HSP90 inhibitors induce GPNMB cell-surface expression by modulating lysosomal positioning and sensitize breast cancer cells to glembatumumab vedotin

Combination therapy involving HSP90 inhibitors for combating cancer: an overview of clinical and preclinical progress

The molecular chaperone heat shock protein 90 (HSP90) regulates multiple crucial signalling pathways in cancer by driving the maturation of key signalling components, thereby playing a crucial role in tumorigenesis and drug resistance in cancer. Inhibition of HSP90 results in metastable conformational collapse of its client proteins and their proteasomal degradation. Considerable efforts have been devoted to the development of small-molecule inhibitors targeting HSP90, and more than 20 inhibitors have been evaluated in clinical trials for cancer therapy. However, owing to disadvantages such as organ toxicity and drug resistance, only one HSP90 inhibitor has been approved for use in clinical settings. In recent years, HSP90 inhibitors used in combination with other anti-cancer therapies have shown remarkable potential in the treatment of cancer. HSP90 inhibitors work synergistically with various anti-cancer therapies, including chemotherapy, targeted therapy, radiation therapy and immunotherapy. HSP90 inhibitors can improve the pharmacological effects of the above-mentioned therapies and reduce treatment resistance. This review provides an overview of the use of combination therapy with HSP90 inhibitors and other anti-cancer therapies in clinical and preclinical studies reported in the past decade and summarises design strategies and prospects for these combination therapies. Altogether, this review provides a theoretical basis for further research and application of these combination therapies in the treatment of cancer.

Truncated GPNMB, a microglial transmembrane protein, serves as a scavenger receptor for oligomeric β-amyloid peptide1-42 in primary type 1 microglia

Glycoprotein non-metastatic melanoma protein B (GPNMB) is up-regulated in one subtype of microglia (MG) surrounding senile plaque depositions of amyloid-beta (Aβ) peptides. However, whether the microglial GPNMB can recognize the fibrous Aβ peptides as ligands remains unknown. In this study, we report that the truncated form of GPNMB, the antigen for 9F5, serves as a scavenger receptor for oligomeric Aβ1-42 (o-Aβ1-42 ) in rat primary type 1 MG. 125 I-labeled o-Aβ1-42 exhibited specific and saturable endosomal/lysosomal degradation in primary-cultured type 1 MG from GPNMB-expressing wild-type mice, whereas the degradation activity was markedly reduced in cells from Gpnmb-knockout mice. The Gpnmb-siRNA significantly inhibits the degradation of 125 I-o-Aβ1-42 by murine microglial MG5 cells. Therefore, GPNMB contributes to mouse MG's o-Aβ1-42 clearance. In rat primary type 1 MG, the cell surface expression of truncated GPNMB was confirmed by a flow cytometric analysis using a previously established 9F5 antibody. 125 I-labeled o-Aβ1-42 underwent endosomal/lysosomal degradation by rat primary type 1 MG in a dose-dependent fashion, while the 9F5 antibody inhibited the degradation. The binding of 125 I-o-Aβ1-42 to the rat primary type 1 MG was inhibited by 42% by excess unlabeled o-Aβ1-42 , and by 52% by the 9F5 antibody. Interestingly, the 125 I-o-Aβ1-42 degradations by MG-like cells from human-induced pluripotent stem cells was inhibited by the 9F5 antibody, suggesting that truncated GPNMB also serve as a scavenger receptor for o-Aβ1-42 in human MG. Our study demonstrates that the truncated GPNMB (the antigen for 9F5) binds to oligomeric form of Aβ1-42 and functions as a scavenger receptor on MG, and 9F5 antibody can act as a blocking antibody for the truncated GPNMB.

ImmunoPET Imaging Identifies the Optimal Timepoint for Combination Therapy in Xenograft Models of Triple-Negative Breast Cancer

