Formin-like protein 2 promotes cell proliferation by a p27-related mechanism in human breast cancer cells

CIP/KIP and INK4 families as hostages of oncogenic signaling

CIP/KIP and INK4 families of Cyclin-dependent kinase inhibitors (CKIs) are well-established cell cycle regulatory proteins whose canonical function is binding to Cyclin-CDK complexes and altering their function. Initial experiments showed that these proteins negatively regulate cell cycle progression and thus are tumor suppressors in the context of molecular oncology. However, expanded research into the functions of these proteins showed that most of them have non-canonical functions, both cell cycle-dependent and independent, and can even act as tumor enhancers depending on their posttranslational modifications, subcellular localization, and cell state context. This review aims to provide an overview of canonical as well as non-canonical functions of CIP/KIP and INK4 families of CKIs, discuss the potential avenues to promote their tumor suppressor functions instead of tumor enhancing ones, and how they could be utilized to design improved treatment regimens for cancer patients.

Characterization of Expression and Function of the Formins FHOD1, INF2, and DAAM1 in HER2-Positive Breast Cancer

PURPOSE

Human epidermal growth factor receptor 2 (HER2)-targeted therapies, such as trastuzumab, benefit patients with HER2-positive metastatic breast cancer; however, owing to traditional pathway activation or alternative signaling, resistance persists. Given the crucial role of the formin family in shaping the actin cytoskeleton during cancer progression, these proteins may function downstream of the HER2 signaling pathway. Our aim was to uncover the potential correlations between formins and HER2 expression using a combination of public databases, immunohistochemistry, and functional in vitro assays.

METHODS

Using online databases, we identified a negative prognostic correlation between specific formins mRNA expression in HER2-positive cancers. To validate these findings at the protein level, immunohistochemistry was performed on HER2 subtype breast cancer tumors to establish the links between staining patterns and clinical characteristics. We then knocked down individual or combined formins in MDA-MB-453 and SK-BR-3 cells and investigated their effects on wound healing, transwell migration, and proliferation. Furthermore, we investigated the effects of erb-b2 receptor tyrosine kinase 2 (ERBB2)/HER2 small interfering RNA (siRNA)-mediated knockdown on the PI3K/Akt and MEK/ERK1 pathways as well as on selected formins.

RESULTS

Our results revealed that correlations between INF2, FHOD1, and DAAM1 mRNA expression and ERBB2 in HER2-subtype breast cancer were associated with worse outcomes. Using immunohistochemistry, we found that high FHOD1 protein expression was linked to higher histological grades and was negatively correlated with estrogen and progesterone receptor positivity. Upon formins knockdown, we observed effects on wound healing and transwell migration, with a minimal impact on proliferation, which was evident through single and combined knockdowns in both cell lines. Notably, siRNA-mediated knockdown of HER2 affected FHOD1 and INF2 expression, along with the phosphorylated Akt/MAPK states.

CONCLUSION

Our study highlights the roles of FHOD1 and INF2 as downstream effectors of the HER2/Akt and HER2/MAPK pathways, suggesting that they are potential therapeutic targets in HER2-positive breast cancer.

Role of PAX2 in breast cancer verified by bioinformatics analysis and in vitro validation

Background

Breast cancer (BC) is the most frequently diagnosed cancer in women and the second most common cancer among newly diagnosed cancers worldwide. Studies have shown that paired box 2 (PAX2) participates in the tumorigenesis of some cancer cells, but its role in BC is still unclear.

Methods

Transcriptome expression profiles and clinicopathological information of BC were downloaded from The Cancer Genome Atlas (TCGA) database to explore the expression level and prognostic value of PAX2. Gene set enrichment analysis (GSEA) and functional enrichment analysis were performed to investigate the functions and pathways of PAX2. Moreover, real-time reverse transcriptase-polymerase chain reaction (RT-qPCR) was used to determine the expression of PAX2 in BC tissues, and the predictive value of PAX2 in clinical samples was assessed. Cell Counting Kit-8 (CCK-8) assay was used to evaluate cell growth. The migration and invasive capacities of cells were assessed by wound healing assay and Transwell assay.

Results

PAX2 was upregulated in the TCGA-BC datasets. GSEA suggested that PAX2 may be involved in the regulation of signaling pathways such as MAPK. Moreover, PAX2 was overexpressed in BC tissues, and PAX2 expression was associated with tumor size and lymph node metastasis. PAX2 deficiency could promote the growth, migration, and invasion of BC cells.

