Long Noncoding RNA RP11-278A23.1, a Potential Modulator of p53 Tumor Suppression, Contributes to Colorectal Cancer Progression.

Recently, many studies revealed that long noncoding RNAs (lncRNAs) play important roles in cancers. To identify lncRNAs contributing to colorectal cancers, we screened lncRNAs through expression and survival analyses in datasets from The Cancer Genome Atlas (TCGA). The screen revealed that RP11-278A23.1 expression is significantly increased in colorectal cancer tissues compared with normal tissues and that high RP11-278A23.1 expression correlates with poor prognosis. The knockdown of RP11-278A23.1 inhibited the growth of and promoted apoptosis in colorectal cancer cells. Next, to comprehensively examine differentially expressed genes after RP11-278A23.1 knockdown, RNA sequencing was performed in HCT116 cells. The expression of p21, a p53 target gene, was significantly upregulated, and the expression of several p53 target proapoptotic genes was also altered. RP11-278A23.1 knockdown increased p53 expression at the translational level but not at the transcriptional level. Interestingly, RP11-278A23.1 knockdown also altered the expression of these proapoptotic genes in DLD1 cells with mutated p53 and in p53-knockout HCT116 cells. These results suggest that RP11-278A23.1 modifies the expression of these apoptosis-related genes in p53-dependent and p53-independent manners. In summary, lncRNA RP11-278A23.1 contributes to colorectal cancer progression by promoting cell growth and inhibiting apoptosis, suggesting that this lncRNA may be a useful therapeutic target.

Astrocyte-induced mGluR1 activates human lung cancer brain metastasis via glutamate-dependent stabilization of EGFR.

There are limited methods to stably analyze the interactions between cancer cells and glial cells in vitro, which hinders our molecular understanding. Here, we develop a simple and stable culture method of mouse glial cells, termed mixed-glial culture on/in soft substrate (MGS), which serves well as a platform to study cancer-glia interactions. Using this method, we find that human lung cancer cells become overly dependent on metabotropic glutamate receptor 1 (mGluR1) signaling in the brain microenvironment. Mechanistically, interactions with astrocytes induce mGluR1 in cancer cells through the Wnt-5a/prickle planar cell polarity protein 1 (PRICKLE1)/RE1 silencing transcription factor (REST) axis. Induced mGluR1 directly interacts with and stabilizes the epidermal growth factor receptor (EGFR) in a glutamate-dependent manner, and these cells then become responsive to mGluR1 inhibition. Our results highlight increased dependence on mGluR1 signaling as an adaptive strategy and vulnerability of human lung cancer brain metastasis.

TM4SF1-AS1 inhibits apoptosis by promoting stress granule formation in cancer cells.

Long noncoding RNAs (lncRNAs) play pivotal roles in tumor development. To identify dysregulated lncRNAs in gastric cancer (GC), we analyzed genome-wide trimethylation of histone H3 lysine 4 (H3K4me3) to screen for transcriptionally active lncRNA genes in the non-tumorous gastric mucosa of patients with GC and healthy individuals. We found that H3K4me3 at TM4SF1-AS1 was specifically upregulated in GC patients and that the expression of TM4SF1-AS1 was significantly elevated in primary and cultured GC cells. TM4SF1-AS1 contributes to GC cell growth in vitro and in vivo, and its oncogenic function is mediated, at least in part, through interactions with purine-rich element-binding protein α (Pur-α) and Y-box binding protein 1 (YB-1). TM4SF1-AS1 also activates interferon signaling in GC cells, which is dependent on Pur-α and RIG-I. Chromatin isolation by RNA purification (ChIRP)-mass spectrometry demonstrated that TM4SF1-AS1 was associated with several stress granule (SG)-related proteins, including G3BP2, RACK1, and DDX3. Notably, TM4SF1-AS1 promoted SG formation and inhibited apoptosis in GC cells by sequestering RACK1, an activator of the stress-responsive MAPK pathway, within SGs. TM4SF1-AS1-induced SG formation and apoptosis inhibition are dependent on Pur-α and YB-1. These findings suggested that TM4SF1-AS1 contributes to tumorigenesis by enhancing SG-mediated stress adaptation.

