5-Aminolevulinic acid-mediated photodynamic therapy in combination with kinase inhibitor lapatinib enhances glioblastoma cell death.

5-Aminolevulinic acid (ALA) is an intraoperative imaging agent approved for protoporphyrin IX (PpIX) fluorescence-guided resection of glioblastoma (GBM). It is currently under clinical evaluation for photodynamic therapy (PDT) after the completion of GBM surgery. We previously showed that lapatinib, a clinical kinase inhibitor of epidermal growth factor receptor 1 & 2 (EGFR and HER2), enhanced PpIX fluorescence in a panel of GBM cell lines by blocking ABCG2 (ATP-binding cassette super-family G member 2)-mediated PpIX efflux, which suggests its potential for improving ALA for GBM surgery and PDT. Here we show that lapatinib enhanced PDT-induced cytotoxicity by promoting GBM cell death with the induction of apoptosis followed by necrosis. While the induction of tumor cell apoptosis was massive and rapid in the H4 cell line with no detectable Bcl-2 and a low level of Bcl-xL, it was delayed and much less in extent in A172, U-87 and U-118 cell lines with higher levels of pro-survival Bcl-2 family proteins. Lapatinib treatment alone neither reduced GBM cell viability nor had any significant effect on EGFR downstream signaling. Its enhancement of ALA-PDT was largely due to the increase of intracellular PpIX particularly in the mitochondria, resulting in the activation of mitochondria-mediated apoptosis in H4 cells. Our present study demonstrates that lapatinib inhibits ABCG2-mediated PpIX efflux and sensitizes GBM cells to ALA-PDT by inducing tumor cell death.

Treatment of Extraneural Metastases of Myxopapillary Ependymomas With Dose-Dense Temozolomide and Lapatinib.

Myxopapillary ependymomas (MPEs) are rare tumors of the central nervous system, and outcomes are generally worse with recurrent disease. These tumors can rarely metastasize outside the neuraxis. We present a case of a 35-year-old female with a history of MPEs who developed extraneural metastases 11 years after her initial gross total resection. Sites of metastases included multiple bilateral intrapulmonary and pleural-based masses with pleural effusion and a pelvic mass. The patient was treated with dose-dense TMZ and lapatinib and had a mixed radiographic response after 12 cycles of treatment. This is the first known case of extraneural metastases of MPEs to demonstrate a radiographic response to dose-dense TMZ and lapatinib. This case presentation discusses the need to establish optimal treatment of extraneural ependymal metastases, duration of treatment, and strategy for the management of recurrent diseases.

Targeting autophagy: a promising approach for the treatment of breast cancer brain metastases.

Patients with breast tumors that metastasize to the brain have limited treatment options and a very poor prognosis. More effective therapeutic strategies are desperately needed for this patient population. Recent evidence demonstrates that brain metastases arising from breast tumors display altered energy production that results in enhanced autophagy. Preclinical studies have shown that genetically or pharmacologically disrupting the autophagy pathway significantly decreases the brain metastatic burden, resulting in improved animal survival and increased sensitivity to lapatinib. These findings pave the way for the development of novel strategies targeting autophagy for breast cancer patients with brain metastatic disease.

PI3K PROTAC overcomes the lapatinib resistance in PIK3CA-mutant HER2 positive breast cancer.

