Chemoresistance In Human Cancer Research Articles

Crosstalk between tumor-associated macrophages and tumor cells promotes chemoresistance via CXCL5/PI3K/AKT/mTOR pathway in gastric cancer

Background5-fluorouracil (5-FU)-based chemotherapy regimen has been widely used for the treatment of gastric cancer, but meanwhile the development of chemotherapeutic resistance remains a major clinical challenge. Tumor microenvironment (TME) frequently correlates with the development of chemoresistance in human cancer. As a major component of TME, the role of tumor-associated macrophages (TAMs) in the chemoresistance of gastric cancer has not been fully elucidated.MethodsImmunohistochemistry (IHC) was applied to detect the density of TAMs in clinical samples of 103 patients with gastric cancer who had undergone 5-FU-based neoadjuvant chemotherapy. 5-FU-resistant gastric cell lines MKN45-R and HGC27-R were established, macrophages were then separately co-cultured with MKN45-R, HGC27-R cells and their parental cells. The effect of gastric cancer cells on the polarization of macrophages, the biological function of M2-polaried macrophages and the mechanism for promoting 5-FU-resistance were investigated. Then the correlation between the expression of CXC motif chemokine ligand 5 (CXCL5) and the infiltration of hemoglobin scavenger receptor (CD163) positive and mannose receptor (CD206) positive macrophages was analyzed, the prognostic value of CXCL5 expression in clinical samples was further explored.ResultsThe high infiltration of macrophages marked by CD68 in gastric cancer samples was significantly associated with the resistance of gastric cancer to chemotherapy. Gastric cancer cells could modulate macrophages to M2-like polarization through indirect co-culture, and chemoresistant cells were more efficient in inducing macrophages polarization to M2 phenotype. Co-culturing M2-polarized macrophages in turn enhanced 5-FU-resistance of gastric cancer cells, and it was further verified that CXCL5 derived from M2-polarized macrophages promoted chemoresistance through activing the PI3K/AKT/mTOR pathway. Besides, high level of CXCL5 could recruit monocytes to form more M2-polarized macrophages. Clinically, high expression of CXCL5 in gastric cancer samples was associated with the high infiltration of CD163 positive macrophages and CD206 positive macrophages, and patients with high expression of CXCL5 presented lower overall survival (OS) rates than those with low expression of CXCL5.ConclusionInteraction between TAMs and gastric cancer cells promoted chemoresistance in gastric cancer via CXCL5/PI3K/AKT/mTOR pathway. Thus, targeting TAMs and blocking the cell–cell crosstalk between TAMs and gastric cancer cells may represent prospective therapeutic strategies for patients with gastric cancer.

Long non-coding RNA opa-interacting protein 5 antisense transcript 1 (LncRNA OIP5-AS1) promoted cisplatin resistance in nasopharyngeal carcinoma via the miR-378a-3p/nicotinamide N-methyltransferase axis

LncRNAs involve in chemoresistance of human cancers. However, the role and molecular mechanisms of lncRNA OIP5-AS1 in the chemoresistance of NPC are still unexplored. In our study, upregulated OIP5-AS1 was found in cisplatin (CDDP)-resistant NPC tumors and cell lines. Functional assays revealed OIP5-AS1 knockdown suppressed malignant behaviors, but stimulated apoptosis of CDDP-resistant NPC cells. Furthermore, we demonstrated OIP5-AS1 positively regulated NNMT by directly targeting miR-378a-3p. In addition, its inhibition partially abolished the inhibitory effects of OIP5-AS1 silencing on malignancy of CDDPresistant NPC cells, whereas NNMT knockdown reverse these effects. In sum, our results indicated OIP5-AS1 contributed to the CDDP resistance of NPC by sponging miR-378a-3p to increase NNMT expression.

Deubiquitinating enzyme USP9X regulates metastasis and chemoresistance in triple-negative breast cancer by stabilizing Snail1.