MYEOV overexpression induced by demethylation of its promoter contributes to pancreatic cancer progression via activation of the folate cycle/c-Myc/mTORC1 pathway.

BACKGROUND: While molecular targeted drugs and other therapies are being developed for many tumors, pancreatic cancer is still considered to be the malignant tumor with the worst prognosis. We started this study to identify prognostic genes and therapeutic targets of pancreatic cancer. METHODS: To comprehensively identify prognostic genes in pancreatic cancer, we investigated the correlation between gene expression and cancer-specific prognosis using transcriptome and clinical information datasets from The Cancer Genome Atlas (TCGA). In addition, we examined the effects of the suppression of candidate prognostic genes in pancreatic cancer cell lines. RESULT: We found that patients with high expression levels of MYEOV, a primate-specific gene with unknown function, had significantly shorter disease-specific survival times than those with low expression levels. Cox proportional hazards analysis revealed that high expression of MYEOV was significantly associated with poor survival and was an independent prognostic factor for disease-specific survival in pancreatic cancer patients. Analysis of multiple cancer samples revealed that the MYEOV promoter region is methylated in noncancer tissues but is demethylated in tumors, causing MYEOV overexpression in tumors. Notably, the knockdown of MYEOV suppressed the expression of MTHFD2 and other folate metabolism-related enzyme genes required for the synthesis of amino acids and nucleic acids and also restored the expression of c-Myc and mTORC1 repressors. CONCLUSION: There is a significant correlation between elevated MYEOV expression and poor disease-specific survival in pancreatic cancer patients. MYEOV enhances the activation of several oncogenic pathways, resulting in the induction of pancreatic cancer cell proliferation. Overall, MYEOV acts as an oncogene in pancreatic cancer. Furthermore, MYEOV may be a prognostic biomarker and serve as an 'actionable' therapeutic target for pancreatic cancers.

Multiomics identifies the link between intratumor steatosis and the exhausted tumor immune microenvironment in hepatocellular carcinoma.

BACKGROUND AND AIMS: Immunotherapy has become the standard-of-care treatment for hepatocellular carcinoma (HCC), but its efficacy remains limited. To identify immunotherapy-susceptible HCC, we profiled the molecular abnormalities and tumor immune microenvironment (TIME) of rapidly increasing nonviral HCC. APPROACHES AND RESULTS: We performed RNA-seq of tumor tissues in 113 patients with nonviral HCC and cancer genome sequencing of 69 genes with recurrent genetic alterations reported in HCC. Unsupervised hierarchical clustering classified nonviral HCCs into three molecular classes (Class I, II, III), which stratified patient prognosis. Class I, with the poorest prognosis, was associated with TP53 mutations, whereas class III, with the best prognosis, was associated with cadherin-associated protein beta 1 (CTNNB1) mutations. Thirty-eight percent of nonviral HCC was defined as an immune class characterized by a high frequency of intratumoral steatosis and a low frequency of CTNNB1 mutations. Steatotic HCC, which accounts for 23% of nonviral HCC cases, presented an immune-enriched but immune-exhausted TIME characterized by T cell exhaustion, M2 macrophage and cancer-associated fibroblast (CAF) infiltration, high PD-L1 expression, and TGF-ß signaling activation. Spatial transcriptome analysis suggested that M2 macrophages and CAFs may be in close proximity to exhausted CD8+ T cells in steatotic HCC. An in vitro study showed that palmitic acid-induced lipid accumulation in HCC cells upregulated PD-L1 expression and promoted immunosuppressive phenotypes of cocultured macrophages and fibroblasts. Patients with steatotic HCC, confirmed by chemical-shift MR imaging, had significantly longer PFS with combined immunotherapy using anti-PD-L1 and anti-VEGF antibodies. CONCLUSIONS: Multiomics stratified nonviral HCCs according to prognosis or TIME. We identified the link between intratumoral steatosis and immune-exhausted immunotherapy-susceptible TIME.