Although anti-HER2 therapy has made significant strides in reducing metastasis and relapse in HER2-positive breast cancer, resistance to agents like trastuzumab, pertuzumab, and lapatinib frequently develops in patients undergoing treatment. Previous studies suggest that the hyperactivation of the PI3K-AKT signaling pathway by PIK3CA/PTEN gene mutations is implicated in HER2 resistance. In this study, we introduce a novel PI3K-p110α Proteolysis TAargeting Chimera (PROTAC) that effectively inhibits the proliferation of breast cancer cells by degrading PI3K-p110α. When tested in two lapatinib-resistant cell lines, JIMT1 and MDA-MB-453, both of which harbor PIK3CA mutations, the PI3K PROTAC notably reduced cell proliferation and induced G1 phase cell cycle arrest. Importantly, even at very low concentrations, PI3K PROTAC restored sensitivity to lapatinib. Furthermore, the efficacy of PI3K PROTAC surpassed that of Alpelisib, a selective PI3K-p110α kinase inhibitor in clinic. The superior performance of PI3K PROTAC was also confirmed in lapatinib-resistant breast cancer xenograft tumors and patient-derived breast cancer organoids (PDOs). In conclusion, this study reveals that the novel PI3K PROTAC we synthesized could serve as an effective agent to overcome lapatinib resistance.

Tocopherol-human serum albumin nanoparticles enhance lapatinib delivery and overcome doxorubicin resistance in breast cancer.

Introduction: HER2, a tyrosine kinase receptor, is amplified in HER2-positive breast cancer, driving cell signaling and growth. Aim: This study aimed to combat multidrug resistance in Dox-insensitive breast adenocarcinoma by creating a nanoformulation therapy with a tyrosine kinase inhibitor. Methodology: Human serum albumin (HSA) was conjugated with α-D-tocopherol succinate to form nanoaggregates loaded with lapatinib (Lapa). Results: The resulting Lapa@HSA(VE) NPs were 117.2 nm in size and demonstrated IC50 values of 10.25 µg/ml on MCF7 (S) and 8.02 µg/ml on MCF7 (R) cell lines. Conclusion: Lapa@HSA(VE) NPs showed no hepatotoxicity, unlike free Lapa, as seen in acute toxicity studies in rats.

[Box: see text].

Targeting AFP-RARß complex formation: a potential strategy for treating AFP-positive hepatocellular carcinoma.

Alpha-fetoprotein (AFP) is a glycoprotein primarily expressed during embryogenesis, with declining levels postnatally. Elevated AFP levels correlate with pathological conditions such as liver fibrosis, cirrhosis, and hepatocellular carcinoma (HCC). Recent investigations underscore AFP's intracellular role in HCC progression, wherein it forms complexes with proteins like Phosphatase and tensin homolog (PTEN), Caspase 3 (CASP3), and Retinoic acid receptors and Retinoid X receptors (RAR/RXR). RAR and RXR regulate gene expression linked to cell death and tumorigenesis in normal physiology. AFP impedes RAR/RXR dimerization, nuclear translocation, and function, promoting gene expression favoring cancer progression in HCC that provoked us to target AFP as a drug candidate. Despite extensive studies, inhibitors targeting AFP to disrupt complex formation and activities remain scarce. In this study, employing protein-protein docking, amino acid residues involved in AFP-RARß interaction were identified, guiding the definition of AFP's active site for potential inhibitor screening. Currently, kinase inhibitors play a significant role in cancer treatment and, the present study explores the potential of repurposing FDA-approved protein kinase inhibitors to target AFP. Molecular docking with kinase inhibitors revealed Lapatinib as a candidate drug of the AFP-RARß complex. Molecular dynamics simulations and binding energy calculations, employing Mechanic/Poisson-Boltzmann Surface Area (MM-PBSA), confirmed Lapatinib's stability with AFP. The study suggests Lapatinib's potential in disrupting the AFP-RARß complex, providing a promising avenue for treating molecularly stratified AFP-positive HCC or its early stages.

Sideroflexin-1 promotes progression and sensitivity to lapatinib in triple-negative breast cancer by inhibiting TOLLIP-mediated autophagic degradation of CIP2A.

