TP53-dependence on the effect of doxorubicin and Src inhibitor combination therapy.

The anticancer effects of Src kinase inhibitors are controversial. This study found an association between alterations in the TP53 gene and the synergy score for combination treatment with doxorubicin and an Src kinase inhibitor using human osteosarcoma cell lines (MG63 and U2OS) and human colon cancer cell line. Doxorubicin was found to activate signal transducer and activator of transcription 3 via Src kinase in cancer cells harboring alterations in TP53. A drug combination study using patient-derived cells confirmed that an Src kinase inhibitor synergizes with doxorubicin in cancer cells harboring alterations in TP53, while antagonizing its effect in cancer cells expressing wild-type TP53. Our findings suggest that genetic alterations in TP53 are a critical factor in determining the use of a combination treatment of doxorubicin and Src inhibitors.

TP53 alteration determines the combinational cytotoxic effect of doxorubicin and an antioxidant NAC.

The anticancer effect of doxorubicin is closely related to the generation of reactive oxygen species. On the contrary, doxorubicin-induced reactive oxygen species induces heart failure, a critical side effect of doxorubicin. Antioxidant supplementation has been proposed to reduce the side effects. However, the use of antioxidants may hamper the anticancer effect of doxorubicin. In this study, doxorubicin-induced reactive oxygen species was shown to differentially affect cancer cells based on their TP53 genetic status; doxorubicin-induced apoptosis was attenuated by an antioxidant, N-acetylcysteine, in TP53 wild cells; however, N-acetylcysteine caused a synergistic increase in the apoptosis rate in TP53-altered cells. N-acetylcysteine prevented phosphorylation of P53 protein that had been induced by doxorubicin. However, N-acetylcysteine increased the cleavage of poly (ADP-ribose) polymerase in the presence of doxorubicin. Synergy score of 26 patient-derived cells were evaluated after the combination treatment of doxorubicin and N-acetylcysteine. The synergy score was significantly higher in TP53-altered group compared with those in TP53 wild group. In conclusion, TP53 genetic alteration is a critical factor that determines the use of antioxidant supplements during doxorubicin treatment.

RRP12 is a crucial nucleolar protein that regulates p53 activity in osteosarcoma cells.

RRP12 (ribosomal RNA processing 12 homolog), a nucleolar protein, plays important roles in cell cycle progression and the response to deoxyribonucleic acid (DNA) damage in yeast cells. However, its role has not been investigated in mammalian cells that possess p53, which has close functional association to nucleolus. We explored the role of RRP12 in nucleolar stress condition using an osteosarcoma cell line, U2OS. To induce DNA damage and nucleolar disruption, two cytotoxic drugs, doxorubicin and actinomycin D were used. Cytotoxic stress resulted nucleolar disruption induced cell cycle arrest and apoptosis in U2OS cells. However, RRP12 overexpression promoted resistance to cytotoxic stress. In contrast, RRP12 silencing enhanced susceptibility to cytotoxic stress. During drug treatment, p53 activity and cell death were suppressed by RRP12 overexpression but promoted by RRP12 silencing. This study demonstrated that RRP12 was crucial for cell survival during cytotoxic stress via the repression of p53 stability. Thus, targeting RRP12 may enhance chemotherapeutic effect in cancers.

Novel MFSD7-ATP5I fusion promotes migration and invasion of human sarcoma.

Fusion genes have been implicated in the development and progression of several types of sarcomas, serving as valuable diagnostic and prognostic markers, as well as potential therapeutic targets. We discovered a novel major facilitator superfamily domain-containing 7 (MFSD7) and adenosine triphosphate 5I (ATP5I) gene fusion from sarcomas. In this study, the MFSD7-ATP5I fusion transcript was screened using RNA sequencing in 55 sarcoma samples and sixteen normal samples. The MFSD7-ATP5I fusion transcript was detected in 58% of sarcoma samples. The correlation between the expression of MFSD7-ATP5I fusion transcript and clinicopathological information was analyzed, and MFSD7-ATP5I expression is associated with marked pleomorphism and lower tumor necrosis. Cell migration and invasion was significantly reduced by knock-down of MFSD7-ATP5I. Cell migration and invasion was increased by overexpression of MFSD7-ATP5I. A phosphokinase assay demonstrated that MFSD7-ATP5I is involved in the GSK-3 pathway. The current study found that MFSD7-ATP5I is associated with increasing pleomorphism and decreasing necrosis of tumors. And our gain and loss of function experiments prove that MFSD7-ATP5I promotes the invasiveness of tumor cells.

PTCH1 regulates anchorage-independent growth and bone invasion of non-small cell lung cancer cells.