Breast cancer is one of the most common malignancies in women worldwide. Triple-negative breast cancer (TNBC) is a highly aggressive and metastatic subtype that has the characteristics of easy recurrence, poor prognosis as well as lack of targeted therapeutics. Snail1, a key factor regulating epithelial-mesenchymal transition (EMT) process, contributing to metastasis and chemoresistance in human cancers. However, the molecular mechanism of Snail1 stabilization in cancers is not fully understood. Here, we demonstrate that the deubiquitinating enzyme USP9X deubiquitinates and stabilizes Snail1, thereby promoting metastasis and chemoresistance. The depletion and pharmacological inhibition of USP9X by WP1130, an inhibitor of USP9X, downregulate endogenous Snail1 protein, inhibit cell migration, invasion, metastasis, and increase cellular sensitivity to cisplatin and paclitaxel both in vitro and in vivo, whereas the reconstitution of Snail1 in cells with USP9X depletion at least partially reverses these phenotypes. Overall, our study establishes the USP9X-Snail1 axis as an important regulatory mechanism of breast cancer metastasis and chemoresistance and provides a rationale for potential therapeutic interventions in the treatment of TNBC.

Circular RNA hsa_circ_0011298 enhances Taxol resistance of non-small cell lung cancer by regulating miR-486-3p/CRABP2 axis.

BackgroundCircular RNAs (circRNAs) serve as critical regulators in the chemoresistance of human cancers, including non‐small cell lung cancer (NSCLC). We aimed to explore the role of hsa_circ_0011298 (circ_0011298) and its mechanism in Taxol resistance of NSCLC.MethodsCirc_0011298, microRNA‐486‐3p (miR‐486‐3p), and CRABP2 mRNA expression were determined using qRT‐PCR. EdU and MTT assays were used to detect cell proliferation. Cell cycle distribution and cell apoptosis were detected by flow cytometry. Cell migratory and invasive abilities were detected using transwell assay. Cellular glycolysis was determined by specific kits. Protein levels were examined by western blot. Dual‐luciferase reporter and RIP assays were performed to confirm the relationship between miR‐486‐3p and circ_0011298 or CRABP2. Xenograft mice model was established to confirm the function of circ_0011298 in vivo.ResultsCirc_0011298 was overexpressed in Taxol‐resistant NSCLC cells and tissues. Circ_0011298 knockdown enhanced Taxol sensitivity by decreasing cell proliferation, migration, invasion, and glycolysis and inducing apoptosis and cell cycle arrest in Taxol‐resistant NSCLC cells. Circ_0011298 was a sponge of miR‐486‐3p, and the impact of circ_0011298 silencing on Taxol resistance was rescued by miR‐486‐3p inhibition. Moreover, miR‐486‐3p directly targeted CRABP2, and miR‐486‐3p inhibited Taxol resistance by targeting CRABP2. Furthermore, circ_0011298 regulated CRABP2 expression through targeting miR‐486‐3p. Importantly, circ_0011298 interference elevated Taxol sensitivity of NSCLC in vivo.ConclusionCirc_0011298 elevated Taxol resistance of NSCLC by sponging miR‐486‐3p and upregulating CRABP2, providing a possible circRNA‐targeted therapy for NSCLC.

LncRNA SNHG11 enhances bevacizumab resistance in colorectal cancer by mediating miR-1207-5p/ABCC1 axis.

Long noncoding RNAs (lncRNAs) have been reported to serve as vital regulators in the chemoresistance of human cancers, including colorectal cancer (CRC). In this study, we aimed to explore the functions of lncRNA small nucleolar RNA host gene 11 (SNHG11) in the resistance of CRC to bevacizumab. Quantitative real-time PCR, western blot assay or immunohistochemistry assay were performed to examine the expression of SNHG11, microRNA-1207-5p (miR-1207-5p), ATP binding cassette subfamily C member 1 (ABCC1) and Ki67. Cell Counting Kit-8 assay was conducted to evaluate bevacizumab resistance and cell viability. 5'-ethynyl-2'-deoxyuridine analysis, flow cytometry analysis and wound-healing assay were conducted for cell proliferation, apoptosis and migration, respectively. Dual-luciferase reporter assay and RNA immunoprecipitation assay were employed to analyze the relations among SNHG11, miR-1207-5p and ABCC1. Murine xenograft model assay was employed to analyze bevacizumab resistance in vivo. The exosomes were observed under transmission electron microscopy. SNHG11 was overexpressed in bevacizumab-resistant CRC tissues and cells. Knockdown of SNHG11 restrained bevacizumab resistance, repressed cell proliferation and migration, and promoted apoptosis in bevacizumab-resistant CRC cells. MiR-1207-5p served as the target of SNHG11 and SNHG11 regulated bevacizumab resistance by targeting miR-1207-5p. ABCC1 was the target gene of miR-1207-5p. Overexpression of miR-1207-5p inhibited bevacizumab resistance and cell progression in bevacizumab-resistant CRC cells, with ABCC1 elevation abrogated the impacts. SNHG11 silencing repressed bevacizumab resistance in vivo. In addition, exosomal SNHG11 was upregulated in bevacizumab-resistant CRC cells. SNHG11 contributes to bevacizumab resistance in CRC depending on the modulation of miR-1207-5p and ABCC1.