(1) Purpose: The glycoprotein non-metastatic melanoma B (gpNMB) is a type 1 transmembrane protein that is overexpressed in numerous cancers, including triple-negative breast cancer (TNBC). Its overexpression is associated with lower overall survival of patients with TNBC. Tyrosine kinase inhibitors such as dasatinib can upregulate gpNMB expression, which has the potential to enhance therapeutic targeting with anti-gpNMB antibody drug conjugates such as glembatumumab vedotin (CDX-011). Our primary aim is to quantify the degree and identify the timeframe of gpNMB upregulation in xenograft models of TNBC after treatment with the Src tyrosine kinase inhibitor, dasatinib, by longitudinal positron emission tomography (PET) imaging with the 89Zr-labeled anti-gpNMB antibody ([89Zr]Zr-DFO-CR011). The goal is to identify the timepoint at which to administer CDX-011 after treatment with dasatinib to enhance therapeutic efficacy using noninvasive imaging. (2) Methods: First, TNBC cell lines that either express gpNMB (MDA-MB-468) or do not express gpNMB (MDA-MB-231) were treated with 2 μM of dasatinib in vitro for 48 h, followed by Western blot analysis of cell lysates to determine differences in gpNMB expression. MDA-MB-468 xenografted mice were also treated with 10 mg/kg of dasatinib every other day for 21 days. Subgroups of mice were euthanized at 0-, 7-, 14-, and 21-days post treatment, and tumors were harvested for Western blot analysis of tumor cell lysates for gpNMB expression. In a different cohort of MDA-MB-468 xenograft models, longitudinal PET imaging with [89Zr]Zr-DFO-CR011 was performed before treatment at 0 (baseline) and at 14 and 28 days after treatment with (1) dasatinib alone (2) CDX-011 (10 mg/kg) alone, or (3) sequential treatment of dasatinib for 14 days then CDX-011 to determine changes in gpNMB expression in vivo relative to baseline. As a gpNMB-negative control, MDA-MB-231 xenograft models were imaged 21 days after treatment with dasatinib, combination of CDX-011 and dasatinib, and vehicle control. (3) Results: Western blot analysis of MDA-MB-468 cell and tumor lysates showed that dasatinib increased expression of gpNMB in vitro and in vivo at 14 days post treatment initiation. In PET imaging studies of different cohorts of MDA-MB-468 xenografted mice, [89Zr]Zr-DFO-CR011 uptake in tumors (SUVmean = 3.2 ± 0.3) was greatest at 14 days after treatment initiation with dasatinib (SUVmean = 4.9 ± 0.6) or combination of dasatinib and CDX-011 (SUVmean= 4.6 ± 0.2) compared with that at baseline (SUVmean = 3.2 ± 0.3). The highest tumor regression after treatment was observed in the combination-treated group with a percent change in tumor volume relative to baseline (%CTV) of -54 ± 13 compared with the vehicle control-treated group (%CTV = +102 ± 27), CDX-011 group (%CTV = -25 ± 9.8), and dasatinib group (%CTV = -23 ± 11). In contrast, the PET imaging of MDA-MB-231 xenografted mice indicated no significant difference in the tumor uptake of [89Zr]Zr-DFO-CR011 between treated (dasatinib alone or in combination with CDX-011) and vehicle-control groups. (4) Conclusions: Dasatinib upregulated gpNMB expression in gpNMB-positive MDA-MB-468 xenografted tumors at 14 days post treatment initiation, which can be quantified by PET imaging with [89Zr]Zr-DFO-CR011. Furthermore, combination therapy with dasatinib and CDX-011 appears to be a promising therapeutic strategy for TNBC and warrants further investigation.

CCN3/NOV promotes metastasis and tumor progression via GPNMB-induced EGFR activation in triple-negative breast cancer

Triple-negative breast cancer (TNBC) is the most aggressive subtype of breast cancer. TNBC patients typically exhibit unfavorable outcomes due to its rapid growth and metastatic potential. Here, we found overexpression of CCN3 in TNBC patients. We identified that CCN3 knockdown diminished cancer stem cell formation, metastasis, and tumor growth in vitro and in vivo. Mechanistically, ablation of CCN3 reduced activity of the EGFR/MAPK pathway. Transcriptome profiling revealed that CCN3 induces glycoprotein nonmetastatic melanoma protein B (GPNMB) expression, which in turn activates the EGFR pathway. An interrogation of the TCGA dataset further supported the transcriptional regulation of GPNMB by CCN3. Finally, we showed that CCN3 activates Wnt signaling through a ligand-dependent or -independent mechanism, which increases microphthalmia-associated transcription factor (MITF) protein, a transcription factor inducing GPNMB expression. Together, our findings demonstrate the oncogenic role of CCN3 in TNBC, and we propose CCN3 as a putative therapeutic target for TNBC.

Heterocyclic Compounds as Hsp90 Inhibitors: A Perspective on Anticancer Applications

Heat shock proteins (Hsps) have garnered special attention in cancer therapy as molecular chaperones with regulatory/mediatory effects on folding, maintenance/stability, maturation, and conformation of proteins as well as their effects on prevention of protein aggregation. Hsp90 ensures the stability of various client proteins needed for the growth of cells or the survival of tumor cells; therefore, they are overexpressed in tumor cells and play key roles in carcinogenesis. Accordingly, Hsp90 inhibitors are recognized as attractive therapeutic agents for investigations pertaining to tumor suppression. Natural Hsp90 inhibitors comprising geldanamycin (GM), reclaimed analogs of GM including 17-AAG and DMAG, and radicicol, a natural macrocyclic antifungal, are among the first potent Hsp90 inhibitors. Herein, recently synthesized heterocyclic compounds recognized as potent Hsp90 inhibitors are reviewed along with the anticancer effects of heterocyclic compounds, comprising purine, pyrazole, triazine, quinolines, coumarin, and isoxazoles molecules.

GPNMB: a potent inducer of immunosuppression in cancer

The immune system is comprised of both innate and adaptive immune cells, which, in the context of cancer, collectively function to eliminate tumor cells. However, tumors can actively sculpt the immune landscape to favor the establishment of an immunosuppressive microenvironment, which promotes tumor growth and progression to metastatic disease. Glycoprotein-NMB (GPNMB) is a transmembrane glycoprotein that is overexpressed in a variety of cancers. It can promote primary tumor growth and metastasis, and GPNMB expression correlates with poor prognosis and shorter recurrence-free survival in patients. There is growing evidence supporting an immunosuppressive role for GPNMB in the context of malignancy. This review provides a description of the emerging roles of GPNMB as an inducer of immunosuppression, with a particular focus on its role in mediating cancer progression by restraining pro-inflammatory innate and adaptive immune responses.