Inhibition of the monocarboxylate transporter MCT1 by AZD3965 results in an increase in glycolysis in human tumor cell lines and xenografts. This is indicated by changes in the levels of specific ...glycolytic metabolites and in changes in glycolytic enzyme kinetics. These drug-induced metabolic changes translate into an inhibition of tumor growth in vivo. Thus, we combined AZD3965 with fractionated radiation to treat small cell lung cancer (SCLC) xenografts and showed that the combination provided a significantly greater therapeutic effect than the use of either modality alone. These results strongly support the notion of combining MCT1 inhibition with radiotherapy in the treatment of SCLC and other solid tumors.
Small-cell lung cancer (SCLC), an aggressive neuroendocrine tumor with early dissemination and dismal prognosis, accounts for 15-20% of lung cancer cases and ∼200,000 deaths each year. Most cases are ...inoperable, and biopsies to investigate SCLC biology are rarely obtainable. Circulating tumor cells (CTCs), which are prevalent in SCLC, present a readily accessible 'liquid biopsy'. Here we show that CTCs from patients with either chemosensitive or chemorefractory SCLC are tumorigenic in immune-compromised mice, and the resultant CTC-derived explants (CDXs) mirror the donor patient's response to platinum and etoposide chemotherapy. Genomic analysis of isolated CTCs revealed considerable similarity to the corresponding CDX. Most marked differences were observed between CDXs from patients with different clinical outcomes. These data demonstrate that CTC molecular analysis via serial blood sampling could facilitate delivery of personalized medicine for SCLC. CDXs are readily passaged, and these unique mouse models provide tractable systems for therapy testing and understanding drug resistance mechanisms.
The ER (endoplasmic reticulum) is a fascinating organelle that is highly dynamic, undergoing constant movement and reorganization. It has many key roles, including protein synthesis, folding and ...trafficking, calcium homoeostasis and lipid synthesis. It can expand in size when needed, and the balance between tubular and lamellar regions can be altered. The distribution and organization of the ER depends on both motile and static interactions with microtubules and the actin cytoskeleton. In the present paper, we review how the ER moves, and consider why this movement may be important for ER and cellular function.
Small cell lung cancer (SCLC) is a neuroendocrine lung cancer characterized by fast growth, early dissemination, and rapid resistance to chemotherapy. We identified a population of long-term ...tumor-propagating cells (TPCs) in a mouse model of SCLC. This population, marked by high levels of EpCAM and CD24, is also prevalent in human primary SCLC tumors. Murine SCLC TPCs are numerous and highly proliferative but not intrinsically chemoresistant, indicating that not all clinical features of SCLC are linked to TPCs. SCLC TPCs possess a distinct transcriptional profile compared to non-TPCs, including elevated MYC activity. Genetic and pharmacological inhibition of MYC in SCLC cells to non-TPC levels inhibits long-term propagation but not short-term growth. These studies identify a highly tumorigenic population of SCLC cells in mouse models, cell lines, and patient tumors and a means to target them in this most fatal form of lung cancer.
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•CD24High CD44Low EpCAMHigh mark tumor-propagating cells (TPCs) in mouse SCLC•SCLC TPCs generate non-TPCs and are proliferative and abundant but not chemoresistant•Elevated MYC activity is required for the maintenance of TPCs in SCLC tumors•A low dose of the transcriptional inhibitor JQ1 inhibits long-term SCLC growth
Jahchan et al. use a genetically engineered mouse model of small cell lung cancer (SCLC) to functionally characterize cancer stem cells (tumor-propagating cells, TPCs). SCLC TPCs are numerous in tumors, cycle quickly, are chemosensitive, and depend on elevated MYC activity for their ability to propagate tumors.
