[Discontinuation of tyrosine kinase inhibitors before epiphyseal closure leading to improved short stature in pediatric chronic myelogenous leukemia].

A 3-year-old boy was referred to our hospital with splenomegaly. Blood tests revealed hyperleukocytosis and bone marrow examination showed major BCR::ABL1 fusion, leading to the diagnosis of chronic myelogenous leukemia (CML). Due to intolerance, the tyrosine kinase inhibitor (TKI) was changed from imatinib to dasatinib to nilotinib. The patient achieved molecular remission but became markedly short in stature, measuring 129.3 cm (height standard deviation score [SDS] -3.3) at the age of 12. TKI therapy was discontinued at age 12 years and 10 months, which was 9 years and 8 months after the start of TKI and 1 year and 6 months after achievement of MR4.0, as discontinuation before epiphyseal closure would not improve short stature. At 2 years and 6 months after discontinuation, the patient's height improved to 156.1 cm (SDS-2.0) without relapse. Growth suppression by TKIs is a problem in the management of pediatric CML. This case illustrates how improvement in severe short stature can be achieved by discontinuing TKI therapy before epiphyseal closure.

Narazaciclib, a novel multi-kinase inhibitor with potent activity against CSF1R, FLT3 and CDK6, shows strong anti-AML activity in defined preclinical models.

CSF1R is a receptor tyrosine kinase responsible for the growth/survival/polarization of macrophages and overexpressed in some AML patients. We hypothesized that a novel multi-kinase inhibitor (TKi), narazaciclib (HX301/ON123300), with high potency against CSF1R (IC50 ~ 0.285 nM), would have anti-AML effects. We tested this by confirming HX301's high potency against CSF1R (IC50 ~ 0.285 nM), as well as other kinases, e.g. FLT3 (IC50 of ~ 19.77 nM) and CDK6 (0.53 nM). An in vitro proliferation assay showed that narazaciclib has a high growth inhibitory effect in cell cultures where CSF1R or mutant FLT3-ITD variants that may be proliferation drivers, including primary macrophages (IC50 of 72.5 nM) and a subset of AML lines (IC50 < 1.5 µM). In vivo pharmacology modeling of narazaciclib using five AML xenografts resulted in: inhibition of MV4-11 (FLT3-ITD) subcutaneous tumor growth and complete suppression of AM7577-PDX (FLT3-ITD/CSF1Rmed) systemic growth, likely due to the suppression of FLT3-ITD activity; complete suppression of AM8096-PDX (CSF1Rhi/wild-type FLT3) growth, likely due to the inhibition of CSF1R ("a putative driver"); and nonresponse of both AM5512-PDX and AM7407-PDX (wild-type FLT3/CSF1Rlo). Significant leukemia load reductions in bone marrow, where disease originated, were also achieved in both responders (AM7577/AM8096), implicating that HX301 might be a potentially more effective therapy than those only affecting peripheral leukemic cells. Altogether, narazaciclib can potentially be a candidate treatment for a subset of AML with CSF1Rhi and/or mutant FLT3-ITD variants, particularly second generation FLT3 inhibitor resistant variants.

Mutation analysis of BCR-ABL1 kinase domain in chronic myeloid leukemia patients with tyrosine kinase inhibitors resistance: a Malaysian cohort study.

