Lung cancer is a leading cause of cancer deaths. Non-small cell lung cancer (NSCLC) accounts for many lung cancers, with up to one-third of patients with stage III of the disease. Despite advances in treatment modality, locally advanced NSCLC presents a therapeutic challenge. In terms of extent and size of the primary tumor, and nodal status, stage III NSCLC is a heterogeneous disease. The accepted treatment for locally advanced NSCLC is a multi-modal strategy including chemotherapy, radiation therapy, and surgery. However, with outcomes remaining poor, the most appropriate treatment remains controversial.

Induction chemotherapy (IC) in locally advanced NSCLC has revealed conflicting data [1,2]. IC may eradicate micrometastasis and assess tumor sensitivity to chemotherapy, and this information may be valuable for follow-up chemotherapy at the adjuvant and palliative stages. IC can diffuse more efficiently into the tumor, making it more advantageous than postradiation or surgery, and most importantly, lead to downstaging, thereby resulting in a higher percentage of curative resections. Conversely, there are drawbacks, including a delay in definitive local treatment and the potential for increased morbidity because of chemotherapy-induced toxicities. Therefore, many studies have focused on determining a more accurate prediction of tumor response, to select patients that would benefit most from IC.

The excision repair cross-complementation group 1 (ERCC1) enzyme plays a key role in the nucleotide excision repair system. It recognizes and removes platinum-induced DNA adducts; thus, its expression is associated with platinum resistance [3-5].

Hypoxia, hypoglycemia, and acidosis are main characteristics of tumor microenvironment, that lead to chronic endoplasmic reticulum (ER) stress. Glucose-regulated protein of molecular mass 78 (GRP78), a member of heat shock protein family, is a molecular chaperone in ER. Under ER stress, GRP78 activates a pro-survival pathway using an autophagy mechanism, and this leads to the protection and survival of cancer cells and chemoresistance [6,7]. Autophagy is a lysosomal pathway involved in cellular defense, with beclin-1 playing a key role in this mechanism [8]. Recently, several studies have been focusing on the role of autophagy in cancer. Autophagy has been suggested to be involved in taxane cytotoxicity, although this correlation is under investigation [9-13].

This purpose of this study was to assess the clinicopathologic and prognostic significance of ERCC1, beclin-1, and GRP78 in patients with locally advanced NSCLC receiving docetaxel-platinum IC, along with efficacy and safety of the treatment.

This study was conducted to find predictive and prognostic biomarkers in patients with locally advanced NSCLC receiving docetaxel-platinum IC, in company with efficacy and safety of IC. Our results suggested beclin-1 as a prognostic biomarker, and IC as a safe and effective treatment option.

In our study, patients with high expression of beclin-1 revealed longer OS, while significant predictive role of its expression in terms of IC such as RFS or tumor response was not identified. However, high beclin-1 expression revealed a tendency towards longer RFS. Since only four patients (12.9%) revealed low expression of beclin-1, further study with an expanded cohort and standardizing method of beclin-1 assessment is needed. Autophagy maintains intracellular homeostasis which has conflicting roles in cancer cells, anti-tumors and pro-tumors. Beclin-1 is essential for autophagosome formation, and in human cancer, its downregulation and tumor suppressive role have been reported [12,14-16]. In cervical and duodenal cancer, low beclin-1 expression was associated with poor prognosis and in cervical cancer, the expression of beclin-1 in tumor tissue was lower compared to adjacent normal tissue [15,16]. In breast cancer, autophagy enhanced paclitaxel-induced cell death and autophagy-related markers are downregulated in docetaxel-resistant breast cancer cell lines [17]. Meanwhile, by contrast with aforementioned studies and our results, in endometrial and pancreatic cancer, high beclin-1 expression was associated with poor prognosis, suggesting a pro-tumor role of beclin-1 [18,19]. In NSCLC, autophagy and beclin-1 have been studied as well and conflicting results were reported. Wang et al. [12] and Kim et al. [20] reported consistent results with our study that low beclin-1 expression was associated with aggressive behavior and poor prognosis. Whereas several preclinical studies with NSCLC cell lines reported different results supporting pro-tumor role of autophagy, revealing contribution of autophagy to taxane resistance. In this context, autophagy was proposed as a therapeutic target to overcome chemoresistance [11,13]. In our study and the abovementioned studies, Wang et al. [12] and Kim et al. [20] reported a majority of patients had squamous cell histology (64.5%, 51.9%, and 51.9%, respectively), while the NSCLC cell lines in the preclinical studies revealing a pro-tumor role of autophagy were all adenocarcinoma cell lines [11-13]. Hence, in NSCLC, the role of autophagy may be different according to histology. The different roles of autophagy according to histologic subtype were not identified in our study, so further study is needed in an expanded cohort and preclinical setting with squamous histology cell lines. Beclin-1 expression did not have a significant predictive role in terms of IC such as RFS or tumor response; however, high beclin-1 expression revealed a tendency towards longer RFS.

In our study, high expression of GRP78 revealed longer RFS and OS compared to low expression group with no statistical significance. Emerging data indicates that ER stress and autophagy are involved in human cancer, specifically in carcinogenesis, disease aggressiveness, metastasis, and sensitivity/resistance to anti-tumor treatment [6-10]. Kim et al. [20] reported that expression of GRP78 and beclin-1 in NSCLC correlates with low tumor stage and longer survival, and that their expressions correlated with each other. Conversely, Sun et al. [21] reported that GRP78 mRNA expression was significantly higher (71.9%) in stage III/IV NSCLC, like our result of 71.7%. Additionally, in a small interfering RNA experiment, they have revealed that GRP78 promotes metastasis and anti-apoptosis.

Besides the undefined roles of autophagy and ER stress in NSCLC, several factors may contribute to results with lack of statistical significance [9,10,17]. First, we focused on locally advanced disease, mainly IIIB. We had limited sample numbers (n = 31), and there is concern in serving biopsied tissue as a representative sample for whole tumor.

Being not in accord with previous studies, neither predictive nor prognostic role of ERCC1 was identified in our study. A recent study suggested that IHC analysis with commercially available 8F1 antibodies did not specifically detect the unique functional ERCC1 isoform, thereby limiting its use in the clinic towards therapeutic decision making [22].

In the present study, the response rate of docetaxel-platinum IC was higher (67.8%) than those of previous studies employing paclitaxel-carboplatin IC (40% to 55%), and median OS (23.1 months) was similar to those of previous reports (OS, 16 to 29 months). Considering that about a quarter of patients in this study had stage IIIB disease, while previous reports focused on stage IIIA disease, the result of this study is notable [23-25]. In terms of toxicities, the present study revealed a higher incidence of grade 3/4 neutropenia (78.4%) than that with paclitaxel-carboplatin or gemcitabine-cisplatin IC [23,25]. Ethnic differences of pharmacogenomics in docetaxel metabolism may contribute to the serious hematologic toxicities. However, these were transient and successfully managed in all patients using G-CSF and isolation care. In addition, these toxicities did not lead to delay in the follow-up definitive local treatment, and we observed no treatment-related death. The addition of adjuvant treatment after definitive treatment was identified as a viable prognostic factor in RFS and OS. Hence, IC followed by surgery and adjuvant treatment could be an optimal sequence. And the addition of immunotherapy and detection of cell free tumor DNA after definitive treatment might play roles in the treatment of locally advanced NSCLC [26].

Our findings suggested beclin-1 expression as a favorable prognostic biomarker in locally advanced NSCLC. Further study is required to validate biomarkers related to autophagy and ER stress in NSCLC.