An Emerging Role for Tubulin Isotypes in Modulating Cancer Biology and Chemotherapy Resistance.

Tubulin proteins, as components of the microtubule cytoskeleton perform critical cellular functions throughout all phases of the cell cycle. Altered tubulin isotype composition of microtubules is emerging as a feature of aggressive and treatment refractory cancers. Emerging evidence highlighting a role for tubulin isotypes in differentially influencing microtubule behaviour and broader functional networks within cells is illuminating a complex role for tubulin isotypes regulating cancer biology and chemotherapy resistance. This review focuses on the role of different tubulin isotypes in microtubule dynamics as well as in oncogenic changes that provide a survival or proliferative advantage to cancer cells within the tumour microenvironment and during metastatic processes. Consideration of the role of tubulin isotypes beyond their structural function will be essential to improving the current clinical use of tubulin-targeted chemotherapy agents and informing the development of more effective cancer therapies.

Complete Khoisan and Bantu genomes from southern Africa.

The genetic structure of the indigenous hunter-gatherer peoples of southern Africa, the oldest known lineage of modern human, is important for understanding human diversity. Studies based on mitochondrial and small sets of nuclear markers have shown that these hunter-gatherers, known as Khoisan, San, or Bushmen, are genetically divergent from other humans. However, until now, fully sequenced human genomes have been limited to recently diverged populations. Here we present the complete genome sequences of an indigenous hunter-gatherer from the Kalahari Desert and a Bantu from southern Africa, as well as protein-coding regions from an additional three hunter-gatherers from disparate regions of the Kalahari. We characterize the extent of whole-genome and exome diversity among the five men, reporting 1.3 million novel DNA differences genome-wide, including 13,146 novel amino acid variants. In terms of nucleotide substitutions, the Bushmen seem to be, on average, more different from each other than, for example, a European and an Asian. Observed genomic differences between the hunter-gatherers and others may help to pinpoint genetic adaptations to an agricultural lifestyle. Adding the described variants to current databases will facilitate inclusion of southern Africans in medical research efforts, particularly when family and medical histories can be correlated with genome-wide data.

ID proteins regulate diverse aspects of cancer progression and provide novel therapeutic opportunities.

The inhibitor of differentiation (ID) proteins are helix-loop-helix transcriptional repressors with established roles in stem cell self-renewal, lineage commitment, and niche interactions. While deregulated expression of ID proteins in cancer was identified more than a decade ago, emerging evidence has revealed a central role for ID proteins in neoplastic progression of multiple tumor types that often mirrors their function in physiological stem and progenitor cells. ID proteins are required for the maintenance of cancer stem cells, self-renewal, and proliferation in a range of malignancies. Furthermore, ID proteins promote metastatic dissemination through their role in remodeling the tumor microenvironment and by promoting tumor-associated endothelial progenitor cell proliferation and mobilization. Here, we discuss the latest findings in this area and the clinical opportunities that they provide.

New insights into the role of ID proteins in breast cancer metastasis: a MET affair.

The establishment of lethal metastases depends on the capacity of a small number of cancer cells to regenerate a tumor after entering a target organ. Stankic and colleagues have identified a role for the inhibitor of differentiation protein, ID1, as a critical regulator of breast cancer stem-like properties and metastatic colonization. Under the control of tumor growth factor-beta signaling, ID1 induces mesenchymal-epithelial transition at the metastatic site by antagonizing the activity of the basic helix-loop-helix transcription factor Twist1. This study sheds light on mechanisms that initiate metastatic outgrowth, and strengthens the concept that epithelial-mesenchymal plasticity is crucial at different stages of metastasis.

ßIII-tubulin suppression enhances the activity of Amuvatinib to inhibit cell proliferation in c-Met positive non-small cell lung cancer cells.

Non-Small Cell Lung Carcinoma (NSCLC) remains a leading cause of cancer death. Resistance to therapy is a significant problem, highlighting the need to find new ways of sensitising tumour cells to therapeutic agents. ßIII-tubulin is associated with aggressive tumours and chemotherapy resistance in a range of cancers including NSCLC. ßIII-tubulin expression has been shown to impact kinase signalling in NSCLC cells. Here, we sought to exploit this interaction by identifying co-activity between ßIII-tubulin suppression and small-molecule kinase inhibitors. To achieve this, a forced-genetics approach combined with a high-throughput drug screen was used. We show that activity of the multi-kinase inhibitor Amuvatinib (MP-470) is enhanced by ßIII-tubulin suppression in independent NSCLC cell lines. We also show that this compound significantly inhibits cell proliferation among ßIII-tubulin knockdown cells expressing the receptor tyrosine kinase c-Met. Together, our results highlight that ßIII-tubulin suppression combined with targeting specific receptor tyrosine kinases may represent a novel therapeutic approach for otherwise difficult-to-treat lung carcinomas.

ßIII-Tubulin Gene Regulation in Health and Disease.

