A previously identified apoptosis inhibitor iASPP confers resistance to chemotherapeutic drugs by suppressing senescence in cancer cells

Inhibitor of apoptosis stimulating protein of p53 protects against MPP+-induced neurotoxicity of dopaminergic neurons

Inhibitor of apoptosis stimulating protein of p53 (iASPP) is related to the pathogenesis of several neurological disorders by affecting the oxidative stress and survival of neurons. However, whether iASPP has a role in Parkinson disease (PD) remains to be determined. This work explored the potential regulatory effect of iASPP in an in vitro model of PD based on 1-methyl-4-phenylpyridinium (MPP+)-evoked neurotoxicity of dopaminergic neurons in culture. MN9D neurons were treated with MPP+ at 200 µM in the culture media for 24 h to induce neurotoxicity. Overexpression and silencing of iASPP in neurons were achieved by infecting recombinant adenovirus expressing iASPP and sh-iASPP, respectively. Protein expression was examined by immunoblotting. MPP+-evoked neurotoxicity of dopaminergic neurons was determined by cell viability, TUNEL, and flow cytometric assays. The transcriptional activity of nuclear erythroid factor 2-like 2 (Nrf2) was assessed by luciferase reporter assay. Kelch-like ECH-associated protein 1 (Keap1)-knockout neurons were generated by lentiCRISPR/Cas9-Keap1 constructs. Expression levels of iASPP declined in MPP+-stimulated neurons. Overexpression of iASPP in neurons exhibited inhibitory effects on MPP+-evoked apoptosis, α-synuclein accumulation, and oxidative stress, while iASPP-deficient neurons were more sensitive to MPP+-induced neurotoxicity. Overexpression of iASPP led to an enhancing effect on Nrf2 activation in MPP+-stimulated neurons. Mechanism research revealed that iASPP may contribute to the activation of Nrf2 by competing with Nrf2 in binding with Keap1. Notably, the regulatory effect of iASPP on Nrf2 was diminished in Keap1-knockout neurons. The chemical inhibition of Nrf2 or knockdown of Nrf2 abrogated the protective effects of iASPP on MPP+-induced neurotoxicity. To conclude, iASPP protects dopaminergic neurons against MPP+-induced neurotoxicity through modulation of the Keap1/Nrf2 axis. Therefore, iASPP may play a crucial role in mediating the loss of dopaminergic neurons in PD, and targeting the iASPP-Nrf2 axis could be a promising strategy for treating PD.

A new perspective on prostate cancer treatment: the interplay between cellular senescence and treatment resistance

The emergence of resistance to prostate cancer (PCa) treatment, particularly to androgen deprivation therapy (ADT), has posed a significant challenge in the field of PCa management. Among the therapeutic options for PCa, radiotherapy, chemotherapy, and hormone therapy are commonly used modalities. However, these therapeutic approaches, while inducing apoptosis in tumor cells, may also trigger stress-induced premature senescence (SIPS). Cellular senescence, an entropy-driven transition from an ordered to a disordered state, ultimately leading to cell growth arrest, exhibits a dual role in PCa treatment. On one hand, senescent tumor cells may withdraw from the cell cycle, thereby reducing tumor growth rate and exerting a positive effect on treatment. On the other hand, senescent tumor cells may secrete a plethora of cytokines, growth factors and proteases that can affect neighboring tumor cells, thereby exerting a negative impact on treatment. This review explores how radiotherapy, chemotherapy, and hormone therapy trigger SIPS and the nuanced impact of senescent tumor cells on PCa treatment. Additionally, we aim to identify novel therapeutic strategies to overcome resistance in PCa treatment, thereby enhancing patient outcomes.

