Molecular Cancer Research最新文献

Cancer remains one of the most formidable challenges in the medical field in this century, largely because of its poorly understood pathogenesis. Fortunately, recent advancements in the understanding of cancer pathogenesis have helped identify more therapeutic targets for improved treatment outcomes. The WNT signaling pathways are highly conserved cascades that participate in diverse physiologic processes, such as embryonic development, tissue homeostasis, and tissue regeneration. Ferroptosis, a unique iron-dependent form of cell death that is distinct from apoptosis, is driven by lipid peroxidation and excessive reactive oxygen species production. Emerging evidence shows that the dysregulation of WNT signaling pathways and ferroptosis, as well as their intricate cross-talk, plays crucial roles in cancer progression and therapeutic resistance, indicating their potential as targets for cancer therapies. This review provides a comprehensive overview of the current understanding of the cross-talk between WNT signaling pathways and ferroptosis in the pathogenesis and progression of cancer, with a specific focus on the regulatory role of the canonical WNT cascade in cancer-related ferroptosis. In addition, we discuss the pharmacologic mechanisms of current strategies that inhibit canonical WNT signaling and/or induce ferroptosis in cancer treatment. We propose that combining canonical WNT pathway inhibitors and ferroptosis inducers with current therapies represents a promising therapeutic strategy for personalized cancer treatment.

Extravasation is a key step in tumor metastasis. Epstein‒Barr virus plays a crucial role in nasopharyngeal carcinoma (NPC) metastasis. However, the functions and molecular mechanisms of Epstein‒Barr virus during tumor cell extravasation remain unclear. Here, we showed that the expression of pyroptosis-associated proteins is greater in the endothelial cells of metastatic NPC tissues than in those of nontumor tissues exosomes derived from NPC cells promoted endothelial cell pyroptosis, vascular permeability, and tumor cell extravasation. Moreover, we found that BART2-5p is abundant in serum exosomes from patients with NPC metastasis and in NPC cells and that it regulates endothelial cell pyroptosis in premetastatic organs via MRE11A. Exosomes containing a BART2-5p inhibitor and AAV-MRE11A attenuated endothelial cell pyroptosis and tumor metastasis. Moreover, in the endothelial cells of metastatic tissues from patients with NPC, the BART2-5p level was positively associated with pyroptosis-related protein expression. Collectively, our findings suggest that exosomal BART2-5p is involved in premetastatic niche formation, identifying secreted BART2-5p as a potential therapeutic target for NPC metastasis. Implications: The finding that secreted BART2-5p is involved in premetastatic niche formation may aid the development of a potential therapeutic target for NPC metastasis.

Cooperativity between mutant p53 and mutant KRAS, although recognized, is poorly understood. In pancreatic cancer, mutant p53 induces splicing factor hnRNPK causing isoform switch producing overexpression of GTPase activating protein 17 isoform 1 (GAP17-1). GAP17-1 is mis-localized in the cytosol, instead of the membrane, due to insertion of exon 17 encoding a PPLP motif, thus allowing mutant KRAS to remain in the GTP bound hyperactive state. However, the role of PPLP in influencing GAP17-1 mis-localization remains unclear. We show that Smad Ubiquitination Regulatory Factor 2 (SMURF2), a known stabilizer of mutant KRAS, interacts with GAP17-1 via the PPLP motif and displaces it from the membrane, facilitating mutant p53 mediated mutant KRAS hyperactivation. We used cell lines with known KRAS and TP53 mutations, characterized Smurf2 expression in multiple pancreatic cancer mouse models (iKras*; iKras*, p53*, and p48-Cre; Kras*) and performed single cell RNAseq and tissue microarray on preclinical and clinical samples. We found that SMURF2 silencing profoundly reduces survival of mutant TP53; KRAS driven cells. We show that a GAP17-1 AALA mutant does not bind to SMURF2, stays in the membrane, and keeps mutant KRAS in the GDP bound state to inhibit downstream signaling. In mouse models, mutant KRAS and SMURF2 upregulation are correlated in pancreatic intraepithelial neoplasia (PanIN) and ductal adenocarcinoma (PDA) lesions. Furthermore, PDA patients who received neoadjuvant therapy and express moderate to high SMURF2 show decreased overall survival (p=0.04). Implications: In TP53 and KRAS double mutated pancreatic cancer, SMURF2 driven GAP17-1 membrane expulsion facilitates mutant p53-KRAS oncogenic synergy.