OBJECTIVE: Mutational analysis of BCR::ABL1 kinase domain (KD) is a crucial component of clinical decision algorithms for chronic myeloid leukemia (CML) patients with failure or warning responses to tyrosine kinase inhibitor (TKI) therapy. This study aimed to detect BCR::ABL1 KD mutations in CML patients with treatment resistance and assess the concordance between NGS (next generation sequencing) and Sanger sequencing (SS) in detecting these mutations. RESULTS: In total, 12 different BCR::ABL1 KD mutations were identified by SS in 22.6% (19/84) of patients who were resistant to TKI treatment. Interestingly, NGS analysis of the same patient group revealed an additional four different BCR::ABL1 KD mutations in 27.4% (23/84) of patients. These mutations are M244V, A344V, E355A, and E459K with variant read frequency below 15%. No mutation was detected in 18 patients with optimal response to TKI therapy. Resistance to TKIs is associated with the acquisition of additional mutations in BCR::ABL1 KD after treatment with TKIs. Additionally, the use of NGS is advised for accurately determining the mutation status of BCR::ABL1 KD, particularly in cases where the allele frequency is low, and for identifying mutations across multiple exons simultaneously. Therefore, the utilization of NGS as a diagnostic platform for this test is very promising to guide therapeutic decision-making.

Necroptosis blockade prevents lung injury in severe influenza.

Severe influenza A virus (IAV) infections can result in hyper-inflammation, lung injury and acute respiratory distress syndrome1-5 (ARDS), for which there are no effective pharmacological therapies. Necroptosis is an attractive entry point for therapeutic intervention in ARDS and related inflammatory conditions because it drives pathogenic lung inflammation and lethality during severe IAV infection6-8 and can potentially be targeted by receptor interacting protein kinase 3 (RIPK3) inhibitors. Here we show that a newly developed RIPK3 inhibitor, UH15-38, potently and selectively blocked IAV-triggered necroptosis in alveolar epithelial cells in vivo. UH15-38 ameliorated lung inflammation and prevented mortality following infection with laboratory-adapted and pandemic strains of IAV, without compromising antiviral adaptive immune responses or impeding viral clearance. UH15-38 displayed robust therapeutic efficacy even when administered late in the course of infection, suggesting that RIPK3 blockade may provide clinical benefit in patients with IAV-driven ARDS and other hyper-inflammatory pathologies.

Real-world efficacy and safety of tofacitinib treatment in Asian patients with ulcerative colitis.

BACKGROUND: Real-world data on tofacitinib (TOF) covering a period of more than 1 year for a sufficient number of Asian patients with ulcerative colitis (UC) are scarce. AIM: To investigate the long-term efficacy and safety of TOF treatment for UC, including clinical issues. METHODS: We performed a retrospective single-center observational analysis of 111 UC patients administered TOF at Hyogo Medical University as a tertiary inflammatory bowel disease center. All consecutive UC patients who received TOF between May 2018 and February 2020 were enrolled. Patients were followed up until August 2020. The primary outcome was the clinical response rate at week 8. Secondary outcomes included clinical remission at week 8, cumulative persistence rate of TOF administration, colectomy-free survival, relapse after tapering of TOF and predictors of clinical response at week 8 and week 48. RESULTS: The clinical response and remission rates were 66.3% and 50.5% at week 8, and 47.1% and 43.5% at week 48, respectively. The overall cumulative clinical remission rate was 61.7% at week 48 and history of anti-tumor necrosis factor-alpha (TNF-α) agents use had no influence (P = 0.25). The cumulative TOF persistence rate at week 48 was significantly lower in patients without clinical remission than in those with remission at week 8 (30.9% vs 88.1%; P < 0.001). Baseline partial Mayo Score was significantly lower in responders vs non-responders at week 8 (odds ratio: 0.61, 95% confidence interval: 0.45-0.82, P = 0.001). Relapse occurred in 45.7% of patients after TOF tapering, and 85.7% of patients responded within 4 wk after re-increase. All 6 patients with herpes zoster (HZ) developed the infection after achieving remission by TOF. CONCLUSION: TOF was more effective in UC patients with mild activity at baseline and its efficacy was not affected by previous treatment with anti-TNF-α agents. Most relapsed patients responded again after re-increase of TOF and nearly half relapsed after tapering off TOF. Special attention is needed for tapering and HZ.

Recording and classifying MET receptor mutations in cancers.

