Inhibition of Rac1 reverses enzalutamide resistance in castration-resistant prostate cancer

The Roles of RAC1 and RAC1B in Colorectal Cancer and Their Potential Contribution to Cetuximab Resistance

Colorectal cancer (CRC) is one of the most diagnosed cancers and a leading contributor to cancer-related deaths in the United States. Clinically, standard treatment regimens include surgery, radiation, and chemotherapy; however, there has been increasing development and clinical use of targeted therapies for CRC. Unfortunately, many patients develop resistance to these treatments. Cetuximab, the first targeted therapy approved to treat advanced CRC, is a monoclonal antibody that targets the epidermal growth factor receptor and inhibits downstream pathway activation to restrict tumor cell growth and proliferation. CRC resistance to cetuximab has been well studied, and common resistance mechanisms include constitutive signal transduction through downstream protein mutations and promotion of the epithelial-to-mesenchymal transition. While the most common resistance mechanisms are known, a proportion of patients develop resistance through unknown mechanisms. One protein predicted to contribute to therapy resistance is RAC1, a small GTPase that is involved in cytoskeleton rearrangement, cell migration, motility, and proliferation. RAC1 has also been shown to be overexpressed in CRC. Despite evidence that RAC1 and its alternative splice isoform RAC1B play important roles in CRC and the pathways known to contribute to cetuximab resistance, there is a need to directly study the relationship between RAC1 and RAC1B and cetuximab resistance. This review highlights the recent studies investigating RAC1 and RAC1B in the context of CRC and suggests that these proteins could play a role in resistance to cetuximab.

Early diagnosis and prognostic potential of RAC3 in bladder tumor

BACKGROUND AND PURPOSE

Bladder tumors are among the most prevalent malignancies in the urinary system, and RAC3 has been linked to various types of cancer. This article seeks to explore the potential of RAC3 as both an early diagnostic marker for bladder tumors and a novel therapeutic target.

METHODS/PATIENTS

The expression of RAC3 in bladder tissue was detected using immunohistochemical staining. Additionally, the protein expression of RAC3 was measured and quantified through enzyme-linked immunosorbent assay (ELISA). Subsequently, the correlation between the expression level of RAC3 and bladder tumors was investigated through multifactorial analysis and survival analysis.

RESULTS

Our findings revealed that RAC3 expression was upregulated in bladder tumor tissues. Moreover, we observed higher levels of RAC3 expression in the serum and urine of patients with bladder tumors compared to those with non-bladder tumors. Additionally, we identified a significant positive correlation between RAC3 expression levels and the stage, degree of differentiation, and infiltration of bladder tumors. Importantly, high RAC3 expression emerged as an influential factor in the poor prognosis of bladder tumors, as patients with high RAC3 expression exhibited a lower overall survival rate than those with low RAC3 expression.

CONCLUSION

Based on our results, RAC3 shows promise as both a marker for early diagnosis of bladder tumors and a potential therapeutic target.

Mechanism-centric regulatory network identifies NME2 and MYC programs as markers of Enzalutamide resistance in CRPC

Heterogeneous response to Enzalutamide, a second-generation androgen receptor signaling inhibitor, is a central problem in castration-resistant prostate cancer (CRPC) management. Genome-wide systems investigation of mechanisms that govern Enzalutamide resistance promise to elucidate markers of heterogeneous treatment response and salvage therapies for CRPC patients. Focusing on the de novo role of MYC as a marker of Enzalutamide resistance, here we reconstruct a CRPC-specific mechanism-centric regulatory network, connecting molecular pathways with their upstream transcriptional regulatory programs. Mining this network with signatures of Enzalutamide response identifies NME2 as an upstream regulatory partner of MYC in CRPC and demonstrates that NME2-MYC increased activities can predict patients at risk of resistance to Enzalutamide, independent of co-variates. Furthermore, our experimental investigations demonstrate that targeting MYC and its partner NME2 is beneficial in Enzalutamide-resistant conditions and could provide an effective strategy for patients at risk of Enzalutamide resistance and/or for patients who failed Enzalutamide treatment.

Chlorogenic Acid Inhibits Proliferation, Migration and Invasion of Pancreatic Cancer Cells via AKT/GSK-3β/β-catenin Signaling Pathway

BACKGROUND

Chlorogenic acid (CA, United States Patent No. 10772340), a natural biologically active food ingredient, displays potent antitumor activity against a variety of cancer cells. However, the mechanism underlying its anticancer effect is not well elucidated.

