Treatment Of Resistant Cancer Research Articles

Inhibition of PSF activity overcomes resistance to treatment in cancers harboring mutant p53.

Mutations in the TP53 tumor suppressor genes are prevalent in aggressive cancers. Pharmacological reactivation of dysfunctional p53 due to mutations is a promising strategy for treating such cancers. Recently, a multifunctional proline- and glutamine-rich protein, PTB-associated splicing factor (PSF), was identified as a key driver of aggressive cancers. PSF promotes the expression of numerous oncogenes by modulating epigenetic and splicing mechanisms. We previously screened a small-molecule library and discovered compound No.10-3 as a potent PSF inhibitor. Here, we report the discovery of a No.10-3 analog, C-30, as a potent PSF inhibitor. Compared to No.10-3, C-30 treatment specifically suppressed the growth and induced apoptosis of mutant p53-bearing and therapy-resistant cancer cells. Interestingly, C-30 activated a set of p53-regulated genes in therapy-resistant cancer cells. A comprehensive analysis of PSF and p53 binding regions demonstrated a higher level of PSF-binding potential in mutant p53-expressing cancer cells around genomic regions identified as p53-binding peaks in p53-wild type cancer cells. Treatment of mutant p53-expressing cancer cells with C-30 decreases PSF binding around these sites, leading to activated histone acetylation. We further demonstrated that C-30 impaired tumor growth and increased the expression of p53-target genes in vivo. These results suggested that C-30 produces tumor-suppressive effects similar to the functional reactivation of p53, providing a rationale for the inhibition of PSF activity as a promising therapy against treatment-resistant cancer.

Synergistic anticancer efficacy of polydatin and sorafenib against the MCF-7 breast cancer cell line via inhibiting of PI3K/AKT/mTOR pathway and reducing resistance to treatment

Polydatin (PD), a glucoside derivative of resveratrol, has been investigated for its potential to mitigate sorafenib (SOF) side effects and combat multidrug resistance in cancer treatment. The study evaluated its mechanism of action for inhibiting the protein kinase B/mTOR pathway in promoting breast cancer proliferation. The combined PD and SOF have synergistic effects with a combination index (CI) < 1 in the liver (HepG2) and breast (MCF-7) cancer cell lines. Molecular docking studies were conducted to analyze interactions of PD& SOF with protein kinases as well as apoptotic and multidrug resistance proteins, including AKT1, PI3K, mTOR, Apaf-1, and ABCB1 in MCF-7 cells. Experimental validation through real-time PCR confirmed. PD has a strong binding affinity, particularly with AKT1 (-56 kcal/mol) and ABCB1 (-27.16 kcal/mol), a gene associated with multidrug resistance. These interactions were linked to anti-proliferative anti-angiogenic effects and reduced resistance to treatment, demonstrating PD has potential therapeutic benefits. Furthermore, PD combined with SOF induced apoptosis, inhibited cell growth, and arrested MCF-7 cells in the sub-G1 phase with increased intracellular ROS. This was accompanied by reduced expression of AKT1 and ABCB1 genes, reinforcing the anticancer efficacy of PD/SOF combination therapy. In conclusion, the findings suggest that PD/SOF could serve as a promising anticancer treatment strategy, warranting further investigation for potential clinical applications and mechanistic studies in vivo.

Association of Neurokinin-1 Receptor Signaling Pathways with Cancer.

Numerous biochemical reactions leading to altered cell proliferation cause tumorigenesis and cancer treatment resistance. The mechanisms implicated include genetic and epigenetic changes, modified intracellular signaling, and failure of control mechanisms caused by intrinsic and extrinsic factors alone or combined. No unique biochemical events are responsible; entangled molecular reactions conduct the resident cells in a tissue to display uncontrolled growth and abnormal migration. Copious experimental research supports the etiological responsibility of NK-1R (neurokinin-1 receptor) activation, alone or cooperating with other mechanisms, in cancer appearance in different tissues. Consequently, a profound study of this receptor system in the context of malignant processes is essential to design new treatments targeting NK-1R-deviated activity. This study reviews and discusses recent literature that analyzes the main signaling pathways influenced by the activation of neurokinin 1 full and truncated receptor variants. Also, the involvement of NK-1R in cancer development is discussed. NK-1R can signal through numerous pathways and cross-talk with other receptor systems. The participation of override or malfunctioning NK-1R in malignant processes needs a more precise definition in different types of cancers to apply satisfactory and effective treatments. A long way has already been traveled: the current disposal of selective and effective NK-1R antagonists and the capacity to develop new drugs with biased agonistic properties based on the receptor's structural states with functional significance opens immediate research action and clinical application.