Triple-negative breast cancer (TNBC) is the most aggressive subtype of breast cancer and it lacks specific therapeutic targets and effective treatment protocols. By analyzing a proteomic TNBC dataset, we found significant upregulation of sideroflexin 1 (SFXN1) in tumor tissues. However, the precise function of SFXN1 in TNBC remains unclear. Immunoblotting was performed to determine SFXN1 expression levels. Label-free quantitative proteomics and liquid chromatography-tandem mass spectrometry were used to identify the downstream targets of SFXN1. Mechanistic studies of SFXN1 and cellular inhibitor of PP2A (CIP2A) were performed using immunoblotting, immunofluorescence staining, and reverse transcription-quantitative polymerase chain reaction (RT-qPCR). Functional experiments were used to investigate the role of SFXN1 in TNBC cells. SFXN1 was significantly overexpressed in TNBC tumor tissues and was associated with unfavorable outcomes in patients with TNBC. Functional experiments demonstrated that SFXN1 promoted TNBC growth and metastasis in vitro and in vivo. Mechanistic studies revealed that SFXN1 promoted TNBC progression by inhibiting the autophagy receptor TOLLIP (toll interacting protein)-mediated autophagic degradation of CIP2A. The pro-tumorigenic effect of SFXN1 overexpression was partially prevented by lapatinib-mediated inhibition of the CIP2A/PP2A/p-AKT pathway. These findings may provide a new targeted therapy for patients with TNBC.

Enhancing PDT efficacy in NMIBC: Efflux inhibitor mediated improvement of PpIX levels and efficacy of the combination of PpIX-PDT and SO-cleavable prodrugs.

Protoporphyrin IX (PpIX)-based photodynamic therapy (PDT) has shown limited efficacy in nonmuscle-invasive bladder cancer (NMIBC). To improve PDT efficacy, we developed singlet oxygen-cleavable prodrugs. These prodrugs, when combined with PpIX-PDT, induce cancer cell death through both PDT and drug release mechanisms. Inhibition of PpIX efflux was reported to be an effective strategy to improve PpIX-PDT in certain cancer cells. Our main goal was to investigate whether adding an efflux inhibitor to the combination of PpIX and prodrugs can improve the PpIX levels in bladder cancer cells and the release of active drugs, thus improving the overall efficacy of the treatment. We treated bladder cancer cell lines with lapatinib and evaluated intracellular PpIX fluorescence, finding significantly increased accumulation. Combining lapatinib with prodrugs led to significantly reduced cell viability compared to prodrugs or PpIX-PDT alone. The effect of lapatinib depended on the expression level of the efflux pump in bladder cancer cells. Interestingly, lapatinib increased paclitaxel (PTX) prodrug uptake by threefold compared to prodrug alone. Adding an efflux inhibitor (e.g., lapatinib) into bladder instillation solutions could be a straightforward and effective strategy for NMIBC treatment, particularly in tumors expressing efflux pumps, with the potential for clinical translation.

INPP4B suppresses HER2-induced mesenchymal transition in HER2+ breast cancer and enhances sensitivity to Lapatinib.

Human epidermal growth factor receptor 2 positive (HER2+) breast cancer (BC) tends to metastasize and has a bad prognosis due to its high malignancy and rapid progression. Inositol polyphosphate 4-phosphatase isoenzymes type II (INPP4B) plays unequal roles in the development of various cancers. However, the function of INPP4B in HER2+ BC has not been elucidated. Here we found that INPP4B expression was significantly lower in HER2+ BC and positively correlated with the prognosis by bioinformatics and tissue immunofluorescence analyses. Overexpression of INPP4B inhibited cell proliferation, migration, and growth of xenografts in HER2+ BC cells. Conversely, depletion of INPP4B reversed these effects and activated the PDK1/AKT and Wnt/ß-catenin signaling pathways to promote epithelial-mesenchymal transition (EMT) progression. Moreover, INPP4B overexpression blocked epidermal growth factor (EGF) -induced cell proliferation, migration and EMT progression, whereas INPP4B depletion antagonized HER2 depletion in reduction of cell proliferation and migration of HER2+ BC cells. Additionally, Lapatinib (LAP) inhibited HER2+ BC cell survival, proliferation and migration, and its effect was further enhanced by overexpression of INPP4B. In summary, our results illustrate that INPP4B suppresses HER2+ BC growth, migration and EMT, and its expression level affects patient outcome, further providing new insights into clinical practice.

