Chemotherapy disrupts activity of translational regulatory proteins in bone marrow stromal cells

Multiple myeloma and bone marrow mesenchymal stem cells' crosstalk: Effect on translation initiation

Multiple myeloma (MM) malignant plasma cells reside in the bone marrow (BM) and convert it into a specialized pre-neoplastic niche that promotes the proliferation and survival of the cancer cells. BM resident mesenchymal stem cells (BM-MSCs) are altered in MM and in vitro studies indicate their transformation by MM proximity is within hours. The response time frame suggested that protein translation may be implicated. Thus, we assembled a co-culture model of MM cell lines with MSCs from normal donors (ND) and MM patients to test our hypothesis. The cell lines (U266, ARP-1) and BM-MSCs (ND, MM) were harvested separately after 72 h of co-culture and assayed for proliferation, death, levels of major translation initiation factors (eIF4E, eIF4GI), their targets, and regulators. Significant changes were observed: BM-MSCs (ND and MM) co-cultured with MM cell lines displayed elevated proliferation and death as well as increased expression/activity of eIF4E/eIF4GI; MM cell lines co-cultured with MM-MSCs also displayed higher proliferation and death rates coupled with augmented translation initiation factors; in contrast, MM cell lines co-cultured with ND-MSCs did not display elevated proliferation only death and had no changes in eIF4GI levels/activity. eIF4E expression was increased in one of the cell lines. Our study demonstrates that there is direct dialogue between the MM and BM-MSCs populations that includes translation initiation manipulation and critically affects cell fate. Future research should be aimed at identifying therapeutic targets that may be used to minimize the collateral damage to the cancer microenvironment and limit its recruitment into the malignant process. © 2015 Wiley Periodicals, Inc.

Matrix metalloproteinase-2 polymorphisms and clinical outcome of Chinese patients with nonsmall cell lung cancer treated with first-line, platinum-based chemotherapy

BACKGROUND

Matrix metalloproteinase-2 (MMP-2) is well known for its critical role in cell survival and cancer development. It also plays an important role in hematopoietic recovery after chemotherapy-induced myelosuppression. In this study, the authors investigated the association of MMP-2 polymorphisms with treatment efficacy and the occurrence of severe toxicity in patients with nonsmall cell lung cancer (NSCLC) who were receiving first-line, platinum-based chemotherapy.

METHODS

A pharmacogenetic association study was performed in 663 Chinese patients who had inoperable stage III/IV NSCLC and were receiving first-line, platinum-based regimens. Information about objective response, progression-free survival, overall survival, grade 3 or 4 gastrointestinal toxicity (nausea/vomiting), and hematologic toxicity (neutropenia, anemia, thrombocytopenia) was available. Sixteen tag single nucleotide polymorphisms (SNPs) of MMP-2 were assessed.

RESULTS

In 7 polymorphisms, significant associations were observed with the incidence of grade 3 or 4 neutropenia. The variant homozygotes of reference SNP rs12934241 exhibited the most significant effect on the risk of neutropenia, leading to an incidence rate that increased from 12.3% (for the C/C genotype) to 50% (for the T/T genotype; odds ratio, 8.33; P = 8.8 × 10(-5)). Stratified analyses indicated that rs12934241 exhibited a much stronger influence in the cisplatin-gemcitabine regimen subgroup than subgroups that received other regimens (P(interaction) = .003). Further haplotype analyses produced results that were consistent with results from single-SNP analyses. However, no significant association was observed between MMP-2 polymorphisms and treatment efficacy, including response rate, clinical benefit, progression-free survival, and overall survival.

CONCLUSIONS

To the authors' knowledge, this study provides the first evidence for a predictive role of MMP-2 polymorphisms in the variability of severe chemotherapy-related neutropenia among Chinese patients with platinum-treated, advanced NSCLC.