Cisplatin resistance and malignant behaviors of lung cancer cells are promoted by circ_0002360 via targeting miR-6751-3p to regulate the expression of ZNF300.

BackgroundCircular RNAs (circRNAs) are key regulators in oncogenesis and chemoresistance of human cancers. Herein, we focused on the roles of circ_0002360 in regulating lung cancer progression and cisplatin (DDP) resistance.MethodsThe detection of circ_0002360, microRNA‐6751‐3p (miR‐6751‐3p) and zinc finger protein 300 (ZNF300) was conducted via reverse transcription‐quantitative polymerase chain reaction assay. Cell sensitivity was determined using cell counting kit‐8 assay. Proliferation detection was performed by colony formation assay and EdU assay. The migrated cells were examined via transwell assay. Cell apoptosis analysis was carried out through flow cytometry and caspase 3 activity assay. Western blot was used to examine the protein levels. Target interaction was confirmed through dual‐luciferase reporter assay and RNA immunoprecipitation assay. Circ_0002360 function in vivo was performed via xenograft tumor assay.ResultsCirc_0002360 was overexpressed in DDP‐resistant lung cancer tissues and cells. Silencing circ_0002360 inhibited DDP resistance, proliferation and migration but enhanced apoptosis of DDP‐resistant cells. Circ_0002360 could elevate ZNF300 expression. DDP resistance and lung cancer progression were also impeded by ZNF300 downregulation. ZNF300 overexpression reversed the function of circ_0002360 knockdown in DDP‐resistant lung cancer cells. The regulation of circ_0002360 for ZNF300 was achieved by sponging miR‐6751‐3p. Circ_0002360 promoted DDP resistance in xenograft mice through mediating the miR‐6751‐3p/ZNF300 axis.ConclusionCirc_0002360 targeted miR‐6751‐3p to regulate ZNF300 level, thus elevating DDP resistance and promoting the malignant progression of lung cancer cells.

RAP1/TERF2IP-A Multifunctional Player in Cancer Development.

Simple SummaryRAP1 (TERF2IP) is a member of the shelterin complex that protects telomeric DNA and plays a critical role in maintaining chromosome stability. However, mammalian RAP1 was recently found to have additional functions apart from telomeres, acting as a regulator of the NF-κB pathway and transcription factor, and has been suggested that they have putative roles in cancer development. Here, we focus on the main roles of RAP1 in different mechanisms of oncogenesis, progression, and chemoresistance, and consider the clinical significance of findings about its regulation and biological functions.Mammalian RAP1 (TERF2IP), the most conserved shelterin component, plays a pleiotropic role in the regulation of a variety of cellular processes, including cell metabolism, DNA damage response, and NF-κB signaling, beyond its canonical telomeric role. Moreover, it has been demonstrated to be involved in oncogenesis, progression, and chemoresistance in human cancers. Several mutations and different expression patterns of RAP1 in cancers have been reported. However, the functions and mechanisms of RAP1 in various cancers have not been extensively studied, suggesting the necessity of further investigations. In this review, we summarize the main roles of RAP1 in different mechanisms of cancer development and chemoresistance, with special emphasis on the contribution of RAP1 mutations, expression patterns, and regulation by non-coding RNA, and briefly discuss telomeric and non-telomeric functions.

CircPRDM2 Contributes to Doxorubicin Resistance of Osteosarcoma by Elevating EZH2 via Sponging miR-760.

