Aim: Cisplatin resistance remains a major obstacle to the effective treatment of tongue squamous cell carcinoma (TSCC). This study is dedicated to elucidating the role and mechanism of circular RNA (circRNA) hsa-circ-0001030 in modulating cisplatin sensitivity and metabolic reprogramming in TSCC.

Methods: CircRNA sequencing, quantitative polymerase chain reaction, and RNA fluorescence in situ hybridization were used to test hsa-circ-0001030 expression in TSCC tissues and cell lines. Gain-of-function assays (colony formation, cell counting kit-8, Transwell assay, and xenograft models) were conducted to evaluate proliferation, invasion, and cisplatin response. Mechanistic studies, including RNA pull-down, RNA-binding protein immunoprecipitation, and western blotting, were performed to identify pyruvate kinase M2 (PKM2) as a binding partner of hsa-circ-0001030 and to assess glycolytic activity, glucose uptake, and lactate production.

Results: Hsa-circ-0001030 was markedly downregulated in TSCC and cisplatin-resistant cells. Overexpression of hsa-circ-0001030 suppressed tumor growth, migration, and glycolytic flux, while enhancing cisplatin sensitivity both in vitro and in vivo. Mechanistically, hsa-circ-0001030 directly bound to PKM2 at nucleotides 138-169, inhibited PKM2 enzymatic activity, restraining tetramer formation and increased tyrosine 105 (Tyr105) phosphorylation and thereby blocking PKM2-driven glycolysis. Clinically, low hsa-circ-0001030 expression correlated with advanced tumor-node-metastasis stage, poor differentiation, and unsatisfying prognosis in TSCC patients.

Conclusion: Hsa-circ-0001030 acted as a tumor-suppressive circRNA that might depress PKM2-dependent metabolic reprogramming and cisplatin resistance in TSCC, highlighting its potential as a prognostic biomarker and therapeutic target for overcoming chemoresistance.

Aim: Antibody-drug conjugates (ADCs) feature an antibody recognizing a specific protein joined to a potent toxic payload. Numerous ADCs have received U.S. Food and Drug Administration (FDA) approval; however, clinical resistance arises. Resistance mechanisms include decreased expression or mutation of the antibody target, impaired payload release, or increased expression of adenosine triphosphate (ATP)-binding cassette (ABC) efflux transporters associated with multidrug resistance. We therefore sought to characterize the interactions of ABC multidrug transporters with ADC payloads.

Methods: We performed a high-throughput screen with 27 common ADC payloads using cell lines expressing ABC transporters P-glycoprotein [P-gp, encoded by ABC subfamily B member 1 (ABCB1)] or ABC subfamily B member G2 (ABCG2, encoded by ABCG2). Confirmatory assays were also performed using cells transfected to express P-gp, ABCG2, or multidrug resistance-associated protein 1 (MRP1, encoded by ABCC1).

Results: Several commonly used ADC payloads were substrates of P-gp, including calicheamicin γ1, monomethyl auristatin E, mertansine (DM1), and ravtansine (DM4). All the pyrrolobenzodiazepines tested - SJG136, SGD-1882, SG2057, and SG3199 - were substrates of P-gp, ABCG2, and MRP1. The modified anthracyclines nemorubicin and its metabolite PNU-159682 were poorly transported by both ABCB1 and ABCG2 and displayed nanomolar to picomolar toxicity. Further, we found that the efficacy of the FDA-approved ADC mirvetuximab soravtansine, with DM4 as the toxic payload, was decreased in cell lines expressing P-gp. In contrast, Duocarmycin DM and PNU-159682 were exquisitely toxic to a panel of 99 cancer cell lines of varying origins.

Conclusion: Several commonly used ADC payloads can be transported by ABC transporters, potentially leading to transporter-mediated drug resistance in patients. Future ADCs should be developed using payloads that are not ABC transporter substrates.

The reciprocal feedback between cancer stem cells (CSCs) and cancer-associated fibroblasts (CAFs) is increasingly recognized as a driver of therapeutic resistance and tumor evolution. According to the “soil and seed” hypothesis, CAFs create a biochemical and biomechanical “soil” for CSCs to seed, grow, and thrive. In turn, CSCs manipulate and transform fibroblasts to promote CSC traits, thus completing the loop of CAF-CSC crosstalk through bidirectional molecular communication within the tumor microenvironment. This review encompasses recent advances in CAF heterogeneity, including conserved and malignancy-specific subtypes, as well as the molecular dialogue driving resistance. We also briefly discuss emerging therapeutic approaches, particularly the potential of natural compounds to target both CSCs and CAFs. By bridging mechanistic insights with translational innovations, this review provides a roadmap for breaking the CSC-CAF alliance, offering hope for overcoming therapeutic resistance and improving cancer outcomes.

Aim: Non-small cell lung cancer (NSCLC) represents most lung cancer cases and remains associated with poor outcomes, mainly due to multidrug resistance (MDR). Extracellular vesicles (EVs) are crucial for intercellular communication and significantly influence chemotherapy resistance. This study aimed to characterize the EVs proteome of drug-sensitive and MDR NSCLC cell lines to identify therapeutic targets to counteract MDR.

