INPP4B and RAD50 have an interactive effect on survival after breast cancer

The INPP4B paradox: Like PTEN, but different

Cancer is a complex and heterogeneous disease marked by the dysregulation of cancer driver genes historically classified as oncogenes or tumour suppressors according to their ability to promote or inhibit tumour development and growth, respectively. Certain genes display both oncogenic and tumour suppressor functions depending on the biological context, and as such have been termed dual-role cancer driver genes. However, because of their context-dependent behaviour, the tumourigenic mechanism of many dual-role genes is elusive and remains a significant knowledge gap in our effort to understand and treat cancer. Inositol polyphosphate 4-phosphatase type II (INPP4B) is an emerging dual-role cancer driver gene, primarily known for its role as a negative regulator of the phosphoinositide 3-kinase (PI3K)/AKT signalling pathway. In response to growth factor stimulation, class I PI3K generates PtdIns(3,4,5)P₃ at the plasma membrane. PtdIns(3,4,5)P₃ can be hydrolysed by inositol polyphosphate 5-phosphatases to generate PtdIns(3,4)P₂, which, together with PtdIns(3,4,5)P₃, facilitates the activation of AKT to promote cell proliferation, survival, migration, and metabolism. Phosphatase and tensin homology on chromosome 10 (PTEN) and INPP4B are dual-specificity phosphatases that hydrolyse PtdIns(3,4,5)P₃ and PtdIns(3,4)P₂, respectively, and thus negatively regulate PI3K/AKT signalling. PTEN is a bona fide tumour suppressor that is frequently lost in human tumours. INPP4B was initially characterised as a tumour suppressor akin to PTEN, and has been implicated as such in a number of cancers, including prostate, thyroid, and basal-like breast cancers. However, evidence has since emerged revealing INPP4B as a paradoxical oncogene in several malignancies, with increased INPP4B expression reported in AML, melanoma and colon cancers among others. Although the tumour suppressive function of INPP4B has been mostly ascribed to its ability to negatively regulate PI3K/AKT signalling, its oncogenic function remains less clear, with proposed mechanisms including promotion of PtdIns(3)P-dependent SGK3 signalling, inhibition of PTEN-dependent AKT activation, and enhancing DNA repair mechanisms to confer chemoresistance. Nevertheless, research is ongoing to identify the factors that dictate the tumourigenic output of INPP4B in different human cancers. In this review we discuss the dualistic role that INPP4B plays in the context of cancer development, progression and treatment, drawing comparisons to PTEN to explore how their similarities and, importantly, their differences may account for their diverging roles in tumourigenesis.

Analysis of differentially expressed proteins between HER2 positive and triple negative breast cancer and their prognostic significance

Both triple negative breast cancer (TNBA) and HER2-positive breast cancer lack expression of estrogen receptor alpha (ER) and progesterone receptor (PR), while human epidermal growth factor receptor 2 (HER2) in TNBC is also negative. This study aimed to identify the differentially expressed proteins (DEPs) between TNBC and HER2-positive breast cancer and to improve understanding of their role in the prognosis of breast cancer. By analyzing the breast cancer data set in The Cancer Proteome Atlas (TCPA) database, 15 DEPs between TNBC and HER2-positive breast cancer were identified. GO and pathway enrichment analysis were performed on DEPs, and the protein-protein interaction (PPI) network was constructed. The overall survival (OS) analysis of the breast cancer protein dataset in the Kaplan-Meier plotter showed that low expression of ACC1 suggested a higher OS of HER2-positive breast cancer (HR = 5.34, P < 0.05) and TNBC (HR = 2.88, P < 0.05). And TNBC patients with high TBA1B (HR = 0.16, P < 0.01) or low INPP4B (HR = 3.47, P < 0.05) expression have a better prognosis. Our research provides new insights into the prognostic indicators of TNBC and HER2-positive breast cancer, which could be further studied.