A Lipophilic Salt Form to Enhance the Lipid Solubility and Certain Biopharmaceutical Properties of Lapatinib.

Lapatinib (LTP) commercially available as lapatinib ditosylate (LTP-DTS) salt is the only drug approved for the treatment of HER-positive metastatic breast cancer. A low and pH-dependent solubility results in poor and variable oral bioavailability, thus driving significant interest in molecular modification and formulation strategies of the drug. Furthermore, due to very high crystallinity, LTP and LTP-DTS have low solubility in lipid excipients, making it difficult to be delivered by lipid-based carrier systems. Thus, the present work reports a new salt form of LTP with a docusate counterion to enhance the pharmaceutical properties of the drug (LTP-DOC). NMR spectra showed a downfield shift of the methylene singlet proton from 3.83 and 4.41 ppm, indicating a lowering of electron density on the adjacent nitrogen atom and confirming the formation of amine-sulfonyl salt through the specified basic nitrogen center located adjacent to the furan ring. PXRD diffractograms of LTP-DOC indicated a reduced crystallinity of the prepared salt. The dissolution, equilibrium solubility, lipid excipient solubility, partitioning coefficient, distribution coefficient, tabletability, and in vitro cytotoxicity of the lipophilic salt of LTP were investigated. The equilibrium solubility data showed that LTP-DOC possesses a pH-independent solubility profile in the pH range of 3.5 to 7.4 with a 3.14 times higher permeability coefficient than commercial ditosylate salt. Furthermore, the prepared LTP-DOC salts showed twice higher log P than the free base and 8 times higher than LTP-DTS. The prepared LTP-DOC was found to have 4- to 9-fold higher solubility in lipid excipients like Capmul MCM C8 and Maisine CC compared to the ditosylate salt. The LTP-DOC salt was tabletable and showed approximately 1.2 times lower dissolution than commercial ditosylate salt, indicating extended-release behavior. A cytotoxicity study of LTP-DOC salt showed an approximately 2.5 times lower IC50 value than the LTP-free base and 1.7 times lower than commercial ditosylate salt with an approximately 3 times higher selectivity index. The investigations strongly indicate a high translational potential of the prepared salt form in maintaining solubility-lipophilicity interplay, enhancing the drug's bioavailability, and developing lipidic formulations.

DUSP6 inhibition overcomes neuregulin/HER3-driven therapy tolerance in HER2+ breast cancer.

Despite clinical benefits of tyrosine kinase inhibitors (TKIs) in cancer, most tumors can reactivate proliferation under TKI therapy. Here we present transcriptional profiling of HER2+ breast cancer cells transitioning from dormant drug tolerant cells to re-proliferating cells under continuous HER2 inhibitor (HER2i) therapy. Focusing on phosphatases, expression of dual-specificity phosphatase DUSP6 was found inhibited in dormant cells, but strongly induced upon regrowth. DUSP6 expression also selectively associated with poor patient survival in HER2+ breast cancers. DUSP6 overexpression conferred apoptosis resistance, whereas its pharmacological blockade prevented therapy tolerance development under HER2i therapy. DUSP6 targeting also synergized with clinically used HER2i combination therapies. Mechanistically DUSP6 is a positive regulator of HER3 expression, and its impact on HER2i tolerance was mediated by neuregulin-HER3 axis. In vivo, genetic targeting of DUSP6 reduced tumor growth in brain metastasis model, whereas its pharmacological targeting induced synthetic lethal therapeutic effect in combination with HER2i. Collectively this work demonstrates that DUSP6 drives escape from HER2i-induced dormancy, and that DUSP6 is a druggable target to overcome HER3-driven TKI resistance.