Toxoflavin analog D43 exerts antiproliferative effects on breast cancer by inducing ROS-mediated apoptosis and DNA damage

Triple-negative breast cancer (TNBC) is regarded as the deadliest subtype of breast cancer because of its high heterogeneity, aggressiveness, and limited treatment options. Toxoflavin has been reported to possess antitumor activity. In this study, a series of toxoflavin analogs were synthesized, among which D43 displayed a significant dose-dependent inhibitory effect on the proliferation of TNBC cells (MDA-MB-231 and HCC1806). Additionally, D43 inhibited DNA synthesis in TNBC cells, leading to cell cycle arrest at the G2/M phase. Furthermore, D43 consistently promoted intracellular ROS generation, induced DNA damage, and resulted in apoptosis in TNBC cells. These effects could be reversed by N-acetylcysteine. Moreover, D43 significantly inhibited the growth of breast cancer patient-derived organoids and xenografts with a favorable biosafety profile. In conclusion, D43 is a potent anticancer agent that elicits significant antiproliferation, oxidative stress, apoptosis, and DNA damage effects in TNBC cells, and D43 holds promise as a potential candidate for the treatment of TNBC.

Development of a ferroptosis-based model to predict prognosis, tumor microenvironment, and drug response for lung adenocarcinoma with weighted genes co-expression network analysis

Objective: The goal of this study was to create a risk model based on the ferroptosis gene set that affects lung adenocarcinoma (LUAD) patients' prognosis and to investigate the potential underlying mechanisms. Material and Methods: A cohort of 482 LUAD patients from the TCGA database was used to develop the prognostic model. We picked the module genes from the ferroptosis gene set using weighted genes co-expression network analysis (WGCNA). The least absolute shrinkage and selection operator (LASSO) and univariate cox regression were used to screen the hub genes. Finally, the multivariate Cox analysis constructed a risk prediction score model. Three other cohorts of LUAD patients from the GEO database were included to validate the prediction ability of our model. Furthermore, the differentially expressed genes (DEG), immune infiltration, and drug sensitivity were analyzed. Results: An eight-gene-based prognostic model, including PIR, PEBP1, PPP1R13L, CA9, GLS2, DECR1, OTUB1, and YWHAE, was built. The patients from the TCGA database were classified into the high-RS and low-RS groups. The high-RS group was characterized by poor overall survival (OS) and less immune infiltration. Based on clinical traits, we separated the patients into various subgroups, and RS had remarkable prediction performance in each subgroup. The RS distribution analysis demonstrated that the RS was significantly associated with the stage of the LUAD patients. According to the study of immune cell infiltration in both groups, patients in the high-RS group had a lower abundance of immune cells, and less infiltration was associated with worse survival. Besides, we discovered that the high-RS group might not respond well to immune checkpoint inhibitors when we analyzed the gene expression of immune checkpoints. However, drug sensitivity analysis suggested that high-RS groups were more sensitive to common LUAD agents such as Afatinib, Erlotinib, Gefitinib, and Osimertinib. Conclusion: We constructed a novel and reliable ferroptosis-related model for LUAD patients, which was associated with prognosis, immune cell infiltration, and drug sensitivity, aiming to shed new light on the cancer biology and precision medicine.

lncRNA HITT Inhibits Lactate Production by Repressing PKM2 Oligomerization to Reduce Tumor Growth and Macrophage Polarization

Lactic acid acidifies the tumor microenvironment and promotes multiple critical oncogenic processes, including immune evasion. Pyruvate kinase M2 (PKM2) is a dominant form of pyruvate kinase (PK) expressed in cancers that plays essential roles in metabolic reprograming and lactate production, rendering it as an attractive therapeutic target of cancer. However, the mechanism underlying PKM2 regulation remains unclear. Here, we show that long noncoding RNA (lncRNA) HIF-1α inhibitor at transcription level (HITT) inhibits lactate production in a PKM2-dependent manner. Mechanistically, it physically interacts with PKM2 mapped to a region that has been involved in both dimer (less-active) and tetramer (more-active) formation, inhibiting PKM2 oligomerization and leading to dramatic reduction of PK activity. Under glucose starvation, HITT was reduced as a result of miR-106 induction, which subsequently facilitates PKM2 oligomerization and increases vulnerability to apoptosis under glucose starvation stress. In addition, the interaction also reduces lactate secretion from cancer cells, which subsequently polarizes macrophages toward an M2-like anti-inflammatory phenotype and thus possibly contributes to immune escape in vivo. This study highlights an important role of an lncRNA in regulating PKM2 activity and also reveals a metabolic regulatory effect of PKM2 on macrophage polarization.

