MRMT-1 rat breast carcinoma cells and models of bone metastases: improvement of an in vitro system to mimic the in vivo condition

Unveiling the therapeutic potential of plant steroid peimine: A study on apoptotic induction in MRMT-1 cell line-induced breast cancer in rats

BACKGROUND

Breast cancer stands as a leading contributor to global cancer-related mortality. Progressing Research and Medical Innovations Elevate Treatment Choices and Results for Breast Cancer. Among these, Peimine, a natural steroid inherent in plants, notably within the Fritillaria species, demonstrates the capability to trigger apoptosis in breast cancer cells through the mitochondrial membrane permeation pathway. Nevertheless, its impact on an appropriate cancer model remains an area necessitating further exploration.

AIM

This study explored the in vivo anticancer effects of peimine on MRMT-1 Cell-line induced breast cancer in rats.

METHOD

Cancer was induced by the administration of MRMT-1 (6 x 106 cells) cells in the mammary pads of SD rats. The daily drug treatmentcommenced on day 14 and continued till 39 days. Peimine was administered in two doses (0.24 mg/kg and 0.48 mg/kg p.o) to examine its efficacy in curing breast cancer while tamoxifen was used as standard.

RESULTS

A reduction in tumour size was observed in the peimine-treated groups. Peimine can correct the changed blood cell count in addition to its anti-tumour activity. In peimine-treated rats, imbalanced immune marker IgE, serum oxidative marker, and tissue apoptotic markers like cytochrome c and calcium level were shown to be restored significantly.

CONCLUSION

Our findings imply that quinine has beneficial effects as an anti-neoplastic medication for breast cancer, most likely through its apoptotic activity. More research is necessary to thoroughly understand their mechanisms of action, ideal dose, and potential side effects.

Stromal Co-Cultivation for Modeling Breast Cancer Dormancy in the Bone Marrow

Cancers metastasize to the bone marrow before primary tumors can be detected. Bone marrow micrometastases are resistant to therapy, and while they are able to remain dormant for decades, they recur steadily and result in incurable metastatic disease. The bone marrow microenvironment maintains the dormancy and chemoresistance of micrometastases through interactions with multiple cell types and through structural and soluble factors. Modeling dormancy in vitro can identify the mechanisms of these interactions. Modeling also identifies mechanisms able to disrupt these interactions or define novel interactions that promote the reawakening of dormant cells. The in vitro modeling of the interactions of cancer cells with various bone marrow elements can generate hypotheses on the mechanisms that control dormancy, treatment resistance and reawakening in vivo. These hypotheses can guide in vivo murine experiments that have high probabilities of succeeding in order to verify in vitro findings while minimizing the use of animals in experiments. This review outlines the existing data on predominant stromal cell types and their use in 2D co-cultures with cancer cells.

An in vitro 3D bone metastasis model by using a human bone tissue culture and human sex-related cancer cells

One of the main limitations, when studying cancer-bone metastasis, is the complex nature of the native bone environment and the lack of reliable, simple, inexpensive models that closely mimic the biological processes occurring in patients and allowing the correct translation of results. To enhance the understanding of the mechanisms underlying human bone metastases and in order to find new therapies, we developed an in vitro three-dimensional (3D) cancer-bone metastasis model by culturing human breast or prostate cancer cells with human bone tissue isolated from female and male patients, respectively. Bone tissue discarded from total hip replacement surgery was cultured in a rolling apparatus system in a normoxic or hypoxic environment. Gene expression profile, protein levels, histological, immunohistochemical and four-dimensional (4D) micro-CT analyses showed a noticeable specificity of breast and prostate cancer cells for bone colonization and ingrowth, thus highlighting the species-specific and sex-specific osteotropism and the need to widen the current knowledge on cancer-bone metastasis spread in human bone tissues. The results of this study support the application of this model in preclinical studies on bone metastases and also follow the 3R principles, the guiding principles, aimed at replacing/reducing/refining (3R) animal use and their suffering for scientific purposes.

The active role of osteoporosis in the interaction between osteoblasts and bone metastases

INTRODUCTION

To minimize the severity of bone metastases and to delay their onset, it is important to analyze the underlying biological mechanisms. The present study focused on the link between OP and metastatic cells, with particular attention to osteoblast behavior.

METHODS

Osteoblasts (OB) were isolated from the trabecular bone of iliac crest of healthy (SHAM) and ovariectomized (OVX) adult female rats and co-cultured with MRMT-1 rat breast carcinoma cells as conditioned medium (CM) or alone (CTR) for 24h, 7 and 14 days and tested for cell viability, morphology and synthetic activity, i.e. C-terminal procollagen type I, alkaline phosphatase, osteoprotegerin, receptor activator for nuclear factor KB ligand and interleukin-8.