Expand available targets for CAR-T therapy to overcome tumor drug resistance based on the "Evolutionary Traps".

Based on the concept of "Evolutionary Traps", targeting survival essential genes obtained during tumor drug resistance can effectively eliminate resistant cells. While, it still faces limitations. In this study, lapatinib-resistant cells were used to test the concept of "Evolutionary Traps" and no suitable target stand out because of the identified genes without accessible drug. However, a membrane protein PDPN, which is low or non-expressed in normal tissues, is identified as highly expressed in lapatinib-resistant tumor cells. PDPN CAR-T cells were developed and showed high cytotoxicity against lapatinib-resistant tumor cells in vitro and in vivo, suggesting that CAR-T may be a feasible route for overcoming drug resistance of tumor based on "Evolutionary Trap". To test whether this concept is cell line or drug dependent, we analyzed 21 drug-resistant tumor cell expression profiles reveal that JAG1, GPC3, and L1CAM, which are suitable targets for CAR-T treatment, are significantly upregulated in various drug-resistant tumor cells. Our findings shed light on the feasibility of utilizing CAR-T therapy to treat drug-resistant tumors and broaden the concept of the "Evolutionary Trap".

Human Blood Serum Counteracts EGFR/HER2-Targeted Drug Lapatinib Impact on Squamous Carcinoma SK-BR-3 Cell Growth and Gene Expression.

Lapatinib is a targeted therapeutic inhibiting HER2 and EGFR proteins. It is used for the therapy of HER2-positive breast cancer, although not all the patients respond to it. Using human blood serum samples from 14 female donors (separately taken or combined), we found that human blood serum dramatically abolishes the lapatinib-mediated inhibition of growth of the human breast squamous carcinoma SK-BR-3 cell line. This antagonism between lapatinib and human serum was associated with cancelation of the drug induced G1/S cell cycle transition arrest. RNA sequencing revealed 308 differentially expressed genes in the presence of lapatinib. Remarkably, when combined with lapatinib, human blood serum showed the capacity of restoring both the rate of cell growth, and the expression of 96.1% of the genes expression of which were altered by the lapatinib treatment alone. Co-administration of EGF with lapatinib also restores the cell growth and cancels alteration of expression of 95.8% of the genes specific to lapatinib treatment of SK-BR-3 cells. Differential gene expression analysis also showed that in the presence of human serum or EGF, lapatinib was unable to inhibit the Toll-Like Receptor signaling pathway and alter expression of genes linked to the Gene Ontology term of Focal adhesion.

Lapatinib combined with doxorubicin causes dose-dependent cardiotoxicity partially through activating the p38MAPK signaling pathway in zebrafish embryos.

Because of its enhanced antitumor efficacy, lapatinib (LAP) is commonly used clinically in combination with the anthracycline drug doxorubicin (DOX) to treat metastatic breast cancer. While it is well recognized that this combination chemotherapy can lead to an increased risk of cardiotoxicity in adult women, its potential cardiotoxicity in the fetus during pregnancy remains understudied. Here, we aimed to examine the combination of LAP chemotherapy and DOX-induced cardiotoxicity in the fetus using a zebrafish embryonic system and investigate the underlying pathologic mechanisms. First, we examined the dose-dependent cardiotoxicity of combined LAP and DOX exposure in zebrafish embryos, which mostly manifested as pericardial edema, bradycardia, cardiac function decline and reduced survival. Second, we revealed that a significant increase in oxidative stress concurrent with activated MAPK signaling, as indicated by increased protein expression of phosphorylated p38 and Jnk, was a notable pathophysiological event after combined LAP and DOX exposure. Third, we showed that inhibiting MAPK signaling by pharmacological treatment with the p38MAPK inhibitor SB203580 or genetic ablation of the map2k6 gene could significantly alleviate combined LAP and DOX exposure-induced cardiotoxicity. Thus, we provided both pharmacologic and genetic evidence to suggest that inhibiting MAPK signaling could exert cardioprotective effects. These findings have implications for understanding the potential cardiotoxicity induced by LAP and DOX combinational chemotherapy in the fetus during pregnancy, which could be leveraged for the development of new therapeutic strategies.

