Targeting tumor microenvironment to curb chemoresistance via novel drug delivery strategies

Role of long non-coding RNAs in the regulation of ferroptosis in tumors

Normal cells begin to grow indefinitely and immortalize to form tumor cells after an external stimulus resulting in a genetic mutation. Effective killing of tumor cells is the basis of various cancer therapies. Ferroptosis is a class of cell death types dependent on iron and cellular lipid peroxidation. Tumors themselves are iron-dependent, and conventional radiotherapy also sensitizes cancer cells to ferroptosis. Increasing the sensitivity of tumor cells to ferroptosis may be a potential therapeutic strategy to overcome the resistance mechanisms of conventional cancer therapy. Long noncoding RNAs (LncRNAs) are a class of transcripts more than 200 nucleotides in length that regulate gene expression at multiple levels and are involved in biological processes such as cell differentiation, cell cycle arrest, and maintenance of tumor stemness. Recent studies have found that lncRNAs regulate ferroptosis of tumor cells through multiple mechanisms and may influence or ameliorate tumor resistance to chemotherapeutic agents. With the continuous maturation of nanomaterials technology, it may provide new means for cancer treatment by regulating the levels of ferroptosis-related lncRNAs inside tumors as well as increasing the levels of Fe2+ and ROS inside tumors. In this paper, we systematically introduce the regulatory mechanism of lncRNAs in ferroptosis, the role of ferroptosis in tumor immunotherapy and the application of lncRNAs combined with ferroptosis in nanomaterials, which provides new perspectives for tumor therapy.

Tumor-derived exosome PPP3CB induce gemcitabine resistance by regulating miR-298/STAT3 in pancreatic cancer

Purpose

Due to resistance to gemcitabine (GEM), patients with pancreatic cancer (PC) usually have poor prognosis and low survival rate. The purpose of our research was to explore the impact of exosome PPP3CB on GEM resistance in PC, and concurrently analyze the regulatory role of the miR-298/STAT3 signaling pathway.

Methods

Exosomes isolated from PC cells were verified by transmission electron microscopy (TEM), nanoparticle tracking analysis (NTA) and western blotting (WB). The interaction between PPP3CB and miR-298 was verified using dual-luciferase reporter gene assay, followed by evaluation of cell growth and death using CCK8 assay, EdU staining, and flow cytometry.

Results

Increased PPP3CB expression was observed in GEM-resistant PC cells. Exosomes from PC cells and GEM-resistant PC cells were successfully extracted by ultra-high speed centrifugation. Confocal microscopy showed internalization of fluorescein amide (FAM)-labeled GEM-resistant exosomes by PC cells. PPP3CB enhanced the proliferation of GEM-resistant PC cells and inhibited their apoptosis, whereas down-regulation of PPP3CB promoted the death of PC cells and inhibited the proliferation of GEM-resistant PC cells, and enhance the susceptibility of PC cells to GEM. Additionally, PPP3CB positively regulated STAT3 expression in PC cells by down-regulating miR-298, thus promoting the growth and inhibiting the death of PC cells.

Conclusion

PC cell-derived exosome PPP3CB enhances STAT3 expression by downregulating miR-298, stimulating cell growth, and suppressing cell death, thereby increasing the resistance of PC cells to GEM.

Upregulation of MELK promotes chemoresistance and induces macrophage M2 polarization via CSF-1/JAK2/STAT3 pathway in gastric cancer

BACKGROUND

Gastric cancer (GC) stands out as one of the most prevalent malignancies affecting the digestive system, characterized by a substantial incidence rate and mortality. Maternal embryonic leucine zipper kinase (MELK) has been implicated in the advancement of various cancer types and the modulation of the tumor microenvironment. This study aims to delve into the involvement of MELK in chemoresistance and the tumor microenvironment of GC.

METHODS

The MELK expression was detected using quantitative real-time polymerase chain reaction (qRT-PCR), western blotting and immunohistochemistry. Lentiviral transfection was employed to establish stable cell lines with either overexpressed or silenced MELK. The impact of MELK on the chemoresistance of GC cells and the polarization of macrophages was investigated through in vitro and in vivo functional assays. Additionally, the correlation between MELK and the cytokines colony-stimulating factor 1 (CSF-1), as well as stromal macrophages, was analysed. The prognostic significance of MELK, CSF-1, and CD206 expression levels in clinical samples was further investigated.

RESULTS

MELK was found to be highly expressed in chemoresistant GC cells and tissues. Furthermore, both in vitro and in vivo assays indicated that MELK overexpression conferred chemoresistance in GC cells. Additionally, MELK overexpression was observed to induce M2 macrophage polarization via the CSF-1/JAK2/STAT3 pathway, thereby contributing to chemoresistance within the tumor microenvironment. The expression of MELK in GC tissues from neoadjuvant chemotherapy patients correlated positively with CSF-1 and CD206. Moreover, patients with higher expression levels of MELK, CSF-1, or CD206 exhibited significantly shorter OS and DFS rates.