BackgroundCircular RNAs (circRNAs) are implicated in the chemoresistance of human cancers. However, the functions of circRNA PR/SET domain 2 (circPRDM2) in the resistance of osteosarcoma (OS) to doxorubicin (DXR) are unknown.MethodsQuantitative real-time polymerase chain reaction (qRT-PCR) assay was conducted to determine the levels of circPRDM2, microRNA-760 (miR-760) and enhancer of zeste homolog 2 (EZH2). RNase R assay was used to analyze the characteristics of circPRDM2. IC50 of DXR was estimated by Cell Counting Kit-8 (CCK-8) assay. Colony formation assay was performed for cell colony formation ability. Wound-healing assay and transwell assay were utilized for cell migration and invasion. Flow cytometry analysis was conducted for cell apoptosis. Western blot assay was employed for protein levels. Dual-luciferase reporter assay, RNA immunoprecipitation (RIP) assay and RNA pull-down assay were adopted to analyze the relationships among circPRDM2, miR-760 and EZH2. Murine xenograft model assay was utilized to explore DXR resistance in vivo.ResultsCircPRDM2 level was enhanced in DXR-resistant OS tissues and cells. CircPRDM2 deficiency inhibited IC50 of DXR, colony formation, migration and invasion and facilitated apoptosis in DXR-resistant OS cells in vitro. CircPRDM2 was identified as the sponge for miR-760. MiR-760 inhibition reversed the inhibitory effects of circPRDM2 knockdown on DXR resistance and cell progression in DXR-resistant OS cells. Moreover, EZH2 was identified as the target gene of miR-760 and EZH2 overexpression abolished miR-760-mediated impacts on DXR sensitivity and malignant behaviors in DXR-resistant OS cells. Also, circPRDM2 silencing improved DXR sensitivity in vivo.ConclusionOur study demonstrated the role of circPRDM2/miR-760/EZH2 axis in enhancing DXR resistance.

Long non-coding RNA LINC00173 enhances cisplatin resistance in hepatocellular carcinoma via the microRNA-641/RAB14 axis.

A growing body of evidence indicates that long non-coding RNAs (lncRNAs) play crucial roles in the chemoresistance of human cancers. However, the molecular mechanisms underlying the functions of certain lncRNAs in the chemotherapeutic resistance of hepatocellular carcinoma (HCC) remain unclear. The aim of the present study was to investigate the function and potential mechanism of action of lncRNA LINC00173 in HCC cisplatin (DDP) resistance. Reverse transcription-quantitative PCR analysis indicated that LINC00173 was highly expressed in DDP-resistant HCC tissues and cell lines, and high expression levels of LINC00173 were found to be associated with poor prognosis in patients with HCC. Moreover, LINC00173-knockdown improved the DDP sensitivity of DDP-resistant HCC cells. A luciferase reporter assay also demonstrated that microRNA (miR)-641 was a direct target of LINC00173. miR-641 inhibition restored the promoting effect of LINC00173 knockdown on DDP sensitivity in HCC cells. Furthermore, RAB14 was identified as a target of miR-641, and RAB14 overexpression restrained the inducing effect of LINC00173 knockdown on HCC cell DDP sensitivity. The findings of the present study demonstrated that LINC00173 increased DDP resistance in HCC via the miR-641/RAB14 axis, which may represent a promising therapeutic strategy for HCC.

Exosomes Derived From Macrophages Enhance Aerobic Glycolysis and Chemoresistance in Lung Cancer by Stabilizing c-Myc via the Inhibition of NEDD4L.

As one of the most common and lethal cancer, lung cancer severely threatens the health of human. It has been reported that tumor-associated macrophages promote initiation, progression, as well as chemoresistance in human cancers. However, the underneath molecular mechanism that drives chemoresistance in lung cancer is yet not fully characterized. In this article, we demonstrated that M2 macrophage-derived exosomes (MDE) is the key factor to promote cisplatin-resistance in lung cancer. MDE exhibited high expression level of several miRNA including miR-3679-5p. Mechanistically, miR-3679-5p was delivered to lung cancer cells by MDE, downregulating the expression of a known E3 ligase, NEDD4L, which has been identified as a key regulator controlling the stability of c-Myc. Such decreased NEDD4L expression level resulted in the stabilization of c-Myc and elevated glycolysis. The enhanced glycolysis drives the chemoresistance in lung cancer. Taken together, our findings not only show that M2 macrophage induce chemoresistance in lung cancer through MDE mediated miR-3679-5R/NEDD4L/c-Myc signaling cascade, but also shed the light on the mechanism of the cross-talk between M2 macrophage and lung cancers. By pinpointing a potential novel survival signaling pathway, our data could provide a new potential therapeutic target for lung cancer treatment and management.

Circ-RNF111 contributes to paclitaxel resistance in breast cancer by elevating E2F3 expression via miR-140-5p.