Proteomic Assessment of SKBR3/HER2+ Breast Cancer Cellular Response to Lapatinib and Investigational Ipatasertib Kinase Inhibitors.

Modern cancer treatment approaches aim at achieving cancer remission by using targeted and personalized therapies, as well as harnessing the power of the immune system to recognize and eliminate the cancer cells. To overcome a relatively short-lived response due to the development of resistance to the administered drugs, combination therapies have been pursued, as well. To expand the outlook of combination therapies, the objective of this study was to use high-throughput data generation technologies such as mass spectrometry and proteomics to investigate the response of HER2+ breast cancer cells to a mixture of two kinase inhibitors that has not been adopted yet as a standard treatment regime. The broader landscape of biological processes that are affected by inhibiting two major pathways that sustain the growth and survival of cancer cells, i.e., EGFR and PI3K/AKT, was investigated by treating SKBR3/HER2+ breast cancer cells with Lapatinib or a mixture of Lapatinib/Ipatasertib small molecule drugs. Changes in protein expression and/or activity in response to the drug treatments were assessed by using two complementary quantitative proteomic approaches based on peak area and peptide spectrum match measurements. Over 900 proteins matched by three unique peptide sequences (FDR<0.05) were affected by the exposure of cells to the drugs. The work corroborated the anti-proliferative activity of Lapatinib and Ipatasertib, and, in addition to cell cycle and growth arrest processes enabled the identification of several multi-functional proteins with roles in cancer-supportive hallmark processes. Among these, immune response, adhesion and migration emerged as particularly relevant to the ability to effectively suppress the proliferation and dissemination of cancer cells. The supplementation of Lapatinib with Ipatasertib further affected the expression or activity of additional transcription factors and proteins involved in gene expression, trafficking, DNA repair, and development of multidrug resistance. Furthermore, over fifty of the affected proteins represented approved or investigational targets in the DrugBank database, which through their protein-protein interaction networks can inform the selection of effective therapeutic partners. Altogether, our findings exposed a broad plethora of yet untapped opportunities that can be further explored for enhancing the anti-cancer effects of each drug as well as of many other multi-drug therapies that target the EGFR/ERBB2 and PI3K/AKT pathways. The data are available via ProteomeXchange with identifier PXD051094.

Comparing the toxicity effects of copper oxide nanoparticles conjugated with Lapatinib on breast (MDA-MB-231) and lung (A549) cancer cell lines.

In recent years, the increase in cancer morbidity and mortality has presented scientists with a major challenge in developing new therapeutic agents against cancer cells. This study aims to characterize the anticancer effects of copper oxide nanoparticles (NPs) conjugated with Lapatinib (CuO@Lapatinib) on breast and lung cancer cell lines. The physicochemical properties of the NPs were characterized by fourier-transform infrared (FT-IR) spectroscopy, X-ray diffraction (XRD), scanning and transmission electron microscopy, energy dispersive X-ray spectroscopy (EDS), dynamic light scattering (DLS), and zeta potential analyses. The antiproliferative potential of the NPs in the breast (MDA-MB-231) and lung (A549) cancer cell lines and a normal cell line (MRC5) was investigated by MTT (3-(4,5-Dimethylthiazol-2-yl)-2,5-Diphenyltetrazolium Bromide) assay. Flow cytometry and Hoechst staining were used to evaluate cell apoptosis and cell cycle analysis. The reactive oxygen species (ROS) levels in the treated and control cells were also determined. The NPs were spherical, with a size range of 20-59nm, a DLS size of 338nm, and a zeta potential of -42.9 mV. The half maximal inhibitory concentration (IC50) of CuO@Lapatinib NPs for the normal, breast cancer, and lung cancer cell lines was 105, 98, and 87 µg/ml, respectively. Treatment with CuO@Lapatinib NPs caused considerable apoptosis induction in breast cancer (from 0.65% to 68.96%) and lung cancer cell lines (from 1.11% to 44.11%). Also, an increased level of cell cycle arrest at the S phase was observed in both cancer cell lines. The ROS level in the breast and lung cancer cell lines after treatment with CuO@Lapatinib NPs increased by 3.45 and 21.04 folds, respectively. Nuclear morphological alterations, including chromatin condensation and fragmentation, were observed in both cancer cell lines. This study indicates CuO@Lapatinib is a potent antiproliferative compound with more efficient inhibitory effects on lung cancer than breast cancer cells, which can be related to the higher ROS generation in the A549 cell line.

