A homeobox protein, NKX6.1, up-regulates interleukin-6 expression for cell growth in basal-like breast cancer cells

NKX6-1 Is a Less Sensitive But Specific Biomarker of Chromophobe Renal Cell Carcinoma

NKX6-1 is a transcription factor that plays a key role in the development, differentiation, and identity maintenance of beta cells of pancreatic islets. Although NKX6-1 expression has also been discovered in pancreatic well-differentiated neuroendocrine tumors (WDNETs) and duodenal WDNETs, its expression in chromophobe renal cell carcinoma (chRCC) is unexplored. Analysis of mRNA expression and immunohistochemistry of NKX6-1 was performed using the kidney cancer cohort from The Cancer Genome Atlas (TCGA) and paraffin-embedded whole-tissue slides from our 196 collected cases, including 48 chRCCs (43 classic and 5 eosinophilic subtypes), 24 renal oncocytomas (ROs), 46 clear cell renal cell carcinomas, 41 papillary renal cell carcinomas, 14 renal urothelial carcinomas, 7 low-grade oncocytic renal tumors (LOTs), 8 eosinophilic solid and cystic renal cell carcinomas, 3 succinate dehydrogenase-deficient renal cell carcinomas, and 5 renal oncocytic tumors, not otherwise specified. NKX6-1 expression was almost exclusively upregulated in chRCC at both the mRNA and protein levels compared with other renal tumors. NKX6-1 was immunohistochemically positive in 39 of 48 (81.3%) chRCCs, but negative in 46 clear cell renal cell carcinomas, 24 ROs, 7 low-grade oncocytic renal tumors, 8 eosinophilic solid and cystic renal cell carcinomas, 3 succinate dehydrogenase-deficient renal cell carcinomas, and 5 renal oncocytic tumors, not otherwise specified. Diffuse, moderate, and focal NKX6-1 staining were seen in 21, 4, and 14 of the 39 chRCCs, respectively. In contrast, NKX6-1 was focally positive in only 1 of 41 (2.4%) papillary renal cell carcinomas and 2 of 14 (14.3%) renal urothelial carcinomas. Therefore, the sensitivity and specificity of NKX6-1 staining were 81.3% and 98% for chRCC, respectively. In conclusion, NKX6-1 may be a novel potential marker for differentiating chRCC from other renal neoplasms, especially from RO.

NKX6-1 mediates cancer stem-like properties and regulates sonic hedgehog signaling in leiomyosarcoma

Background

Leiomyosarcoma (LMS), the most common soft tissue sarcoma, exhibits heterogeneous and complex genetic karyotypes with severe chromosomal instability and rearrangement and poor prognosis.

Methods

Clinical variables associated with NKX6-1 were obtained from The Cancer Genome Atlas (TCGA). NKX6-1 mRNA expression was examined in 49 human uterine tissues. The in vitro effects of NXK6-1 in LMS cells were determined by reverse transcriptase PCR, western blotting, colony formation, spheroid formation, and cell viability assays. In vivo tumor growth was evaluated in nude mice.

Results

Using The Cancer Genome Atlas (TCGA) and human uterine tissue datasets, we observed that NKX6-1 expression was associated with poor prognosis and malignant potential in LMS. NKX6-1 enhanced in vitro tumor cell aggressiveness via upregulation of cell proliferation and anchorage-independent growth and promoted in vivo tumor growth. Moreover, overexpression and knockdown of NKX6-1 were associated with upregulation and downregulation, respectively, of stem cell transcription factors, including KLF8, MYC, and CD49F, and affected sphere formation, chemoresistance, NOTCH signaling and Sonic hedgehog (SHH) pathways in human sarcoma cells. Importantly, treatment with an SHH inhibitor (RU-SKI 43) but not a NOTCH inhibitor (DAPT) reduced cell survival in NKX6-1-expressing cancer cells, indicating that an SHH inhibitor could be useful in treating LMS. Finally, using the TCGA dataset, we demonstrated that LMS patients with high expression of NKX6-1 and HHAT, an SHH pathway acyltransferase, had poorer survival outcomes compared to those without.

Conclusions

Our findings indicate that NKX6-1 and HHAT play critical roles in the pathogenesis of LMS and could be promising diagnostic and therapeutic targets for LMS patients.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12929-021-00726-6.

NKX6.1 Represses Tumorigenesis, Metastasis, and Chemoresistance in Colorectal Cancer

Accumulating evidence suggests that NKX6.1 (NK homeobox 1) plays a role in various types of cancer. In our previous studies, we identified NKX6.1 hypermethylation as a promising marker and demonstrated that the NKX6.1 gene functions as a metastasis suppressor through the epigenetic regulation of the epithelial-to-mesenchymal transition (EMT) in cervical cancer. More recently, we have demonstrated that NKX6.1 methylation is related to the chemotherapy response in colorectal cancer (CRC). Nevertheless, the biological function of NKX6.1 in the tumorigenesis of CRC remains unclear. In this study, we showed that NKX6.1 suppresses tumorigenic and metastatic ability both in vitro and in vivo. NKX6.1 represses cell invasion partly through the modulation of EMT. The overexpression of NKX6.1 enhances chemosensitivity in CRC cells. To further explore how NKX6.1 exerts its tumor-suppressive function, we used RNA sequencing technology for comprehensive analysis. The results showed that differentially expressed genes (DEGs) were mainly related to cell migration, response to drug, transcription factor activity, and growth factor activity, suggesting that these DEGs are involved in the function of NKX6.1 suppressing cancer invasion and metastasis. Our results demonstrated that NKX6.1 functions as a tumor suppressor partly by repressing EMT and enhancing chemosensitivity in CRC, making it a potential therapeutic target.

