High‐dose, short‐term, anti‐inflammatory treatment with dexamethasone reduces growth and augments the effects of 5‐fluorouracil on dimethyl‐α‐benzanthracene‐induced mammary tumors in rats

Advantages and drawbacks of dexamethasone in glioblastoma multiforme

The most widespread, malignant, and deadliest type of glial tumor is glioblastoma multiforme (GBM). Despite radiation, chemotherapy, and radical surgery, the median survival of afflicted individuals is about 12 months. Unfortunately, existing therapeutic interventions are abysmal. Dexamethasone (Dex), a synthetic glucocorticoid, has been used for many years to treat brain edema and inflammation caused by GBM. Several investigations have recently shown that Dex also exerts antitumoral effects against GBM. On the other hand, more recent disputed findings have questioned the long-held dogma of Dex treatment for GBM. Unfortunately, steroids are associated with various undesirable side effects, including severe immunosuppression and metabolic changes like hyperglycemia, which may impair the survival of GBM patients. Current ideas and concerns about Dex's effects on GBM cerebral edema, cell proliferation, migration, and its clinical outcomes were investigated in this study.

Mechanisms behind context-dependent role of glucocorticoids in breast cancer progression

Glucocorticoids (GCs), mostly dexamethasone (dex), are routinely administered as adjuvant therapy to manage side effects in breast cancer. However, recently, it has been revealed that dex triggers different effects and correlates with opposite outcomes depending on the breast cancer molecular subtype. This has raised new concerns regarding the generalized use of GC and suggested that the context-dependent effects of GCs can be taken into potential consideration during treatment design. Based on this, attention has recently been drawn to the role of the glucocorticoid receptor (GR) in development and progression of breast cancer. Therefore, in this comprehensive review, we aimed to summarize the different mechanisms behind different context-dependent GC actions in breast cancer by applying a multilevel examination, starting from the association of variants of the GR-encoding gene to expression at the mRNA and protein level of the receptor, and its interactions with other factors influencing GC action in breast cancer. The role of GCs in chemosensitivity and chemoresistance observed during breast cancer therapy is discussed. In addition, experiences using GC targeting therapeutic options (already used and investigated in preclinical and clinical trials), such as classic GC dexamethasone, selective glucocorticoid receptor agonists and modulators, the GC antagonist mifepristone, and GR coregulators, are also summarized. Evidence presented can aid a better understanding of the biology of context-dependent GC action that can lead to further advances in the personalized therapy of breast cancer by the evaluation of GR along with the conventional estrogen receptor (ER) and progesterone receptor (PR) in the routine diagnostic procedure.

Stromal integrin α11-deficiency reduces interstitial fluid pressure and perturbs collagen structure in triple-negative breast xenograft tumors

Background

Cancer progression is influenced by a pro-tumorigenic microenvironment. The aberrant tumor stroma with increased collagen deposition, contractile fibroblasts and dysfunctional vessels has a major impact on the interstitial fluid pressure (PIF) in most solid tumors. An increased tumor PIF is a barrier to the transport of interstitial fluid into and within the tumor. Therefore, understanding the mechanisms that regulate pressure homeostasis can lead to new insight into breast tumor progression, invasion and response to therapy. The collagen binding integrin α11β1 is upregulated during myofibroblast differentiation and expressed on fibroblasts in the tumor stroma. As a collagen organizer and a probable link between contractile fibroblasts and the complex collagen network in tumors, integrin α11β1 could be a potential regulator of tumor PIF.

Methods

We investigated the effect of stromal integrin α11-deficiency on pressure homeostasis, collagen organization and tumor growth using orthotopic and ectopic triple-negative breast cancer xenografts (MDA-MB-231 and MDA-MB-468) in wild type and integrin α11-deficient mice. PIF was measured by the wick-in-needle technique, collagen by Picrosirius Red staining and electron microscopy, and uptake of radioactively labeled 5FU by microdialysis. Further, PIF in heterospheroids composed of MDA-MB-231 cells and wild type or integrin α11-deficient fibroblasts was measured by micropuncture.