Tyrosine kinase inhibitors (TKI) directed against MET have been recently approved to treat advanced non-small cell lung cancer (NSCLC) harbouring activating MET mutations. This success is the consequence of a long characterization of MET mutations in cancers, which we propose to outline in this review. MET, a receptor tyrosine kinase (RTK), displays in a broad panel of cancers many deregulations liable to promote tumour progression. The first MET mutation was discovered in 1997, in hereditary papillary renal cancer (HPRC), providing the first direct link between MET mutations and cancer development. As in other RTKs, these mutations are located in the kinase domain, leading in most cases to ligand-independent MET activation. In 2014, novel MET mutations were identified in several advanced cancers, including lung cancers. These mutations alter splice sites of exon 14, causing in-frame exon 14 skipping and deletion of a regulatory domain. Because these mutations are not located in the kinase domain, they are original and their mode of action has yet to be fully elucidated. Less than five years after the discovery of such mutations, the efficacy of a MET TKI was evidenced in NSCLC patients displaying MET exon 14 skipping. Yet its use led to a resistance mechanism involving acquisition of novel and already characterized MET mutations. Furthermore, novel somatic MET mutations are constantly being discovered. The challenge is no longer to identify them but to characterize them in order to predict their transforming activity and their sensitivity or resistance to MET TKIs, in order to adapt treatment.

Real-World Treatment Patterns and Clinical Outcomes among Patients Receiving CDK4/6 Inhibitors for Metastatic Breast Cancer in a Canadian Setting Using AI-Extracted Data.

Cyclin-dependent kinase 4/6 inhibitors (CDK4/6i) are widely used in patients with hormone receptor-positive (HR+)/human epidermal growth factor receptor 2 negative (HER2-) advanced/metastatic breast cancer (ABC/MBC) in first line (1L), but little is known about their real-world use and clinical outcomes long-term, in Canada. This study used Pentavere's previously validated artificial intelligence (AI) to extract real-world data on the treatment patterns and outcomes of patients receiving CDK4/6i+endocrine therapy (ET) for HR+/HER2- ABC/MBC at Sinai Health in Toronto, Canada. Between 1 January 2016 and 1 July 2021, 48 patients were diagnosed with HR+/HER2- ABC/MBC and received CDK4/6i + ET. A total of 38 out of 48 patients received CDK4/6i + ET in 1L, of which 34 of the 38 (89.5%) received palbociclib + ET. In 2L, 12 of the 21 (57.1%) patients received CDK4/6i + ET, of which 58.3% received abemaciclib. In 3L, most patients received chemotherapy (10/12, 83.3%). For the patients receiving CDK4/6i in 1L, the median (95% CI) time to the next treatment was 42.3 (41.2, NA) months. The median (95% CI) time to chemotherapy was 46.5 (41.4, NA) months. The two-year overall survival (95% CI) was 97.4% (92.4, 100.0), and the median (range) follow-up was 28.7 (3.4-67.6) months. Despite the limitations inherent in real-world studies and a limited number of patients, these AI-extracted data complement previous studies, demonstrating the effectiveness of CDK4/6i + ET in the Canadian real-world 1L, with most patients receiving palbociclib as CDK4/6i in 1L.

Chemo-free treatment of adult patients with Ph-positive acute lymphoblastic leukemia: latest updates from the 2023 ASH annual meeting.

The chemo-free concept represents a new direction for managing adult patients with Ph-positive acute lymphoblastic leukemia (Ph + ALL). The tyrosine kinase inhibitors (TKIs), blinatumomab and venetoclax serve as the backbone of chemo-free regimens; several prospective studies involving these drugs have demonstrated high remission rates and promising, albeit short, survival outcomes. This review summarizes the latest updates on chemo-free regimens in the treatment of adult patients with Ph + ALL, presented at the 2023 ASH annual meeting.

Targeting EGFR degradation by autophagosome degraders.