Prevalence of Pathogenic Germline BRCA1/2 Variants and Their Association with Clinical Characteristics in Patients with Epithelial Ovarian Cancer in a Rural Area of Japan.

The prevalence of germline BRCA1 or BRCA2 pathogenic variants (gBRCA1/2-PV) in patients with primary epithelial ovarian cancer (OC) in a rural area of Japan and their association with clinical characteristics, including treatment response and survival outcome, were investigated. A total of 123 unbiased patients with OC were tested for gBRCA1 and gBRCA2 using next-generation sequencing-based targeted amplicon sequencing. Clinical characteristics of OC patients with and without gBRCA1/2 status were compared. The overall prevalence of gBRCA1/2-PV was 15.4% (19 cases), with gBRCA2-PV (10.5%, 13 cases) being more common than gBRCA1-PV (4.9%, 6 cases). Among the observed gBRCA1/2-PV, several novel variants were included, suggesting that gBRCA1/2-PV unique to the local area exist. gBRCA1/2-PV was significantly more prevalent in OC patients at an older age, with high-grade serous carcinoma, with advanced-stage tumors, and with a family history of breast cancer or hereditary breast and ovarian cancer syndrome (HBOC)-associated cancers. Patients with advanced-stage OC with gBRCA1/2-PV showed a significantly lower recurrence rate and tended to have better progression-free and overall survival than those with wild-type gBRCA1/2. Genetic testing for gBRCA1/2 status in all OC patients is useful not only for diagnosing HBOC in patients and their relatives to assess the risk of HBOC-associated cancers, but also to estimate therapy response and outcomes in patients.

Inhibition of EGFR and MEK surmounts entrectinib resistance in a brain metastasis model of NTRK1-rearranged tumor cells.

Tropomyosin receptor kinase (TRK) inhibitors have demonstrated histology-agnostic efficacy in patients with neurotrophic receptor tyrosine kinase (NTRK) gene fusion. Although responses to TRK inhibitors can be dramatic and durable, duration of response may eventually be limited by acquired resistance via several mechanisms, including resistance mutations such as NTRK1-G595R. Repotrectinib is a second-generation TRK inhibitor, which is active against NTRK1-G595R. However, its efficacy against entrectinib-resistant tumors has not been fully elucidated. In the present study, we established entrectinib-resistant tumor cells (M3B) in a brain metastasis model inoculated with NTRK1-rearranged KM12SM cells and examined the sensitivity of M3B cells to repotrectinib. While M3B cells harbored the NTRK1-G595R mutation, they were unexpectedly resistant to repotrectinib. The resistance was due to extracellular signal-regulated kinase (ERK) reactivation partially mediated by epidermal growth factor receptor (EGFR) activation. We further demonstrate that the triplet combination of repotrectinib, EGFR inhibitor, and MEK inhibitor could sensitize M3B cells in vitro as well as in a brain metastasis model. These results indicate that resistant mutations, such as NTRK1-G595R, and alternative pathway activation, such as ERK activation, could simultaneously occur in entrectinib-resistant tumors, thereby causing resistance to second-generation inhibitor repotrectinib. These findings highlight the importance of intensive examinations to identify resistance mechanisms and application of the appropriate combination treatment to circumvent the resistance.

Dead or alive? Pitfall of survival analysis with TCGA datasets.

We often encounter situations in which data from the TCGA that have been analyzed in papers we read or reviewed cannot be reproduced, even when TCGA datasets are used, especially in survival analyses. Therefore, we attempted to confirm the data source for TCGA survival analysis and found that several websites used to analyze the survival data of TCGA datasets inappropriately handle the survival data, causing differences in statistical analyses. This causes the misinterpretation of results because figures of survival analysis results in several papers are sometimes exactly as generated by these sites, and the results depend on only the tools provided by these sites. We would like to make this situation widely known and raise the problem for scientific soundness.

Early dynamics of circulating tumor DNA predict chemotherapy responses for patients with esophageal cancer.