Microtubule proteins form a dynamic component of the cytoskeleton, and play key roles in cellular processes, such as vesicular transport, cell motility and mitosis. Expression of microtubule proteins are often dysregulated in cancer. In particular, the microtubule protein ßIII-tubulin, encoded by the TUBB3 gene, is aberrantly expressed in a range of epithelial tumours and is associated with drug resistance and aggressive disease. In normal cells, TUBB3 expression is tightly restricted, and is found almost exclusively in neuronal and testicular tissues. Understanding the mechanisms that control TUBB3 expression, both in cancer, mature and developing tissues will help to unravel the basic biology of the protein, its role in cancer, and may ultimately lead to the development of new therapeutic approaches to target this protein. This review is devoted to the transcriptional and posttranscriptional regulation of TUBB3 in normal and cancerous tissue.

ßIII-Tubulin Structural Domains Regulate Mitochondrial Network Architecture in an Isotype-Specific Manner.

ßIII-tubulin is a neuronal microtubule protein that is aberrantly expressed in epithelial cancers. The microtubule network is implicated in regulating the architecture and dynamics of the mitochondrial network, although the isotype-specific role for ß-tubulin proteins that constitute this microtubule network remains unclear. High-resolution electron microscopy revealed that manipulation of ßIII-tubulin expression levels impacts the volume and shape of mitochondria. Analysis of the structural domains of the protein identifies that the C-terminal tail of ßIII-tubulin, which distinguishes this protein from other ß-tubulin isotypes, significantly contributes to the isotype-specific effects of ßIII-tubulin on mitochondrial architecture. Mass spectrometry analysis of protein-protein interactions with ß-tubulin isotypes identifies that ßIII-tubulin specifically interacts with regulators of mitochondrial dynamics that may mediate these functional effects. Advanced quantitative dynamic lattice light sheet imaging of the mitochondrial network reveals that ßIII-tubulin promotes a more dynamic and extended reticular mitochondrial network, and regulates mitochondrial volume. A regulatory role for the ßIII-tubulin C-terminal tail in mitochondrial network dynamics and architecture has widespread implications for the maintenance of mitochondrial homeostasis in health and disease.

ß-tubulin carboxy-terminal tails exhibit isotype-specific effects on microtubule dynamics in human gene-edited cells.

Microtubules are highly dynamic structures that play an integral role in fundamental cellular functions. Different α- and ß-tubulin isotypes are thought to confer unique dynamic properties to microtubules. The tubulin isotypes have highly conserved structures, differing mainly in their C-terminal tail sequences. However, little is known about the importance of the C-terminal tail in regulating and co-ordinating microtubule dynamics. We developed syngeneic human cell models using gene-editing to precisely modify the ß-tubulin C-terminal tail region while preserving the endogenous microtubule network. Fluorescent microscopy of live cells, coupled with advanced image analysis revealed that the ß-tubulin C-terminal tails differentially co-ordinate the collective and individual dynamic behaviour of microtubules by affecting microtubule growth rates and explorative microtubule assembly in an isotype-specific manner. Furthermore, ßI- and ßIII-tubulin C-terminal tails differentially regulate the sensitivity of microtubules to tubulin-binding agents and the microtubule depolymerising protein MCAK. The sequence of the ß-tubulin tail encodes regulatory information that instructs and co-ordinates microtubule dynamics, thereby fine-tuning microtubule dynamics to support cellular functions.

Recent Progress in Energy-Driven Water Splitting.

Hydrogen is readily obtained from renewable and non-renewable resources via water splitting by using thermal, electrical, photonic and biochemical energy. The major hydrogen production is generated from thermal energy through steam reforming/gasification of fossil fuel. As the commonly used non-renewable resources will be depleted in the long run, there is great demand to utilize renewable energy resources for hydrogen production. Most of the renewable resources may be used to produce electricity for driving water splitting while challenges remain to improve cost-effectiveness. As the most abundant energy resource, the direct conversion of solar energy to hydrogen is considered the most sustainable energy production method without causing pollutions to the environment. In overall, this review briefly summarizes thermolytic, electrolytic, photolytic and biolytic water splitting. It highlights photonic and electrical driven water splitting together with photovoltaic-integrated solar-driven water electrolysis.

ID4 controls mammary stem cells and marks breast cancers with a stem cell-like phenotype.

Basal-like breast cancer (BLBC) is a heterogeneous disease with poor prognosis; however, its cellular origins and aetiology are poorly understood. In this study, we show that inhibitor of differentiation 4 (ID4) is a key regulator of mammary stem cell self-renewal and marks a subset of BLBC with a putative mammary basal cell of origin. Using an ID4GFP knock-in reporter mouse and single-cell transcriptomics, we show that ID4 marks a stem cell-enriched subset of the mammary basal cell population. ID4 maintains the mammary stem cell pool by suppressing key factors required for luminal differentiation. Furthermore, ID4 is specifically expressed by a subset of human BLBC that possess a very poor prognosis and a transcriptional signature similar to a mammary stem cell. These studies identify ID4 as a mammary stem cell regulator, deconvolute the heterogeneity of BLBC and link a subset of mammary stem cells to the aetiology of BLBC.