Phosphoinositide 3-Kinase (PI3K) Inhibitors and Breast Cancer: An Overview of Current Achievements

Regulation of mitochondrial apoptosis via siRNA-loaded metallo-alginate hydrogels: A localized and synergistic antitumor therapy

Preventing relapse after resection of a primary tumor continues to be an unmet clinical need. Development of adjuvant biomaterials with the capacity to kill residual cancer cells after tumor resection is of clinical importance. Here we developed a library of metallo-alginate hydrogels containing high concentrations of metallic ions such as Ca2+ in combination with Zn2+, Li+, or Mg2+ to disrupt Ca2+ homeostasis in the mitochondria of cancer cells by local hyperthermia. To synergistically kill tumor cells and suppress the growth of rechallenged tumors, we embedded oncogene-silencing nucleic acids (mTOR siRNA) loaded into polymerc nanoparticles (NPs) composed of poly (β-amino esters) in the metallo-alginate hydrogels, targeting cancer cells that activate multi-drug resistance pathways such PI3K/AKT/mTOR. Metabolomic studies showed alterations in the Warburg effect, mitochondrial transport, and the TCA cycle, confirming cancer cell damage. In vivo studies of this targeted therapy in mice demonstrated a sex-dependent effect. Male B16F10-tumor-bearing mice treated with the synergistic therapy showed restrained tumor growth. In contrast, no therapeutic effect was observed in female counterparts. Our results demonstrate that in situ-formed NP-loaded metallo-alginate hydrogels can modulate two distinct immune signaling networks that are relevant for enhancing cancer cell death. On the basis of our findings, this combination therapy emerges as a promising sex-dependent strategy for clinical translation.

The potential role of targeting the leptin receptor as a treatment for breast cancer in the context of hyperleptinemia: a literature review

Since cancer is becoming a leading cause of death worldwide, efforts should be concentrated on understanding its underlying biological alterations that would be utilized in disease management, especially prevention strategies. Within this context, multiple bodies of evidence have highlighted leptin's practical and promising role, a peptide hormone extracted from adipose and fatty tissues with other adipokines, in promoting the proliferation, migration, and metastatic invasion of breast carcinoma cells. Excessive blood leptin levels and hyperleptinemia increase body fat content and stimulate appetite. Also, high leptin level is believed to be associated with several conditions, including overeating, emotional stress, inflammation, obesity, and gestational diabetes. It has been noted that when leptin has impaired signaling in CNS, causing the lack of its normal function in energy balance, it results in leptin resistance, leading to a rise in its concentration in peripheral tissues. Our research paper will shed highlighting on potentially targeting the leptin receptor and its cellular signaling in suppressing breast cancer progression.

Targeting the PI3K/AKT/mTOR pathway in lung cancer: mechanisms and therapeutic targeting

Owing to its high mortality rate, lung cancer (LC) remains the most common cancer worldwide, with the highest malignancy diagnosis rate. The phosphatidylinositol-3-kinase (PI3K)/protein kinase B (AKT)/mammalian target of rapamycin (mTOR) signaling (PAM) pathway is a critical intracellular pathway involved in various cellular functions and regulates numerous cellular processes, including growth, survival, proliferation, metabolism, apoptosis, invasion, and angiogenesis. This review aims to highlight preclinical and clinical studies focusing on the PAM signaling pathway in LC and underscore the potential of natural products targeting it. Additionally, this review synthesizes the existing literature and discusses combination therapy and future directions for LC treatment while acknowledging the ongoing challenges in the field. Continuous development of novel therapeutic agents, technologies, and precision medicine offers an increasingly optimistic outlook for the treatment of LC.

Monitoring and management of adverse effects associated with trastuzumab deruxtecan: a UAE-specific consensus

Breast cancer is the most frequently diagnosed cancer in the UAE and a leading cause of cancer-related mortality. Although early diagnosis contributes to favorable prognoses, novel treatment modalities like antibody-drug conjugates (ADCs) have significantly broadened the therapeutic landscape for patients in metastatic settings. The recognition of "HER2-low" expression as a targetable category has caused a paradigm shift in the management of breast cancer. Although initially developed to target HER2-positive breast cancer, trastuzumab deruxtecan (T-DXd), an ADC, has now also been approved to treat metastatic or unresectable HER2-low breast cancers. Despite the inherent specificity of an ADC, the risk of off-site toxicity exists and is an essential component while assessing the risk-benefit ratio of the treatment. Developing strategies to balance efficacy and safety is crucial, especially for newly approved therapies like T-DXd. Regional perspectives, cultural beliefs, and demographic factors influence treatment decisions and outcomes. The objective of this paper is to establish a UAE-specific consensus among oncologists on practical T-DXd treatment considerations and management of associated side effects. Establishing a consensus on monitoring and managing T-DXd side effects among experts can promote informed decision-making.

