The FEBS Journal

The Rab25‐ ADAMTS5 axis as a previously undescribed mechanism for sensing tumor microenvironment complexity

The tumor microenvironment (TME), particularly the extracellular matrix (ECM), plays a critical role in cancer progression. Focusing on ovarian cancer, Yuan et al. reveal an ECM‐dependent signaling axis where cancer‐associated fibroblasts (CAFs) enhance the invasiveness of cancer cells via Rab25‐driven upregulation of the protease ADAMTS5. This process is only triggered in the presence of native ECM. In turn, stimulated cancer cells favor CAF invasiveness through a mechanism that remains to be identified. These findings uncover a bidirectional crosstalk between cancer cells and CAFs and highlight the importance of context‐specific in vitro models to decipher ECM‐mediated tumor dynamics.

The protease ADAMTS 5 controls ovarian cancer cell invasion, downstream of Rab25

Ovarian cancer is the 3rd most common gynaecological malignancy worldwide, with a 5‐year survival rate of < 30% in the presence of metastasis. Metastatic progression is characterised by extensive remodelling of the extracellular matrix, primarily mediated by secreted proteases, including members of the ‘a disintegrin and metalloprotease with thrombospondin motif’ (ADAMTS) family. In particular, ADAMTS5 has been reported to be upregulated in ovarian malignant tumours compared to borderline and benign lesions, suggesting it might play a role in metastatic progression. Furthermore, it has been suggested that Rab25, a small GTPase of the Ras family, might upregulate ADAMTS5 expression in ovarian cancer cells. Here we demonstrated that Rab25 promotes ADAMTS5 expression through the activation of the nuclear factor κB (NF‐κB) signalling pathway. Furthermore, ADAMTS5 was necessary and sufficient to stimulate ovarian cancer cell migration through complex fibroblast‐secreted matrices, while selective ADAMTS5 inhibition prevented ovarian cancer spheroid invasion in 3D systems. Finally, in ovarian cancer patients, high ADAMTS5 expression correlated with poor prognosis. Altogether, these data identify ADAMTS5 as a novel regulator of ovarian cancer cell migration and invasion, suggesting it might represent a previously undescribed therapeutic target to prevent ovarian cancer metastasis.

Hypoxia regulates tumour characteristic RNA modifications in ovarian cancers

Analysis of ovarian cancer tissue and normal ovarian tissue revealed 31 RNA modifications with significant differences observed in cancer tissue compared with normal tissue. Moreover, we found Im and chm5U as characteristic RNA modifications in advanced and platinum‐resistant ovarian cancers, respectively. Considering that these differences in RNA modifications may be due to the intra‐tumour microenvironment, we xenografted the ovarian cancer cell line RMG‐1 to create RMG‐1 tumours and compared them with original RMG‐1 cells. As a result, 14 of the 31 RNA modifications showed marked variations during tumorigenesis. Eight RNA modifications (m2,2G, t6A, m7G, m5U, m1G, i6A, m6t6A and m1A), which were upregulated in ovarian cancer tissues and in RMG‐1‐xenografted tumour, were also upregulated under hypoxic conditions. RNAseq analysis, using the matched RNA samples analysed for RNA modifications, showed that 2137 genes were highly expressed in ovarian cancer tissues compared with those in normal ovarian tissues. Of these, 134 genes, which were enriched in a gene set belonging to the hypoxia signalling pathway, were positively correlated with the above eight RNA modifications. These results suggest that the tumour microenvironment, including hypoxia, is important for cancer characteristic RNA modifications.

YTHDF3 mediates HNF1α regulation of cervical cancer radio‐resistance by promoting RAD51D translation in an m6A ‐dependent manner