Unveiling the therapeutic prospects of EGFR inhibition in rotenone-mediated parkinsonism in rats: Modulation of dopamine D3 receptor.

Parkinson's disease (PD) is characterized by the progressive loss of dopaminergic neurons in the substantia nigra. The dopamine D3 receptor (D3R) plays a significant role in the pathogenesis and treatment of PD. Activation of receptor tyrosine kinases (RTKs) inhibits signaling mediated by G protein-coupled receptor (GPCR). Epidermal growth factor receptors (EGFRs) and dopamine D3 receptors in the brain are directly associated with PD, both in terms of its development and potential treatment. Therefore, we investigated the impact of modulating the EGFR, a member of the RTKs family, and the dopamine D3R, a member of the GPCR family. In the present study, 100 mg/kg of lapatinib (LAP) was administered to rotenone-intoxicated rats for three weeks. Our findings indicate that LAP effectively alleviated motor impairment, improved histopathological abnormalities, and restored dopaminergic neurons in the substantia nigra. This restoration was achieved through the upregulation of dopamine D3R and increase of tyrosine hydroxylase (TH) expression, as well as boosting dopamine levels. Furthermore, LAP inhibited the activity of p-EGFR, GRK2, and SCR. Additionally, LAP exhibited antioxidant properties by inhibiting the 4-hydroxynonenal (4-HNE) and PLCγ/PKCßII pathway, while enhancing the antioxidant defense mechanism by increasing GSH-GPX4 pathway. The current study offers insights into the potential repositioning of LAP as a disease-modifying drug for PD. This could be achieved by modulating the dopaminergic system and curbing oxidative stress.

Potential protein kinase inhibitors that target G-quadruplex DNA structures in the human telomeric regions.

Telomeric regions contain Guanine-rich sequences arranged in a planar manner and connected by Hoogsteen hydrogen bonds that can fold into G-quadruplex (G4) DNA structures, and can be stabilized by monovalent metal cations. The presence of G4 DNA holds significance in cancer-related processes, especially due to their regulatory potential at transcriptional and translational levels of oncogene and tumor suppressor genes. The objective of this current research is to explore the evolving realm of FDA-approved protein kinase inhibitors, with a specific emphasis on their capacity to stabilize the G4 DNA structures formed at the human telomeric regions. This involves investigating the possibility of repurposing FDA-approved protein kinase inhibitors as a novel approach for targeting multiple cancer types. In this context, we have selected 16 telomeric G4 DNA structures as targets and 71 FDA-approved small-molecule protein kinase inhibitors as ligands. To investigate their binding affinities, molecular docking of human telomeric G4 DNA with nuclear protein kinase inhibitors and their corresponding co-crystalized ligands were performed. We found that Ponatinib and Lapatinib interact with all the selected G4 targets, the binding free energy calculations, and molecular dynamic simulations confirm their binding efficacy and stability. Thus, it is hypothesized that Ponatinib and Lapatinib may stabilize human telomeric G4 DNA in addition to their ability to inhibit BCR-ABL and the other members of the EGFR family. As a result, we also hypothesize that the stabilization of G4 DNA might represent an additional underlying mechanism contributing to their efficacy in exerting anti-cancer effects.