Distinct mRNA expression profiles and miRNA regulators of the PI3K/AKT/mTOR pathway in breast cancer: insights into tumor progression and therapeutic targets

Background

Breast cancer remains a leading cause of mortality among women, driven by the molecular complexity of its various subtypes. This study aimed to investigate the differential expression of genes and miRNAs involved in the PI3K/AKT/mTOR signaling pathway, a critical regulator of cancer progression.

Methods

We analyzed tumor tissues from five breast cancer subtypes-luminal A, luminal B HER2-negative, luminal B HER2-positive, HER2-positive, and triple-negative breast cancer (TNBC)-and compared them with non-cancerous tissues. Microarray and qRT-PCR techniques were employed to profile mRNAs and miRNAs, while bioinformatic tools predicted miRNA-mRNA interactions. Statistical analysis was performed with a statistical significance threshold (p) < 0.05.

Results

We identified several upregulated genes across all subtypes, with TNBC and HER2-positive cancers showing the most significant changes. Key genes such as COL1A1, COL4A1, PIK3CA, PIK3R1, and mTOR were found to be overexpressed, correlating with increased cancer aggressiveness. miRNA analysis revealed that miR-190a-3p, miR-4729, and miR-19a-3p potentially regulate these genes, influencing the PI3K/AKT/mTOR pathway. For instance, reduced expression of miR-190a-3p may contribute to the overexpression of PIK3CA and other pathway components, enhancing metastatic potential.

Conclusion

Our findings suggest that the PI3K/AKT/mTOR pathway and its miRNA regulators play crucial roles in breast cancer progression, particularly in aggressive subtypes like TNBC. The identified miRNAs and mRNAs hold potential as biomarkers for diagnosis and treatment, but further validation in functional studies is required. This study provides a foundation for targeted therapies aimed at modulating this critical pathway to improve breast cancer outcomes.

Higher risk of recurrence in early-stage breast cancer patients with increased levels of ribosomal protein S6

PI3K/AKT/mTOR pathway is implicated in breast cancer progression and recurrence. The identification of PIK3CA and AKT1 mutations and loss of PTEN serve as selection criterion for targeted therapies involving selective inhibitors. However, they do not consistently align with pathway activation, and high-cost determinations limit their routine application. PI3K-downstream epigenetic regulatory mechanisms broaden the alterations that amplify pathway activity and, consequently, sensitivity to selective inhibitors. In this retrospective observational study, conducted within a cohort of early-stage breast cancer patients, we determined phosphorylated ribosomal protein S6 (pS6) at Ser240/244 by immunohistochemistry as an indicator of PI3K pathway activation. Log-Rank test and Cox proportional hazards regression were used to analyze the clinical relevance of pS6, alone and together with clinicopathological variables, regarding recurrence-free survival. ROC curves and the area under the curves were used to evaluate the calibration and discrimination properties of uni- and multivariate models. Our results show that a high percentage of pS6 positive tumor cells was associated with an unfavorable prognosis in a cohort of 129 hormone receptor positive/HER2 negative breast cancer patients (Hazard Ratio = 5.92; Log-Rank p = 9.5e-08; median follow-up = 53 months). When assessed in combination with lymph node status, the predictive capacity was higher compared to both univariate models individually. In conclusion, pS6 could represent a novel independent marker for predicting recurrence risk in luminal breast cancer.

PLK1 Inhibitor Onvansertib Enhances the Efficacy of Alpelisib in PIK3CA-Mutated HR-Positive Breast Cancer Resistant to Palbociclib and Endocrine Therapy: Preclinical Insights

BACKGROUND

Endocrine therapy (ET) combined with cyclin-dependent kinase 4/6 inhibitors (CDK4/6i) is the preferred first-line treatment for hormone receptor-positive (HR+)/HER2- metastatic breast cancer. Although this is beneficial, acquired resistance leads to disease progression, and patients harboring PIK3CA mutations are treated with targeted therapies such as the PI3Kα inhibitor, alpelisib, alongside ET. Drug-associated resistance mechanisms limit the efficacy of alpelisib, highlighting the need for better combination therapies. This study aimed to evaluate the efficacy of combining alpelisib with a highly specific PLK1 inhibitor, onvansertib, in PIK3CA-mutant HR+ breast cancer preclinical models.

METHODS

We assessed the effect of the alpelisib and onvansertib combination on cell viability, PI3K signaling pathway, cell cycle phase distribution and apoptosis in PI3K-activated HR+ breast cancer cell lines. The antitumor activity of the combination was evaluated in three PIK3CA-mutant HR+ breast cancer patient-derived xenograft (PDX) models, resistant to ET and CDK4/6 inhibitor palbociclib. Pharmacodynamics studies were performed using immunohistochemistry and Simple Western analyses in tumor tissues.

