Therapeutic potential of the PI3K inhibitor LY294002 and PARP inhibitor Talazoparib combination in BRCA-deficient triple negative breast cancer cells

Breast Cancer Stem Cells and Tumor Heterogeneity: Characteristics and Therapeutic Strategies

Breast cancer is one of the most frequently detected malignancies worldwide. It is responsible for more than 15% of all death cases caused by cancer in women. Breast cancer is a heterogeneous disease representing various histological types, molecular characteristics, and clinical profiles. However, all breast cancers are organized in a hierarchy of heterogeneous cell populations, with a small proportion of cancer stem cells (breast cancer stem cells (BCSCs)) playing a putative role in cancer progression, and they are responsible for therapeutic failure. In different molecular subtypes of breast cancer, they present different characteristics, with specific marker profiles, prognoses, and treatments. Recent efforts have focused on tackling the Wnt, Notch, Hedgehog, PI3K/Akt/mTOR, and HER2 signaling pathways. Developing diagnostics and therapeutic strategies enables more efficient elimination of the tumor mass together with the stem cell population. Thus, the knowledge about appropriate therapeutic methods targeting both "normal" breast cancer cells and breast cancer stem cell subpopulations is crucial for success in cancer elimination.

Small molecule agents for triple negative breast cancer: Current status and future prospects

Triple-negative breast cancer (TNBC) is a subtype of breast cancer with poor prognosis. The number of cases increased by 2.26 million in 2020, making it the most commonly diagnosed cancer type in the world. TNBCs lack hormone receptor (HR) and human epidermal growth factor 2 (HER2), which limits treatment options. Currently, paclitaxel-based drugs combined with other chemotherapeutics remain the main treatment for TNBC. There is currently no consensus on the best therapeutic regimen for TNBC. However, there have been successful clinical trials exploring large-molecule monoclonal antibodies, small-molecule targeted drugs, and novel antibody-drug conjugate (ADC). Although monoclonal antibodies have produced clinical success, their large molecular weight can limit therapeutic benefits. It is worth noting that in the past 30 years, the FDA has approved small molecule drugs for HER2-positive breast cancers. The lack of effective targets and the occurrence of drug resistance pose significant challenges in the treatment of TNBC. To improve the prognosis of TNBC, it is crucial to search for effective targets and to overcome drug resistance. This review examines the clinical efficacy, adverse effects, resistance mechanisms, and potential solutions of targeted small molecule drugs in both monotherapies and combination therapies. New therapeutic targets, including nuclear export protein 1 (XPO1) and hedgehog (Hh), are emerging as potential options for researchers and become integrated into clinical trials for TNBC. Additionally, there is growing interest in the potential of targeted protein degradation chimeras (PROTACs), degraders of rogue proteins, as a future therapy direction. This review provides potentially valuable insights with clinical implications.

Predictive, preventive, and personalized medicine in breast cancer: targeting the PI3K pathway

Breast cancer (BC) is a multifaceted disease characterized by distinct molecular subtypes and varying responses to treatment. In BC, the phosphatidylinositol 3-kinase (PI3K) pathway has emerged as a crucial contributor to the development, advancement, and resistance to treatment. This review article explores the implications of the PI3K pathway in predictive, preventive, and personalized medicine for BC. It emphasizes the identification of predictive biomarkers, such as PIK3CA mutations, and the utility of molecular profiling in guiding treatment decisions. The review also discusses the potential of targeting the PI3K pathway for preventive strategies and the customization of therapy based on tumor stage, molecular subtypes, and genetic alterations. Overcoming resistance to PI3K inhibitors and exploring combination therapies are addressed as important considerations. While this field holds promise in improving patient outcomes, further research and clinical trials are needed to validate these approaches and translate them into clinical practice.

Tongqiao Mingmu formula alleviates retinal ganglion cell autophagy through PI3K/AKT/mTOR pathway

Glaucoma is a severe blindness-causing optic nerve disease characterized by a loss of retinal ganglion cells (RGCs). Previous studies have shown that the Tongqiao Mingmu (TQMM) formula can reduce retinal and optic nerve damage, but its mechanism of action requires further elucidation. In this study, an RGC injury model was prepared using glutamate and then treated with serum-containing drug from the TQMM formula (hereafter called "TQMM formula serum"). In the glutamate-induced RGC injury model, cell viability decreased with an increase in glutamate concentration, whereas the expression of autophagy-related biomarkers LC3 and Belicin-1 increased. An adenovirus transfection experiment revealed that glutamate markedly promoted autophagic flux in RGCs. Notably, TQMM formula serum inhibited the expression of autophagy-related biomarkers, reduced autophagy flux, and reversed the damage caused by glutamate to RGCs. Furthermore, the PI3K inhibitor LY294002 was used to intervene in the RGC autophagy model and was found to suppress the PI3K/AKT/mTOR pathway and enhance RGC autophagy. However, TQMM formula serum could generate an opposite effect and upregulate the expressions of the PI3K/AKT/mTOR pathway genes and proteins. In conclusion, the TQMM formula can prevent glutamate-induced autophagy in RGCs, possibly by activating the PI3K/AKT/mTOR pathway and reducing the expression of autophagy-related biomarkers LC3 and Belicin-1 to attenuate autophagy and maintain RGC viability.

