PTTG1 in NSCLC has not been previously performed. In addition, PTTG2 and PTTG3P have been reported to be associated with tumor development (12,13); to the best of our knowledge, no previous study has investigated their expression and roles in NSCLC. Therefore, the present study systematically investigated the expression and prognostic roles of the PTTG family genes in NSCLC.

A comprehensive analysis of the mRNA expression of the PTTG family genes in NSCLC was performed in the present study using the GEPIA, UALCAN and Oncomine databases. The results demonstrated that PTTG1 was significantly upregulated in cancer tissue compared with normal tissue, which was in accordance with the results of previous studies on other types of cancer (79). By contrast, for PTTG2 and PTTG3P expression, the data from the three databases were inconsistent. The results of the GEPIA and Oncomine database analysis suggested that there were no significant differences in PTTG2 and PTTG3P expression between NSCLC and normal lung tissues. However, the results from the UALCAN database indicated an upregulation of PTTG2 and PTTG3P in NSCLC compared with normal tissue. Therefore, further studies on the expression of these genes in NSCLC are required to confirm these results.

The Kaplan Meier-plotter database was used to perform a broad assessment of the prognostic roles of the PTTG family genes in patients with NSCLC. The results demonstrated that patients with NSCLC (1,924 samples) with high PTTG1, PTTG2 and PTTG3P expression exhibited a shorter OS time compared with healthy controls. In different subtypes of patients with NSCLC, PTTG1 and PTTG3P may serve as promising prognostic biomarkers, as their mRNA expression levels were significantly associated with the prognosis of patients with LUAD. However, for patients with LUAD and LUSC, PTTG2 was not significantly associated with prognosis. Only 720 and 524 clinical samples were included in the analysis of the prognostic roles of PTTG2 in patients with LUAD and LUSC, respectively; the relatively small sample counts may have influenced the results.

The present study further determined the associations of the prognostic values of the mRNA expression of PTTG family genes with clinicopathological features, including clinical stage, pathological grade, lymph node metastasis, smoking history and sex. The associations between the levels of PTTG family mRNA expression and chemotherapy or radiotherapy were also assessed. The findings demonstrated that a high expression of PTTG family genes indicated a poor prognosis in patients with clinical stage I disease, patients who had smoked, patients who had never-smoked. No differences were observed in terms of the sex of the patients in the prognosis of patients with NSCLC with high expression of PTTG family genes. High expression levels of PTTG1 and PTTG3P were associated with short survival time of patients with NSCLC who had not received chemotherapy. PTTG family genes demonstrated no significant association with radiotherapy, pathological grade and lymph node status, partially due to the relatively limited sample size. These results may inform the selection of therapeutic choices for NSCLC patients with various PTTG family gene expression levels. Future studies with a larger sample size are required to further reveal the associations of the expression levels of PTTG family genes with these clinicopathological features in patients with NSCLC. Of note, in addition to LUAD and LUSC subtypes, NSCLC also has other subtypes, such as lung adenosquamous carcinoma and large cell lung cancer. Therefore, although PTTG family exhibited unfavorable prognostic values in all NSCLC patients, they may have various prognostic values in LUAD or LUSC.

In conclusion, the results of the present study suggest that PTTG family genes, particularly PTTG1, are significantly overexpressed in LUAD and LUSC. In addition, increased expression of PTTG family genes may serve as promising prognostic biomarkers for patients with NSCLC.

Acknowledgements

Not applicable.

Funding

This study was supported by the 2017 Science and Technology Innovation Team Project of Zhengzhou Railway Vocational and Technical College (grant no. 17060001).

Availability of data and materials

All data generated or analyzed during this study are included in this published article.

Authors' contributions

WL and JC conceived and designed the study. SY, XW and JL wrote the manuscript. SY, XW and JL performed gene expression analysis, survival analysis and prepared figures and tables. BD and KS interpreted the results. BD, KS and WL revised the manuscript. All authors read and approved the final manuscript.

Ethics approval and consent to participate

Not applicable.

Patient consent for publication

Not applicable.

Competing interests

The authors declare that they have no competing interests.

Glossary

Abbreviations

Abbreviations:

NSCLC

non-small cell lung cancer

LUAD

lung adenocarcinoma

LUSC

lung squamous cell carcinoma

PTTG

pituitary tumor transforming gene

GEPIA

Gene Expression Profiling Interactive Analysis

TCGA

The Cancer Genome Atlas

FC

fold-change

OS

overall survival

HR

hazard ratio

CI

confidence interval

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Volume 18 Issue 5

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Spandidos Publications style
Yang S, Wang X, Liu J, Ding B, Shi K, Chen J and Lou W: Distinct expression pattern and prognostic values of pituitary tumor transforming gene family genes in non‑small cell lung cancer. Oncol Lett 18: 4481-4494, 2019.
APA
Yang, S., Wang, X., Liu, J., Ding, B., Shi, K., Chen, J., & Lou, W. (2019). Distinct expression pattern and prognostic values of pituitary tumor transforming gene family genes in non‑small cell lung cancer. Oncology Letters, 18, 4481-4494. https://doi.org/10.3892/ol.2019.10844
MLA
Yang, S., Wang, X., Liu, J., Ding, B., Shi, K., Chen, J., Lou, W."Distinct expression pattern and prognostic values of pituitary tumor transforming gene family genes in non‑small cell lung cancer". Oncology Letters 18.5 (2019): 4481-4494.
Chicago
Yang, S., Wang, X., Liu, J., Ding, B., Shi, K., Chen, J., Lou, W."Distinct expression pattern and prognostic values of pituitary tumor transforming gene family genes in non‑small cell lung cancer". Oncology Letters 18, no. 5 (2019): 4481-4494. https://doi.org/10.3892/ol.2019.10844