BackgroundCircular RNAs (circRNAs) have been demonstrated to act as key regulators in the chemoresistance of human cancers, including breast cancer (BC). Here, we aimed to explore the role of circ‐RNF111 in paclitaxel (PTX) resistance of BC.MethodsQuantitative real‐time polymerase chain reaction (qRT‐PCR) was employed to determine the expression of circ‐RNF111, microRNA‐140‐5p (miR‐140‐5p) and E2F transcription factor 3 (E2F3) mRNA. The half maximal inhibitory concentration (IC50) of PTX, cell viability, colony formation and cell invasion were assessed by cell counting kit‐8 (CCK‐8) assay, colony formation assay and transwell assay, respectively. Glucose consumption and lactate production were determined by specific kits. A murine xenograft model was established to investigate the role of circ‐RNF111 in PTX resistance of BC in vivo. Dual‐luciferase reporter assay and RNA immunoprecipitation (RIP) assay were performed to verify the relationship between miR‐140‐5p and circ‐RNF111 or E2F3. Western blot assay was conducted to examine the protein level of E2F3.ResultsCirc‐RNF111 was upregulated in PTX‐resistant BC tissues and cells. Circ‐RNF111 knockdown restrained IC50 of PTX, cell viability, colony numbers, cell invasion and glycolysis in PTX‐resistant BC cells in vitro and enhanced PTX sensitivity in vivo. MiR‐140‐5p was a target of circ‐RNF111 and miR‐140‐5p expression was negatively correlated with circ‐RNF111 expression in BC tissues. The effect of circ‐RNF111 knockdown on PTX resistance was rescued by miR‐140‐5p deletion. Additionally, miR‐140‐5p could interact with E2F3 and negatively regulate E2F3 expression. Moreover, miR‐140‐5p suppressed IC50 of PTX, cell viability, colony numbers, cell invasion and glycolysis by targeting E2F3.ConclusionsCirc‐RNF111 improved PTX resistance of BC by upregulating E2F3 via sponging miR‐140‐5p.

TCRP1 induces tamoxifen resistance by promoting the activation of SGK1 in MCF‑7 cells.

Tamoxifen is widely used as a highly effective drug for treating estrogen-receptor (ER) alpha-positive breast cancer. However, tamoxifen resistance developed during cancer treatment remains a significant challenge. Tongue cancer resistance-related protein1 (TCRP1), which is recognized as a novel drug target, is related to chemo-resistance in human cancers, moreover, it is often overexpressed in various cancer cells, such as in lung cancer, breast cancer, and tongue cancer. However, the effects of TCRP1 on tamoxifen-resistant breast cancer cells and tissues are far from clear. The present study revealed that TCRP1 induced tamoxifen resistance in breast cancer cells. Western blotting, quantitative real-time polymerase chain reaction (RT-PCR) and immunohistochemical staining were performed to detect the expression level of TCRP1 in vivo and in vitro between primary breast cancer tissues and tamoxifen-resistant breast cancer tissues. The data revealed that the expression of TCRP1 was upregulated in the tamoxifen-resistant breast cancer tissues and human breast cancer cell line, MCF-7. Further study revealed that knocking down TCRP1 inhibited the growth of MCF-7 cells with tamoxifen-resistance (MCF7-R cells) and induced cell apoptosis. Moreover, TCRP1 promoted serum- and glucocorticoid-inducible kinase 1 (SGK1) activation via phosphorylation of phosphoinositide-dependent kinase 1 (PDK1) in MCF7-R cells. In addition, it was also observed that knocking down TCRP1 inhibited tumorigenesis of MCF-7 cells in nude mice. In conclusion, these data indicated that TCRP1 could induce tamoxifen resistance by regulating the PDK1/SGK1 signaling pathway. Thus, TCRP1 could be explored as a promising candidate for treating tamoxifen-resistant breast cancer in the future.

Long noncoding RNA PVT1 acts as an oncogenic driver in human pan-cancer.

