Enhancing 223Ra Treatment Efficacy by Anti-1 Integrin Targeting

Targeting prostate tumor low-molecular weight tyrosine phosphatase for oxidation-sensitizing therapy

Protein tyrosine phosphatases (PTPs) play major roles in cancer and are emerging as therapeutic targets. Recent reports suggest low-molecular weight PTP (LMPTP)-encoded by the ACP1 gene-is overexpressed in prostate tumors. We found ACP1 up-regulated in human prostate tumors and ACP1 expression inversely correlated with overall survival. Using CRISPR-Cas9-generated LMPTP knockout C4-2B and MyC-CaP cells, we identified LMPTP as a critical promoter of prostate cancer (PCa) growth and bone metastasis. Through metabolomics, we found that LMPTP promotes PCa cell glutathione synthesis by dephosphorylating glutathione synthetase on inhibitory Tyr270. PCa cells lacking LMPTP showed reduced glutathione, enhanced activation of eukaryotic initiation factor 2-mediated stress response, and enhanced reactive oxygen species after exposure to taxane drugs. LMPTP inhibition slowed primary and bone metastatic prostate tumor growth in mice. These findings reveal a role for LMPTP as a critical promoter of PCa growth and metastasis and validate LMPTP inhibition as a therapeutic strategy for treating PCa through sensitization to oxidative stress.

The role of integrin family in bone metabolism and tumor bone metastasis

Integrins have been the research focus of cell-extracellular matrix adhesion (ECM) and cytokine receptor signal transduction. They are involved in the regulation of bone metabolism of bone precursor cells, mesenchymal stem cells (MSCs), osteoblasts (OBs), osteoclasts (OCs), and osteocytes. Recent studies expanded and updated the role of integrin in bone metabolism, and a large number of novel cytokines were found to activate bone metabolism pathways through interaction with integrin receptors. Integrins act as transducers that mediate the regulation of bone-related cells by mechanical stress, fluid shear stress (FSS), microgravity, hypergravity, extracellular pressure, and a variety of physical factors. Integrins mediate bone metastasis of breast, prostate, and lung cancer by promoting cancer cell adhesion, migration, and survival. Integrin-mediated targeted therapy showed promising prospects in bone metabolic diseases. This review emphasizes the latest research results of integrins in bone metabolism and bone metastasis and provides a vision for treatment strategies.

Ra-223 induces clustered DNA damage and inhibits cell survival in several prostate cancer cell lines

The bone-seeking radiopharmaceutical Xofigo (Radium-223 dichloride) has demonstrated both extended survival and palliative effects in treatment of bone metastases in prostate cancer. The alpha-particle emitter Ra-223, targets regions undergoing active bone remodeling and strongly binds to bone hydroxyapatite (HAp). However, the toxicity mechanism and properties of Ra-223 binding to hydroxyapatite are not fully understood. By exposing 2D and 3D (spheroid) prostate cancer cell models to free and HAp-bound Ra-223 we here studied cell toxicity, apoptosis and formation and repair of DNA double-strand breaks (DSBs). The rapid binding with a high affinity of Ra-223 to bone-like HAp structures was evident (KD= 19.2 × 10-18 M) and almost no dissociation was detected within 24 h. Importantly, there was no significant uptake of Ra-223 in cells. The Ra-223 alpha-particle decay produced track-like distributions of the DNA damage response proteins 53BP1 and ɣH2AX induced high amounts of clustered DSBs in prostate cancer cells and activated DSB repair through non-homologous end-joining (NHEJ). Ra-223 inhibited growth of prostate cancer cells, independent of cell type, and induced high levels of apoptosis. In summary, we suggest the high cell killing efficacy of the Ra-223 was attributed to the clustered DNA damaged sites induced by α-particles.

223Ra Induces Transient Functional Bone Marrow Toxicity

223Ra is a bone-seeking, α-particle-emitting radionuclide approved for the treatment of patients with metastatic prostate cancer and is currently being tested in a variety of clinical trials for primary and metastatic cancers to bone. Clinical evaluation of 223Ra hematologic safety showed a significantly increased rate of neutropenia and thrombocytopenia in patients, hinting at myelosuppression as a side effect. Methods: In this study, we investigated the consequences of 223Ra treatment on bone marrow biology by combining flow cytometry, single-cell RNA sequencing, three-dimensional multiphoton microscopy and bone marrow transplantation analyses. Results: 223Ra accumulated in bones and induced zonal radiation damage confined to the bone interface, followed by replacement of the impaired areas with adipocyte infiltration, as monitored by 3-dimensional multiphoton microscopy ex vivo. Flow cytometry and single-cell transcriptomic analyses on bone marrow hematopoietic populations revealed transient, nonspecific 223Ra-mediated cytotoxicity on resident populations, including stem, progenitor, and mature leukocytes. This toxicity was paralleled by a significant decrease in white blood cells and platelets in peripheral blood-an effect that was overcome within 40 d after treatment. 223Ra exposure did not impair full hematopoietic reconstitution, suggesting that bone marrow function is not permanently hampered. Conclusion: Our results provide a comprehensive explanation of 223Ra reversible effects on bone marrow cells and exclude long-term myelotoxicity, supporting safety for patients.

Comprehensive Analysis of the Expression and Prognosis for ITGBs: Identification of ITGB5 as a Biomarker of Poor Prognosis and Correlated with Immune Infiltrates in Gastric Cancer

Background: Integrin β superfamily members (ITGBs) are documented to play important roles in various biological processes, and accumulating evidence suggests that ITGBs are associated with carcinogenic effects in several malignancies. Gastric cancer (GC) is a complicated and highly heterogeneous disease; however, the expression and prognostic values of eight ITGBs and potential mechanism in GC remain largely unclear.

Methods: The expression and prognostic significance of ITGBs in GC were systematically analyzed through Gene Expression Profiling Interactive Analysis, Human Protein Atlas, Kaplan–Meier Plotter, and cBioPortal databases. Then, the mRNA transcription data and corresponding clinical data of GC were downloaded from the Gene Expression Omnibus database as a testing cohort, and differentially expressed and prognostic genes were identified. The correlation between ITGB5 expression and overall survival and various clinical parameters were found by using univariate/multivariable Cox regression and Kaplan–Meier survival analysis. Additionally, differential analysis of gene expression profiles in low- and high-ITGB5 expression groups and pathway enrichment analysis was performed. Finally, the correlation of ITGB5 expression with immune infiltrates in GC was clarified.

Results: Compared with adjacent normal tissue, the results reveal that the mRNA levels of ITGB1-2 and ITGB4-8 are significantly higher in GC, and immunohistochemistry results show the consistency between RNA and protein expression levels. Cox regression and Kaplan–Meier survival analysis indicate that high ITGB5 expression contributes to a poor prognosis and could be an independent prognostic factor in GC patients. Besides this, gene functional enrichment analysis indicates that ITGB5 expression is significantly associated with extracellular matrix organization, cell-substrate adhesion, and ossification. The KEGG pathway analysis of ITGB5 shows a close association between ITGB5 and focal adhesion, ECM-receptor interaction, phagosome, and PI3K-Akt signaling pathway. Last, the infiltrating level of CD4⁺ T cells, macrophages, and dendritic cells are positively related to the expression of ITGB5, especially macrophages, and lower levels of macrophages predict a better prognosis in GC in our study.

Conclusion: Our findings investigate that ITGB5 may function as a valid biomarker of prognosis, and high expression of ITGB5 predicts poor prognosis for patients with GC. Besides this, it might be a potential target of precision therapy against GC.