Unravelling the Role of PARP1 in Homeostasis and Tumorigenesis: Implications for Anti-Cancer Therapies and Overcoming Resistance

Detailing the connection between homeostatic functions of enzymatic families and eventual progression into tumorigenesis is crucial to our understanding of anti-cancer therapies. One key enzyme group involved in this process is the Poly (ADP-ribose) polymerase (PARP) family, responsible for an expansive number of cellular functions, featuring members well established as regulators of DNA repair, genomic stability and beyond. Several PARP inhibitors (PARPi) have been approved for clinical use in a range of cancers, with many more still in trials. Unfortunately, the occurrence of resistance to PARPi therapy is growing in prevalence and requires the introduction of novel counter-resistance mechanisms to maintain efficacy. In this review, we summarize the updated understanding of the vast homeostatic functions the PARP family mediates and pin the importance of PARPi therapies as anti-cancer agents while discussing resistance mechanisms and current up-and-coming counter-strategies for countering such resistance.

Triple Negative Breast Cancer Treatment Options and Limitations: Future Outlook

Triple negative breast cancer (TNBC) has a negative expression of estrogen receptors (ER), progesterone receptors (PR), and human epidermal growth factor receptors (HER2). The survival rate for TNBC is generally worse than other breast cancer subtypes. TNBC treatment has made significant advances, but certain limitations remain. Treatment for TNBC can be challenging since the disease has various molecular subtypes. A variety of treatment options are available, such as chemotherapy, immunotherapy, radiotherapy, and surgery. Chemotherapy is the most common of these options. TNBC is generally treated with systemic chemotherapy using drugs such as anthracyclines and taxanes in neoadjuvant or adjuvant settings. Developing resistance to anticancer drugs and off-target toxicity are the primary hindrances to chemotherapeutic solutions for cancer. It is imperative that researchers, clinicians, and pharmaceutical companies work together to develop effective treatment options for TNBC. Several studies have suggested nanotechnology as a potential solution to the problem of suboptimal TNBC treatment. In this review, we summarized possible treatment options for TNBC, including chemotherapy, immunotherapy, targeted therapy, combination therapy, and nanoparticle-based therapy, and some solutions for the treatment of TNBC in the future. Moreover, we gave general information about TNBC in terms of its characteristics and aggressiveness.

Novel combination treatment of CDK 4/6 inhibitors with PARP inhibitors in triple negative breast cancer cells

Cyclin-dependent kinase 4/6 (CDK4/6) inhibitors provide promising results for treating hormone receptor-positive breast cancer. However, the efficacy of CDK4/6 inhibitors remains uncertain in triple negative breast cancer (TNBC) patients with particularly carrying RB-deficient tumors. Poly-(ADP-ribose) polymerase (PARP) inhibitors offer a therapeutic strategy for the treatment of BRCA-mutated TNBC patients. However, the acquired drug resistance, changes in the cell cycle regulation, and DNA damage repair have demonstrated the necessity for developing new combination strategies. This preclinical study assessed a combinatory treatment of the CDK4/6 inhibitor abemaciclib with PARP inhibitors talazoparib (TAL) in HCC1937 BRCA-mutated RB-deficient TNBC cells and TAL-resistant HCC1937-R cells through WST-1 analysis, annexin V, cell cycle, acridine orange/propidium iodide staining, RT-PCR, and apoptosis array. Our findings revealed that abemaciclib and TAL combination synergistically suppressed the growth of TNBC cells and overcame TAL resistance through G0/G1 arrest and the activity of both intrinsic and extrinsic apoptotic pathways. These preliminary results suggest that the combination of abemaciclib and TAL could expand the use of these inhibitors in BRCA mutated and RB deficient TNBC patients and potentially overcomes PARP inhibitors resistance.

Rational Combinations of PARP Inhibitors with HRD-Inducing Molecularly Targeted Agents

Cancers with wild-type BRCA, homologous recombination proficiency, or de novo or acquired resistance to PARP inhibition represent a growing population of patients who may benefit from combinatorial PARP inhibitor strategies. We review targeted inhibitors of angiogenesis, epigenetic regulators, and PI3K, MAPK, and other cellular signaling pathways as inducers of homologous recombination deficiency, providing support for the use of PARP inhibitors in contexts not previously considered susceptible to PARP inhibition.