Role and value of the tumor microenvironment in the progression and treatment resistance of gastric cancer (Review)

Role and value of the tumor microenvironment in the progression and treatment resistance of gastric cancer (Review)

Characterization of novel small molecule inhibitors of estrogen receptor-activation function 2 (ER-AF2).

Up to 40% of patients with estrogen receptor (ER)-positive breast cancer will develop resistance against the majority of current ER-directed therapies. Resistance can arise through various mechanisms such as increased expression levels of coregulators, and key mutations acquired in the receptor's ligand binding domain rendering it constitutively active. To overcome these resistance mechanisms, we explored targeting the ER Activation Function 2 (AF2) site, which is essential for coactivator binding and activation. Using artificial intelligence and the deep docking methodology, we virtually screened > 1billion small molecules and identified 290 potential AF2 binders that were then characterized and validated through an iterative screening pipeline of cell-based and cell-free assays. We ranked the compounds based on their ability to reduce the transcriptional activity of the estrogen receptor and the viability of ER-positive breast cancer cells. We identified a lead compound, VPC-260724, which inhibits ER activity at low micromolar range. We confirmed its direct binding to the ER-AF2 site through a PGC1α peptide displacement experiment. Using proximity ligation assays, we showed that VPC-260724 disrupts the interaction between ER-AF2 and the coactivator SRC-3 and reduces the expression of ER target genes in various breast cancer models including the tamoxifen resistant cell line TamR3. In conclusion, we developed a novel ER-AF2 binder, VPC-260724, which shows antiproliferative activity in ER-positive breast cancer models. The use of an ER-AF2 inhibitor in combination with current treatments may provide a novel complementary therapeutic approach to target treatment resistance in ER-positive breast cancer.

CCDC34 maintains stemness phenotype through β-catenin-mediated autophagy and promotes EGFR-TKI resistance in lung adenocarcinoma.

Despite recent advances in treatment strategy, lung cancer remains the leading cause of cancer-related mortality worldwide, and it is a serious threat to human health. Lung adenocarcinoma (LUAD) is the most common histological type of lung cancer, and approximately 40-50% of patients with LUAD in Asian populations have epidermal growth factor receptor (EGFR) mutations. The use of EGFR tyrosine kinase inhibitors (EGFR-TKIs) has revolutionarily improved the prognosis of patients with EGFR-mutated LUAD. However, acquired drug resistance is the main cause of treatment failure. Therefore, new therapeutic strategies are necessary to address the resistance to EGFR-TKIs in patients with LUAD. Cancer stemness-related factors lead to multiple-drug resistance in cancer treatment, including EGFR-TKI resistance. Coiled-coil domain-containing 34 (CCDC34) serves as an oncogene in several types of cancer. However, the role and molecular mechanism of CCDC34 in the malignant progression of LUAD have not been reported to date. In the present study, we found that CCDC34 may be associated with LUAD stemness through weighted gene co-expression network analysis (WGCNA). Furthermore, we demonstrated that CCDC34 promoted LUAD stemness properties through β-catenin-mediated regulation of ATG5-induced autophagy, which was conducive to acquired EGFR-TKI resistance in LUAD in vitro and in vivo. Knockdown CCDC34 can synergistically inhibit tumor growth when combined with EGFR-TKIs. This study reveals a positive association between CCDC34 and the stemness phenotype of LUAD, providing new insights into overcoming EGFR-TKI resistance in LUAD by inhibiting CCDC34 expression.