CONCLUSIONS

Our investigation underscores the critical role of MELK in promoting chemoresistance and inducing M2 macrophage polarization in GC. It proposes novel targets and methods for the treatment of GC, as well as prognostic factors for neoadjuvant chemotherapy.

Pulsatilla Saponins Inhibit Experimental Lung Metastasis of Melanoma via Targeting STAT6-Mediated M2 Macrophages Polarization

Pulsatilla saponins (PS) extracts from Pulsatilla chinensis (Bge.) Regel, are a commonly used traditional Chinese medicine. In the previous study, we found Pulsatilla saponins displayed anti-tumor activity without side effects such as bone marrow suppression. However, the mechanism of the anti-tumor effect was not illustrated well. Since M2-like tumor-associated macrophages (TAMs) that required activation of the signal transducer and activator of transcription 6 (STAT6) for polarization are the important immune cells in the tumor microenvironment and play a key role in tumor progress and metastasis, this study aimed to confirm whether Pulsatilla saponins could inhibit the development and metastasis of tumors by inhibiting the polarization of M2 macrophages. We investigated the relevance of M2 macrophage polarization and the anti-tumor effects of Pulsatilla saponins in vitro and in vivo. In vitro, Pulsatilla saponins could decrease the mRNA level of M2 marker genes Arg1, Fizz1, Ym1, and CD206, and the down-regulation effect of phosphorylated STAT6 induced by IL-4; moreover, the conditioned medium (CM) from bone marrow-derived macrophages (BMDM) treated with Pulsatilla saponins could inhibit the proliferation and migration of B16-F0 cells. In vivo, Pulsatilla saponins could reduce the number of lung metastasis loci, down-regulate the expression of M2 marker genes, and suppress the expression of phosphorylated STAT6 in tumor tissues. Furthermore, we used AS1517499 (AS), a STAT6 inhibitor, to verify the role of PS on M2 macrophage polarization both in vitro and in vivo. We found that Pulsatilla saponins failed to further inhibit STAT6 activation; the mRNA level of Arg1, Fizz1, Ym1, and CD206; and the proliferation and migration of B16-F0 cells after AS1517499 intervention in vitro. Similar results were obtained in vivo. These results illustrated that Pulsatilla saponins could effectively suppress tumor progress by inhibiting the polarization of M2 macrophages via the STAT6 signaling pathway; this revealed a novel mechanism for its anti-tumor activity.

YAP/TAZ Suppress Drug Penetration Into Hepatocellular Carcinoma Through Stromal Activation

BACKGROUND AND AIMS

HCC is the most predominant type of liver cancer affecting 800,000 people globally each year. Various small-molecule compounds targeting diverse oncogenic signaling pathways have been tested for patients with HCC, and clinical outcomes were not satisfactory. In this study, we investigated molecular signaling that determines the efficiency of drug delivery into HCC.

APPROACH AND RESULTS

Hydrodynamics-based transfection (HT) was performed to develop mouse models for HCC induced by various oncogenes. Mice bearing liver cancer were treated with verteporfin at 5 weeks after HT. Multicellular HCC organoid (MCHO) models were established that contained various types of stromal cells, such as hepatic stellate cells, fibroblasts, and endothelial cells together with HCC cells. Tumor organoids were treated with verteporfin, and distributions of the drug in the organoids were assessed using fluorescence microscopy. Murine HCC models developed by HT methods showed that a high Yes-associated protein/Transcriptional co-activator with PDZ-binding motif (YAP/TAZ) activity in HCC cells impaired verteporfin penetration into the cancer. Activation of tumor stroma was observed in HCC with a high YAP/TAZ activity. Consistent with the findings in the in vivo models of HCC, MCHOs with activated YAP/TAZ signaling showed stromal activation and impaired penetration of verteporfin into the tumor organoids. Inhibition of YAP/TAZ transcriptional activity in HCC cells significantly increased drug penetration into the MCHO.

CONCLUSIONS

Drug delivery into liver cancer is impaired by YAP/TAZ signaling in tumor cells and subsequent activation of stroma by the signaling. Disrupting or targeting activated tumor stroma might improve drug delivery into HCC with an elevated YAP/TAZ activity.

Therapeutic targets for malignant peripheral nerve sheath tumors

Malignant peripheral nerve sheath tumors (MPNSTs) are rare and aggressive soft-tissue sarcomas with dismal prognosis. Complete resection, which is the only known definitive therapy, is not feasible with every tumor, and local recurrence after surgery is another challenge to successful treatment. Treatments used with other sarcoma types have not proven beneficial to MPNST patients. Targeted therapies blocking several signaling pathways known to drive MPNST pathogenesis have also not improved patient outcomes in clinical trials. This review discusses existing therapies and targeted chemotherapeutic options currently being tested clinically, and potential therapeutic avenues identified in preclinical studies that include targeting signaling pathways such as the HIPPO-YAP pathway and epigenetic mechanisms as well as multi-agent strategies.

