Cytotoxic effects of targeted agent alone or with chemotherapy in the treatment of adenoid cystic carcinoma: a preclinical study

Adenoid cystic carcinoma (ACC) is a rare malignancy characterized by high incidence of relapse. When relapsing, ACC has an indolent but relentless behaviour, thus leading to a poor long-term prognosis. The treatment of choice of relapsing ACC remains surgery followed by radiotherapy, whenever feasible. Therapeutic weapons are limited to systemic drugs. The most widely used chemotherapy regimen is the combination of cisplatin and doxorubicin, however with low response rate and not long lasting; there is also a lack of alternatives for second line therapies in case of disease progression. Therefore, a more comprehensive strategy aimed at identifying at preclinical level the most promising drugs or combination is clearly needed. In this study, the cytotoxic effects of two standard chemotherapy drugs, cisplatin and doxorubicin, and of five targeted therapy-drugs was tested in vitro, on an h-TERT immortalized ACC cell line, and in vivo, on zebrafish embryos with ACC tumoral cell xenograft. Then, combinations of one standard chemotherapy drug plus one targeted therapy drug were also evaluated, in order to find the best treatment strategy for ACC. Data obtained demonstrated that both vorinostat and olaparib significantly increased the standard chemotherapy cytotoxic effects, suggesting new interesting therapeutic options for ACC.

HMGA1 negatively regulates NUMB expression at transcriptional and post transcriptional level in glioblastoma stem cells

Glioblastoma (GBM) is a lethal, fast-growing brain cancer, affecting 2-3 per 100,000 adults per year. It arises from multipotent neural stem cells which have reduced their ability to divide asymmetrically and hence divide symmetrically, generating increasing number of cancer stem cells, fostering tumor growth. We have previously demonstrated that the architectural transcription factor HMGA1 is highly expressed in brain tumor stem cells (BTSCs) and that its silencing increases stem cell quiescence, reduces self-renewal and sphere-forming efficiency in serial passages, suggesting a shift from symmetric to asymmetric division. Since NUMB expression is fundamental for the fulfillment of asymmetric division in stem cells, and is lost or reduced in many tumors, including GBM, we have investigated the ability of HMGA1 to regulate NUMB expression. Here, we show that HMGA1 negatively regulates NUMB expression at transcriptional level, by binding its promoter and counteracting c/EBP-β and at posttranscriptional level, by regulating the expression of MSI1 and of miR-146a. Finally, we report that HMGA1 knockdown-induced NUMB upregulation leads to the downregulation of the NOTCH1 pathway. Therefore, the data reported here indicate that HMGA1 negatively regulates NUMB expression in BTSCs, further supporting HMGA1 targeting as innovative and effective anti-cancer therapy.

Neurotrophin channeling of neural progenitor cell differentiation

The act of defining neuropoietic progenitor/stem cells is still in its early phases. Epidermal growth factor (EGF) stimulates extended proliferation of aggregates of subventricular striatal cells, taken from E15 mouse striatum, termed neurospheres in liquid culture. We have shown here and in previous work, using either immunohistochemistry or RT-PCR, that neurosphere cells express 13 cytokines (32 tested) and 20 cytokine receptors (28 tested), with 11 potential paracrine and nine potential autocrine loops. The neurotrophin receptors, Trk A, B, and C, were all expressed. Using a newly developed FACS single cell deposition technique, we evaluated the capacity of single EGF stimulated neurosphere cells to respond to the ligands for Trk A and B, nerve growth factor (NGF), and brain-derived neurotrophin factor (BDNF). Addition of NGF or BDNF to EGF for 14 days had no effect, but removal of EGF at day 14 with subsequent addition of BDNF or NGF resulted in an increase in neuronal and astroglial, but not oligodendrocyte, colony cells at 21 and 28 days of culture for BDNF, and of both cell types at 28 days for NGF. Tri-lineage colonies increased at day 21 with BDNF and at day 28 for both NGF and BDNF. Gross colony morphology also showed changes with neurotrophin addition, forming multiple individual cell balls or filamentous spreads. When EGF was withdrawn, a threshold effect was observed, with small, but not large, colonies ceasing growth. BDNF and NGF showed no effects on cell proliferation when compared to EGF controls, as determined by 5'-bromo-2-deoxyuridine (BrdU) incorporation and thus, they appear to affect differentiation of progenitor cells. These data indicate a sequential action of cytokines with EGF maintaining viability and proliferation and blocking differentiation. Removal of EGF is then permissive for the differentiating effects of BDNF and NGF. These data further indicate that the majority of EGF neurosphere clones have neurotrophin dependent tri-lineage potential.

Correlates between hematopoiesis and neuropoiesis: neural stem cells

There are many parallels between the neuropoietic and lymphohematopoietic systems. The lymphohematopoietic stem/progenitor cell system has been extensively characterized, but there are still major questions relating to the definitive stem cell assay, the structure of the system (i.e., hierarchical versus cell cycle-based), and the nature of differentiation (i.e., stochastic versus deterministic). Recent data have established the existence of an epidermal growth factor (EGF)-responsive neural stem cell in adult mice. We have studied these neural progenitor/stem cells in fetal (day 15) and 2-day postnatal mice and established a single-cell progenitor assay and a variety of putative uni-, bi-, and tripotential stem cells that form in response to EGF. Neurospheres are the EGF-responsive neural units that grow in liquid culture, and we have found that cells derived from these neurospheres express a wide array of cytokines and their receptors. This will provide a window on the hemopoietic progenitor system analogous to that created by the description of in vitro growth of clonal hematopoietic progenitors.

Expression and function of colony-stimulating factors and their receptors in human prostate carcinoma cell lines

BACKGROUND

The predeliction for prostate carcinoma cells to metastasize to bone suggests the hypothesis that bone and/or bone marrow-derived factors may promote prostate carcinoma cell growth or survival, or serve as chemoattractants for these cells.

METHODS

We screened three prostate carcinoma cell lines, DU-145, PC-3, and LNCaP, for the expression of several hematopoiesis-associated colony-stimulating factors (CSFs) and their receptors using RT-PCR (reverse transcriptase-polymerase chain reaction) and immunohistochemical methods, and examined their functional effects.

RESULTS

All of these cell lines express granulocyte-macrophage colony-stimulating factor (GM-CSF) and macrophage colony-stimulating factor (M-CSF), and the DU-145 and PC-3 lines express stem-cell factor (SCF), as determined by RT-PCR and ELISA. Each of these cell lines expresses the receptors for SCF, GM-CSF, M-CSF, and granulocyte colony-stimulating factor (G-CSF). M-CSF enhanced the soft-agar clonogenicity of PC-3 and DU-145 cells, and GM-CSF stimulated all three cell lines. SCF stimulated the clonogenic growth of DU-145 cells. G-CSF marginally abrogated the induction of cell death in the PC-3 and LNCaP cell lines under serum-free conditions. GM-CSF and M-CSF stimulated modest chemotaxis of PC-3, DU-145, and LNCaP cells (most prominently in PC-3 cells).

CONCLUSIONS

These data suggest that 1) CSFs may be part of a network of paracrine and autocrine loops that modulate prostate carcinoma cell activity, and 2) the growth-stimulatory, survival-enhancing, and/or chemotactic actions of bone marrow-derived CSFs on prostate carcinoma cells may explain in part why bone is a preferential site of prostatic carcinoma metastases.