RESULTS

The combination synergistically inhibited cell viability, suppressed PI3K signaling, induced G2/M arrest and apoptosis in PI3K-activated cell lines. In the three PDX models, the combination demonstrated superior anti-tumor activity compared to the single agents. Pharmacodynamic studies confirmed the inhibition of both PLK1 and PI3K activity and pronounced apoptosis in the combination-treated tumors.

CONCLUSIONS

Our findings support that targeting PLK1 and PI3Kα with onvansertib and alpelisib, respectively, may be a promising strategy for patients with PIK3CA-mutant HR+ breast cancer failing ET + CDK4/6i therapies and warrant clinical evaluation.

PI3K/AKT/mTOR signaling pathway: an important driver and therapeutic target in triple-negative breast cancer

Triple-negative breast cancer (TNBC) is a highly heterogeneous tumor lacking estrogen receptor (ER), progesterone receptor (PR), and human epidermal growth factor receptor 2 (HER2) expression. It has higher aggressiveness and metastasis than other subtypes, with limited effective therapeutic strategies, leading to a poor prognosis. The phosphoinositide 3-kinase (PI3K)/protein kinase B (AKT)/mechanistic target of rapamycin (mTOR) signaling pathway is prevalently over-activated in human cancers and contributes to breast cancer (BC) growth, survival, proliferation, and angiogenesis, which could be an interesting therapeutic target. This review summarizes the PI3K/AKT/mTOR signaling pathway activation mechanism in TNBC and discusses the relationship between its activation and various TNBC subtypes. We also report the latest clinical studies on kinase inhibitors related to this pathway for treating TNBC. Our review discusses the issues that need to be addressed in the clinical application of these inhibitors.

Allosteric PI3Kα Inhibition Overcomes On-target Resistance to Orthosteric Inhibitors Mediated by Secondary PIK3CA Mutations

PIK3CA mutations occur in ∼8% of cancers, including ∼40% of HR-positive breast cancers, where the PI3K-alpha (PI3Kα)-selective inhibitor alpelisib is FDA approved in combination with fulvestrant. Although prior studies have identified resistance mechanisms, such as PTEN loss, clinically acquired resistance to PI3Kα inhibitors remains poorly understood. Through serial liquid biopsies and rapid autopsies in 39 patients with advanced breast cancer developing acquired resistance to PI3Kα inhibitors, we observe that 50% of patients acquire genomic alterations within the PI3K pathway, including PTEN loss and activating AKT1 mutations. Notably, although secondary PIK3CA mutations were previously reported to increase sensitivity to PI3Kα inhibitors, we identified emergent secondary resistance mutations in PIK3CA that alter the inhibitor binding pocket. Some mutations had differential effects on PI3Kα-selective versus pan-PI3K inhibitors, but resistance induced by all mutations could be overcome by the novel allosteric pan-mutant-selective PI3Kα-inhibitor RLY-2608. Together, these findings provide insights to guide strategies to overcome resistance in PIK3CA-mutated cancers.

SIGNIFICANCE

In one of the largest patient cohorts analyzed to date, this study defines the clinical landscape of acquired resistance to PI3Kα inhibitors. Genomic alterations within the PI3K pathway represent a major mode of resistance and identify a novel class of secondary PIK3CA resistance mutations that can be overcome by an allosteric PI3Kα inhibitor. See related commentary by Gong and Vanhaesebroeck, p. 204 . See related article by Varkaris et al., p. 240 . This article is featured in Selected Articles from This Issue, p. 201.

LINC00969 inhibits proliferation with metastasis of breast cancer by regulating phosphorylation of PI3K/AKT and ILP2 expression through HOXD8

Background

Breast cancer (BC) is a malignancy that is inadequately treated and poses a significant global health threat to females. The aberrant expression of long noncoding RNAs (lncRNAs) acts as a complex with a precise regulatory role in BC progression. LINC00969 has been linked to pyroptotic cell death and resistance to gefitinib in lung cancer cells. However, the precise function and regulatory mechanisms of LINC00969 in BC remain largely unexplored.

Methods

Cell proliferation, migration, and invasion of BC cells were evaluated using CCK-8 and Transwell assays. Western blotting was employed to analyze the protein expression levels of HOXD8, ILP2, PI3K, t-AKT, and p-AKT.