Increasing evidence indicates that long noncoding RNAs (lncRNAs) play pivotal roles during tumorigenesis in multiple types of cancers. However, little is known about the exact role of plasmacytoma variant translocation 1 (PVT1) in human pan-cancer. Here, we report the oncogenic role and function of PVT1 in human pan-cancer, including breast cancer. The expression of PVT1 in human tumor tissues and nontumor tissues, the upstream regulation of PVT1 and the relationship between its expression and prognosis and chemoresistance were examined by using The Cancer Genome Atlas data. PVT1 expression is higher in human cancer tissues compared with adjacent noncancerous tissues, and patients with high levels of PVT1 expression usually have tumors with a higher TNM stage. High PVT1 expression is also associated with worse disease outcomes in patients with cancer. Hypomethylation and transcription factor binding in the PVT1 promoter locus activates its transcriptional expression. Guilt by association analysis revealed that PVT1 may be involved in processes associated with tumorigenesis. Moreover, PVT1 may trigger chemoresistance in human cancer. These results indicated that PVT1 may act as an oncogenic driver and maybe a potential therapeutic target in human cancer.

Gercumin synergizes the action of 5-fluorouracil and oxaliplatin against chemoresistant human cancer colon cells

Advanced colon cancer is extremely difficult to cure, underscoring the need to develop novel therapeutic agents. Prenylated curcumins that are semisynthetic curcumin derivatives with significant anti-cancer potential have been studied herein to assess their therapeutic potential for colon cancer and tested to this aim in vitro for their growth inhibitory properties against 5-fluorouracil + oxaliplatin resistant human colon cancer CR-HT29 and HCT-116 cells. The resulting most active product, gercumin (mono-O-geranylcurcumin), has been further tested for its synergistic effects with FOLFOX (a combination of 5-fluorouracil and oxaliplatin) on the same cell lines. Activity of this combination on colonosphere formation was also investigated. Gercumin was able to suppress the growth of cancer cells with a potency similar to that of curcumin. A synergistic effect of this compound and FOLFOX was also observed. doses tested for synergy in the colonosphere assays did not show greater suppression of colonosphere formation than independent treatment with either reagent alone. Only one of the combinations was shown to be more effective at suppressing colonosphere formation [gercumin 5 μM + FOLFOX (2x)]. Thus, the growth inhibitory effects of curcumin against human cancer cells can be modulated and enhanced by the introduction of hydrophobic chains, normally found in several natural compounds, like the geranyl one. Such compounds are also able to synergize with known chemotherapeutics.

Circ_0003418 Inhibits Tumorigenesis And Cisplatin Chemoresistance Through Wnt/β-Catenin Pathway In Hepatocellular Carcinoma.

BackgroundAccumulating evidences indicate that circRNAs play important roles in the progression and chemoresistance of human cancers. The present study is designated for researching the roles of circ_0003418 in hepatocellular carcinoma (HCC).MethodsWe detected the expression profile of circ_0003418 in human HCC tissues and cell lines by quantitative real-time-PCR assays. CCK-8 assay, transwell migration assay, transwell invasion assay and drug-sensitivity analysis were carried out to estimate the effects of circ_0003418 on HCC cells' proliferation, migration, invasion and resistance to cisplatin, respectively. Mouse xenograft model was conducted to monitor the role of circ_0003418 in cisplatin resistance in vivo. Western blotting was performed to explore the changes of the Wnt/β-catenin pathway after knockdown of circ_0003418. The rescue experiment was carried out to explore circ_0003418-activated biological functions through Wnt/β-catenin pathway.ResultsThe expression level of circ_0003418 was downregulated in HCC tissues and cell lines, and the level correlated with tumor size, TNM stage and HBsAg level in HCC patients. circ_0003418 knockdown promoted HCC cells' proliferation, migration, and invasion. Additionally, suppression of circ_0003418 enhanced cisplatin resistance of HCC cells in vivo and vitro. Knockdown of circ_0003418 activated the Wnt/β-catenin signalling pathway in HCC cells. The effect of circ-0003418 on sensitivity of HCC cells to cisplatin was reversed after inhibition of Wnt/β-catenin pathway.Conclusioncirc-0003418 exerts an antitumorigenic role in HCC and advances the sensitivity of HCC cells to cisplatin by restraining the Wnt/β-catenin pathway. Thus, circ-0003418 may represent a novel biomarker and provide us a new strategy for the treatment of HCC.

Long noncoding RNA FER1L4 acts as an oncogenic driver in human pan‐cancer

The function of Fer-1 like family member 4 (FER1L4) in human pan-cancer is unknown. Expression of FER1L4 in tumor tissues and nontumor tissues, upstream regulation of FER1L4, and the relationship between its expression with prognosis and chemoresistance were examined by The Cancer Genome Atlas and Gene Expression Omnibus databases. Next, these results were validated in breast tumor and paired nontumor tissues in our cohort. FER1L4 expression is higher in tumor tissues compared with the adjacent nontumor tissues. High FER1L4 expression is associated with worse disease outcomes. Hypomethylation and H3K4me3 accumulation in FER1L4 promoter locus activate its transcriptional expression. Moreover, FER1L4 may trigger chemoresistance in human cancer. Gene Ontology enrichment analysis revealed that FER1L4 may be involved in processes associated with tumorigenesis. These results indicated that FER1L4 may act as an oncogenic driver and it may be a potential therapy target in human cancer.