Chromosomal instability in gastric cancer cells is associated with the amplification of oncogenes that encode receptor tyrosine kinases (RTKs), such as HER2 and FGFR2; such gene amplification varies from cell to cell and manifests as genetic heterogeneity within tumours. The intratumoural genetic heterogeneity of RTK gene amplification causes heterogeneity in RTK protein expression, which has been suggested to be associated with therapeutic resistance to RTK inhibitors; however, the underlying mechanism is not fully understood. Here, we show that extrachromosomal DNA (ecDNA) causes intratumoural genetic heterogeneity in RTKs and drug resistance due to diverse dynamic changes. We analysed the dynamics of FGFR2 and MYC ecDNA in a gastric cancer cell line after single-cell cloning. Similar to those in parental cells, the copy numbers of FGFR2 and MYC in subclones differed significantly between cells, indicating intraclonal genetic heterogeneity. Furthermore, the ecDNA composition differed between subclones, which affected FGFR2 protein expression and drug sensitivity. Interestingly, clone cells that were resistant to the FGFR2 inhibitor AZD4547 presented diverse changes in ecDNA, including chimeric ecDNA, large ecDNA and increased ecDNA numbers; these changes were associated with high expression and rephosphorylation of FGFR2. Conversely, when resistant clone cells were cultured under conditions that excluded AZD4547, the ecDNA status became similar to that of the original clone cells, and the inhibitory effect on cell growth was restored. Implications: Our results show that dynamic quantitative and qualitative changes in ecDNA can drive the intratumoural genetic heterogeneity of RTKs and resistance to RTK inhibitors.

Atypical teratoid rhabdoid tumor (ATRT) is a highly aggressive pediatric brain tumor driven by the loss of SMARCB1, which results in epigenetic dysregulation of the genome. SMARCB1 loss affects lineage commitment and differentiation by controlling gene expression. We hypothesized that additional epigenetic factors co-operate with SMARCB1 loss to control cell self-renewal and drive ATRT. We performed an unbiased epigenome targeted screen to identify genes that co-operate with SMARCB1 and identified SIRT2 as a key regulator. Using in vitro pluripotency assays combined with in vivo single cell RNA transcriptomics, we examined the impact of SIRT2 on differentiation of ATRT cells. We employed a series of orthotopic murine models treated with SIRT2 inhibitors to examine the impact on survival and clinical applicability. We found that ATRT cells are highly dependent on SIRT2 for survival. Genetic or chemical inhibition led to decrease cell self-renewal and induction of differentiation in tumor spheres and in vivo models. We found that SIRT2 inhibition can restore gene expression programs lost due to SMARCB1 loss and reverse the differentiation block in ATRT in vivo. Finally, we showed the in vivo efficacy of a clinically relevant inhibitor demonstrating SIRT2 inhibition as a potential therapeutic strategy. We concluded that SIRT2 is a critical dependency in SMARCB1 deficient ATRT cells and acts by controlling the pluripotency-differentiation switch. Thus, SIRT2 inhibition is a promising therapeutic approach that warrants further investigation and clinical development. Implications: SIRT2 inhibition is a molecular vulnerability in SMARCB1-deleted tumors.

Approximately 97% of the human genome comprises non-coding sequences, with nearly half originating from transposable elements. Among these, retrotransposons represent a critical subclass that replicates via a "copy-and-paste" mechanism and significantly influences the regulation of host genomes. In both normal and pathological contexts, retrotransposons contribute a vast reservoir of regulatory elements that can modulate the expression of genes. If left unchecked, retrotransposons can substantially affect host transcriptional programs and genomic integrity. Therefore, various mechanisms, including epigenetic modifications, are employed to mitigate their potentially deleterious effects. In diseases such as cancers, the epigenome is often significantly reprogrammed, which can lead to retrotransposon dysregulation. Drawing insights from recent studies conducted in human and murine cells, this review examines how retrotransposons expand the complexity of mammalian genomes, describes the impact of their epigenetic dysregulation in cancer development, and highlights the potential of targeting these sequences for therapeutic strategies.

Small-cell lung cancer (SCLC) has a dismal five-year survival rate of less than 7%, with limited advances in first line treatment over the past four decades. Tumor-initiating cells (TICs) contribute to resistance and relapse, a major impediment to SCLC treatment. Here, we identify Kinase Suppressor of Ras 1 (KSR1), a molecular scaffold for the Raf/MEK/ERK signaling cascade, as a critical regulator of SCLC TIC formation and tumor initiation in vivo. We further show that KSR1 mediates cisplatin resistance in SCLC. While 50-70% of control cells show resistance after 6-week exposure to cisplatin, CRISPR/Cas9-mediated KSR1 knockout prevents resistance in >90% of SCLC cells in ASCL1, NeuroD1, and POU2F3 subtypes. KSR1 KO significantly enhances the ability of cisplatin to decrease SCLC TICs via in vitro extreme limiting dilution analysis (ELDA), indicating that KSR1 disruption enhances the cisplatin toxicity of cells responsible for therapeutic resistance and tumor initiation. The ability of KSR1 disruption to prevent cisplatin resistant in H82 tumor xenograft formation supports this conclusion. Previous studies indicate ERK activation inhibits SCLC tumor growth and development. We observe a minimal effect of pharmacological ERK inhibition on cisplatin resistance and no impact on TIC formation via in vitro ELDA. However, mutational analysis of the KSR1 DEF domain, which mediates interaction with ERK, suggests that ERK interaction with KSR1 is essential for KSR1-driven cisplatin resistance. These findings reveal KSR1 as a potential therapeutic target across multiple SCLC subtypes. Implications: Genetic manipulation of KSR1 in SCLC reveals its contribution to cisplatin resistance and tumor initiation.

