PDZK1 suppresses TNBC development and sensitizes TNBC cells to erlotinib via the EGFR pathway.

Epidermal growth factor receptor (EGFR)-targeted drugs (erlotinib, etc.) are used to treat multiple types of tumours. EGFR is highly expressed in most triple-negative breast cancer (TNBC) patients. However, only a small proportion of TNBC patients benefit from EGFR-targeted drugs in clinical trials, and the resistance mechanism is unclear. Here, we found that PDZ domain containing 1 (PDZK1) is downregulated in erlotinib-resistant TNBC cells, suggesting that PDZK1 downregulation is related to erlotinib resistance in TNBC. PDZK1 binds to EGFR. Through this interaction, PDZK1 promotes EGFR degradation by enhancing the binding of EGFR to c-Cbl and inhibits EGFR phosphorylation by hindering EGFR dimerisation. We also found that PDZK1 is specifically downregulated in TNBC tissues and correlated with a poor prognosis in TNBC patients. In vitro and in vivo functional assays showed that PDZK1 suppressed TNBC development. Restoration of EGFR expression or kinase inhibitor treatment reversed the degree of cell malignancy induced by PDZK1 overexpression or knockdown, respectively. PDZK1 overexpression sensitised TNBC cells to erlotinib both in vitro and in vivo. In conclusion, PDZK1 is a significant prognostic factor for TNBC and a potential molecular therapeutic target for reversing erlotinib resistance in TNBC cells.

HKDC1 upregulation promotes glycolysis and disease progression, and confers chemoresistance onto gastric cancer.

There is increasing evidence that hexokinase is involved in cell proliferation and migration. However, the function of the hexokinase domain containing protein-1 (HKDC1) in gastric cancer (GC) remains unclear. Immunohistochemistry analysis and big data mining were used to evaluate the correlation between HKDC1 expression and clinical features in GC. In addition, the biological function and molecular mechanism of HKDC1 in GC were studied by in vitro and in vivo assays. Our study indicated that HKDC1 expression was upregulated in GC tissues compared with adjacent nontumor tissues. High expression of HKDC1 was associated with worse prognosis. Functional experiments demonstrated that HKDC1 upregulation promoted glycolysis, cell proliferation, and tumorigenesis. In addition, HKDC1 could enhance GC invasion and metastasis by inducing epithelial-mesenchymal transition (EMT). Abrogation of HKDC1 could effectively attenuate its oncogenic and metastatic function. Moreover, HKDC1 promoted GC proliferation and migration in vivo. HKDC1 overexpression conferred chemoresistance to cisplatin, oxaliplatin, and 5-fluorouracil (5-Fu) onto GC cells. Furthermore, nuclear factor kappa-B (NF-κB) inhibitor PS-341 could attenuate tumorigenesis, metastasis, and drug resistance ability induced by HKDC1 overexpression in GC cells. Our results highlight a critical role of HKDC1 in promoting glycolysis, tumorigenesis, and EMT of GC cells via activating the NF-κB pathway. In addition, HKDC1-mediated drug resistance was associated with DNA damage repair, which further activated NF-κB signaling. HKDC1 upregulation may be used as a potential indicator for choosing an effective chemotherapy regimen for GC patients undergoing chemotherapy.

HN1L/AP-2γ/PLK1 signaling drives tumor progression and chemotherapy resistance in esophageal squamous cell carcinoma.

Hematological and neurological expressed 1 like (HN1L) is a newly identified oncogene in lung cancer and hepatocellular carcinoma recently identified by our team, but its roles in the development and treatment of esophageal squamous cell carcinoma (ESCC) remain incompletely cataloged. Here, using ESCC tissue array and public database analysis, we demonstrated that HN1L was highly expressed in ESCC tissues, which was associated with tumor tissue invasion, poor clinical stage and short survival for ESCC patients. Loss- and gain-of-function studies in ESCC cells revealed that HN1L enhances ESCC cell metastasis and proliferation in vitro and in mice models. Moreover, high level of HN1L reduces the sensibility of ESCC cells to chemotherapeutic drugs, such as Docetaxel. Mechanism studies revealed that HN1L activated the transcription of polo-like kinase 1 (PLK1) by interacting with transcription factor AP-2γ, which increased the expression of malignancy related proteins Cyclin D1 and Slug in ESCC cells. Blocking PLK1 with inhibitor BI-2356 abrogated the oncogenic function of HN1L and significantly suppressed ESCC progression by combining with chemotherapy. Therefore, this study demonstrates the vital pro-tumor role of HN1L/AP-2γ/PLK1 signaling axis in ESCC, offering a potential therapeutic strategy for ESCC patients with high HN1L by blocking PLK1.

Long noncoding RNA PENG upregulates PDZK1 expression by sponging miR-15b to suppress clear cell renal cell carcinoma cell proliferation.

PDZK1 downregulation was reported to independently predict poor prognosis of clear cell renal cell carcinoma (ccRCC) patients and induce ccRCC development and progression. However, the underlying mechanism of PDZK1 downregulation remains unknown. Competing endogenous RNA (ceRNA) networks are emerging as new players in gene regulation and are associated with cancer development. ceRNAs regulate other RNA transcripts by competing for shared miRNAs. To investigate the role and mechanism of ceRNAs in PDZK1 downregulation and the development of ccRCC, we searched databases for miRNAs and lncRNAs that regulate PDZK1 expression in ccRCC tissues and assessed their effects in ccRCC. We found that miR-15b was expressed at higher levels in ccRCC tissues, and its upregulation was clinically associated with lower PDZK1 level, larger tumor size and shorter survival time of ccRCC patients. Conversely, a novel lncRNA (lncPENG) was expressed at a lower level in ccRCC tissues, and its downregulation was associated with the same effects as upregulation of miR-15b. Downregulation of miR-15b and upregulation of lncPENG resulted in a significant increase in PDZK1 level and inhibition of proliferation in vitro and in vivo. Mechanistically, lncPENG directly bound to miR-15b and effectively functioned as a sponge for miR-15b to modulate the expression of PDZK1. Thus, lncPENG may function as a ceRNA to attenuate miR-15b-dependent PDZK1 downregulation and inhibit cell proliferation, suggesting that it may be clinically valuable as a therapeutic target and a prognostic biomarker of ccRCC.