Liposomal drug delivery in an in vitro 3D bone marrow model for multiple myeloma

Purpose

Liposomal drug delivery can improve the therapeutic index of treatments for multiple myeloma. However, an appropriate 3D model for the in vitro evaluation of liposomal drug delivery is lacking. In this study, we applied a previously developed 3D bone marrow (BM) myeloma model to examine liposomal drug therapy.

Material and methods

Liposomes of different sizes (~75-200 nm) were tested in a 3D BM myeloma model, based on multipotent mesenchymal stromal cells, endothelial progenitor cells, and myeloma cells cocultured in hydrogel. The behavior and efficacy of liposomal drug therapy was investigated, evaluating the feasibility of testing liposomal drug delivery in 3D in vitro. Intracellular uptake of untargeted and integrin α₄β₁ (very late antigen-4) targeted liposomes was compared in myeloma and supporting cells, as well as the effectivity of free and liposome-encapsulated chemotherapy (bortezomib, doxorubicin). Either cocultured myeloma cell lines or primary CD138⁺ myeloma cells received the treatments.

Results

Liposomes (~75-110 nm) passively diffused throughout the heterogeneously porous (~80-850 nm) 3D hydrogel model after insertion. Cellular uptake of liposomes was observed and was increased by targeting very late antigen-4. Liposomal bortezomib and doxorubicin showed increased cytotoxic effects toward myeloma cells compared with the free drugs, using either a cell line or primary myeloma cells. Cytotoxicity toward supporting BM cells was reduced using liposomes.

Conclusion

The 3D model allows the study of liposome-encapsulated molecules on multiple myeloma and supporting BM cells, looking at cellular targeting, and general efficacy of the given therapy. The advantages of liposomal drug delivery were demonstrated in a primary myeloma model, enabling the study of patient-to-patient responses to potential drugs and treatment regimes.

Hyaluronic acid conjugated multi-walled carbon nanotubes for colon cancer targeting

Purpose of the present research was to evaluate in vitro and in vivo potential of gemcitabine (GEM) loaded hyaluronic acid (HA) conjugated PEGylated multi-walled carbon nanotubes (GEM/HA-PEG-MWCNTs) for effective colon cancer targeting. HA was conjugated onto the surface of aminated or PEGylated MWCNTs which were evaluated for size, surface morphology, entrapment efficiency (~90%), in vitro drug release, in vitro cytotoxicity and in vivo performance in Sprague Dawley rats. In vitro release showed that the release rate of GEM in acidic conditions (pH 5.3) was faster than physiological conditions (PBS, pH 7.4) followed by a sustained release pattern. The developed GEM/HA-PEG-MWCNTs indicated significantly less hemolytic toxicity (7.73 ± 0.4%) paralleled to free GEM (18.71 ± 0.44%) and showed higher cytotoxicity against HT-29 colon cancer cell line. The antitumor study assured that GEM/HA-PEG-MWCNTs significantly reduced tumor volume as compared to free GEM and increased survival rate without noticeable loss in body weight. In vivo studies showed an improvement in pharmacokinetics in terms of remarkable escalation in mean residence time, half-life, AUC, AUMC, median survival time in tumor bearing rats treated with GEM/HA-MWCNTs and GEM/HA-PEG-MWCNTs as compared to free GEM (p ˂ 0.001). These outcomes proved engineered MWCNTs as a safe and effective nanomedicine in colon cancer targeting.

A novel long non-coding RNA-PRLB acts as a tumor promoter through regulating miR-4766-5p/SIRT1 axis in breast cancer

Accumulating evidence indicates that long non-coding RNAs (lncRNAs) play a critical role in cancerous processes as either oncogenes or tumor suppressor genes. Here, we demonstrated that lncRNA-PRLB (progression-associated lncRNA in breast cancer) was upregulated in human breast cancer tissues and breast cancer cell lines. Further evaluation verified that lncRNA-PRLB was positively correlated with the extent of metastasis, and its expression was correlated with shorter survival time of breast cancer patients. We identified microRNA miR-4766-5p as an inhibitory target of lncRNA-PRLB. Both lncRNA-PRLB overexpression and miR-4766-5p knockdown could remarkably enhance cell growth, metastasis, and chemoresistance. We also determined that sirtuin 1 (SIRT1) was an inhibitory target of miR-4766-5p, and that SIRT1 was inhibited by both lncRNA-PRLB knockdown and miR-4766-5p overexpression. Significantly, we found that the promotion of cell proliferation and metastasis, the acquisition of chemoresistance, and the increased expression of SIRT1 induced by lncRNA-PRLB overexpression could be partly abrogated by ectopic expression of miR-4766-5p. Taken together, our findings indicated that lncRNA could regulate the progression and chemoresistance of breast cancer via modulating the expression levels of miR-4766-5p and SIRT1, which may have a pivotal role in breast cancer treatment and prognosis prediction.