High-throughput transcriptome analysis reveals that the loss of Pten activates a novel NKX6-1/RASGRP1 regulatory module to rescue microphthalmia caused by Fgfr2-deficient lenses

FGFR signaling is critical to development and disease pathogenesis, initiating phosphorylation-driven signaling cascades, notably the RAS-RAF-MEK-ERK and PI3 K-AKT cascades. PTEN antagonizes FGFR signaling by reducing AKT and ERK activation. Mouse lenses lacking FGFR2 exhibit microphakia and reduced ERK and AKT phosphorylation, widespread apoptosis, and defective lens fiber cell differentiation. In contrast, simultaneous deletion of both Fgfr2 and Pten restores ERK and AKT activation levels as well as lens size, cell survival and aspects of fiber cell differentiation; however, the molecular basis of this "rescue" remains undefined. We performed transcriptomic analysis by RNA sequencing of mouse lenses with conditional deletion of Fgfr2, Pten or both Fgfr2 and Pten, which reveal new molecular mechanisms that uncover how FGFR2 and PTEN signaling interact during development. The FGFR2-deficient lens transcriptome demonstrates overall loss of fiber cell identity with deregulated expression of 1448 genes. We find that ~ 60% of deregulated genes return to normal expression levels in lenses lacking both Fgfr2 and Pten. Further, application of customized filtering parameters to these RNA-seq data sets identified 68 high-priority candidate genes. Bioinformatics analyses showed that the cis-binding motif of a high-priority homeodomain transcription factor, NKX6-1, was present in the putative promoters of ~ 78% of these candidates. Finally, biochemical reporter assays demonstrate that NKX6-1 activated the expression of the high-priority candidate Rasgrp1, a RAS-activating protein. Together, these data define a novel regulatory module in which NKX6-1 directly activates Rasgrp1 expression to restore the balance of ERK and AKT activation, thus providing new insights into alternate regulation of FGFR downstream events.

SALL4 - KHDRBS3 network enhances stemness by modulating CD44 splicing in basal-like breast cancer

Understanding the mechanism by which cancer cells enhance stemness facilitates cancer therapies. Here, we revealed that a stem cell transcription factor, SALL4, functions to enhance stemness in basal-like breast cancer cells. We used shRNA-mediated knockdown and gene overexpression systems to analyze gene functions. To evaluate stemness, we performed a sphere formation assay. In SALL4 knockdown cells, the sphere formation ability was reduced, indicating that SALL4 enhances stemness. CD44 is a membrane protein and is known as a stemness factor in cancer. CD44 splicing variants are involved in cancer stemness. We discovered that SALL4 modulates CD44 alternative splicing through the upregulation of KHDRBS3, a splicing factor for CD44. We cloned the KHDRBS3-regulated CD44 splicing isoform (CD44v), which lacks exons 8 and 9. CD44v overexpression prevented a reduction in the sphere formation ability by KHDRBS3 knockdown, indicating that CD44v is positively involved in cancer stemness. In addition, CD44v enhanced anoikis resistance under the control of the SALL4 - KHDRBS3 network. Basal-like breast cancer is an aggressive subtype among breast cancers, and there is no effective therapy so far. Our findings provide molecular targets for basal-like breast cancer therapy. In the future, this study may contribute to the establishment of drugs targeting cancer stemness.

The Sal-like 4 - integrin α6β1 network promotes cell migration for metastasis via activation of focal adhesion dynamics in basal-like breast cancer cells

During metastasis, cancer cell migration is enhanced. However, the mechanisms underlying this process remain elusive. Here, we addressed this issue by functionally analyzing the transcription factor Sal-like 4 (SALL4) in basal-like breast cancer cells. Loss-of-function studies of SALL4 showed that this transcription factor is required for the spindle-shaped morphology and the enhanced migration of cancer cells. SALL4 also up-regulated integrin gene expression. The impaired cell migration observed in SALL4 knockdown cells was restored by overexpression of integrin α6 and β1. In addition, we clarified that integrin α6 and β1 formed a heterodimer. At the molecular level, loss of the SALL4 - integrin α6β1 network lost focal adhesion dynamics, which impairs cell migration. Over-activation of Rho is known to inhibit focal adhesion dynamics. We observed that SALL4 knockdown cells exhibited over-activation of Rho. Aberrant Rho activation was suppressed by integrin α6β1 expression, and pharmacological inhibition of Rho activity restored cell migration in SALL4 knockdown cells. These results indicated that the SALL4 - integrin α6β1 network promotes cell migration via modulation of Rho activity. Moreover, our zebrafish metastasis assays demonstrated that this gene network enhances cell migration in vivo. Our findings identify a potential new therapeutic target for the prevention of metastasis, and provide an improved understanding of cancer cell migration.