Unveiling the Tumor Microenvironment Through Fibroblast Activation Protein Targeting in Diagnostic Nuclear Medicine: A Didactic Review on Biological Rationales and Key Imaging Agents

The tumor microenvironment (TME) is a dynamic and complex medium that plays a central role in cancer progression, metastasis, and treatment resistance. Among the key elements of the TME, cancer-associated fibroblasts (CAFs) are particularly important for their ability to remodel the extracellular matrix, promote angiogenesis, and suppress anti-tumor immune responses. Fibroblast activation protein (FAP), predominantly expressed by CAFs, has emerged as a promising target in both cancer diagnostics and therapeutics. In nuclear medicine, targeting FAP offers new opportunities for non-invasive imaging using radiolabeled fibroblast activation protein inhibitors (FAPIs). These FAP-specific radiotracers have demonstrated excellent tumor detection properties compared to traditional radiopharmaceuticals such as [18F]FDG, especially in cancers with low metabolic activity, like liver and biliary tract tumors. The most recent FAPI derivatives not only enhance the accuracy of positron emission tomography (PET) imaging but also hold potential for theranostic applications by delivering targeted radionuclide therapies. This review examines the biological underpinnings of FAP in the TME, the design of FAPI-based imaging agents, and their evolving role in cancer diagnostics, highlighting the potential of FAP as a target for precision oncology.

Leveraging Multi-omics to Disentangle the Complexity of Ovarian Cancer.

To better understand ovarian cancer lethality and treatment resistance, sophisticated computational approaches are required that address the complexity of the tumor microenvironment, genomic heterogeneity, and tumor evolution. The ovarian cancer tumor ecosystem consists of multiple tumors and cell types that support disease growth and progression. Over the last two decades, there has been a revolution in -omic methodologies to broadly define components and essential processes within the tumor microenvironment, including transcriptomics, metabolomics, proteomics, genome sequencing, and single-cell analyses. While most of these technologies comprehensively characterize a single biological process, there is a need to understand the biological and clinical impact of integrating multiple -omics platforms. Overall, multi-omics is an intriguing analytic framework that can better approximate biological complexity; however, data aggregation and integration pipelines are not yet sufficient to reliably glean insights that affect clinical outcomes.

Abstract C029: PM2.5-induced drug resistance in lung cancer

Abstract Long-term exposure to PM2.5 air pollution is a significant contributor to lung cancer incidence. Our previous studies have shown that such exposure promotes lung cancer progression by activating the EGFR (epidermal growth factor receptor) and AhR (aryl hydrocarbon Receptor) pathways. We observed that in lung cancer cells with EGFR mutations, prolonged PM2.5 exposure induces EGFR activation, resulting in accelerated tumor cell growth both in vitro and in vivo. This suggests that PM2.5 may play a role in the resistance to EGFR-TKI (tyrosine kinase inhibitor) therapies, raising concerns about treatment efficacy. To explore this, we exposed the EGFR-mutant lung cancer cell line to PM2.5 for 90 days. Our results revealed that long-term exposure not only reduced the therapeutic effect of EGFR-TKIs but also increased the expression of cMyc, a gene linked to poor prognosis and drug resistance. We further confirmed that PM2.5-induced EGFR-TKI resistance is driven by the AhR-cMyc pathway. AhR, activated by environmental toxins in PM2.5, increases cMyc expression, leading to drug resistance. When we administered cMyc inhibitors, the PM2.5-exposed cells regained sensitivity to EGFR-TKI therapy. These findings indicate that targeting the AhR-cMyc pathway could be a promising approach to overcome PM2.5-induced resistance in lung cancer treatment. Further research is needed to explore the broader implications of environmental pollution on cancer therapy and to develop strategies to counteract the effects of pollutants like PM2.5. Citation Format: Chi-Yuan Chen, Chieh-Wen Chan, Tong-Hong Wang. PM2.5-induced drug resistance in lung cancer [abstract]. In: Proceedings of the AACR Special Conference in Cancer Research: Tumor-body Interactions: The Roles of Micro- and Macroenvironment in Cancer; 2024 Nov 17-20; Boston, MA. Philadelphia (PA): AACR; Cancer Res 2024;84(22_Suppl):Abstract nr C029.

Single cell and spatial transcriptomics highlight the interaction of club-like cells with immunosuppressive myeloid cells in prostate cancer

Prostate cancer treatment resistance is a significant challenge facing the field. Genomic and transcriptomic profiling have partially elucidated the mechanisms through which cancer cells escape treatment, but their relation toward the tumor microenvironment (TME) remains elusive. Here we present a comprehensive transcriptomic landscape of the prostate TME at multiple points in the standard treatment timeline employing single-cell RNA-sequencing and spatial transcriptomics data from 120 patients. We identify club-like cells as a key epithelial cell subtype that acts as an interface between the prostate and the immune system. Tissue areas enriched with club-like cells have depleted androgen signaling and upregulated expression of luminal progenitor cell markers. Club-like cells display a senescence-associated secretory phenotype and their presence is linked to increased polymorphonuclear myeloid-derived suppressor cell (PMN-MDSC) activity. Our results indicate that club-like cells are associated with myeloid inflammation previously linked to androgen deprivation therapy resistance, providing a rationale for their therapeutic targeting.