ECHS1 suppresses renal cell carcinoma development through inhibiting mTOR signaling activation.

Although the management of patients with renal cell carcinoma (RCC) has changed drastically in recent years, it is still faced with the evolving challenge. Elucidation of the mechanisms underlying RCC will help the development of therapies, as well as biomarkers for early diagnosis. In this study, ccRCC tissues from patients in different stages were subject to iTRAQ-based proteomics analysis. 130 common differentially expressed proteins (DEPs) in different stages were found and lipid metabolism pathway was obviously dysregulated in all stages. These 130 common DEPs were enriched in four highly connected subnetworks including metabolic pathway, the TCA cycle, oxidative phosphorylation and fatty acid metabolism. ECHS1, a key enzyme in fatty acid metabolism, was further investigated. ECHS1 expression was significantly downregulated in ccRCC tissues and ECHS1 level discriminated ccRCC tissues in general and in stage I from adjacent normal tissues well and with the area under the receiver operating characteristic curve (AUC) of more than 0.7. ECHS1 overexpression suppressed RCC cell proliferation and migration through inhibiting mTOR pathway activation. ECHS1 may be a novel target for ccRCC therapeutic interventions and diagnostic biomarker for ccRCC.

SIRT5-mediated SDHA desuccinylation promotes clear cell renal cell carcinoma tumorigenesis.

Metabolic reprogramming is a prominent feature of clear cell renal cell carcinoma (ccRCC). Protein succinylation influences cell metabolism, but its effects on ccRCC tumorigenesis remain largely uncharacterized. In this study, we investigated the lysine succinylome of ccRCC tissues by using tandem mass tag labeling, affinity enrichment, liquid chromatography-tandem mass spectrometry and integrated bioinformatics analyses. Proteins involved in metabolic process, the tricarboxylic acid (TCA) cycle, oxidation-reduction and transport processes were subject to succinylation. A total of 135 sites in 102 proteins were differentially succinylated between ccRCC and adjacent normal tissues. Succinate dehydrogenase complex subunit A (SDHA), which is involved in both the TCA cycle and oxidative phosphorylation, was desuccinylated at lysine 547 in ccRCC. SDHA desuccinylation by mimetic mutation (K547R) suppressed its activity through the inhibition of succinate dehydrogenase 5 (SDH5) binding, further promoted ccRCC cell proliferation. The desuccinylase sirtuin5 (SIRT5) was found to interact with SDHA, and SIRT5 silencing led to the hypersuccinylation and reactivation of SDHA. SIRT5 was also found to be upregulated in ccRCC tissues, and its silencing inhibited ccRCC cell proliferation. This indicates that SIRT5 promotes ccRCC tumorigenesis through inhibiting SDHA succinylation. This is the first quantitative study of lysine succinylome in ccRCC, through which we identified succinylation in core enzymes as a novel mechanism regulating various ccRCC metabolic pathways. These results expand our understanding about the mechanisms of ccRCC tumorigenesis and highlight succinylation as a novel therapeutic target for ccRCC.

New mechanistic insights of clear cell renal cell carcinoma from integrated miRNA and mRNA expression profiling studies.

Differentially expressed (DE) microRNAs (miRNAs) in clear cell renal cell carcinoma (ccRCC) tissues from pooled samples were reported to affect the tumorigenesis and progression of ccRCC. However, systematic studies on the miRNA-mRNA regulatory networks involved in various pathways in all four stages of the disease are lacking. In this study, we applied microarray technology to perform an integrated analysis of the miRNome and transcriptome in ccRCC tissues from patients at different stages of ccRCC. A total of 604 DEmiRNAs and 6892 DEgenes (DEGs) were identified by comparison with corresponding adjacent normal tissues. The pairing of miRNAs with DEGs were searched using validated miRWalk module, and the pairs were confirmed by comparing with DEmiRNAs in our study. Our results demonstrated that different stages of ccRCC had distinct miRNA/mRNA profiles. However, four common pathways (the complement and coagulation cascades, the pathway for the metabolism of xenobiotics by cytochrome P450, the PPAR signaling pathway, and the pathway for aldosterone-regulated sodium reabsorption) were enriched by targets of DEmiRNAs at all stages of ccRCC. We carried out an extensive analysis of data on miR-16, which had the most target genes, and found that its differential expression was validated in The Cancer Genome Atlas dataset. We also verified the correlation between miR-16 expression and target pathways by gene set enrichment analysis and in vitro experiments. High miR-16 level was also associated with shorter survival time in ccRCC. Our work presents a systematic profiling of miRNA, mRNA and pathways regulated by miRNAs in different stages of ccRCC. Our cross-omics results also identify four common pathways that function aberrantly in all stages of the disease. These pathways are likely to be critical in occurrence and progression of ccRCC. These common dysfunctional pathways have the potential to serve as therapeutic targets and diagnostic biomarkers, whereas miRNAs (miR-20, 484, 497) differentially expressed in only stage I tissues and in blood could be used to diagnose early-stage ccRCC patients.