We investigated whether early circulating tumor DNA (ctDNA) changes, measured using digital PCR (dPCR), can predict later chemotherapy responses in esophageal squamous cell cancer (ESCC). We compared the dynamics of ctDNA and tumor volumes during chemotherapy in 42 ESCC. The accuracy of predictions of later chemotherapy responses was evaluated by the ratio of the variant allele frequency of ctDNA (post-/pre-ctDNA) and the total tumor volume (post-/pre-volume) before and after an initial chemotherapy cycle using a receiver-operating characteristic curve analysis. Total positive and negative objective responses (ORs) were defined as either >50 or ≤50% reductions, respectively, in the total tumor volume at the end of first-line chemotherapy. Mutation screening of 43 tumors from 42 patients revealed 96 mutations. The pretreatment dPCR-ctDNA data were informative in 38 patients, using 70 selected mutations (1-3 per patient). The areas under the curve (AUCs) for the post-/pre-volume and post-/pre-ctDNA levels used in predicting the total OR were 0.85 and 0.88, respectively. The optimal cutoff value of post-/pre-ctDNA was 0.13. In 20 patients with post-/pre-volume ≥50%, the total OR could be predicted by the post-/pre-ctDNA with high accuracy; the AUC by post-/pre-ctDNA was higher than that by post-/pre-volume (0.85 versus 0.76, respectively). Patients with low post-/pre-ctDNA (n = 18) had a significantly better overall survival rate than those with high post-/pre-ctDNA (n = 20; P = 0.03). Early ctDNA changes after an initial cycle of chemotherapy predict later responses to treatment with high accuracy in ESCC patients.

Detection of novel fusion genes by next-generation sequencing-based targeted RNA sequencing analysis in adenoid cystic carcinoma of head and neck.

OBJECTIVE: Adenoid cystic carcinoma (AdCC) is a rare, indolent salivary gland tumor that is reported to be driven by fusion genes. However, MYB/MYBL1-NFIB fusions have been detected in <60% of all AdCC cases and the oncogenic driver mutations in approximately 40% of AdCC remain unknown. Our aim was to identify novel gene fusions in AdCC. STUDY DESIGN: We investigated 20 AdCC cases using a targeted RNA sequencing panel to identify gene fusions and performed quantitative real-time reverse transcription polymerase chain reaction to assess MYB, MYBL1, and NFIB expression levels. RESULTS: A total of 36 fusion transcripts in 15 cases were detected and validated by Sanger sequencing. The MYB-NFIB and MYBL1-NFIB fusion genes were detected in 9 and 3 cases, respectively, in a mutually exclusive manner. Furthermore, novel gene fusions, namely, NFIB-EPB41L2, MAP7-NFIB, NFIB-MCMDC2, MYBL1-C8orf34, C8orf34-NFIB, and NFIB-CASC20, were identified. Among them, NFIB-EPB41L2 and NFIB-MCMDC2 are thought to activate MYB and MYBL1 expression, respectively, through the insertion of a genomic segment in proximity to MYB and MYBL1 genes, respectively. CONCLUSION: Six novel gene fusions other than MYB/MYBL1-NFIB were identified. The detection of novel fusion genes and investigation of the molecular mechanism will contribute to the development of novel molecular targeted therapies for this disease.

Functionally confirmed compound heterozygous ADAM17 missense loss-of-function variants cause neonatal inflammatory skin and bowel disease 1.

A disintegrin and metalloprotease 17 (ADAM17) is the major sheddase that processes more than 80 substrates, including tumour necrosis factor-α (TNFα). The homozygous genetic deficiency of ADAM17 causing a complete loss of ADAM17 expression was reported to be linked to neonatal inflammatory skin and bowel disease 1 (NISBD1). Here we report for the first time, a family with NISBD1 caused by functionally confirmed compound heterozygous missense variants of ADAM17, namely c.1699T>C (p.Cys567Arg) and c.1799G>A (p.Cys600Tyr). Both variants were detected in two siblings with clinical features of NISBD1, such as erythroderma with exudate in whole body, recurrent skin infection and sepsis and prolonged diarrhoea. In a cell-based assay using Adam10/17 double-knockout mouse embryonic fibroblasts (Adam10/17-/- mEFs) exogenously expressing each of these mutants, phorbol 12-myristate 13-acetate-stimulated shedding was strongly reduced compared with wild-type ADAM17. Thus, in vitro functional assays demonstrated that both missense variants cause the loss-of-function of ADAM17, resulting in the development of NISBD1. Our study further expands the spectrum of genetic pathology underlying ADAM17 in NISBD1 and establishes functional assay systems for its missense variants.