RESULTS

Osteoblast morphology showed a reduced organization in the OVX group, in particular in the CM condition. Conversely, the analysis of cell viability revealed significantly higher values in the OVXCM group with respect to the SHAMCM group at all experimental times, whereas the OVXCTR group had significantly lower values at 7 and 14 days in comparison to those of the SHAM group. ALP release was significantly lower in the CM condition than that of CTR at all timepoints, and so was procollagen type I at 7 and 14 days. The RANKL/OPG ratio showed significantly higher values in OVX osteoblasts in comparison with those of the SHAM group, both in CTR and in CM conditions at each experimental time. Finally, OVXCM showed significantly higher values of IL-8 than those of SHAMCM at 7 and 14 days.

CONCLUSIONS

The results clearly indicate an influence of the metastatic cells on the osteoblastic physiology at different levels: morphology, viability, release of typical proteins, and also IL-8 as a proinflammatory cytokine, especially marked by osteoporosis. Further investigations might highlight the relationship between osteoblasts and breast cancer cells, which might be useful to improve common drugs used against osteoporosis and bone metastases, by enhancing the bone deposition/tumor progression ratio.

Intrathecal injection of lentivirus-mediated glial cell line-derived neurotrophic factor RNA interference relieves bone cancer-induced pain in rats

Bone cancer pain is a common symptom in cancer patients with bone metastases and the underlying mechanisms are largely unknown. The aim of this study is to explore the endogenous analgesic mechanisms to develop new therapeutic strategies for bone-cancer induced pain (BCIP) as a result of metastases. MRMT-1 tumor cells were injected into bilateral tibia of rats and X-rays showed that the area suffered from bone destruction, accompanied by an increase in osteoclast numbers. In addition, rats with bone cancer showed apparent mechanical and thermal hyperalgesia at day 28 after intratibial MRMT-1 inoculation. However, intrathecal injection of morphine or lentivirus-mediated glial cell line-derived neurotrophic factor RNAi (Lvs-siGDNF) significantly attenuated mechanical and thermal hyperalgesia, as shown by increases in paw withdrawal thresholds and tail-flick latencies, respectively. Furthermore, Lvs-siGDNF interference not only substantially downregulated GDNF protein levels, but also reduced substance P immunoreactivity and downregulated the ratio of pERK/ERK, where its activation is crucial for pain signaling, in the spinal dorsal horn of this model of bone-cancer induced pain. In this study, Lvs-siGDNF gene therapy appeared to be a beneficial method for the treatment of bone cancer pain. As the effect of Lvs-siGDNF to relieve pain was similar to morphine, but it is not a narcotic, the use of GDNF RNA interference may be considered as a new therapeutic strategy for the treatment of bone cancer pain in the future.

Electrochemotherapy is effective in the treatment of rat bone metastases

Bone metastases impair general health status, quality of life and survival of patients. Electrochemotherapy (ECT), which combines electroporation (EP) and the administration of anticancer drugs, has been recently introduced into clinical practice for the local treatment of solid tumours. In the present study, the ability of EP with bleomycin (Bleo) to induce MRMT-1 rat breast cancer cell death was investigated in vitro. Then, an in vivo model for bone metastases was set up by the inoculation of MRMT-1 cells in rat proximal tibia. 7 days after tumour induction the animals were treated with Bleo, EP, Bleo followed by EP (ECT), or left untreated. ECT eliminated the tumour in 6 out of 8 (75 %) treated metastases. Radiological evaluation showed that the Honore score in ECT-treated animals was significantly lower when compared with the other groups (p < 0.0005) and not significantly different from healthy controls. Bone morphology in ECT-treated animals, evaluated by histological and microtomographical analyses, showed intact cortical and trabecular bone structure with new bone apposition. Histomorphometric evaluation showed that ECT-treated metastases had significantly higher bone volume, trabecular number, trabecular thickness and bone mineral density compared with those of untreated metastases (respectively p < 0.0005 for BV/TV, Tb.N and BMD; p < 0.05 for Tb.Th) or metastases treated with Bleo (p < 0.05 for BV/TV, Tb.N, p < 0.005 for BMD) or EP (p < 0.005 for BV/TV, Tb.N; p < 0.0005 for BMD). These findings suggest that early ECT treatment of bone metastases is minimally invasive, safe and effective, thus providing pre-clinical evidence for its use in the treatment of human bone metastases.