Highlights of This Issue

MAIT cells are most enriched in the liver, comprising up to 50% of all intrahepatic T cells. Duan and colleagues aimed at determining the distribution, phenotype, function, and clinical relevance of MAIT cells in human HCC. They found that HCC-infiltrating MAIT cells' cytotoxic capability was significantly impaired with upregulation of PD-1, CTLA-4 and TIM-3. Still worse, infiltrating MAIT cells were reprogramed to a tumor-promoting direction as exemplified by RNA-seq, cytokine secretion profile and in vitro coculture assay, and correlated with dismal clinical outcomes. This study shows promise for modulating MAIT cells' function in antitumor therapy in HCC.Overcoming tumor-related immunosuppression presents a significant obstacle to successful cancer treatment. To activate the host's antitumor immunity, Viitala and colleagues exploited macrophage reprogramming as an alternative approach to stimulate CD8+ T-cell–mediated tumor cell killing. Genetic deficiency or immunotherapeutic targeting of macrophage Clever-1 induced IL-12 secretion and MHCII expression by tumor-associated macrophages, and markedly impaired solid tumor growth in multiple syngeneic mouse tumor models. Notably, the effects were similar to those achieved by PD-1 checkpoint inhibition, and thus support the clinical evaluation of Clever-1 blockade as a novel cancer treatment strategy.NOTCH1 loss-of-function mutations are common in head and neck squamous cell carcinoma (HNSCC). Sambandam and colleagues demonstrate that NOTCH1-mutant HNSCC undergoes cell death when exposed to PI3K inhibitors, which was linked to drug-induced suppression of PDK1. In contrast, PIK3CA mutant cell lines merely undergo cell cycle arrest when exposed to the same drugs. This is the first study to establish a therapeutic vulnerability of NOTCH1-mutant HNSCC to any class of drugs and may inform the development of the first biomarker-driven therapy for HNSCC. This research led to the initiation of a clinical trial testing a PI3K/mTOR inhibitor in NOTCH1 mutant HNSCC (NCT03740100).Chemokine receptor CXCR2 drives immune escape and chemoresistance in human cancers. To explore its role in gastric cancer (GC) metastasis, Zhou and colleagues established the lymph node metastasis model and a coculture system of GC cells and macrophages to demonstrate that macrophages promote migration of GC by activating a CXCR2/STAT3 feed-forward loop in a CXCL1/CXCL5-dependent manner, and GC cells increase the expression of CXCL1/CXCL5 in macrophages by secreting TNF-α. This study identified a CXCR2 dominated cross-talk between GC cells and macrophages, and thus provides a potential therapeutic target for GC treatment.

Abstract 1901: Structural basis for selective therapeutic targeting of BFL-1 in cancer by a covalent stapled peptide inhibitor

Abstract BCL-2 family proteins are master regulators of the mitochondrial apoptotic pathway and dictate whether a cell will live or die in response to stress. Cancer cells hijack the anti-apoptotic arm of this signaling network, overexpressing BCL-2, MCL-1, and BFL-1, to enforce cellular immortality. Whereas BCL-2 has been drugged by the selective small-molecule inhibitor, venetoclax, and new MCL-1 inhibitor molecules have just entered phase I clinical testing, anti-apoptotic BFL-1 remains undrugged. Importantly, the expression of BFL-1 can cause resistance to these molecules and has been independently linked to the pathogenesis and chemoresistance of human cancers, including melanomas and hematologic malignancies. Given the emergence of BCL-2 family proteins as high-priority cancer targets, solving their structures, alone and in complex with their natural BH3 domain ligands, yields important blueprints for drug design. Whereas the structures of numerous “BH3-in-groove” complexes have been solved, the corresponding panel of apo structures remains incomplete. Here, we report the crystal structure of apo BFL-1 at 1.69 Å resolution, revealing similarities and key differences among unliganded anti-apoptotic targets. Unlike all other BCL-2 proteins, apo BFL-1 contains a surface-accessible cysteine within its BH3-binding groove, allowing for selective covalent targeting by BH3-based stapled peptide inhibitors. The crystal structure of a complex between BFL-1 and a cysteine-reactive and stapled NOXA BH3 α-helix demonstrated the sulfhydryl bond and fortuitous interactions between the acrylamide-bearing moiety and a newly formed hydrophobic cavity. Comparison of the apo and BH3-liganded structures further revealed an induced conformational change. The two BFL-1 structures expand our understanding of the surface landscapes available for selective targeting of BFL-1, and inform a new therapeutic strategy for overcoming BFL-1-dependent apoptotic blockades in human cancer. Citation Format: Edward P. Harvey, Hyuk-Soo Seo, Rachel M. Guerra, Gregory H. Bird, Sirano Dhe-Paganon, Loren D. Walensky. Structural basis for selective therapeutic targeting of BFL-1 in cancer by a covalent stapled peptide inhibitor [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 1901.