Results

Stromal integrin α11-deficiency decreased PIF in both the orthotopic breast cancer models. A concomitant perturbed collagen structure was seen, with fewer aligned and thinner fibrils. Integrin α11-deficiency also impeded MDA-MB-231 breast tumor growth, but no effect was observed on drug uptake. No effects were seen in the ectopic model. By investigating the isolated effect of integrin α11-positive fibroblasts on MDA-MB-231 cells in vitro, we provide evidence that PIF regulation was mediated by integrin α11-positive fibroblasts.

Conclusion

We hereby show the importance of integrin α11β1 in pressure homeostasis in triple-negative breast tumors, indicating a new role for integrin α11β1 in the tumor microenvironment. Our data suggest that integrin α11β1 has a pro-tumorigenic effect on triple-negative breast cancer growth in vivo. The significance of the local microenvironment is shown by the different effects of integrin α11β1 in the orthotopic and ectopic models, underlining the importance of choosing an appropriate preclinical model.

Electronic supplementary material

The online version of this article (10.1186/s12885-019-5449-z) contains supplementary material, which is available to authorized users.

Glucocorticoid receptor and breast cancer

Stress enhances glucocorticoid (GC) synthesis, which alters inflammation and immune responses, as well as cellular proliferation and apoptosis in a number of tissues. Increasingly, stress has been associated with cancer progression, and in particular in breast cancer. Consequently, an operational glucocorticoid receptor system in breast tissue influences breast cancer development. In this review, we summarize the data on the GC/GR system in normal and tumoral breast tissue. We also review the molecular mechanisms by which GCs control apoptosis and proliferation in breast cancer models and how GCs alter the chemotherapy of breast cancer treatment when used in combination. Finally, we discuss the participation of GR in breast tumorigenesis under hormone replacement therapy.

Increasing tumoral 5-fluorouracil concentrations during a 5-day continuous infusion: a microdialysis study

Purpose

Response to anticancer therapy is believed to be directly related to the concentration of the anticancer drug in the tumor itself. Assessment of intra-tumor drug pharmacokinetics can be helpful to gain more insight into mechanisms involved in the (in)sensitivity of tumors to anticancer therapy. We explored the pharmacokinetics of 5-fluorouracil in both plasma and tumor tissue during a 5-day continuous infusion of 5-fluorouracil in patients with cancer. Sampling for measurement of 5-fluorouracil in tumor tissue was performed using microdialysis.

Experimental design

In seven patients with an accessible (sub)cutaneous tumor treated with a continuous 5-fluorouracil infusion, plasma and microdialysate samples from tumor and normal adipose tissue were collected over a period of 5 days.

Results

For six patients, drug concentrations in both tumor tissue and plasma were available. Concentration–time curves of unbound 5-fluorouracil were lower in tumor tissue compared to the curves in plasma, but exposure ratios of tumor tissue versus plasma increased during the 5-day infusion period. The presence of circadian rhythmicity of 5-fluorouracil pharmacokinetics in the tumor itself was demonstrated as 5-fluorouracil concentrations in tumor extracellular fluid were higher during the night than during daytime.

Conclusion

Microdialysis was successfully employed in patients with cancer during a continuous 5-day 5-fluorouracil infusion. Plasma and tumor pharmacokinetics of 5-fluorouracil differed substantially with increasing 5-fluorouracil concentrations in tumor over time, possibly resulting from a lowered interstitial fluid pressure by 5-fluorouracil itself. This microdialysis 5-fluorouracil model might be useful to monitor the effect of drug delivery modulating strategies in future studies.

Hyperoxia increases the uptake of 5-fluorouracil in mammary tumors independently of changes in interstitial fluid pressure and tumor stroma

Background

Hypoxia is associated with increased resistance to chemo- and radiation-therapy. Hyperoxic treatment (hyperbaric oxygen) has previously been shown to potentiate the effect of some forms of chemotherapy, and this has been ascribed to enhanced cytotoxicity or neovascularisation. The aim of this study was to elucidate whether hyperoxia also enhances any actual uptake of 5FU (5-fluorouracil) into the tumor tissue and if this can be explained by changes in the interstitium and extracellular matrix.