OBJECTIVE

In the present study, we hope to dissect the mechanism underlying the anticancer effects of CA in pancreatic cancer cells.

METHODS

The cytotoxicity of CA in pancreatic cancer cells was determined by MTT assay. Flow cytometry was performed to evaluate the cells apoptosis, while a clonogenic assay was carried out to check the colony formation of cancer cells. Transwell assay was performed to assess the cells migration and invasion. The protein expression of AKT/GSK-3β/β-catenin signaling pathway was detected by Western Blot.

RESULTS

Our data indicated that CA inhibited the proliferation of PANC-28 and PANC-1 cells in a dose and time-dependent manner. CA was able to inhibit colony formation, migration, and invasion ability and trigger apoptosis in PANC-28 and PANC-1 cells. Further study showed that CA down-regulated the expression of AKT, p-AKT(Thr308), p-GSK-3β(Ser9), β-catenin, N-cadherin, and vimentin while enhancing the expression of cleaved-caspase 3 and cleaved-caspase 7 in PANC-28 and PANC-1 cells.

CONCLUSION

Our study provides significant evidence that CA is able to inhibit the growth of pancreatic cancer via the AKT/GSK-3β/β-catenin signaling pathway.

Rac1 as a Target to Treat Dysfunctions and Cancer of the Bladder

Bladder pathologies, very common in the aged population, have a considerable negative impact on quality of life. Novel targets are needed to design drugs and combinations to treat diseases such as overactive bladder and bladder cancers. A promising new target is the ubiquitous Rho GTPase Rac1, frequently dysregulated and overexpressed in bladder pathologies. We have analyzed the roles of Rac1 in different bladder pathologies, including bacterial infections, diabetes-induced bladder dysfunctions and bladder cancers. The contribution of the Rac1 protein to tumorigenesis, tumor progression, epithelial-mesenchymal transition of bladder cancer cells and their metastasis has been analyzed. Small molecules selectively targeting Rac1 have been discovered or designed, and two of them—NSC23766 and EHT 1864—have revealed activities against bladder cancer. Their mode of interaction with Rac1, at the GTP binding site or the guanine nucleotide exchange factors (GEF) interaction site, is discussed. Our analysis underlines the possibility of targeting Rac1 with small molecules with the objective to combat bladder dysfunctions and to reduce lower urinary tract symptoms. Finally, the interest of a Rac1 inhibitor to treat advanced chemoresistance prostate cancer, while reducing the risk of associated bladder dysfunction, is discussed. There is hope for a better management of bladder pathologies via Rac1-targeted approaches.

Overexpressed or hyperactivated Rac1 as a target to treat hepatocellular carcinoma

Despite novel targeted and immunotherapies, the prognosis remains bleak for patients with hepatocellular carcinoma (HCC), especially for advanced and/or metastatic forms. The rapid emergence of drug resistance is a major obstacle in the success of chemo-, targeted-, immuno-therapies of HCC. Novel targets are needed. The prominent roles of the small GTPase Rac1 in the development and progression of HCC are discussed here, together with its multiple protein partners, and the targeting of Rac1 with RNA-based regulators and small molecules. We discuss the oncogenic functions of Rac1 in HCC, including the contribution of Rac1 mutants and isoform Rac1b. Rac1 is a ubiquitous target, but the protein is frequently overexpressed and hyperactivated in HCC. It contributes to the aggressivity of the disease, with key roles in cancer cell proliferation, tumor metastasis and resistance to treatment. Small molecule targeting Rac1, indirectly or directly, have shown anticancer effects in HCC experimental models. Rac1-binding agents such as EHT 1864 and analogues offer novel opportunities to combat HCC. We discuss the different modalities to repress Rac1 overactivation in HCC with small molecules and the combination with reference drugs to promote cancer cell death and to repress cell invasion. We highlight the necessity to combine Rac1-targeted approach with appropriate biomarkers to select Rac1 activated tumors. Our analysis underlines the prominent oncogenic functions of Rac1 in HCC and discuss the modalities to target this small GTPase. Rac1 shall be considered as a valid target to limit the acquired and intrinsic resistance of HCC tumors and their metastatic potential.