Results

LINC00969 was drastically reduced in BC tissues LINC00969 overexpression markedly suppressed proliferation, migration, and invasion, and blocked PI3K and p-AKT protein expression in MCF-7 cells. Activation of the PI3K/AKT pathway reversed the suppressive effect of LINC0096 overexpression on the proliferation, migration, and invasion of MCF-7 cells. Moreover, LINC00969 overexpression enhanced HOXD8 and blocked ILP2 protein expression in MCF-7 cells. In contrast, activating the PI3K/AKT pathway had no effect on HOXD8 and blocked ILP2 protein expression in MCF-7 cells overexpressing LINC00969. HOXD8 knockdown enhanced ILP2, PI3K, and p-AKT protein expression, and the proliferation, migration, and invasion of MCF-7 cells co-transfected with si-HOXD8 and ov-LINC00969. LINC00969 regulated HOXD8 via binding to miR-425-5p.

Conclusion

LINC00969 inhibits the proliferation and metastasis of BC cells by regulating PI3K/AKT phosphorylation through HOXD8/ILP2.

Localization and Quantification of Post-Translational Modifications of Proteins Using Electron Activated Dissociation Fragmentation on a Fast-Acquisition Time-of-Flight Mass Spectrometer

Protein post-translational modifications (PTMs) are crucial and dynamic players in a large variety of cellular processes and signaling. Proteomic technologies have emerged as the method of choice to profile PTMs. However, these analyses remain challenging due to potential low PTM stoichiometry, the presence of multiple PTMs per proteolytic peptide, PTM site localization of isobaric peptides, and neutral losses. Collision-induced dissociation (CID) is commonly used to characterize PTMs, but the application of collision energy can lead to neutral losses and incomplete peptide sequencing for labile PTM groups. In this study, we assessed the performance of an alternative fragmentation, electron activated dissociation (EAD), to characterize, site localize, and quantify peptides with labile modifications in comparison to CID, both operated on a recently introduced fast-scanning quadrupole-time-of-flight (QqTOF) mass spectrometer. We analyzed biologically relevant phosphorylated, succinylated, malonylated, and acetylated synthetic peptides using targeted parallel reaction monitoring (PRM or MRMHR) assays. We report that electron-based fragmentation preserves the malonyl group from neutral losses. The novel tunable EAD kinetic energy maintained labile modification integrity and provided better peptide sequence coverage with strong PTM-site localization fragment ions. Activation of a novel trap-and-release technology significantly improves the duty cycle and provided significant MS/MS sensitivity gains by an average of 6-11-fold for EAD analyses. Evaluation of the quantitative EAD PRM workflows revealed high reproducibility with coefficients of variation of ∼2-7%, as well as very good linearity and quantification accuracy. This novel workflow combining EAD and trap-and-release technology provides high sensitivity, alternative fragmentation information to achieve confident PTM characterization and quantification.

PI3K/AKT/mTOR signaling transduction pathway and targeted therapies in cancer

The PI3K/AKT/mTOR (PAM) signaling pathway is a highly conserved signal transduction network in eukaryotic cells that promotes cell survival, cell growth, and cell cycle progression. Growth factor signalling to transcription factors in the PAM axis is highly regulated by multiple cross-interactions with several other signaling pathways, and dysregulation of signal transduction can predispose to cancer development. The PAM axis is the most frequently activated signaling pathway in human cancer and is often implicated in resistance to anticancer therapies. Dysfunction of components of this pathway such as hyperactivity of PI3K, loss of function of PTEN, and gain-of-function of AKT, are notorious drivers of treatment resistance and disease progression in cancer. In this review we highlight the major dysregulations in the PAM signaling pathway in cancer, and discuss the results of PI3K, AKT and mTOR inhibitors as monotherapy and in co-administation with other antineoplastic agents in clinical trials as a strategy for overcoming treatment resistance. Finally, the major mechanisms of resistance to PAM signaling targeted therapies, including PAM signaling in immunology and immunotherapies are also discussed.

Antitumor Activity of s-Triazine Derivatives: A Systematic Review

1,3,5-triazine derivatives, also called s-triazines, are a series of containing-nitrogen heterocyclic compounds that play an important role in anticancer drug design and development. To date, three s-triazine derivatives, including altretamine, gedatolisib, and enasidenib, have already been approved for refractory ovarian cancer, metastatic breast cancer, and leukemia therapy, respectively, demonstrating that the s-triazine core is a useful scaffold for the discovery of novel anticancer drugs. In this review, we mainly focus on s-triazines targeting topoisomerases, tyrosine kinases, phosphoinositide 3-kinases, NADP+-dependent isocitrate dehydrogenases, and cyclin-dependent kinases in diverse signaling pathways, which have been extensively studied. The medicinal chemistry of s-triazine derivatives as anticancer agents was summarized, including discovery, structure optimization, and biological applications. This review will provide a reference to inspire new and original discoveries.