Epitranscriptomics in oncology: The double-edged role of RNA modifications in cancer and resistance

Epitranscriptomics, the study of RNA modifications such as N6-methyladenosine (m6A), has emerged as a pivotal field in cancer research. These chemical modifications influence gene expression, protein translation and cellular behavior, driving critical processes like tumor initiation, progression and metastasis. Furthermore, RNA modifications contribute to cancer stem cell plasticity, promoting survival and therapy resistance. Treatment resistance, a major obstacle in cancer therapy, is often driven by aberrant RNA modifications that affect the stability of coding and non-coding RNAs, leading to enhanced DNA repair, drug efflux and immune evasion. As a result, targeting RNA-modifying enzymes has gained attention as a novel therapeutic strategy. Inhibitors of "writers," "erasers" and "readers" of these modifications are currently being explored to restore sensitivity to conventional therapies. This commentary discusses the emerging role of RNA modifications in cancer progression and treatment resistance, highlighting the potential for novel therapeutic interventions in combatting drug-resistant cancers.

Loss of XIST lncRNA unlocks stemness and cellular plasticity in ovarian cancer

Plasticity, a key hallmark of cancer, enables cells to transition into different states, driving tumor heterogeneity. This cellular plasticity is associated with cancer progression, treatment resistance, and relapse. Cancer stem cells (CSCs) play a central role in this process, yet the molecular factors underlying cancer cell stemness remain poorly understood. In this study, we explored the role of XIST (X-inactive specific transcript) long noncoding RNA in ovarian cancer stemness and plasticity through in silico and in vitro analyses. We found that XIST is significantly down-regulated in ovarian tumors, with low XIST expression linked to a higher stemness index and lower overall survival. Knocking down XIST in ovarian cancer cells enhanced stemness, particularly increasing mesenchymal-like CSCs, and under hypoxic conditions, it promoted epithelial-like CSC markers. Our findings suggest that XIST loss leads to CSC enrichment and cellular plasticity in ovarian cancer, pointing to potential therapeutic targets for patients with low XIST expression.

STEM-15. THE IMPACT OF TUMOR TREATING FIELDS (TTFIELDS) ON CANCER STEM-LIKE CELLS ISOLATED FROM THE SUB-VENTRICULAR ZONE OF GLIOBLASTOMA PATIENTS

Abstract Treatment of glioblastoma (GBM) is challenging due to its heterogeneous nature, invasive potential, and poor response to standard-of-care treatments. Areas of residual disease represent the source of the recurrent tumor that is fatal for GBM patients. However, targeting the residual disease is not offered as part of the standard of care because these areas are difficult to identify. Our laboratory was the first to identify and characterize residual disease in the sub-ventricular zone (SVZ) of the lateral ventricles of GBM patients. In this study, we are examining the impact of Tumor Treating Fields (TTFields) on treatment-resistant cancer stem-like cells (CSCs) isolated from the SVZ of 12 GBM patients using single-cell transcriptomics and functional phenotyping analysis. These cells are maintained in conditions that preserve the molecular profile of the original patient tumor, thus representing bona fide models to study the impact of TTFields on GBM residual disease. Our results show that: CSCs isolated from the SVZ from different individuals show different sensitivity to TTFields, the anti-proliferative effects of TTFields are maintained at different plating cell densities, and when the frequency of TTFields increase from 50 kHz to 200 kHz, CSCs undergo morphological changes (e.g., fewer spheres and fewer connections between cells). We used 100 μM Temozolomide and ionizing radiation (10 Gy) mimicking the standard of care of GBM patients, and the growth of the treatment-resistant CSCs was inhibited by TTFields (200 kHz). To elucidate how TTFields impact the cellular and molecular characteristics of CSCs in their microenvironment, ongoing work focuses on single-cell transcriptomics and functional phenotyping analysis. These results extend our understanding of the mechanisms of action of TTFields, specifically on how TTFields have the potential to alter the cytokine-mediated cross-talk between CSCs of the SVZ and their microenvironment.

New Emerging Therapeutic Strategies Based on Manipulation of the Redox Regulation Against Therapy Resistance in Cancer.