Several generations of epidermal growth factor receptor (EGFR) tyrosine kinase inhibitors have been developed for the treatment of non-small cell lung cancer (NSCLC) in clinic. However, emerging drug resistance mediated by new EGFR mutations or activations by pass, leads to malignant progression of NSCLC. Proteolysis targeting chimeras (PROTACs) have been utilized to overcome the drug resistance acquired by mutant EGFR, newly potent and selective degraders are still need to be developed for clinical applications. Herein, we developed autophagosome-tethering compounds (ATTECs) in which EGFR can be anchored to microtubule-associated protein-1 light chain-3B (LC3B) on the autophagosome with the assistance of the LC3 ligand GW5074. A series of EGFR-ATTECs have been designed and synthesized. Biological evaluations showed that these compounds could degrade EGFR and exhibited moderate inhibitory effects on certain NSCLC cell lines. The ATTEC 12c potently induced the degradation of EGFR with a DC50 value of 0.98 µM and a Dmax value of 81% in HCC827 cells. Mechanistic exploration revealed that the lysosomal pathway was mainly involved in this degradation. Compound 12c also exhibited promising inhibitory activity, as well as degradation efficiency in vivo. Our study highlights that EGFR-ATTECs could be developed as a new expandable EGFR degradation tool and also reveals a novel potential therapeutic strategy to prevent drug resistance acquired EGFR mutations.

Discovery and optimization of 4-pyrazolyl-2-aminopyrimidine derivatives as potent spleen tyrosine kinase (SYK) inhibitors.

Spleen tyrosine kinase (Syk) is a key signal transduction mediator of the B cell receptor (BCR) signaling pathway. Abnormal BCR signaling plays a key role in initiation and development of B-cell-derived hematological malignancies, therefore, Syk represents a potential target for inhibiting the BCR signaling resulting in a therapeutic effect in these cancers. Herein, we describe a novel series of SYK inhibitors with 4-(3'-pyrazolyl)-2-amino-pyrimidine scaffold. Extensive study of structure-activity relationships led to the identification of 1 (NMS-0963), a highly potent Syk inhibitor (IC50 = 3 nM) endowed with high selectivity within a panel of tested kinases and high antiproliferative activity in SYK-dependent BaF3-TEL/SYK cells and in other BCR-dependent hematological tumor cell lines. Additionally, 1 effectively inhibited Syk phosphorylation and downstream signaling mediators of the BCR in treated cells. In in vivo pharmacokinetics studies, 1, displayed good pharmacokinetics properties, with linear exposure with dose and excellent oral bioavailability. These findings suggest that 1 is a promising new Syk inhibitor for treating BCR-dependent hematological cancers.

Chronic myeloid leukaemia: Biology and therapy.

Chronic myeloid leukaemia (CML) is caused by BCR::ABL1. Tyrosine kinase-inhibitors (TKIs) are the initial therapy. Several organizations have reported milestones to evaluate response to initial TKI-therapy and suggest when a change of TKI should be considered. Achieving treatment-free remission (TFR) is increasingly recognized as the optimal therapy goal. Which TKI is the best initial therapy for which persons and what depth and duration of molecular remission is needed to achieve TFR are controversial. In this review we discuss these issues and suggest future research directions.

Randomized Phase II Study of Gemcitabine With or Without ATR Inhibitor Berzosertib in Platinum-Resistant Ovarian Cancer: Final Overall Survival and Biomarker Analyses.

