Luo et al. Cancer Cell Int (2021) 21:49 https://doi.org/10.1186/s12935-021-01756-8 Cancer Cell International PRIMARY RESEARCH Open Access Prognostic values, ceRNA network, and immune regulation function of SDPR in KRAS-mutant lung cancer Xiaoqing Luo†, Shunli Peng†, Sijie Ding, Qin Zeng, Rong Wang, Yueyun Ma, ShiYu Chen, Yanxia Wang and Wei Wang* Abstract Background: Serum Deprivation Protein Response (SDPR) plays an important role in formation of pulmonary alveoli. However, the functions and values of SDPR in lung cancer remain unknown. We explored prognostic value, expression pattern, and biological function of SDPR in non-small cell lung cancer (NSCLC) and KRAS-mutant lung cancers. Methods: SDPR expression was evaluated by quantitative real-time PCR (RT-qPCR), immunohistochemistry (IHC), and Western blot on human NSCLC cells, lung adenocarcinoma tissue array, KRAS-mutant transgenic mice, TCGA and GEO datasets. Prognostic values of SDPR were evaluated by Kaplan–Meier and Cox regression analysis. Bioinformatics implications of SDPR including SDPR-combined transcription factors (TFs) and microRNAs were predicted. In addition, correlations between SDPR, immune checkpoint molecules, and tumor infltration models were illustrated. Results: SDPR expression was downregulated in tumor cells and tissues. Low SDPR expression was an independ- ent factor that correlated with shorter overall survival of patients both in lung cancer and KRAS-mutant subgroups. Meanwhile, ceRNA network was constructed to clarify the regulatory and biological functions of SDPR. Negative correlations were found between SDPR and immune checkpoint molecules (PD-L1, TNFRSF18, TNFRSF9, and TDO2). Moreover, diversity immune infltration models were observed in NSCLC with diferent SDPR expression and copy number variation (CNV) patterns. Conclusions: This study elucidated regulation network of SDPR in KRAS-mutant NSCLC, and it illustrated correlations between low SDPR expression and suppressed immune system, unfolding a prognostic factor and potential target for the treatment of lung cancer, especially for KRAS-mutant NSCLC. Keywords: SDPR (CAVIN2), KRAS mutation, Lung cancer, PD-L1, Immunotherapy Background [EGFR], anaplastic lymphoma kinase [ALK] [3]. Kirsten Lung cancer is the most common and lethal cancer rat sarcoma viral oncogene homolog (KRAS) mutation is among all cancer types [1]. With the conception of indi- frequently detected in lung adenocarcinoma and closely vidualized therapy [2], signifcant progress has been related with smoking status [4–6]. Several researches made based on specifc pathologic subtype and molecu- show that KRAS mutation is the most common genetic lar aberrations (e.g., epidermal growth factor receptor alteration type, and it occurs in approximately 10–25% of lung cancer in Western and Asia countries [7–9]. Te *Correspondence: [email protected] efective clinical strategies of EGFR [10], ALK [11], and †Xiaoqing Luo and Shunli Peng contribute equally to this study rearranged during transfection [RET] [12] aberrations Department of Radiation Oncology, Nanfang Hospital, Southern Medical remains to be explored for tumors with KRAS mutations University, Guangzhou 510515, People’s Republic of China © The Author(s) 2021. This article is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons licence, and indicate if changes were made. The images or other third party material in this article are included in the article’s Creative Commons licence, unless indicated otherwise in a credit line to the material. If material is not included in the article’s Creative Commons licence and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this licence, visit http://creat iveco mmons .org/licen ses/by/4.0/. The Creative Commons Public Domain Dedication waiver (http://creat iveco mmons .org/publi cdoma in/ zero/1.0/) applies to the data made available in this article, unless otherwise stated in a credit line to the data. Luo et al. Cancer Cell Int (2021) 21:49 Page 2 of 15 [2]. Te RAS gene family encodes a small hydrolyzed has rarely been explored. Our study explored the gene guanosine triphosphate GTPase membrane-bound signature, regulation, and efect of SDPR on tumor and protein, which interacts with downstream efectors to immune infltration, based on comprehensive bioinfor- activate transduction of cellular survival signals, such matics analysis, evaluation of lung cancer specimens, and as RAF-MEK-ERK, PI3K-AKT-mTOR, and RALGDS- preclinical experiments. RA [13–15]. Frequent mutant RAS subtypes include KRAS (86%), neuroblastoma rat sarcoma viral oncogene Methods