Breast cancer represents a major health challenge. The majority of breast cancer deaths are due to cancer progression/recurrence for which no efficient therapies exist. Aggressive breast cancers are characterized by loss of cellular differentiation. Defining molecular mechanisms/targets contributing to cancer aggressiveness is needed to guide the design of new screening and targeted treatments. Here, we describe a novel tumor promoting function for the Cleavage and Polyadenylation Factor-6 (CPSF6). Importantly, aggressive breast cancer cells of luminal B, HER2-overexpressing and triple negative subtypes show dependency on CPSF6 for viability and tumorigenic capacity. Mechanistically, we found CPSF6 to interact with components of the A-to-I RNA editing machinery, paraspeckles and ADAR1 enzyme, and to be required for their physical integrity. Clinically, we found CPSF6 and all core paraspeckles proteins to be overexpressed in human breast cancer cases and their expression to correlate with poor patient outcomes. Finally, we found prolactin, a key mammary differentiation factor, to suppress CPSF6/RNA editing activity. Together, this study revealed CPSF6 as a molecular target with clinical relevance for prognosis and therapy in breast cancer.

Background Epithelial mesenchymal plasticity (EMP) is deemed vital in breast cancer progression, metastasis, stemness and resistance to therapy. Therefore, characterizing molecular mechanisms contributing to EMP are in need enabling the development of more advanced therapeutics against breast cancer. While kinesin superfamily proteins (KIFs) are well known for their role in intracellular cargo movement, our knowledge of their function in breast tumorigenesis is still limited. Methods Various breast cancer cell lines representing different molecular subtypes were used to determine the role of kinesine-1 subunits KIF5B/KLC1 in regulation of EMP. Findings In breast cancer, we show that kinesin family member 5B (KIF5B) and its partner protein kinesin light chain 1 (KLC1), subunits of kinesin-1, to play differential roles in regulating EMP and tumorigenesis. Indeed, we found KIF5B to be expressed in triple negative (TN)-basal-like/claudin low breast cancer subtype and to be an inducer of epithelial-mesenchymal transition (EMT), stemness, invasiveness, tumor formation and metastatic colonization. Whereas, we found KLC1 to be expressed in epithelial/luminal breast cancer subtypes and to be a suppressor of EMT, invasion, metastasis and stem cell markers expression as well as to be an inducer of epithelial/luminal phenotype. Interestingly, in TN-basal-like/claudin low cells we found a novel nuclear accumulation of KIF5B and its interaction with the EMT transcriptional regulator Snail1 independent of KLC1. In addition, TGF-β mediated pro-invasive activity was found to be dependent on KIF5B expression. In contrast, the epithelial differentiation factor and EMT suppressor prolactin (PRL) was found to repress KIF5B gene expression and KIF5B-Snail1 nuclear accumulation, but enhanced KLC1 gene expression and KIF5B-KLC1 interaction. Interpretation Together, these results highlight a new paradigm for kinesin-1 function in breast tumorigenesis by regulating EMP programing and aggressiveness. Fund This work was supported by the Canadian Institutes of Health Research (operating grants #233437 and 233438) granted to Suhad Ali.

Dedifferentiation increased cellular plasticity and stemness are established derivers of tumor heterogeneity, metastasis and therapeutic failure resulting in incurable cancers. Therefore, it is essential to decipher pro/forward-differentiation mechanisms in cancer that may serve as therapeutic targets. We found that interfering with expression of the receptor for the lactogenic hormone prolactin (PRLR) in breast cancer cells representative of the luminal and epithelial breast cancer subtypes (hormone receptor positive (HR+) and HER2-enriched (HER2-E) resulted in loss of their differentiation state, enriched for stem-like cell subpopulations, and increased their tumorigenic capacity in a subtype-specific manner. Loss of PRLR expression in HR+ breast cancer cells caused their dedifferentiation generating a mesenchymal-basal-like phenotype enriched in CD44+ breast cancer stem-like cells (BCSCs) showing high tumorigenic and metastatic capacities and resistance to anti-hormonal therapy. Whereas loss of PRLR expression in HER2-E breast cancer cells resulted in loss of their luminal differentiation yet enriched for epithelial ALDH+ BCSC population showing elevated HER2-driven tumorigenic, multi-organ metastatic spread, and resistance to anti-HER2 therapy. Collectively, this study defines PRLR as a driver of precise luminal and epithelial differentiation limiting cellular plasticity, stemness, and tumorigenesis and emphasizing the function of pro/forward-differentiation pathways as a foundation for the discovery of anti-cancer therapeutic targets.

In paddy fields, overuse of nitrogen fertilizer to maximize yields can lead to excessive economic loss and degradation of the environment. Therefore, studying the effects of urea–chitosan nanohybrid as a slow released source of nitrogen fertilizer on rice cultivation was the aim of our study. The effects of fertilization applications, namely: CU: control treatment; U1: application of a full recommended dose of classical urea (165 kg N ha−1); U2: adding recommended dose of classical urea by 80% + exogenous urea–chitosan nanohybrid 250 mg N/L; U3: adding recommended dose of classical urea by 80% + exogenous urea–chitosan nanohybrid 500 mg N/L; U4: adding recommended dose of classical urea by 60% + exogenous urea–chitosan nanohybrid 250 mg N/L; U5: adding recommended dose of classical urea by 60% + exogenous urea–chitosan nanohybrid 500 mg N/L; U6: adding recommended dose of classical urea by 40% + exogenous urea–chitosan nanohybrid 250 mg N/L; and U7: adding recommended dose of classical urea by 40% + exogenous urea–chitosan nanohybrid 500 mg N/L on growth indicators, yield-related components, grain productivity, and N uptake status of rice plants were investigated during two successive seasons. As a result, significant achievements concerning growth, yield and yield-related traits were obtained when rice plants were fertilized with exogenous urea–chitosan nanohybrid (i.e., 500 mg N/L) + 60% classical urea without a significant decline in the studied traits compared to the full recommended dose of classical urea. Accordingly, this investigation revealed that chitosan nanohybrid at 500 mg N/L as a compensatory alternative can be used in saving 40% of classical urea requirement.