Generating the extended endoplasmic reticulum (ER) network depends on microtubules, which act as tracks for motor-driven ER tubule movement, generate the force to extend ER tubules by means of ...attachment to growing microtubule plus-ends and provide static attachment points. We have analysed ER dynamics in living VERO cells and find that most ER tubule extension is driven by microtubule motors. Surprisingly, we observe that ~50% of rapid ER tubule movements occur in the direction of the centre of the cell, driven by cytoplasmic dynein. Inhibition of this movement leads to an accumulation of lamellar ER in the cell periphery. By expressing dominant-negative kinesin-1 constructs, we show that kinesin-1 drives ER tubule extension towards the cell periphery and that this motility is dependent on the KLC1B kinesin light chain splice form but not on KLC1D. Inhibition of kinesin-1 promotes a shift from tubular to lamellar morphology and slows down the recovery of the ER network after microtubule depolymerisation and regrowth. These observations reconcile previous conflicting studies of kinesin-1 function in ER motility in vivo. Furthermore, our data reveal that cytoplasmic dynein plays a role in ER motility in a mammalian cultured cell, demonstrating that ER motility is more complex than previously thought.
Microtubules and their associated proteins (MAPs) underpin the polarity of specialised cells. Adenomatous polyposis coli (APC) is one such MAP with a multifunctional agenda that requires precise ...intracellular localisations. Although APC has been found to associate with kinesin-2 subfamily members, the exact mechanism for the peripheral localization of APC remains unclear. Here we show that the heavy chain of kinesin-1 directly interacts with the APC C-terminus, contributing to the peripheral localisation of APC in fibroblasts. In rat hippocampal neurons the kinesin-1 binding domain of APC is required for its axon tip enrichment. Moreover, we demonstrate that APC requires interactions with both kinesin-2 and kinesin-1 for this localisation. Underlining the importance of the kinesin-1 association, neurons expressing APC lacking kinesin-1-binding domain have shorter axons. The identification of this novel kinesin-1-APC interaction highlights the complexity and significance of APC localisation in neurons.
In this project, the role that kinesin-1, its cargoes and the Rab family proteins in migration and focal adhesion dynamics has been investigated. When considering cell movement, the majority of ...studies have focussed on commonly studied themes such as cell polarity, Rho GTPases and the role of specific integrins and substrates. This project is novel in many respects, including the approaches taken.
In this project, the role that kinesin-1, its cargoes and the Rab family proteins in migration and focal adhesion dynamics has been investigated. When considering cell movement, the majority of ...studies have focussed on commonly studied themes such as cell polarity, Rho GTPases and the role of specific integrins and substrates. This project is novel in many respects, including the approaches taken. In our initial studies we have employed a specific inhibitor of kinesin-1 to address these questions. We have demonstrated that the inhibition of kinesin-1 results in a statistically significant increase in the proportion of the cell that is covered by focal adhesions which leads to a highly statistically significant inhibition of cell movement. We postulate that this inhibition of migration may be via an effect on focal adhesions, but probably more prominently via an effect on Adenomatous Polyposis Coli protein (APC) localisation. APC is known to be involved in control of migration and the peripheral localisation of APC is required for this role 1, 2. An interaction between kinesin-1 and APC has been demonstrated and moreover it has been shown that kinesin-1 is required for the peripheral localisation of APC. For the first time, several Rab proteins have been screened simultaneously for a role in cell migration. Furthermore, the movement of these Rab positive vesicles has been recorded in cells migrating on 3D matrices. A clear localisation of Rab11 to areas of membrane retraction and a localisation of Rab22 to structures resembling macropinosomes has been observed. In addition, the over-expression of Rab8 leads to a striking change in cell morphology and an apparent retraction defect. Experiments to determine the contributions of individual Rab proteins to the migratory ability of cells using dominant negative and constitutively active constructs suffered from a lack of reproducibility, but these experiments resulted in the generation of multiple dominant negative and constitutively active Rab constructs that will be useful for future experiments. These experiments also helped to highlight important considerations for the study of migration that resulted in a much greater reproducibility of the migration experiments when kinesin-1 was inhibited. The effect of Rab proteins and their dominant negative and constitutively active mutants on focal adhesion size was also investigated but the data were variable.
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