homolog (NRAS) (11%), and Harvey rat sarcoma viral Cell lines and reagents oncogene homolog (HRAS) (3%) [16]. In case of NSCLC, Human non-small cell lung cancer cells (HCC4006, H23, KRAS mutations occur predominantly in codons 12 and H358, SK-LU-1 and H1299) were purchased from Ameri- 13, and most frequent variants include G12C, G12V, and can Type Culture Collection (ATCC), Virginia., America. G12D [9, 17]. Human embryonal lung cell (MRC-5) was purchased Recently, a series of compounds targeting KRAS- from the Type Culture Collection of the Chinese Acad- G12C variant have been developed and achieved prom- emy of Sciences, Shanghai, China [30]. HCC4006, H23, ising efects in preclinical experiments and phase I H358 and H1299 cells were maintained in RPMI 1640 clinical trials [18–20]. However, it is not clear whether supplemented medium, MRC-5 cells were maintained KRAS mutation, especially G12V and G12D variant, in Dulbecco’s Modifed Eagle’s Medium (DMEM), and can have any clinical benefts. Meanwhile, patients with SK-LU-1 cell lines was maintained in Minimum Essential co-occurring TP53/KRAS mutations showed remark- Medium (MEM), respectively. All cells were cultured in able clinical response to immune checkpoint inhibitors standard environment as descried previously [31]. (CPI) [21]. Moreover, patients with KRAS mutation had favorable clinical benefts of anti-PD-1/PD-L1 immuno- Transgenic mouse and establishment of KRAS‑mutant lung therapy [22], and high PD-L1 expression in tumor cells cancer models was associated with improved overall survival in KRAS Te LSL-KRAS mice (B6.129S4-KRAStm4Tyj/JNju) were mutant patients [23]. However, the loss of STK11/LKB1 purchased from Nanjing biomedical institution of Nan- promoted programmed PD-1/PD-L1 inhibitor resist- jing University, Nanjing, China, and housed in specifc ance [24]. Tese studies indicated that the presence of pathogen-free (SPF) institution of Experimental ani- co-occurring genetic events and the mutant KRAS allelic mal center in Southern Medical University, Guangzhou, content increase biological heterogeneities of KRAS- China. Cre recombinase induced Adeno-associated mutant NSCLC, which complicates the treatment of viruses (AAV-CMV-bGloin-Cre) were purchase from KRAS-mutant lung cancers. Shanghai genechem Co., Ltd., China. AAV-CMV-bGloin- To investigate the gene expression signature in KRAS- Cre virus was in tracheally instilled into LSL-KRAS mice oncogene-driven lung cancer, we compared the difer- to induce KRAS-oncogene expression [32]. After further ences between KRAS-mutant tumors and normal lung 4–6 months, visible tumor nodules were observed in lung tissue derived from a genetically engineered mouse tissue. Finally, tumor-bearing mice were sacrifced, and model (GEMM), based on expression profling and com- tumor tissue and normal lung tissue were collected. prehensive bioinformatics analysis. Several diferentially expressed genes (DEG) were screened according to the Reverse transcription, quantitative real‑time PCR gene expression profle, but SDPR was the only DEG that and Western blot decreased in both GEMM tumors. Reverse transcription, quantitative real-time PCR SDPR (also known as C AVIN2, NC_000002.12, gene ID and Western blot were performed as described previ- 8436), a key substrate for protein kinase C, was found to ously [33]. Oligonucleotide primers used for detection play a critical role in inducing membrane curvature and of human-SDPR, human-GAPDH (internal control), participating in the formation of caveolae [25]. It has human-DACH1 and mouse-DACH1 were as follows: been reported that SDPR is a potential diagnostic indi- human-SDPR: 5′-CTC CGA CGC AAC CATTT-3′(sense); cator in cancers such as hepatocellular carcinoma and 5′-CTT TCT TGA GGC TAT CCA CTT-3′ (antisense); gastric cancer [26–28]. However, it remains unknown human-GAPDH: 5′-AGA AGG TGG GGC TCA TTT G-3′ whether SDPR could be a predictor or target for lung (sense); 5′-AGG GGC CAT CCA CAG TCT TC-3′ (anti- cancer, especially in KRAS-mutant group. Moreover, sense); human-DACH1: 5′-GGA ATG GAT TGT GGC SDPR is considered a suppressor gene in papillary thy- TGA AC-3′ (sense); 5′-GGT ATT GGA CTG GTA CAT roid cancer [29], but the regulatory mechanism of SDPR CAAG-3′ (antisense); mouse-DACH1: 5′-AGT GGT GGT remains to be illustrated. Meanwhile, the connection TCT TGG GAT AAGG-3′ (sense); 5′-TGA GAG GAT GGC between SDPR and tumor microenvironment (TME) TAA CTG GAA-3′ (antisense) [34]. All the reactions were Luo et al. Cancer Cell Int (2021) 21:49 Page 3 of 15 performed in triplicate for each sample. Cycle threshold