Genetic analyses of a secondary poroma and trichoblastoma in a HRAS-mutated sebaceous nevus.

A sebaceous nevus is a congenital skin hamartoma caused by postzygotic HRAS or KRAS mosaic mutations. With age, affected individuals may develop secondary tumors within a sebaceous nevus. RAS mutations are harbored from the onset of sebaceous nevus, and further mutations can be expected to be required in order to explain the initiation of secondary tumors. However, genetic analyses of the secondary tumors have not been conducted. Herein, we describe the rare coexistence of a poroma and a trichoblastoma arising in a sebaceous nevus. This is the first report of an investigation of multiple genes in a secondary tumor in an SN. First, HRAS c.37G>C, which is the common mutation in sebaceous nevus, was detected in all three lesions (sebaceous nevus, poroma, and trichoblastoma). Next, to elucidate the potential second-hit mutations in the secondary poroma and trichoblastoma, we applied a panel sequencing for skin cancers that was newly developed in our institution. Our comparison of the mutational profile of 95 skin cancer-related genes in each of the three lesions newly revealed TP53 p.R158P in the poroma and NOTCH2 p.G329S in the trichoblastoma. TP53 p.R158P has been determined as a pathogenic mutation in other tumors, and NOTCH2 p.G329S was a novel mutation. We identified two novel mutations that may have contributed to the pathogenesis of the secondary tumor's development. The roles of the mutations remain unclear.

Proteasomal degradation of polycomb-group protein CBX6 confers MMP-2 expression essential for mesothelioma invasion.

The aggressive invasiveness of malignant mesothelioma limits cancer therapy, however, the molecular mechanisms underlying the invasiveness remain largely unknown. Here we found that the matrix metalloproteinase-2 (MMP-2) was required for the invasion of mesothelioma cells in the collagen matrix and the gene expression of MMP-2 was correlated with the invasive phenotype. The MMP-2 gene expression was regulated by DNA and histone methylation around the transcription start site, implicating the involvement of the polycomb repressive complex (PRC). Knockdown of PRC component chromobox 6 (CBX6) promoted MMP-2 expression and invasion of mesothelioma cells. Transcriptome analysis suggested that CBX6 regulates sets of genes involved in cancer cell migration and metastasis. In invasive but not non-invasive cells, CBX6 was constantly unstable owing to ubiquitination and protein degradation. In human tissues, CBX6 localized in the nuclei of normal mesothelium and benign mesothelioma, but the nuclear staining of CBX6 was lost in malignant mesothelioma. These results suggest involvement of proteasomal degradation of CBX6 in mesothelioma progression.

p53-induced ARVCF modulates the splicing landscape and supports the tumor suppressive function of p53.

p53 is one of the most important tumor suppressor genes, and the exploration of p53-target genes is important for elucidation of its functional mechanisms. In this study, we identified Armadillo Repeat gene deleted in Velo-Cardio-Facial syndrome (ARVCF) as a direct target of p53 through ChIP-sequencing analysis. Activated p53 protein was found to bind to two distinct sites in the ARVCF gene, resulting in induction of ARVCF expression at both the mRNA and protein levels. We revealed that the knockdown of ARVCF inhibited p53-induced apoptosis. Interestingly, ARVCF interacted with hnRNPH2, which is involved in pre-mRNA splicing, and ARVCF knockdown induced dynamic changes in alternative splicing patterns. These results suggest that p53-induced ARVCF indirectly, but not directly, regulates p53 target selectivity through splicing alterations of specific genes. Thus, we demonstrated that the induction of ARVCF expression contributed to the tumor suppressive function of p53. Recently, it has been reported that many tumors have thousands of alternative splicing events that are not detectable in normal samples. ARVCF may play a role in alternative splicing events in cancer and may provide clues to explore novel approaches for cancer diagnosis and therapy.