Background: Resistance to standard therapeutic methods, including chemotherapy, immunotherapy, and targeted therapy, remains a critical challenge in effective cancer treatment. Redox homeostasis modification has emerged as a promising approach to address medication resistance. Objective: This review aims to explore the mechanisms of redox alterations and signaling pathways contributing to treatment resistance in cancer. Methods: In this study, a comprehensive review of the molecular mechanisms underlying drug resistance governed by redox signaling was conducted. Emphasis was placed on understanding how tumor cells manage increased reactive oxygen species (ROS) levels through upregulated antioxidant systems, enabling resistance across multiple therapeutic pathways. Results: Key mechanisms identified include alterations in drug efflux, target modifications, metabolic changes, enhanced DNA damage repair, stemness preservation, and tumor microenvironment remodeling. These pathways collectively facilitate tumor cells' adaptive response and resistance to various cancer treatments. Conclusion: Developing a detailed understanding of the interrelationships between these redox-regulated mechanisms and therapeutic resistance holds potential to improve treatment effectiveness, offering valuable insights for both fundamental and clinical cancer research. Antioxid. Redox Signal. 00, 000-000.

Role of ABCC5 in cancer drug resistance and its potential as a therapeutic target.

Over 90% of treatment failures in cancer therapy can be attributed to multidrug resistance (MDR), which can develop intracellularly or through various routes. Numerous pathways contribute to treatment resistance in cancer, but one of the most significant pathways is intracellular drug efflux and reduced drug concentrations within cells, which are controlled by overexpressed drug efflux pumps. As a member of the family of ABC transporter proteins, ABCC5 (ATP Binding Cassette Subfamily C Member 5) reduces the intracellular concentration of a drug and its subsequent effectiveness using an ATP-dependent method to pump the drug out of the cell. Numerous studies have demonstrated that ABCC5 is strongly linked to both poor prognosis and poor treatment response. In addition, elevated ABCC5 expression is noted in a wide variety of malignancies. Given that ABCC5 is regulated by several pathways in a broad range of cancer types, it is a prospective target for cancer treatment. This review examined the expression, structure, function, and role of ABCC5 in various cancer types.

De novo detection of somatic variants in high-quality long-read single-cell RNA sequencing data.

In cancer, genetic and transcriptomic variations generate clonal heterogeneity, leading to treatment resistance. Long-read single-cell RNA sequencing (LR scRNA-seq) has the potential to detect genetic and transcriptomic variations simultaneously. Here, we present LongSom, a computational workflow leveraging high-quality LR scRNA-seq data to call de novo somatic single-nucleotide variants (SNVs), including in mitochondria (mtSNVs), copy-number alterations (CNAs), and gene fusions, to reconstruct the tumor clonal heterogeneity. Before somatic variants calling, LongSom re-annotates marker gene based cell types using cell mutational profiles. LongSom distinguishes somatic SNVs from noise and germline polymorphisms by applying an extensive set of hard filters and statistical tests. Applying LongSom to human ovarian cancer samples, we detected clinically relevant somatic SNVs that were validated against matched DNA samples. Leveraging somatic SNVs and fusions, LongSom found subclones with different predicted treatment outcomes. In summary, LongSom enables de novo variant detection without the need for normal samples, facilitating the study of cancer evolution, clonal heterogeneity, and treatment resistance.

Synergistic Combination of Quercetin and Mafosfamide in Treatment of Bladder Cancer Cells.

Bladder cancer, which has a rising incidence, is the 10th most common cancer. The transitional cell carcinoma histotype is aggressive and often current therapies are ineffective. We investigated the anti-proliferative effect of quercetin, a natural flavonoid, in combination with the alkylating agent mafosfamide (MFA) on two human bladder cancer cell lines, namely RT112 and J82, representing the progression from low-grade to high-grade tumors, respectively. In both cell types, the combined treatment led to a synergic reduction in cell viability confirmed by a combination index of less than one, though different biological responses were noted. In J82 cells, MFA alone and, to a lesser extent, with quercetin caused cell cycle arrest in the G2/M phase, but only the combined treatment triggered apoptotic cell death. In contrast, in RT112 cells, quercetin induced autophagy, evidenced by the autophagosome formation and the increase in LC-3 lipidation. Interestingly, the synergistic effect was observed only when cells were pre-treated with MFA for 24 h before adding quercetin, not in the reverse order. This suggests that quercetin may help overcome MFA resistance to apoptosis. Although further studies are needed, investigating the combined effects of quercetin and MFA could help elucidate the mechanisms of drug resistance in bladder cancer treatment.