Genetic interactions between INPP4B and RAD50 is prognostic of breast cancer survival

RAD50 is commonly depleted in basal-like breast cancer with concomitant absence of INPP4B and several tumor suppressors such as BRCA1 and TP53. Our previous study revealed that INPP4B and RAD50 interact and such an interaction is associated with breast cancer survival at the transcriptional, translational and genomic levels. In the present study, we explored single nucleotide polymorphisms (SNPs) of these two genes that have synergistic effects on breast cancer survival to decipher mechanisms driving their interactions at the genetic level. The Cox's proportional hazards model was used to test whether SNPs of these two genes are interactively associated with breast cancer survival, following expression quantitative trait loci (eQTL) analysis and functional investigations. Our study revealed two disease-associating blocks, each encompassing five and two non-linkage disequilibrium linked SNPs of INPP4B and RAD50, respectively. Concomitant presence of any rare homozygote from each disease-associating block is synergistically prognostic of poor breast cancer survival. Such synergy is mediated via bypassing pathways controlling cell proliferation and DNA damage repair, which are represented by INPP4B and RAD50. Our study provided genetic evidence of interactions between INPP4B and RAD50, and deepened our understandings on the orchestrated genetic machinery governing tumor progression.

RAD50 germline mutations are associated with poor survival in BRCA1/2-negative breast cancer patients

RAD50 is a highly conserved DNA double-strand break (DSB) repair gene. However, the associations between RAD50 germline mutations and the survival and risk of breast cancer have not been fully elucidated. Here, we aimed to investigate the clinical impact of RAD50 germline mutations in a large cohort of unselected breast cancer patients. In our study, RAD50 germline mutations were determined using next-generation sequencing in 7657 consecutive unselected breast cancer patients without BRCA1/2 mutations. We also screened for RAD50 recurrent mutations (L719fs, K994fs, and H1269fs) in 5000 healthy controls using Sanger sequencing. We found that 26 out of 7,657 (0.34%) patients had RAD50 pathogenic mutations, and 16 patients carried one of the three recurrent mutations (L719fs, n = 6 cases; K994fs, n = 5 cases; and H1269fs, n = 5 cases); the recurrent mutation rate was 0.21%. The frequency of the three recurrent mutations in the 5,000 healthy controls was 0.18% (9/5,000). These mutations did not confer an increased risk of breast cancer in the studied patients [odds ratios (OR), 1.16; 95% confidence interval (CI), 0.51-2.63; p = 0.72]. Nevertheless, multivariate analysis revealed that RAD50 pathogenic mutations were an independent unfavourable predictor of recurrence-free survival (RFS) [adjusted hazard ratio (HR) 2.66; 95% CI, 1.18-5.98; p = 0.018] and disease-specific survival (DSS; adjusted HR 4.36; 95% CI, 1.58-12.03; p = 0.004) in the entire study cohort. Our study suggested that RAD50 germline mutations are not associated with an increased risk of breast cancer, but patients with RAD50 germline mutations have unfavourable survival compared to patients without these mutations.

Differentially expressed and survival-related proteins of lung adenocarcinoma with bone metastasis

Despite recent advances in targeted and immune‐based therapies, the poor prognosis of lung adenocarcinoma (LUAD) with bone metastasis (BM) remains a challenge. First, two‐dimensional gel electrophoresis (2‐DE) was used to identify proteins that were differentially expressed in LUAD with BM, and then matrix‐assisted laser desorption/ionization time of flight mass spectrometry (MALDI‐TOF‐MS) was used to identify these proteins. Second, the Cancer Genome Atlas (TCGA) was used to identify mutations in these differentially expressed proteins and Kaplan–Meier plotter (KM Plotter) was used to generate survival curves for the analyzed cases. Immunohistochemistry (IHC) was used to check the expression of proteins in 28 patients with BM and nine patients with LUAD. Lastly, the results were analyzed with respect to clinical features and patient's follow‐up. We identified a number of matched proteins from 2‐DE. High expression of enolase 1 (ENO1) (HR = 1.67, logrank P = 1.9E‐05), ribosomal protein lateral stalk subunit P2 (RPLP2) (HR = 1.77, logrank P = 2.9e‐06), and NME/NM23 nucleoside diphosphate kinase 2 (NME1‐NME2) (HR = 2.65, logrank P = 3.9E‐15) was all significantly associated with poor survival (P < 0.05). Further, ENO1 was upregulated (P = 0.0004) and calcyphosine (CAPS1) was downregulated (P = 5.34E‐07) in TCGA LUAD RNA‐seq expression data. IHC revealed that prominent ENO1 staining (OR = 7.5, P = 0.034) and low levels of CAPS1 (OR = 0.01, P < 0.0001) staining were associated with BM incidence. Finally, we found that LUAD patients with high expression of ENO1 and RPLP2 had worse overall survival. This is the first instance where the genes ENO1, RPLP2, NME1‐NME2 and CAPS1 were associated with disease severity and progression in LUAD patients with BM. Thus, with this study, we have identified potential biomarkers and therapeutic targets for this disease.