Recent advances in cancer therapy using PARP inhibitors

When DNA repair is inadequate it increases the chances of the genome becoming unstable and it undergoes a malignant mutation. The deficiency of DNA repair PARP proteins may be leveraged for cancer therapy by increasing genomic instability and causing massive DNA damage in cancer cells. DNA repair components are under increased demand in cancer cells because of the continuous replication of DNA. The oncogenic loss of BRCA and an inefficient DNA repair led to cancer cells being dependent on particular DNA repair pathways, like the Poly (ADP-ribose) polymerase pathway. Breast cancer gene 1 and 2 plays a crucial role in DNA repair and genome integrity explaining how BRCA1 and BRCA2 mutations raise the menace of cancer. PARP inhibitors inhibit the base exclusion repair pathway, resulting in the buildup of unrepaired single strand breaks, which cause inflated replication forks in the S phase and subsequently the development of damaging double stranded breaks. Cells having BRCA mutations are unable to repair DNA breaks, leading to apoptosis and eventually death of cancer cells. Numerous indicators, such as a lack of homologous recombination and a high degree of replication pressure, indicate that this therapy will be very effective. Combining PARP inhibitors with chemotherapy, an immune checkpoint inhibitor, and a targeted drug is an effective strategy for combating PARP inhibitors resistance. Several PARP-based combination approaches are in preclinical and clinical development. Various clinical trials are successfully completed and some are undergoing to evaluate the efficacy of these molecules. This review will describe the current views and clinical updates on PARP inhibitors.

Rapid DNA interstrand cross-linking of Pt(IV) compound

Pt(IV) anticancer compounds have been developed for several decades to overcome the drawbacks of their Pt(II) congeners, and the reduction of Pt(IV) to Pt(II) has been commonly regarded as a necessary step in the activation of Pt(IV) compounds prior to targeting DNA. However, blockage of glutathione (GSH) biosynthesis resulted in a slight effect on the cytotoxicity of oxoplatin in yeast Saccharomyces cerevisiae strains, urging us to reconsider the mechanism of actions for the "inert" Pt(IV) complexes. Using X-ray absorption near-edge spectroscopy (XANES), our data demonstrated that Pt(IV) complex oxoplatin could bind to DNA in a tetravalent state. Both alkaline denaturing agarose electrophoresis and thermal denaturation-renaturation assay revealed that oxoplatin could rapidly produce stable interstrand crosslinks (ICLs), which can further translate into a fast cell-killing process in cancer cells. Using quantitative real-time PCR and immunofluorescence analysis, we also proved that Pt(IV) complex oxoplatin could induce a quick intracellular response of the FA/BRCA pathway in cancer cells that involves the DNA interstrand crosslinking repair system, and this quick response to ICLs was independent with the intracellular GSH levels. Cell cycle analysis showed that short incubation with oxoplatin can induce a strong S phase arrest in HeLa cells, indicating that the rapid interstrand crosslinks produced by oxoplatin might stall the replication fork, result in the double-strand breaks, and eventually induce cell death. Our results implied that, besides the reduction mechanism to release the Pt(II) congeners, direct and rapid interstrand cross-linking with DNA by Pt(IV) compounds might be a unique mechanism for Pt(IV) compounds, which may provide new insight for the development of next-generation platinum-based drugs.

Circular RNA circPTK2 modulates migration and invasion via miR-136/NFIB signaling on triple-negative breast cancer cells in vitro

OBJECTIVE AND BACKGROUND

Triple-negative breast cancer (TNBC) is an aggressive breast type of cancer with poor prognosis and high mortality rates. CircRNAs have been widely investigated, due to their crucial role in cancer progression. We aimed to elucidate the function of circPTK2 (has_circ_0003221) in TNBC and explore the mechanism in progression of TNBC.

METHODS

qPCR was performed to validate the expression of circPTK2 and related mRNA in TNBC tissue and cell lines. CCK-8, EdU, Transwell assay were conducted to detect the proliferation, migration and invasion of circPTK2 and miR-136 on TNBC cells. RIP and dual-luciferase reporter assay were used to confirm the interaction among circPTK2, miR-136 and NFIB. Si-circPTK2, mimic and inhibitor of miR-136 were transfected in TNBC cells to confirm the mechanism of circPTK2 and miR-136 in TNBC cells.

RESULTS

CircPTK2 were downregulated in TNBC tissues and cell lines. CircPTK2 significantly promoted the proliferation, migration, and invasion of TNBC cells. CircPTK2 was confirmed to be a sponge of miR-136, and directly regulated NFBI and AKT/PI3K pathway. A rescue assay validated circPTK2/miR-136/NFIB axis in TNBC cells.

CONCLUSION

CircPTK2 promoted TNBC progression and development. circPTK2/miR-136/NFIB might be an effective biomarker for TNBC.