Renal angiomyolipoma (AML) harboring a missense mutation of TSC2 with copy-neutral loss of heterozygosity (CN-LOH).

Angiomyolipoma (AML) is classified as a perivascular epithelioid cell neoplasm, mostly occurring in the kidney. Twenty percent of patients with renal AML have tuberous sclerosis complex (TSC) caused by germline variation in the TSC1 or TSC2 gene. In this paper, we report the first case of renal AML harboring somatic missense mutations of the TSC2 gene and concomitant copy-neutral loss of heterozygosity (CN-LOH). The patient presented with solitary renal AML and pulmonary lymphangiomyomatosis and without other findings suggestive of TSC. Exome sequencing analysis of the renal AML, however, identified a pathogenic somatic missense mutation in the TSC2 gene (NM_000548:c.5228G>A:p. R1743Q), although no other somatic mutation was detected. Furthermore, no germline mutation in TSC1 or TSC2 was detected. Interestingly, the mutant allele ratio was too high for a somatic heterozygous mutation without loss of heterozygosity (LOH). Furthermore, no copy number variation was detected around the TSC2 locus (16p13.3). To clarify the allelic status, we analyzed heterozygous single-nucleotide polymorphisms (SNPs) in chromosome 16. In these SNPs, an unbalanced allele ratio was accumulated inside the 16p13.3 region. These results suggested copy-neutral LOH (CN-LOH). Consequently, we concluded that the missense mutation of the TSC2 gene and CN-LOH of the TSC2 locus caused renal AML.

Claudin-6 is a single prognostic marker and functions as a tumor-promoting gene in a subgroup of intestinal type gastric cancer.

BACKGROUND: We aimed to identify novel tumor-promoting drivers highly expressed in gastric cancer (GC) that contribute to worsened prognosis in affected patients. METHODS: Genes whose expression was increased and correlated with worse prognosis in GC were screened using datasets from the Cancer Genome Atlas and Gene Expression Omnibus. We examined Claudin-6 (CLDN6) immunoreactivity in GC tissues and the effect of CLDN6 on cellular functions in GC cell lines. The mechanisms underlying GC-promoting function of CLDN6 were also investigated. RESULTS: CLDN6 was identified as a gene overexpressed in GC tumors as compared with adjacent non-tumorous tissues and whose increased expression was positively correlated with worse overall survival of GC patients, particularly those with Lauren's intestinal type GC, in data from multiple publicly available datasets. Additionally, membranous CLDN6 immunoreactivity detected in intestinal type GC tumors was correlated with worse overall survival. In CLDN6-expressing GC cells, silencing of CLDN6 inhibited cell proliferation and migration/invasion abilities, possibly via suppressing transcription of YAP1 and its downstream transcriptional targets at least in part. CONCLUSIONS: This study identified CLDN6 as a GC-promoting gene, suggesting that CLDN6 to be a possible single prognostic marker and promising therapeutic target for a subset of GC patients.

Prognostic significance of GAD1 overexpression in patients with resected lung adenocarcinoma.

BACKGROUND AND OBJECTIVES: In a previous genome-wide screening, we identified hypermethylated CpG islands around glutamate decarboxylase 1 (GAD1) in lung adenocarcinoma (LADC). In this study, we aimed to investigate the methylation and expression status of GAD1 and its prognostic value in patients with LADC. METHODS: GAD1 methylation and mRNA expression status were analyzed using 33 tumorous and paired non-tumorous LADC samples and publicly available datasets. The prognostic value of GAD1 overexpression was investigated using publicly available datasets of mRNA levels and 162 cases of LADC by immunohistochemistry. RESULTS: The methylation and mRNA expression levels of GAD1, each having a positive correlation, were significantly higher in LADC tumors than in paired non-tumorous tissues. LADC patients with higher GAD1 mRNA expression showed significantly poorer prognosis for overall survival in publicly available datasets. Higher immunoreactivity of GAD1 was significantly associated with the pathological stage, pleural invasion, lymph vessel invasion, and poorer prognosis for cancer-specific and disease-free survival. Multivariate analysis revealed that GAD1 protein overexpression is an independent prognosticator for disease-free survival. CONCLUSIONS: GAD1 mRNA and protein expression levels were significant prognostic factors in LADC, suggesting that they might be useful biomarkers to stratify patients with worse clinical outcomes after resection.