PURPOSE: The multicenter, open-label, randomized phase 2 NCI-9944 study (NCT02595892) demonstrated that addition of ATR inhibitor (ATRi) berzosertib to gemcitabine increased progression-free survival (PFS) compared to gemcitabine alone (hazard ratio [HR]=0.57, one-sided log-rank P = .044, which met the one-sided significance level of 0.1 used for sample size calculation). METHODS: We report here the final overall survival (OS) analysis and biomarker correlations (ATM expression by immunohistochemistry, mutational signature 3 and a genomic biomarker of replication stress) along with post-hoc exploratory analyses to adjust for crossover from gemcitabine to gemcitabine/berzosertib. RESULTS: At the data cutoff of January 27, 2023 (>30 months of additional follow-up from the primary analysis), median OS was 59.4 weeks with gemcitabine/berzosertib versus 43.0 weeks with gemcitabine alone (HR 0.79, 90% CI 0.52 to 1.2, one-sided log-rank P = .18). An OS benefit with addition of berzosertib to gemcitabine was suggested in patients stratified into the platinum-free interval ≤3 months (N = 26) subgroup (HR, 0.48, 90% CI 0.22 to 1.01, one-sided log-rank P =.04) and in patients with ATM-negative/low (N = 24) tumors (HR, 0.50, 90% CI 0.23 to 1.08, one-sided log-rank P = .06). CONCLUSION: The results of this follow-up analysis continue to support the promise of combined gemcitabine/ATRi therapy in platinum resistant ovarian cancer, an active area of investigation with several ongoing clinical trials.

New Treatment Options for Patients With Oncogene-Addicted Non-Small Cell Lung Cancer Focusing on EGFR-Mutant Tumors.

Druggable oncogene-driven non-small cell lung cancer has led to innovative systemic treatment options, improving patients' outcome. This benefit is not only achieved in the metastatic setting but also in the postsurgical setting, such as in lung cancers harboring a common sensitizing EGFR mutation or ALK-rearrangement. To enhance the outcome of these patients, we need to understand the mechanisms of acquired resistance and evaluate the role of new drugs with novel mechanisms of action in the treatment landscape. In this chapter, we review treatment strategies of EGFR-mutant tumors in all stages, the mechanisms of acquired strategies, and novel therapies in this subset.

Regorafenib and glioblastoma: a literature review of preclinical studies, molecular mechanisms and clinical effectiveness.

Glioblastoma IDH wild type (GBM) is a very aggressive brain tumour, characterised by an infiltrative growth pattern and by a prominent neoangiogenesis. Its prognosis is unfortunately dismal, and the median overall survival of GBM patients is short (15 months). Clinical management is based on bulk tumour removal and standard chemoradiation with the alkylating drug temozolomide, but the tumour invariably recurs leading to patient's death. Clinical options for GBM patients remained unaltered for almost two decades until the encouraging results obtained by the phase II REGOMA trial allowed the introduction of the multikinase inhibitor regorafenib as a preferred regimen in relapsed GBM treatment by the National Comprehensive Cancer Network (NCCN) 2020 Guideline. Regorafenib, a sorafenib derivative, targets kinases associated with angiogenesis (VEGFR 1-3), as well as oncogenesis (c-KIT, RET, FGFR) and stromal kinases (FGFR, PDGFR-b). It was already approved for metastatic colorectal cancers and hepatocellular carcinomas. The aim of the present review is to focus on both the molecular and clinical knowledge collected in these first three years of regorafenib use in GBM.

Prognostic implications of combining EGFR-TKIs and radiotherapy in Stage IV lung adenocarcinoma with 19-Del or 21-L858R mutations: A real-world study.