Methods

One group of tumor bearing rats was exposed to repeated hyperbaric oxygen (HBO) treatment (2 bar, pO₂ = 2 bar, 4 exposures à 90 min), whereas one group was exposed to one single identical HBO treatment. Animals housed under normal atmosphere (1 bar, pO₂ = 0.2 bar) served as controls. Three doses of 5FU were tested for dose response. Uptake of [³H]-5FU in the tumor was assessed, with special reference to factors that might have contributed, such as interstitial fluid pressure (P_if), collagen content, oxygen stress (measured as malondialdehyd levels), lymphatics and transcapillary transport in the tumors.

Results

The uptake of the cytostatic agent increases immediately after a single HBO treatment (more than 50%), but not 24 hours after the last repeated HBO treatment. Thus, the uptake is most likely related to the transient increase in oxygenation in the tumor tissue. Factors like tumor P_if and collagen content, which decreased significantly in the tumor interstitium after repeated HBO treatment, was without effect on the drug uptake.

Conclusion

We showed that hyperoxia increases the uptake of [³H]-5FU in DMBA-induced mammary tumors per se, independently of changes in P_if, oxygen stress, collagen fibril density, or transendothelial transport alone. The mechanism by which such an uptake occur is still not elucidated, but it is clearly stimulated by elevated pO₂.

Peritumoral TNFalpha administration influences tumour stroma structure and physiology independently of growth in DMBA-induced mammary tumours

BACKGROUND

Systemic treatment of malignancies with high doses of tumour necrosis factor-alpha (TNFalpha) has an anticancer effect, but also serious side effects. The aim of the present study was to elucidate the effects of local TNFalpha administration alone or in combination with chemotherapy on tumour stroma structure and physiology in di-methyl-benz-anthracene (DMBA)-induced mammary carcinomas in rats.

METHODS

TNFalpha (500 ng/mL in a volume of 5 microL) was given s.c. around the carcinoma and 5-fluorouracil (5-FU) (1.5 mg/kg, volume of 0.2 mL) was given i.p on days 1, 4, 7 and 10.

RESULTS

Treatment with TNFalpha resulted in a significant reduction of tumour interstitial fluid pressure (TIFP: 75-87%, p < 0.02-0.001), as well as in the number of tumour-infiltrating macrophages, extracellular volume (ECV) and collagen fibril density in carcinoma. In addition, pH was lowered in tumours treated with TNFalpha, suggesting decreased aerobic metabolism. Treatment with TNFalpha, however, had no effect on tumour growth, arterial blood pressure, tumour vessel density, plasma volume or body weight. Concentrations of locally produced VEGF and IL-1beta in carcinoma interstitial fluid or in serum were not affected by TNFalpha. The study demonstrated that these cytokines are produced locally in the tumour. Furthermore, TNFalpha had no effect on efficacy of treatment with 5-FU.

CONCLUSIONS

Locally administered TNFalpha did not affect DMBA-induced mammary tumour growth or vasculature, but reduced inflammation and ECM structure, suggesting the latter to be of importance in the observed reduction in TIFP.

Application of prolonged microdialysis sampling in carboplatin-treated cancer patients

Purpose

To better understand the mechanisms underlying (in)sensitivity of tumors to anticancer drugs, assessing intra-tumor drug pharmacokinetics (PKs) could be important. We explored the feasibility of microdialysis in tumor tissue for multiple days in a clinical setting, using carboplatin as model drug.

Methods

Plasma and microdialysate samples from tumor and adipose normal tissues were collected up to 47 h after dosing in eight carboplatin-treated patients with an accessible (sub)cutaneous tumor.

Results

Pharmacokinetics were evaluable in tumor tissue in 6/8 patients and in adipose normal tissue in 3/8 patients. Concentration–time curves of unbound platinum in both the tissues followed the pattern of the curves in plasma, with exposure ratios of tissue versus plasma ranging from 0.64 to 1.46.

Conclusions

Microdialysis can be successfully employed in ambulant patients for multiple days, which enables one to study tissue PK of anticancer drugs in normal and malignant tissues in more detail.