Acquisition of metastatic potential by cancer cells is related to cancer stemness and anchorage-independent growth. The onset and progression of cancer are known to involve Hedgehog (HH) signaling that is activated by the binding of HH to the Patched 1 (PTCH1) receptor. However, the functions and mechanisms of action of PTCH1 in the context of bone metastasis remain to be elucidated. In this study, lentivirally-delivered shRNA was used to deplete PTCH1 levels, which resulted in the inhibition of spherical colony formation by the human non-small cell lung cancer (NSCLC) cell line; this suggested that PTCH1 promotes anchorage-independent growth. Concordantly, knockdown of PTCH1 resulted in significantly reduced migration and invasion of NSCLC cells; this was accompanied by the downregulation of MMP7 and SOX2. PTCH1 knockdown resulted in decreased bone destruction and osteoclastogenesis in a mouse bone metastasis model. These results indicate that PTCH1 may be an important regulator of bone invasion, and strongly suggest that knockdown of PTCH1 may decrease the anchorage-independent growth and metastatic potential of NSCLC.

GNAQ knockdown promotes bone metastasis through epithelial-mesenchymal transition in lung cancer cells.

AIMS: Bone metastasis ultimately occurs due to a complex multistep process, during which the interactions between cancer cells and bone microenvironment play important roles. Prior to colonization of the bone, cancer cells must succeed through a series of steps that will allow them to gain migratory and invasive properties; epithelial-to-mesenchymal transition (EMT) is known to be integral here. The aim of this study was to determine the effects of G protein subunit alpha Q (GNAQ) on the mechanisms underlying bone metastasis through EMT pathway. METHODS: A total of 80 tissue samples from patients who were surgically treated during January 2012 to December 2014 were used in the present study. Comparative gene analysis revealed that the GNAQ was more frequently altered in metastatic bone lesions than in primary tumour sites in lung cancer patients. We investigated the effects of GNAQ on cell proliferation, migration, EMT, and stem cell transformation using lung cancer cells with GNAQ-knockdown. A xenograft mouse model tested the effect of GNAQ using micro-CT analyses and histological analyses. RESULTS: GNAQ-knockdown showed down-regulation of tumour growth through mitogen-activated protein kinase (MAPK) signalling in lung cancer cells, but not increased apoptosis. We found that GNAQ-knockdown induced EMT and promoted invasiveness. GNAQ-knockdown cells injected into the bone marrow of murine tibia induced tumour growth and bone-to-lung metastasis, whereas it did not in control mice. Moreover, the knockdown of GNAQ enhanced cancer stem cell-like properties in lung cancer cells, which resulted in the development of resistance to chemotherapy. CONCLUSION: The present study reveals that the GNAQ-knockdown induced cancer stem cell-like properties. Cite this article: Bone Joint Res 2021;10(5):310-320.

Effect of GNAQ alteration on RANKL-induced osteoclastogenesis in human non-small-cell lung cancer.

AIMS: Receptor activator of nuclear factor-κB ligand (RANKL) is a key molecule that is expressed in bone stromal cells and is associated with metastasis and poor prognosis in many cancers. However, cancer cells that directly express RANKL have yet to be unveiled. The current study sought to evaluate how a single subunit of G protein, guanine nucleotide-binding protein G(q) subunit alpha (GNAQ), transforms cancer cells into RANKL-expressing cancer cells. METHODS: We investigated the specific role of GNAQ using GNAQ wild-type cell lines (non-small-cell lung cancer cell lines; A549 cell lines), GNAQ knockdown cell lines, and patient-derived cancer cells. We evaluated GNAQ, RANKL, macrophage colony-stimulating factor (M-CSF), nuclear transcription factor-κB (NF-κB), inhibitor of NF-κB (IκB), and protein kinase B (Akt) signalling in the GNAQ wild-type and the GNAQ-knockdown cells. Osteoclastogenesis was also evaluated in both cell lines. RESULTS: In the GNAQ-knockdown cells, RANKL expression was significantly upregulated (p < 0.001). The expression levels of M-CSF were also significantly increased in the GNAQ-knockdown cells compared with control cells (p < 0.001). GNAQ knockdown cells were highly sensitive to tumour necrosis factor alpha (TNF-α) and showed significant activation of the NF-κB pathway. The expression levels of RANKL were markedly increased in GNAQ mutant compared with GNAQ wild-type in patient-derived tumour tissues. CONCLUSION: The present study reveals that the alterations of GNAQ activate NF-κB pathway in cancers, which increase RANKL and M-CSF expression and induce osteoclastogenesis in cancers.Cite this article: Bone Joint Res. 2020;9(1):29-35.