OBJECTIVE: To elucidate the potential benefits of combining radiotherapy and epidermal growth factor receptor-tyrosine kinase inhibitors (EGFR-TKIs) for individuals with Stage IV lung adenocarcinoma (LUAD) harboring either exon 19 deletion (19-Del) or exon 21 L858R mutation (21-L858R). METHODS: In this real-world retrospective study, 177 individuals with Stage IV LUAD who underwent EGFR-TKIs and radiotherapy at Shandong Cancer Hospital from June 2012 to August 2017 were included. The main focus of this real-world study was overall survival (OS). RESULTS: The clinical characteristics of patients with Stage IV LUAD harboring 19-Del were similar to those harboring 21-L858R (p > 0.05). Overall, the patients had a median OS (mOS) of 32.0 months (95% confidence interval [CI]: 28.6-35.5). Subsequently, multivariate analysis indicated that both EGFR mutations and thoracic radiotherapy were independent predictors of OS (p = 0.001 and 0.013). Furthermore, subgroup analysis highlighted a longer OS for the 19-Del group compared to the 21-L858R group, especially when EGFR-TKIs were combined with bone metastasis or thoracic radiotherapy (mOS: 34.7 vs. 25.1 months and 51.0 vs. 29.6 months; p = 0.0056 and 0.0013, respectively). However, no significant differences were found in OS when considering patients who underwent brain metastasis radiotherapy (mOS: 34.7 vs. 25.1 months; p = 0.088). CONCLUSIONS: Patients with Stage IV LUAD harboring 19-Del experience a notably prolonged OS following combined therapy with EGFR-TKIs and radiotherapy, while this OS benefit is observed despite the absence of substantial differences in the clinical characteristics between the 19-Del and 21-L858R groups.

[The Effect and Safety of Flumatinib in Patients with Chronic Myelogenous Leukemia Failed First-and Second-line Treatment].

OBJECTIVE: To analyze the efficacy and safety of flumatinib, a second-generation tyrosine kinase inhibitor (TKI) independently developed in China, in patients with chronic myelogenous leukemia in chronic phase (CML-CP) who falied first-line and second-line treatment. METHODS: The clinical data of 30 CML-CP patients treated with flumatinib in Lianyungang First People's Hospital from January 2020 to September 2022 were collected retrospectively. Among them, 15 patients who received imatinib first-line treatment but failed treatment were included in the second-line group, and the other 15 patients who failed second-line treatment with nilotinib or dasatinib were included in the third-line group. The hematological and molecular responses of the patients in the two groups at 3, 6 and 12 months of treatment, and the event-free survival (EFS) and adverse reactions of patients at the end of follow-up were statistical analyzed. RESULTS: At 3, 6, and 12 months of treatment, 10, 11, and 12 patients in the second line group achieved major molecular response (MMR), which was higher than that of 3, 4, and 5 patients in the third line group (P =0.010, P =0.011, P =0.010). At 3 months of treatment, 12 and 13 patients achieved complete hematological response (CHR) and early molecular response (EMR) in the second-line group, which was higher than that of 9 and 13 patients in the third-line group, but the difference between the two groups was not statistically significant (P =0.232, P =1.000); At 6 and 12 months of treatment, 6 and 7 patients in the second-line group achieved MR4.5, which were higher than of 3 and 2 cases in the third-line group, but the difference was not statistically significant (P =0.427, P =0.713). The hematological adverse reactions of patients in the second-line group during treatment the period were mainly grade 1-2 thrombocytopenia and anemia, and no grade 3-4 of adverse reactions occurred. In the third-line group, there were 2 cases of grade 1-2 thrombocytopenia, grade 1-2 anemia and white blood cell 3 cases were reduced each, 1 case of grade 3-4 anemia, 2 cases of grade 3-4 neutropenia. The non-hematological adverse reactions in the second-line group were rash (2 cases), headache (1 case), diarrhea (1 case), fatigue (1 case), limb pain (1 case). There were 1 cases of diarrhea, 1 cases of nausea, and 1 cases of edema in the third-line group. There was no statistical significance in hematological and non-hematological adverse reactions between the two groups of patients (P >0.05). At the end of follow-up, the EFS rate of patients in the second-line group was higher than that in the third-line group (100% vs 93.3%), but the difference was not statistically significant (P =0.317). CONCLUSION: The second-generation TKI flumatinib independently developed in China, has good curative effect and safety for CML-CP patients who failed first-line and second-line treatment.

[Research Progress of Targeted Therapy for Chronic Lymphocytic Leukemia/Small Lymphocytic Lymphoma --Review].