Activity of protegrin-1 against mouse Ehrlich ascites carcinoma &lt;i&gt;in vitro&lt;/i&gt; and &lt;i&gt;in vivo&lt;/i&gt;

BACKGROUND: The problem of multidrug resistance in cancer treatment creates an urgent demand for developing new effective antitumor agents. Due to the unusual mechanism of recognizing and damaging tumor cells, antimicrobial peptides are considered as possible prototypes for designing such therapeutics. AIM: This work was aimed to compare the antitumor potential of the promising membranolytic antimicrobial peptide protegrin-1 in vitro and in vivo in Ehrlich ascites carcinoma mice model. MATERIALS AND METHODS: We used two variants of the model by inducing a tumor in solid or ascites form. In the first case, the mice were injected with the peptide twice a week for three weeks, and in the second injections were provided every other day for six days. The activity of antimicrobial peptides against isolated Ehrlich ascites carcinoma cells in vitro was analyzed using MTT-test. RESULTS: Protegrin-1 demonstrated high activity against Ehrlich ascites carcinoma cells in vitro, but had no significant effect on the lifespan of mice bearing solid or ascites form of Ehrlich tumor at the dosing and administration regimens we used. However, treatment with protegrin-1 caused a decrease in the ascites volume and in the number of cells in the ascites fluid. CONCLUSIONS: Protegrin-1 retains its antitumor properties in vivo, but it may be presumed, that to effectively suppress tumor growth it requires a more frequent and prolonged administration compared with conventional antitumor antibiotics, of which we adopted the administration regimen for protegrin-1 in this study.

In Silico Design of Novel EpCAM-Binding Aptamers for Targeted Delivery of RNA Therapeutics.

Aptamers are short DNA or RNA sequences that adopt 3D structures and can bind to protein targets with high binding affinity and specificity. Aptamers exhibit excellent tissue penetration, are inexpensive to produce, and can be internalized by cells. Therefore, aptamers are attractive targeting ligands to direct the delivery of theranostic agents to the desired cells. Epithelial cell adhesion molecule (EpCAM) is a tumor-associated antigen that is aberrantly overexpressed on many epithelial-derived cancers, including on cholangiocarcinoma (CCA) cells. Its expression on treatment-resistant cancer stem cells, along with its abundance in the CCA tumor microenvironment, highlights the need to develop EpCAM-targeted therapies for CCA. Herein, an in silico approach was used to design and screen DNA aptamers capable of binding to the EpCAM monomer and homodimer. Two aptamers, PLD01 and PLD02, met the selection criteria and were validated in vitro. Both aptamers exhibited high affinity for EpCAM+ CCA cells, with negligible binding to EpCAM- leukemia cells. Modified versions of PLD01 and PLD02 were successfully incorporated into the membranes of milk-derived nanovesicles. PLD01-functionalized nanovesicles enabled EpCAM-targeted delivery of the therapeutic cargo to CCA cells. In summary, these EpCAM-targeting aptamers can be utilized to direct the delivery of theranostic agents to EpCAM-expressing cells.

Bispecific Antibodies, Immune Checkpoint Inhibitors, and Antibody-Drug Conjugates Directing Antitumor Immune Responses: Challenges and Prospects.

Tumor immunotherapy includes bispecific antibodies (BsAbs), immune checkpoint inhibitors (ICIs), vaccines, and adoptive cell immunotherapy. BsAbs belong to the family of antibodies that can specifically target two or more different antigens and are a promising option for tumor immunotherapy. Immune checkpoints are antibodies targeting PD-1, PD-L1, and CTLA4 and have demonstrated remarkable therapeutic efficacy in the treatment of hematological and solid tumors, whose combination therapies have been shown to synergistically enhance the antitumor effects of BsAbs. In addition, the clinical efficacy of existing monoclonal antibodies targeting PD-1 (e.g., ipilimumab, nivolumab, pembrolizumab, and cemiplimab) and PD-L1 (e.g., atezolizumab, avelumab, and durvalumab) could also be enhanced by conjugation to small drugs as antibody-drug conjugates (ADCs). The development of truly effective therapies for patients with treatment-resistant cancers can be achieved by optimizing the various components of ADCs.