Dynamic Regulation of Long-Chain Fatty Acid Oxidation by a Noncanonical Interaction between the MCL-1 BH3 Helix and VLCAD

MCL-1 is a BCL-2 family protein implicated in the development and chemoresistance of human cancer. Unlike its anti-apoptotic homologs, Mcl-1 deletion has profound physiologic consequences, indicative of a broader role in homeostasis. We report that the BCL-2 homology 3 (BH3) α helix of MCL-1 can directly engage very long-chain acyl-CoA dehydrogenase (VLCAD), a key enzyme of the mitochondrial fatty acid β-oxidation (FAO) pathway. Proteomic analysis confirmed that the mitochondrial matrix isoform of MCL-1 (MCL-1Matrix) interacts with VLCAD. Mcl-1 deletion, or eliminating MCL-1Matrix alone, selectively deregulated long-chain FAO, causing increased flux through the pathway in response tonutrient deprivation. Transient elevation in MCL-1 upon serum withdrawal, a striking increase in MCL-1 BH3/VLCAD interaction upon palmitic acid titration, and direct modulation of enzymatic activity by the MCL-1 BH3 α helix are consistent with dynamic regulation. Thus, the MCL-1 BH3 interaction with VLCAD revealed a separable, gain-of-function role for MCL-1 in the regulation of lipid metabolism.

KDM5B demethylates H3K4 to recruit XRCC1 and promote chemoresistance

Chemotherapy is the main treatment for human cancers including gastric cancer. However, in response to chemotherapeutic drugs, tumor cells can develop drug resistance by reprogramming intracellular metabolic and epigenetic networks to maintain their intrinsic homeostasis. Previously, we have established cisplatin-resistant gastric cancer cells as a drug resistant model, and elucidated the XRCC1 as the core DNA repair mechanism of drug resistance. This study investigated the regulation of XRCC1 by lysine demethylase 5B (KDM5B) in drug resistance. We found that the methylation level of H3K4 decreased significantly in drug-resistant cells. The chemical inhibitor of H3K4 demethylases, JIB-04, restored the methylation of H3K4 and blocked the co-localization of XRCC1 and γH2AX, eventually improved drug sensitivity. We further found that the expression level of KDM5B increased significantly in drug-resistant cells. Knockdown of KDM5B increased the methylation level of H3K4 and blocked the localization of XRCC1 to the DNA damage site, leads to increased drug sensitivity. In the sensitive cells, overexpression of KDM5B suppressed H3K4 methylation levels, which resulted to resistance to cisplatin. Moreover, we found that the posttranslational modification of KDM5B is responsible for its high expression in drug-resistant cells. Through mass spectrometry screening and co-immunoprecipitation validation, we found that the molecular chaperone HSP90 forms a complex with KDM5B in drug resistance cells. Interestingly, HSP90 inhibitor 17-AAG induced KDM5B degradation in a time-and-dose-dependent manner, indicating that HSP90 protected KDM5B from protein degradation. Targeting inhibition of HSP90 and KDM5B reversed drug resistance both in vitro and in vivo. Taken together, molecular chaperon HSP90 interacted with KDM5B to protect it from ubiquitin-dependent proteasomal degradation. Increased KDM5B demethylated H3K4 and facilitated the recruitment of XRCC1 to repair damaged DNA. Therefore, inhibition of HSP90 or KDM5B represented a novel approach to reverse chemoresistance in human cancers.