Dose- and time-dependence of the host-mediated response to paclitaxel therapy: a mathematical modeling approach

International audienceIt has recently been suggested that pro-tumorigenic host-mediated processes induced in response to chemotherapy counteract the anti-tumor activity of therapy, and thereby decrease net therapeutic outcome. Here we use experimental data to formulate a mathematical model describing the host response to different doses of paclitaxel (PTX) chemotherapy as well as the duration of the response. Three previously described host-mediated effects are used as readouts for the host response to therapy. These include the levels of circulating endothelial progenitor cells in peripheral blood and the effect of plasma derived from PTX-treated mice on migratory and invasive properties of tumor cells in vitro. A first set of mathematical models, based on basic principles of pharmacokinetics/pharmacodynamics, did not appropriately describe the dose-dependence and duration of the host response regarding the effects on invasion. We therefore provide an alternative mathematical model with a dose-dependent threshold, instead of a concentration-dependent one, that describes better the data. This model is integrated into a global model defining all three host-mediated effects. It not only precisely describes the data, but also correctly predicts host-mediated effects at different doses as well as the duration of the host response. This mathematical model may serve as a tool to predict the host response to chemotherapy in cancer patients, and therefore may be used to design chemotherapy regimens with improved therapeutic outcome by minimizing host mediated effects

Microparticles from tumors exposed to radiation promote immune evasion in part by PD-L1

Radiotherapy induces immune-related responses in cancer patients by various mechanisms. Here, we investigate the immunomodulatory role of tumor-derived microparticles (TMPs)-extracellular vesicles shed from tumor cells-following radiotherapy. We demonstrate that breast carcinoma cells exposed to radiation shed TMPs containing elevated levels of immune-modulating proteins, one of which is programmed death-ligand 1 (PD-L1). These TMPs inhibit cytotoxic T lymphocyte (CTL) activity both in vitro and in vivo, and thus promote tumor growth. Evidently, adoptive transfer of CTLs pre-cultured with TMPs from irradiated breast carcinoma cells increases tumor growth rates in mice recipients in comparison with control mice receiving CTLs pre-cultured with TMPs from untreated tumor cells. In addition, blocking the PD-1-PD-L1 axis, either genetically or pharmacologically, partially alleviates TMP-mediated inhibition of CTL activity, suggesting that the immunomodulatory effects of TMPs in response to radiotherapy is mediated, in part, by PD-L1. Overall, our findings provide mechanistic insights into the tumor immune surveillance state in response to radiotherapy and suggest a therapeutic synergy between radiotherapy and immune checkpoint inhibitors

Macrophage-Induced Lymphangiogenesis and Metastasis following Paclitaxel Chemotherapy Is Regulated by VEGFR3

While chemotherapy strongly restricts or reverses tumor growth, the response of host tissue to therapy can counteract its anti-tumor activity by promoting tumor re-growth and/or metastases, thus limiting therapeutic efficacy. Here, we show that vascular endothelial growth factor receptor 3 (VEGFR3)-expressing macrophages infiltrating chemotherapy-treated tumors play a significant role in metastasis. They do so in part by inducing lymphangiogenesis as a result of cathepsin release, leading to VEGF-C upregulation by heparanase. We found that macrophages from chemotherapy-treated mice are sufficient to trigger lymphatic vessel activity and structure in naive tumors in a VEGFR3-dependent manner. Blocking VEGF-C/VEGFR3 axis inhibits the activity of chemotherapy-educated macrophages, leading to reduced lymphangiogenesis in treated tumors. Overall, our results suggest that disrupting the VEGF-C/VEGFR3 axis not only directly inhibits lymphangiogenesis but also blocks the pro-metastatic activity of macrophages in chemotherapy-treated mice

Calcium Regulation of EGF-Induced ERK5 Activation: Role of Lad1-MEKK2 Interaction

The ERK5 cascade is a MAPK pathway that transmits both mitogenic and stress signals, yet its mechanism of activation is not fully understood. Using intracellular calcium modifiers, we found that ERK5 activation by EGF is inhibited both by the depletion and elevation of intracellular calcium levels. This calcium effect was found to occur upstream of MEKK2, which is the MAP3K of the ERK5 cascade. Co-immunoprecipitation revealed that EGF increases MEKK2 binding to the adaptor protein Lad1, and this interaction was reduced by the intracellular calcium modifiers, indicating that a proper calcium concentration is required for the interactions and transmission of EGF signals to ERK5. In vitro binding assays revealed that the proper calcium concentration is required for a direct binding of MEKK2 to Lad1. The binding of these proteins is not affected by c-Src-mediated phosphorylation on Lad1, but slightly affects the Tyr phosphorylation of MEKK2, suggesting that the interaction with Lad1 is necessary for full Tyr phosphorylation of MEKK2. In addition, we found that changes in calcium levels affect the EGF-induced nuclear translocation of MEKK2 and thereby its effect on the nuclear ERK5 activity. Taken together, these findings suggest that calcium is required for EGF-induced ERK5 activation, and this effect is probably mediated by securing proper interaction of MEKK2 with the upstream adaptor protein Lad1