Methods: EVs derived from NSCLC cells were isolated by ultracentrifugation and analyzed for size by nanoparticle tracking analysis, for morphology by transmission electron microscopy, and for EVs markers by Western blotting (WB). Proteomic profiling was performed using liquid chromatography-mass spectrometry (LC-MS), followed by WB validation of relevant proteins. Cell growth and viability were assessed using sulforhodamine B or CellTiter-Glo assays. P-glycoprotein [P-gp, also known as ABCB1: adenosine triphosphate (ATP)-binding cassette subfamily B member 1] activity was determined by rhodamine-123 accumulation assay. SRC-related signaling was investigated by WB.

Results: EVs from the multidrug resistant (MDR) derivative of NCI-H460, a human NSCLC cell line, displayed nine up- and eight down-regulated proteins compared with the drug-sensitive parental cells, including reduced SRC. WB results showed higher phosphorylated form of SRC (p-SRC) expression in MDR cells than in sensitive cells. In contrast, EVs from both cell lines had similar expression levels, suggesting selective intracellular retention in MDR cells. The SRC inhibitor bosutinib potentiated the activity of chemotherapeutics that are P-gp substrates in 2D and in 3D spheroids, without affecting the viability of the human lung fibroblast cell line MRC-5. Moreover, bosutinib reduced P-gp activity, likely by downregulating of phosphorylated caveolin-1.

Conclusion: These findings show reduced selective packaging of p-SRC into EVs shed by MDR cells (MDR-EVs), suggesting an important role for this protein in the MDR phenotype and its potential as a molecular target. Bosutinib, an SRC inhibitor, might be useful as a chemosensitizer of MDR cells.

Aim: Resistance to frontline intensive chemotherapy remains a major clinical challenge in acute myeloid leukemia (AML). Currently, refractory AML is mostly observed in certain genotypes. In in vitro experiments, primary resistance in AML has been associated with nucleotide metabolism. However, the relationship between in vivo nucleotide metabolism, genotype, and the occurrence of complete remission (CR) remains largely unexplored. We aimed to investigate the potential association between in vivo nucleotide pools at AML diagnosis, genotype, and the efficacy of frontline intensive chemotherapy.

Methods: In this prospective pilot study, we quantified the intracellular nucleotide pools in peripheral blood (PBMC) and bone marrow mononuclear cells (BMMC) from 70 AML patients at diagnosis. Nucleotide levels were compared depending on genotype data and the occurrence of CR after the frontline intensive chemotherapy.

Results: No relationship was observed between nucleotide levels and genotype. Specific alterations of certain nucleotide levels in cells from patients who did not achieve CR were identified: elevated guanosine triphosphate (GTP) levels in BMMC and uridine monophosphate (UMP) levels in PBMC, as well as reduced adenosine monophosphate (AMP) levels and energy ratios [AMP/adenosine triphosphate (ATP), AMP + adenosine diphosphate (ADP)/ATP] in PBMC. These results may suggest impaired activity of enzymes such as UMP/cytidine monophosphate (CMP) kinase and reduced AMP-activated protein kinase (AMPK) activation in patients who did not achieve CR.

Conclusion: Our study provides the first in vivo data linking specific alterations in intracellular nucleotide levels to the efficacy of the frontline intensive chemotherapy in AML. These findings offer a novel perspective on the role of nucleotide metabolism in the primary resistance in frontline intensive chemotherapy.

Antibody-drug conjugates (ADCs) targeting trophoblast cell-surface antigen 2 (TROP2) have emerged as a promising therapeutic strategy for the treatment of triple-negative breast cancer (TNBC) and ovarian carcinoma, two malignancies characterized by poor prognosis and limited therapeutic options. ADCs are complex molecules that combine the specificity of monoclonal antibodies with the cytotoxic potency of chemotherapeutic agents, enabling selective delivery of drugs to tumor cells while minimizing systemic toxicity. Recent advances in ADC technology have led to the development of several TROP2-targeting agents, including sacituzumab govitecan and datopotamab deruxtecan, which have demonstrated significant efficacy and acceptable safety in patients with advanced or treatment-resistant TNBC and ovarian carcinoma. Clinical trials have reported improvements in progression-free and overall survival, as well as objective response rates, compared to standard therapies. However, emerging evidence indicates that both primary and acquired resistance mechanisms may limit the long-term efficacy of these agents. Current research efforts are focused on elucidating these resistance pathways, optimizing combination strategies with immunotherapy and targeted agents, and expanding the application of TROP2-targeting ADCs to other tumor types. The integration of biomarker-driven patient selection and next-generation ADC technologies offers new opportunities to overcome resistance and enhance clinical benefit. This review provides a comprehensive overview of the development, clinical implementation, and resistance mechanisms of TROP2-targeting ADCs in TNBC and ovarian carcinoma, underscoring their potential to reshape the therapeutic landscape of these challenging cancers.