Chronic lymphocytic leukemia (CLL)/small lymphocytic lymphoma (SLL) is a relatively inert B lymphocyte proliferative disease. In recent years with the launch of new drugs, chemotherapy has been gradually replaced by targeted therapy, which significantly prolongs the survival of patients and reduces the side effects of treatment. At present, BTK inhibitors, PI3K inhibitors, spleen tyrosine kinase (SYK) inhibitors and BCL-2 inhibitors are the most studied targeted therapeutic drugs for CLL/SLL. This article reviews the research progress of different types of targeted therapeutic drugs in the treatment of CLL/SLL.

Virtual Screening, Docking, and Designing of New VEGF Inhibitors as Anti-cancer Agents.

BACKGROUND: VEGFR-2 tyrosine kinase inhibitors are receiving a lot of attention as prospective anticancer medications in the current drug discovery process. OBJECTIVE: This work aims to explore the PubChem library for novel VEGFR-2 kinase inhibitors. 1H-Indazole-containing drug AXITINIB, or AG-013736 (FDA approved), is chosen as a rational molecule for drug design. This scaffold proved its efficiency in treating cancer and other diseases as well. METHODS: The present study used the virtual screening of the database, protein preparation, grid creation, and molecular docking analyses. RESULTS: The protein was validated on different parameters like the Ramachandran plot, the ERRAT score, and the ProSA score. The Ramachandran plot revealed that 92.1% of the amino acid residues were located in the most favorable region; this was complemented by an ERRAT score (overall quality factor) of 96.24 percent and a ProSA (Z score) of -9.24 percent. The Lipinski rule of five was used as an additional filter for screening molecules. The docking results showed values of binding affinity between -14.08 and -12.34 kcal/mol. The molecule C1 showed the highest docking value of -14.08 Kcal/mol with the maximum number of strong H-bonds by -NH of pyridine to amino acid Cys104 (4.22Å), -NH of indazole to Glu108 (4.72), and Glu70 to bridge H of -NH. These interactions are similar to Axitinib docking interactions like Glu70, Cys104, and Glu102. The docking studies revealed that pi-alkyl bonds are formed with unsubstituted pyridine, whereas important H-bonds are observed with different substitutions around -NH. Based on potential findings, we designed new molecules, and molecular docking studies were performed on the same protein along with ADMET studies. The designed molecules (M1-M4) also showed comparable docking results similar to Axitinib, along with a synthetic accessibility score of less than 4.5. CONCLUSION: The docking method employed in this work opens up new possibilities for the design and synthesis of novel compounds that can act as VEGFR-2 tyrosine kinase inhibitors and treat cancer.

PDZK1 suppresses TNBC development and sensitizes TNBC cells to erlotinib via the EGFR pathway.

Epidermal growth factor receptor (EGFR)-targeted drugs (erlotinib, etc.) are used to treat multiple types of tumours. EGFR is highly expressed in most triple-negative breast cancer (TNBC) patients. However, only a small proportion of TNBC patients benefit from EGFR-targeted drugs in clinical trials, and the resistance mechanism is unclear. Here, we found that PDZ domain containing 1 (PDZK1) is downregulated in erlotinib-resistant TNBC cells, suggesting that PDZK1 downregulation is related to erlotinib resistance in TNBC. PDZK1 binds to EGFR. Through this interaction, PDZK1 promotes EGFR degradation by enhancing the binding of EGFR to c-Cbl and inhibits EGFR phosphorylation by hindering EGFR dimerisation. We also found that PDZK1 is specifically downregulated in TNBC tissues and correlated with a poor prognosis in TNBC patients. In vitro and in vivo functional assays showed that PDZK1 suppressed TNBC development. Restoration of EGFR expression or kinase inhibitor treatment reversed the degree of cell malignancy induced by PDZK1 overexpression or knockdown, respectively. PDZK1 overexpression sensitised TNBC cells to erlotinib both in vitro and in vivo. In conclusion, PDZK1 is a significant prognostic factor for TNBC and a potential molecular therapeutic target for reversing erlotinib resistance in TNBC cells.