The Dichotomous Role of Bone Marrow Derived Cells in the Chemotherapy-Treated Tumor Microenvironment

Bone marrow derived cells (BMDCs) play a wide variety of pro- and anti-tumorigenic roles in the tumor microenvironment (TME) and in the metastatic process. In response to chemotherapy, the anti-tumorigenic function of BMDCs can be enhanced due to chemotherapy-induced immunogenic cell death. However, in recent years, a growing body of evidence suggests that chemotherapy or other anti-cancer drugs can also facilitate a pro-tumorigenic function in BMDCs. This includes elevated angiogenesis, tumor cell proliferation and pro-tumorigenic immune modulation, ultimately contributing to therapy resistance. Such effects do not only contribute to the re-growth of primary tumors but can also support metastasis. Thus, the delicate balance of BMDC activities in the TME is violated following tumor perturbation, further requiring a better understanding of the complex crosstalk between tumor cells and BMDCs. In this review, we discuss the different types of BMDCs that reside in the TME and their activities in tumors following chemotherapy, with a major focus on their pro-tumorigenic role. We also cover aspects of rationally designed combination treatments that target or manipulate specific BMDC types to improve therapy outcomes

Calcium modulates Tyr phosphorylation of MEKK2 but not of Lad1.

<p>HeLa cells transfected with GFP-Lad1 were subject to different treatments as indicated (EGF 20 ng/ml; ionomycin (1 µM) or BAPTA-AM (15 µM) for 15 min; PP2 3 µM). GFP-Lad1 was immunoprecipitated with anti GFP Ab (<b>A, B</b>). Endogenous MEKK2 was immunoprecipitated by anti-MEKK2 Ab (<b>C, D</b>). Their phsophorylation on Tyr residues was detected by pY99 Ab. The experiments in this figure were reproduced 3 times.</p

EGF-induced ERK5 phosphorylation is mediated by c-Src and Lad1 but not by WNK1.

<p>(<b>A</b>) HeLa cells were transfected with GFP-Lad1 or vector control followed by treatment with EGF (20 ng/ml) for the indicated times. ERK5 phosphorylation was determined using upshift of ERK5 in blot. (<b>B</b>) Lad1 shRNA (Sh1<b>–</b>2 µg or Sh2<b>–</b>6 µg) or empty vector (con) were transfected into HeLa cells. The cells were stimulated by EGF and ERK5 phosphorylation was determined by Western blot as in (A). The levels of endogenous Lad1 and MEKK2 were determined by their corresponding Abs as indicated. (<b>C</b>) HeLa cells were transfected with GFP-Lad1 and the activation of ERK5 in response to EGF in the presence of ionomycin or BAPTA-AM was detected by band shift. All the experiments in this figure were reproduced at least three times.</p

Changes in calcium concentrations do not affect Lad1 localization but inhibit nuclear MEKK2 accumulation.

<p>Serum starved HeLa cells were pretreated with vehicle, ionomycin (1 µM) or BAPTA-AM (15 µM) for 15 min and then stimulated with EGF (20 ng/ml) for 10 min. The cells were stained with anti Lad1 or anti MEKK2 Abs and visualized with fluorescent microscopy. This experiment was reproduced 3 times.</p

MEKK2-Lad1 interaction is modulated by calcium.

<p>(<b>A</b>) Exogenously expressed GFP-Lad1 was immunoprecipitated from HeLa cells with indicated treatments. The MEKK2 molecules associated with GFP-Lad1 was detected by anti MEKK2 Ab. The lower panel shows the average quantification of three independent experiments. The error bars represent standard deviation. P values (*: P<0.05; **: P<0.01) were obtained using T-test by comparing the vehicle control group and the iononmycin- or the BAPTA-AM-treated group. (<b>B</b>) MEKK2 was immunoprecipitated from HeLa cells without or with treatment of EGF. It was then incubated with recombinant GST-Lad1 in the presence of various concentrations of calcium. The associated GST-Lad1 was detected by anti Lad1 Ab. The lower panel shows the average quantification of three independent experiments. The error bars represent standard deviation. P values (*: P<0.05) were obtained using T-test within each group, EGF-treated or nontreated, by comparing the interaction at 0.25 µM calcium and that without calcium.</p