Bone marrow mesenchymal stem cells for improving hematopoietic function: an in vitro and in vivo model. Part 2: Effect on bone marrow microenvironment

The aim of the present study was to determine how mesenchymal stem cells (MSC) could improve bone marrow (BM) stroma function after damage, both in vitro and in vivo. Human MSC from 20 healthy donors were isolated and expanded. Mobilized selected CD34⁺ progenitor cells were obtained from 20 HSCT donors. For in vitro study, long-term bone marrow cultures (LTBMC) were performed using a etoposide damaged stromal model to test MSC effect in stromal confluence, capability of MSC to lodge in stromal layer as well as some molecules (SDF1, osteopontin,) involved in hematopoietic niche maintenance were analyzed. For the in vivo model, 64 NOD/SCID recipients were transplanted with CD34+ cells administered either by intravenous (IV) or intrabone (IB) route, with or without BM derived MSC. MSC lodgement within the BM niche was assessed by FISH analysis and the expression of SDF1 and osteopontin by immunohistochemistry. In vivo study showed that when the stromal damage was severe, TP-MSC could lodge in the etoposide-treated BM stroma, as shown by FISH analysis. Osteopontin and SDF1 were differently expressed in damaged stroma and their expression restored after TP-MSC addition. Human in vivo MSC lodgement was observed within BM niche by FISH, but MSC only were detected and not in the contralateral femurs. Human MSC were located around blood vessels in the subendoestal region of femurs and expressed SDF1 and osteopontin. In summary, our data show that MSC can restore BM stromal function and also engraft when a higher stromal damage was done. Interestingly, MSC were detected locally where they were administered but not in the contralateral femur.

Sex steroid ablation enhances hematopoietic recovery following cytotoxic antineoplastic therapy in aged mice

Cytotoxic antineoplastic therapy is widely used in the clinic as a treatment for malignant diseases. The treatment itself, however, leads to long-term depletion of the adaptive immune system, which is more pronounced in older patients, predominantly due to thymic atrophy. We and others have previously shown that withdrawal of sex steroids is able to regenerate the aged thymus and enhance recovery from autologous and allogeneic hematopoietic stem cell transplant. In this study we have examined the effects of sex steroid ablation (SSA) on the recovery of lymphopoiesis in the bone marrow (BM) and thymus following treatment with the chemotherapeutic agent cyclophosphamide (Cy) in middle-aged and old mice. Furthermore, we have also examined the impact of this regeneration on peripheral immunity. SSA enhanced the recovery of BM resident hematopoietic stem cells and lymphoid progenitors and promoted lymphopoiesis. Interestingly, Cy alone caused a profound increase in the recently described common lymphoid progenitor 2 (CLP-2) population in the BM. In the thymus, SSA caused a profound increase in cellularity as well as all intrathymic T-lineage progenitors including early T-lineage progenitors (ETPs) and non-canonical T cell progenitors such as the CLP-2. We also found that these transferred into numerical increases in the periphery with enhanced B and T cell numbers. Furthermore, these lymphocytes were found to have an enhanced functional capacity with no perturbation of the TCR repertoire. Taken together, these results provide the basis for the use of SSA in the clinic to enhance treatment outcomes from cytotoxic antineoplastic therapy.

Cap-dependent translation blockade and fixed dose-rate gemcitabine: interaction in an in vitro bioreactor system

Translation initiation commences with the binding of eIF-4F to the mRNA 5'-end cap. eIF-4F binds the cap structure via its eIF-4E subunit, which is the rate-limiting step for the initiation of translation. This pathway can be inhibited by 4E-binding proteins (4E-BPs). The present study investigated prolonged gemcitabine infusion in combination with reduced eIF-4E function on NSCLC cell viability in an in vitro bioreactor system. To assess attachment to the hollow fibers, cells with dominant active 4E-BP1 were first analyzed by scanning electron microscopy. Cells were treated with 0.5- or 2.5h (fixed dose rate) infusion (same total dose), simulating human plasma gemcitabine concentration-time profiles. An interaction was observed between fixed dose rate infusion gemcitabine and presence of dominant active 4E-BP1. We conclude that cap-dependent translation blockade and fixed dose rate infusion gemcitabine treatment results in a significant interaction affecting cell viability in vitro.

Impact of niche aging on thymic regeneration and immune reconstitution

The immune system undergoes dramatic changes with age-the thymus involutes, particularly from puberty, with the gradual loss of newly produced naïve T cells resulting in a restricted T cell receptor repertoire, skewed towards memory cells. Coupled with a similar, though less dramatic age-linked decline in bone marrow function, this translates to a reduction in immune responsiveness and has important clinical implications particularly in immune reconstitution following cytoablation regimes for cancer treatment or following severe viral infections such as HIV. Given that long-term reconstitution of the immune system is dependent on the bi-directional interplay between primary lymphoid organ stromal cells and the progenitors whose downstream differentiation they direct, regeneration of the thymus is fundamental to developing new strategies for the clinical management of many major diseases of immunological origin. This review will discuss the impact of aging on primary lymphoid organ niches and current approaches for thymic regeneration and immune reconstitution.