INPP4B overexpression suppresses migration, invasion and angiogenesis of human prostate cancer cells

Inositol polyphosphate 4-phosphatase B (INPP4B) has been identified as a tumour suppressor in different human cancers. However, the role of INPP4B in the angiogenesis of human prostate cancer cells remains unclear. In this study, we first compared the expression of INPP4B between prostate cancer tissues and tumour-adjacent normal prostate tissues using immunohistochemistry. Then, we explored the role of INPP4B in prostate cancer progression via transfection of a Flag-INPP4B plasmid into PC3 and DU145 cells in vitro and in vivo. Our results showed that reduced INPP4B staining was significantly correlated with the tumour-node-metastasis stage. Moreover, transfection with Flag-INPP4B plasmid suppressed the migration and invasion of prostate cancer cells through inactivating the PI3K/Akt signalling pathway, at the same time decreased vascular endothelial growth factor secretion and suppressed human umbilical vein endothelial cells proliferation and tube formation. Futhermore, it was also found that INPP4B could inhibit tumour growth and angiogenesis in vivo. Altogether, our results supported that INPP4B acted as a tumour suppressor in human prostate cancer, and provided insights into development of a targeted therapy for this disease.

MicroRNA-590-3p promotes cell proliferation and invasion by targeting inositol polyphosphate 4-phosphatase type II in human prostate cancer cells

Inositol polyphosphate 4-phosphatase type II emerges as a tumor suppressor in prostate cancer, and its loss of expression is associated with poor prognosis for prostate cancer. However, the mechanism of downregulation of inositol polyphosphate 4-phosphatase type II in prostate cancer development has not yet been fully clarified. In this study, microRNA-590-3p was found to be upregulated in both prostate cancer tissues and cell lines. Overexpression of microRNA-590-3p by microRNA-590-3p mimics promoted prostate cancer cell proliferation and invasion and accelerated the growth of xenografted tumors, while microRNA-590-3p inhibitors contributed to inhibition of cellular proliferation and invasion as well as tumor growth. A dual-luciferase reporter assay and expression analysis further confirmed that inositol polyphosphate 4-phosphatase type II was a direct target of microRNA-590-3p. Enforced expression of microRNA-590-3p led to repression of inositol polyphosphate 4-phosphatase type II messenger RNA and protein expression, as well as upregulation of p-Akt, p-FoxO3a, and cyclin D1 and downregulation of p21 expression in prostate cancer cell lines. Overexpression of inositol polyphosphate 4-phosphatase type II could reduce microRNA-590-3p-induced cell proliferation and invasion as well as tumor growth, and decrease microRNA-590-3p-mediated upregulation of cyclin D1 and downregulation of p21 expression in prostate cancer cells. Taken together, our findings reveal that microRNA-590-3p is a potential onco-microRNA that participates in carcinogenesis of human prostate cancer by suppressing inositol polyphosphate 4-phosphatase type II expression and involving the Akt/FoxO3a pathway. MicroRNA-590-3p may represent a potential therapeutic target for prostate cancer patients.