Conclusions

Upregulation of PAX2 inhibited BC cell growth, migration, and invasion, making PAX2 a potential therapeutic target for BC.

LINC00839 promotes malignancy of liver cancer via binding FMNL2 under hypoxia

Liver cancer is one of the most common malignant tumors in the world and metastasis is the leading cause of death associated with liver cancer. Hypoxia is a common feature of solid tumors and enhances malignant character of cancer cells. However, the exact mechanisms involved in hypoxia-driven liver cancer progression and metastasis have not been well clarified so far. The aim of this study was to investigate the contribution of long non-coding RNA (lncRNA) in hypoxia promoting liver cancer progression. We screened and revealed LINC00839 as a novel hypoxia-responsive lncRNA in liver cancer. LINC00839 expression was up-regulated in liver cancer tissues and cell lines, and the patients with high LINC00839 expression had shortened overall survival. LINC00839 further overexpressed under hypoxia and promoted liver cancer cell proliferation, migration, and invasion. Mechanistically, LINC00839 bound multiple proteins that were primarily associated with the metabolism and RNA transport, and positively regulated the expression of Formin-like protein 2 (FMNL2). LINC00839 could promote hypoxia-mediated liver cancer progression, suggesting it may be a clinically valuable biomarker and serve as a molecular target for the diagnosis, prognosis, and therapy of liver cancer.

FMNL2 suppresses cell migration and invasion of breast cancer: a reduction of cytoplasmic p27 via RhoA/LIMK/Cofilin pathway

Formin-like protein 2 (FMNL2) belongs to a highly conserved family of cytoskeletal remodeling proteins that have been reported to be implicated in various actin-dependent physiological and cancer-associated processes. In this study, we mainly investigated the effects of FMNL2 on breast cancer cell migration and invasion, and the underlying mechanisms involved. We found that FMNL2 reduced cell migration and invasion of breast cancer in vitro and in vivo. Further, FMNL2 disrupted actin cytoskeleton rearrangement and hampered the RhoA/LIMK/Cofilin pathway in breast cancer cells. Critically, both Rho inhibitor ZOL and LIMK inhibitor BMS3 significantly abrogated these migration-promoting effects in FMNL2-silencing MDA-MB-231 and BT549 cells. RhoA/LIMK/Cofilin pathway was involved in FMNL2 silencing-induced actin cytoskeleton rearrangement in MDA-MB-231 and BT549 cells. More importantly, cytoplasmic p27 promoted FMNL2-mediated cell migration and invasion through RhoA/LIMK/Cofilin pathway in MCF7 and MDA-MB-231 cells. In addition, the expression and prognosis of FMNL2 were associated with ER in breast cancer. Furthermore, ERα overexpression reduced the protein levels of FMNL2 in breast cancer cells, which were reversed by MG132. In conclusion, FMNL2 suppressed cell migration and invasion of breast cancer by inhibiting RhoA/LIMK/Cofilin pathway through a reduction of cytoplasmic p27. This finding implies that the interference of FMNL2-mediated RhoA/LIMK/Cofilin pathway involving the cytoplasmic p27 may be a promising strategy for ameliorating breast cancer metastasis and prognosis.

Susceptibility of cytoskeletal-associated proteins for tumor progression

The traditional functions of cytoskeletal-associated proteins (CAPs) in line with polymerization and stabilization of the cytoskeleton have evolved and are currently underrated in oncology. Although therapeutic drugs have been developed to target the cytoskeletal components directly in cancer treatment, several recently established therapeutic agents designed for new targets block the proliferation of cancer cells and suppress resistance to existing target agents. It would seem like these targets only work toward inhibiting the polymerization of cytoskeletal components or hindering mitotic spindle formation in cancer cells, but a large body of literature points to CAPs and their culpability in cell signaling, molecular conformation, organelle trafficking, cellular metabolism, and genomic modifications. Here, we review those underappreciated functions of CAPs, and we delineate the implications of cellular signaling instigated by evasive properties induced by aberrant expression of CAPs in response to stress or failure to exert normal functions. We present an analogy establishing CAPs as vulnerable targets for cancer systems and credible oncotargets. This review establishes a paradigm in which the cancer machinery may commandeer the conventional functions of CAPs for survival, drug resistance, and energy generation; an interesting feature overdue for attention.