Activation of lineage-specific gene expression programs is mediated by recruitment of lineage-specific transcription factors and their coactivators to chromatin. The lineage factor PAX8 drives essential gene expression in ovarian cancer cells and is required for tumor proliferation. However, the molecular details surrounding co-factor recruitment and specific activation of transcription by PAX8 remain unknown. Here, we identify an important functional interaction between PAX8 and the SWItch/Sucrose Non-Fermentable (SWI/SNF) chromatin remodeling complex. We show that PAX8 can recruit SWI/SNF complexes to DNA, where they function to open chromatin and facilitate expression of PAX8 target genes. Genetic deletion of PAX8 results in loss of SWI/SNF from PAX8 bound enhancers, loss of expression of associated target genes, and reduced proliferation. These results can be phenocopied by pharmacological inhibition of SWI/SNF ATPase activity. These data indicate that PAX8 mediates the expression of an essential ovarian cancer proliferative program in part by the recruitment of the SWI/SNF complex, highlighting a novel vulnerability in PAX8 dependent ovarian cancer. Implications: PAX8 recruits SWI/SNF complexes to enhancers, to mediate expression of genes essential for ovarian cancer proliferation.

Triple-negative breast cancer (TNBC) presents significant clinical challenges due to its limited treatment options and aggressive behavior, often associated with poor prognosis. This study focuses on Kindlin-2, an adaptor protein, and its role in TNBC progression, particularly in hematopoiesis-mediated immune evasion. TNBC tumors expressing high levels of Kindlin-2 induce a notable reshaping of hematopoiesis, promoting expansion of myeloid cells in bone marrow (BM) and spleen. This shift correlated with increased levels of neutrophils and monocytes in tumor-bearing mice over time. Conversely, genetic knockout of Kindlin-2 mitigated this myeloid bias and fostered T cell infiltration within the tumor microenvironment, indicating Kindlin-2's pivotal role in immune modulation. Further investigations revealed that Kindlin-2 deficiency led to reduced expression of PD-L1, a critical immune checkpoint inhibitor, in TNBC tumors. This molecular change sensitized Kindlin-2-deficient tumors to host anti-tumor immune responses, resulting in enhanced tumor suppression in immune-competent mouse models. Single-cell RNA sequencing, bulk RNA-seq, and immunohistochemistry data supported these findings by highlighting enriched immune-related pathways and increased infiltration of immune cells in Kindlin-2-deficient tumors. Therapeutically, targeting PD-L1 in Kindlin-2-expressing TNBC tumors effectively inhibited tumor growth, akin to the effects observed with genetic Kindlin-2 knockout or PD-L1-KO. Our data underscore Kindlin-2 as a promising therapeutic target in combination with immune checkpoint blockade to bolster anti-tumor immunity and counteract resistance mechanisms typical of TNBC and other immune evasive solid tumors. Implications: Kindlin-2 regulates tumor immune evasion through the systemic modulation of hematopoiesis and PD-L1 expression, which warrants therapeutic targeting of Kindlin-2 in TNBC patients.

The E3 ubiquitin ligase RNF6 has been widely recognized for its role in promoting tumorigenesis in multiple cancers. However, we found it is downregulated in lung adenocarcinoma (LUAD) and the molecular rationale for this discrepancy remains unclear. In the present study, we find that RNF6 but not its ΔRING inactive form inhibits LUAD cell proliferation and migration and sensitizes LUAD to chemotherapy. To understand the molecular mechanism, we utilize affinity purification/tandem mass spectrometry to analyze RNF6-interacting proteins and find that cyclin D2 (CCND2), a key regulator of the G1/S transition in the cell cycle. RNF6 physically binds to CCND2 and mediates its K48-linked polyubiquitination and subsequent degradation. However, ΔRING RNF6 fails to mediate CCND2 for ubiquitination and degradation. Moreover, Thr280 is critically important for CCND2 stability. When Thr280 is mutated, CCND2 becomes more stable and less ubiquitinated by RNF6. Furthermore, RNF6 arrests LUAD cell cycle at the G1 phase by inhibiting the CCND2/pRb signaling pathway, which is consistent with decreased cell proliferation. Lastly, RNF6 curtails the growth of LUAD xenografts in vivo, associated with decreased CCND2 expression. Therefore, RNF6 is a novel E3 ligase of CCND2 and suppresses LUAD cell proliferation. Implications: This study reveals a novel regulation on cell cycle transition in LUAD and suggests the RNF6/CCND2 axis may represent an alternative therapeutic target for the treatment of LUAD.