Inferring Differential Networks by Integrating Gene Expression Data With Additional Knowledge

Evidences increasingly indicate the involvement of gene network rewiring in disease development and cell differentiation. With the accumulation of high-throughput gene expression data, it is now possible to infer the changes of gene networks between two different states or cell types via computational approaches. However, the distribution diversity of multi-platform gene expression data and the sparseness and high noise rate of single-cell RNA sequencing (scRNA-seq) data raise new challenges for existing differential network estimation methods. Furthermore, most existing methods are purely rely on gene expression data, and ignore the additional information provided by various existing biological knowledge. In this study, to address these challenges, we propose a general framework, named weighted joint sparse penalized D-trace model (WJSDM), to infer differential gene networks by integrating multi-platform gene expression data and multiple prior biological knowledge. Firstly, a non-paranormal graphical model is employed to tackle gene expression data with missing values. Then we propose a weighted group bridge penalty to integrate multi-platform gene expression data and various existing biological knowledge. Experiment results on synthetic data demonstrate the effectiveness of our method in inferring differential networks. We apply our method to the gene expression data of ovarian cancer and the scRNA-seq data of circulating tumor cells of prostate cancer, and infer the differential network associated with platinum resistance of ovarian cancer and anti-androgen resistance of prostate cancer. By analyzing the estimated differential networks, we find some important biological insights about the mechanisms underlying platinum resistance of ovarian cancer and anti-androgen resistance of prostate cancer.

Androgen deprivation‑induced OPHN1 amplification promotes castration‑resistant prostate cancer

Androgen deprivation therapy (ADT) is used to treat prostate cancer (PCa). However, ADT may increase the expression of androgen receptor (AR) through the amplification of chromosome X. The gene oligophrenin 1 (OPHN1) is located in the same region as the AR gene, which could be amplified by ADT. Thus, the role of OPHN1 in PCa pathology was investigated. The expression status of OPHN1 in PCa was searched in The Cancer Genome Atlas (TCGA) database. Androgen-sensitive cells LNCaP and 22RV1 were cultured under ADT conditions, and then the expression of OPHN1 was evaluated by northern blotting. The expression of OPHN1 was enhanced or knocked down in LNCaP and 22RV1 cells by transfection. Subsequently, the LNCaP and 22RV1 cells were cultured under ADT, and the viability rate, apoptosis, and migration of cells were assessed by MTT, flow cytometry, and Transwell assay respectively. The expression of OPHN1 was also enhanced or knocked down in androgen-insensitive PC3 cells, and then the effects of OPHN1 on the viability, apoptosis, and migration of PC3 cells were assessed. A mouse xenograft model was created by injecting LNCaP cells with OPHN1 overexpression subcutaneously, and the tumor growth rates were monitored. In TCGA database, amplification of the OPHN1 gene was observed in the PCa tumors. ADT increased the expression of OPHN1 in LNCaP and 22RV1 cells (P<0.05). OPHN1 could promote resistance of LNCaP and 22RV1 cells to ADT by promoting cell survival and preventing their apoptosis (P<0.05). In addition, OPHN1 contributed to cell viability (P<0.05) and enhanced the migration ability in LNCaP, 22RV1 and PC3 cells (P<0.05). In the mouse model, the PCa xenograft with OPHN1 overexpression had a higher growth rate and was more resistant to the ADT condition (P<0.05). In summary, ADT induced the overexpression of OPHN1 in PCa, which facilitated PCa cell survival and promoted PCa progression.

The PTEN Conundrum: How to Target PTEN-Deficient Prostate Cancer

Loss of the tumor suppressor phosphatase and tensin homologue deleted on chromosome 10 (PTEN), which negatively regulates the PI3K-AKT-mTOR pathway, is strongly linked to advanced prostate cancer progression and poor clinical outcome. Accordingly, several therapeutic approaches are currently being explored to combat PTEN-deficient tumors. These include classical inhibition of the PI3K-AKT-mTOR signaling network, as well as new approaches that restore PTEN function, or target PTEN regulation of chromosome stability, DNA damage repair and the tumor microenvironment. While targeting PTEN-deficient prostate cancer remains a clinical challenge, new advances in the field of precision medicine indicate that PTEN loss provides a valuable biomarker to stratify prostate cancer patients for treatments, which may improve overall outcome. Here, we discuss the clinical implications of PTEN loss in the management of prostate cancer and review recent therapeutic advances in targeting PTEN-deficient prostate cancer. Deepening our understanding of how PTEN loss contributes to prostate cancer growth and therapeutic resistance will inform the design of future clinical studies and precision-medicine strategies that will ultimately improve patient care.