Retinoblastoma Inactivation Induces a Protumoral Microenvironment via Enhanced CCL2 Secretion.

Cancer cell-intrinsic properties caused by oncogenic mutations have been well characterized; however, how specific oncogenes and tumor suppressors impact the tumor microenvironment (TME) is not well understood. Here, we present a novel non-cell-autonomous function of the retinoblastoma (RB) tumor suppressor in controlling the TME. RB inactivation stimulated tumor growth and neoangiogenesis in a syngeneic and orthotropic murine soft-tissue sarcoma model, which was associated with recruitment of tumor-associated macrophages (TAM) and immunosuppressive cells such as Gr1+CD11b+ myeloid-derived suppressor cells (MDSC) or Foxp3+ regulatory T cells (Treg). Gene expression profiling and analysis of genetically engineered mouse models revealed that RB inactivation increased secretion of the chemoattractant CCL2. Furthermore, activation of the CCL2-CCR2 axis in the TME promoted tumor angiogenesis and recruitment of TAMs and MDSCs into the TME in several tumor types including sarcoma and breast cancer. Loss of RB increased fatty acid oxidation (FAO) by activating AMP-activated protein kinase that led to inactivation of acetyl-CoA carboxylase, which suppresses FAO. This promoted mitochondrial superoxide production and JNK activation, which enhanced CCL2 expression. These findings indicate that the CCL2-CCR2 axis could be an effective therapeutic target in RB-deficient tumors. SIGNIFICANCE: These findings demonstrate the cell-nonautonomous role of the tumor suppressor retinoblastoma in the tumor microenvironment, linking retinoblastoma loss to immunosuppression.

A novel long non-coding RNA from the HOXA6-HOXA5 locus facilitates colon cancer cell growth.

BACKGROUND: Homeobox A5 (HOXA5), a member of the HOX family, plays an important role in tumor development and morphogenesis, although opposite effects on tumorigenesis have been observed, depending on the tissue type. In this study, we aimed to investigate the role of a novel transcript from the HOXA6-HOXA5 locus in colon cancer tumorigenesis. METHODS: Human colon cancer cell lines were analyzed using next generation sequencing-based targeted mRNA capture. The effects of overexpression and silencing of HOXA5 transcripts were evaluated in vitro and using a xenograft nude mouse model. RESULTS: We identified three novel transcripts (HOXA5 short, long 1, and long 2) transcribed from the HOXA6-HOXA5 locus in HCT116 colon cancer cells using next generation sequencing-based targeted mRNA capture. Knockdown of HOXA5 long 1 and long 2 transcripts did not affect cell growth, while selective silencing of HOXA5 short RNA inhibited cell growth independent of HOXA5 expression. Stable overexpression of HOXA5 short RNA promoted proliferation and migration of colon cancer cell lines HCT116, DLD1, and HT-29 and accelerated tumor growth in the xenograft mouse model. In vitro translation assays suggested HOXA5 short RNA was a functional long non-coding RNA (lncRNA). Consistent with these observations, expression of HOXA5 short RNA was upregulated in advanced colon cancer tissues. Ingenuity Pathway Analysis of differentially expressed genes between HOXA5 short RNA overexpressed and silenced HCT116 cells revealed that HOXA5 short RNA preferentially modified expression of epidermal growth factor (EGF) signal-related genes. Western blot analysis demonstrated that stable overexpression of HOXA5 short RNA increased EGF receptor levels and facilitated its phosphorylation in both HCT116 cells and xenograft tumors. CONCLUSIONS: Our results suggested that HOXA5 short RNA, a novel lncRNA, may play a crucial role in colon tumor growth through activation of EGF signaling.