Effectiveness of lapatinib for enhancing 5-aminolevulinic acid-mediated protoporphyrin IX fluorescence and photodynamic therapy in human cancer cell lines with varied ABCG2 activities.

5-Aminolevulinic acid (ALA) is a prodrug for protoporphyrin IX (PpIX)-mediated photodynamic therapy (PDT) and fluorescence-guided tumor surgery. We previously reported that lapatinib, a repurposed ABCG2 inhibitor, enhanced ALA-induced PpIX fluorescence and PDT by blocking ABCG2-mediated PpIX efflux. In the present study, we evaluated how the variation in ABCG2 activities/protein levels affected tumor cell response to the enhancement of PpIX/PDT by lapatinib and Ko143, an ABCG2 tool inhibitor. ABCG2 activities and protein levels were determined in a panel of human cancer cell lines. Effects of lapatinib and Ko143 on enhancing ALA-PpIX fluorescence and PDT were evaluated and correlated with tumor cell ABCG2 activities. We found that both lapatinib and Ko143 enhanced ALA-PpIX fluorescence and PDT in a dose-dependent manner, although lapatinib exhibited lower efficacy and potency than Ko143 in nearly all cancer cell lines. The EC50 of ABCG2 inhibitors for enhancing ALA-PpIX and PDT had a positive correlation with tumor cell ABCG2 activities, indicating that tumor cell lines with lower ABCG2 activities were more sensitive to ABCG2 inhibitors for PpIX/PDT enhancement. Our results suggest that, for optimal therapeutic enhancement, the dose of ABCG2 inhibitors needs to be tailored based on the ABCG2 expression/activity in tumors.

Overcoming brain-derived therapeutic resistance in HER2+ breast cancer brain metastasis.

Brain metastasis of HER2+ breast cancer occurs in about 50% of all women with metastatic HER2+ breast cancer and confers poor prognosis for patients. Despite effective HER2-targeted treatments of peripheral HER2+ breast cancer with Trastuzumab +/-HER2 inhibitors, limited brain permeability renders these treatments inefficient for HER2+ breast cancer brain metastasis (BCBM). The scarcity of suitable patient-derived in-vivo models for HER2+ BCBM has compromised the study of molecular mechanisms that promote growth and therapeutic resistance in brain metastasis. We have generated and characterized new HER2+ BCBM cells (BCBM94) isolated from a patient HER2+ brain metastasis. Repeated hematogenic xenografting of BCBM94 consistently generated BCBM in mice. The clinically used receptor tyrosine kinase inhibitor (RTKi) Lapatinib blocked phosphorylation of all ErbB1-4 receptors and induced the intrinsic apoptosis pathway in BCBM94. Neuregulin-1 (NRG1), a ligand for ErbB3 and ErbB4 that is abundantly expressed in the brain, was able to rescue Lapatinib-induced apoptosis and clonogenic ability in BCBM94 and in HER2+ BT474. ErbB3 was essential to mediate the NRG1-induced survival pathway that involved PI3K-AKT signalling and the phosphorylation of BAD at serine 136 to prevent apoptosis. High throughput RTKi screening identified the brain penetrable Poziotinib as highly potent compound to reduce cell viability in HER2+ BCBM in the presence of NRG1. Successful in-vivo ablation of BCBM94- and BT474-derived HER2+ brain tumors was achieved upon two weeks of treatment with Poziotinib. MRI revealed BCBM remission upon poziotinib, but not with Lapatinib treatment. In conclusion, we have established a new patient-derived HER2+ BCBM in-vivo model and identified Poziotinib as highly efficacious RTKi with excellent brain penetrability that abrogated HER2+ BCBM brain tumors in our mouse models.