Radiotherapy, as an important primary treatment, has effectively improved the survival of patients with cervical cancer (CC). Some patients, however, do not benefit optimally from radiotherapy because of radio‐resistance. Therefore, identifying radio‐resistance biomarkers and unravelling the underlying mechanisms is of critical importance for these patients. In the present study, we found significant upregulation of hepatocyte nuclear factor 1‐alpha (HNF1α) expression in radio‐resistant cervical cancer tissues and cell lines. Depletion of HNF1α reduced and overexpression of HNF1α promoted the resistance of CC cells to irradiation in vitro and in vivo . HNF1α positively regulated DNA repair protein RAD51 homologue 4 (RAD51D) at the protein level but not at the mRNA level. Mechanistically, upregulation of HNF1α enhanced YTH domain‐containing family protein 3 (YTHDF3) transcription, which in turn promoted RAD51D mRNA N 6 ‐methyladenosine (m6A) modification. YTHDF3 mediates HNF1α regulation of cervical cancer radio‐resistance by promoting RAD51D translation in an m6A‐dependent manner. The HFN1α/YTHDF3/RAD51D regulatory axis was found to play a critical role in conferring radio‐resistance of CC cells. In conclusion, dysregulation of the HFN1α/YTHDF3/RAD51D axis may promote the radio‐resistance of CC cells. Blocking this pathway may provide therapeutic benefits against CC radio‐resistance.

Glycolytic oscillations in HeLa cervical cancer cell spheroids

Previous studies have unravelled glycolytic oscillations in cancer cells, such as HeLa cervical and DU145 prostate cancer cells, using a monolayer culture system. Here, we demonstrate glycolytic oscillations in HeLa cervical cancer cell spheroids. Experiments revealed that a small number of HeLa cells in spheroids exhibited heterogeneous oscillations with a higher frequency than those in monolayers. Model analyses and our previous experiments indicated that the higher frequencies of oscillations in spheroids were mostly due to the increase in glycolytic enzyme activity in the cells, and to the decrease in glucose concentration by diffusional transport of glucose from the surface to inside the spheroids, as well as the increase in cell density through spheroid formation. These results and our previous studies imply that more malignant cancer cells tend to exhibit glycolytic oscillations with higher frequencies than less malignant cells. Adjacent cells in spheroids oscillated within a 10% difference in frequency, but did not synchronize with each other. This suggests that weak cell‐to‐cell interactions might exist among HeLa cells connected with cadherins in the spheroid microenvironment; however, the interactions were not strong enough to induce synchronization of glycolytic oscillations.

FGF–FGFR signaling promotes the development of invasive cervical cancer

Cervical cancer is one of the most frequently diagnosed gynecological malignancies among women worldwide. The main cause of cervical cancer is the human papilloma virus (HPV). Mahmood et al. investigated in detail the role of the fibroblast growth factor (FGF)–FGF receptor (FGFR) signaling axis in the development of the invasive form of the disease. The presented work clearly indicates the FGFR signaling as an additional but important factor for the development of a highly malignant tumor.Comment on https://doi.org/10.1111/febs.16331

FGF signalling facilitates cervical cancer progression

Cervical cancer is one of the most frequently diagnosed cancers in women worldwide. While cervical cancer is caused by human papillomavirus (HPV), not all females infected with HPV develop the disease, suggesting that other factors might facilitate its progression. Growing evidence supports the involvement of the fibroblast growth factor receptor (FGFR) axis in several cancers, including gynecological. However, for cervical cancer, the molecular mechanisms that underpin the disease remain poorly understood, including the role of FGFR signaling. The aim of this study was to investigate FGF(R) signaling in cervical cancer through bioinformatic analysis of cell line and patient data and through detailed expression profiling, manipulation of the FGFR axis, and downstream phenotypic analysis in cell lines (HeLa, SiHa, and CaSki). Expression (protein and mRNA) analysis demonstrated that FGFR1b/c, FGFR2b/c, FGFR4, FGF2, FGF4, and FGF7 were expressed in all three lines. Interestingly, FGFR1 and 2 localized to the nucleus, supporting that nuclear FGFRs could act as transcription factors. Importantly, 2D and 3D cell cultures demonstrated that FGFR activation can facilitate cell functions correlated with invasive disease. Collectively, this study supports an association between FGFR signaling and cervical cancer progression, laying the foundations for the development of therapeutic approaches targeting FGFR in this disease.

Altered fatty acid oxidation via CPT1A promotes epithelial‐to‐mesenchymal transition in ovarian cancer

Metabolic alterations are increasingly recognized as fundamental features of cancer. Recent studies have highlighted the involvement of altered fatty acid oxidation (FAO) at different stages of tumor development. As the rate‐limiting enzyme of FAO, CPT1 plays a crucial role in these metabolic adaptations in cancer cells. However, the regulation of CPT1 expression and activity in tumor cells still requires detailed investigation. Our studies reveal that CPT1A, a variant of CPT1, is significantly upregulated in ovarian cancer (OC) and correlates with poor prognosis. Inhibition of CPT1A, either by siRNA‐mediated knockdown or by etomoxir, reduces the migratory and invasive properties of the OC cells. CPT1A exerts these effects by modulating the expression of epithelial‐to‐mesenchymal transition (EMT)‐associated genes at transcriptional and protein levels. Growth factors such as transforming growth factor beta (TGFβ) are abundant in the tumor microenvironment and modulate the metabolic profile of tumors, thereby promoting EMT. Our findings demonstrate that TGFβ treatment increases the rate of FAO in ovarian cancer cells. Mechanistically, TGFβ mediates this effect by enhancing CPT1A expression and its enzymatic activity in OC cells through an AMPK‐dependent pathway. Additionally, we identified NRF2 as a potential transcriptional regulator of CPT1A within the context of TGFβ‐AMPK signaling. Finally, inhibiting CPT1A successfully attenuates TGFβ‐induced EMT in ovarian cancer cells. Cumulatively, our study underscores the role of CPT1A‐mediated FAO in facilitating ovarian cancer progression through TGFβ‐induced EMT.

Previously undescribed effects and mechanisms of STAT 3 in HPV ‐induced DNA re‐replication in response to DNA damage

Polyploidy is an important inducer of cervical carcinogenesis. However, the mechanism by which the HPV E7 oncoprotein induces cells to cross the cell cycle checkpoint and enter G2 phase for DNA re‐replication remains unclear. We have previously identified the role of WDHD1 in viral oncogene‐induced re‐replication. Here, we demonstrated that HPV E7 activates STAT3 signaling to drive transcriptional upregulation of two replication mediators: WDHD1, a DNA replication initiation factor, and UHRF1, an epigenetic regulator. Mechanistically, STAT3 directly activates WDHD1 gene expression while UHRF1 post‐transcriptionally stabilizes WDHD1, forming a feedforward loop that enables G2‐phase re‐replication and polyploidy. This study reveals a novel STAT3‐WDHD1‐UHRF1 regulatory axis, driving HPV E7‐induced polyploid genomic instability. Given the limited number of genes known to induce DNA re‐replication, these findings reveal HPV E7‐induced polyploidy as a STAT3‐dependent process involving multilayer regulatory crosstalk and provide new therapeutic targets to counteract viral oncogenesis.

Myeloid‐derived suppressor cells promote epithelial ovarian cancer cell stemness by inducing the CSF2/p‐STAT3 signalling pathway

Myeloid‐derived suppressor cells (MDSCs) are known to contribute to tumour immune evasion, and studies have verified that MDSCs can induce cancer stem cells (CSCs) and promote tumour immune evasion in breast cancers, cervical cancers and glioblastoma. However, the potential function of MDSCs in regulating CSCs in epithelial ovarian cancer (EOC) progression is unknown. Our results indicated that compared to nonmalignant ovarian patients, EOC patients showed a significantly increased proportion of MDSCs in the peripheral blood. In addition, MDSCs dramatically promoted tumour sphere formation, cell colony formation and CSC accumulation, and MDSCs enhanced the expression of the stemness biomarkers NANOG and c‐MYC in EOC cells during coculture. Moreover, the mechanisms by which MDSCs enhance EOC stemness were further explored, and 586 differentially expressed genes were found in EOC cells cocultured with or without MDSCs; during coculture, the expression level of colony‐stimulating factor 2 (CSF2) was significantly increased in EOC cells cocultured with MDSCs. Furthermore, the depletion of CSF2 in EOC cells was successfully performed, the promotive effects of MDSCs on EOC cell stemness could be markedly reversed by downregulating CSF2 expression, p‐STAT3 signalling pathway molecules were also altered, and the p‐STAT3 inhibitor could markedly reverse the promotive effects of MDSCs on EOC cell stemness. In addition, the CSF2 expression level was correlated with EOC clinical staging. Therefore, MDSCs enhance the stemness of EOC cells by inducing the CSF2/p‐STAT3 signalling pathway. Targeting MDSCs or CSF2 may be a reasonable strategy for enhancing the efficacy of conventional treatments.DatabaseGene expression data files are available in the GEO databases under the accession number(s) GSE145374.