iASPP is essential for HIF-1α stabilization to promote angiogenesis and glycolysis via attenuating VHL-mediated protein degradation

Hypoxia-inducible factor-1α (HIF-1α) plays central roles in the hypoxia response. It is highly expressed in multiple cancers, but not always correlated with hypoxia. Mutation of the von Hippel-Lindau (VHL) gene, which encodes an E3 ligase, contributes to the constructive activation of HIF-1α in specific tumor types, as exemplified by renal cell carcinoma; but how VHL wild-type tumors acquire this ability is not completely understood. Here, we found that the oncogene iASPP (inhibitor of apoptosis-simulating protein of p53) plays essential roles in such a context. Genetic inhibition of iASPP reduced tumor growth, accompanied by impaired angiogenesis, increased areas of tumor necrosis, and reduced glycolysis that was HIF-1α-dependent. These abilities of iASPP were validated by in vitro assays. Mechanistically, iASPP directly binds VHL at its β domain, a region also involved in HIF-1α binding, therefore blocking VHL's binding and the subsequent degradation of HIF-1α protein under normoxia. iASPP levels correlate with HIF-1α protein and vascular endothelial growth factor (VEGF) and the glucose transporter protein type 1(GLUT1), representative HIF-1α target genes, in human colon cancer tissues. Furthermore, inhibition of iASPP expression synergizes with low toxic dose of the HIF-1α inhibitor YC-1 to inhibit HIF-1α expression and tumor growth. Our findings suggest that iASPP contributes to HIF-1α activation in cancers, and that iASPP-mediated HIF-1α stabilization has potential as a therapeutic approach against cancer.

iASPP suppresses Gp78-mediated TMCO1 degradation to maintain Ca2+ homeostasis and control tumor growth and drug resistance

Accumulating preclinical and clinical evidence has supported a central role for alterations in Ca²⁺ homeostasis in the development of cancer. TMCO1 protein is an identified Ca²⁺-channel protein, while its roles in cancer remain obscure. Here, we found that TMCO1 is increased in colon cancer tissues. In addition, it is a substrate of E3 ligase Gp78. Enhanced oncogene iASPP stabilizes TMCO1 by competitively binding with Gp78. Inhibition of iASPP-TMCO1 sensitizes cancer cells’ response to Ca²⁺-induced apoptosis. This study has improved our fundamental understanding of the Ca²⁺ homeostasis in cancer cells. iASPP-TMCO1 axis may present a promising therapeutic target that can combine the conventional drugs to reinforce Ca²⁺-dependent apoptosis.

Ca²⁺ release from the endoplasmic reticulum (ER) is an essential event in the modulation of Ca²⁺ homeostasis, which is coordinated by multiple biological processes, ranging from cell proliferation to apoptosis. Deregulated Ca²⁺ homeostasis is linked with various cancer hallmarks; thus, uncovering the mechanisms underlying Ca²⁺ homeostasis dynamics may lead to new anticancer treatment strategies. Here, we demonstrate that a reported Ca²⁺-channel protein TMCO1 (transmembrane and coiled-coil domains 1) is overexpressed in colon cancer tissues at protein levels but not at messenger RNA levels in colon cancer. Further study revealed that TMCO1 is a substrate of ER-associated degradation E3 ligase Gp78. Intriguingly, Gp78-mediated TMCO1 degradation at K186 is under the control of the iASPP (inhibitor of apoptosis-stimulating protein of p53) oncogene. Mechanistically, iASPP robustly reduces ER Ca²⁺ stores, mainly by competitively binding with Gp78 and interfering with Gp78-mediated TMCO1 degradation. A positive correlation between iASPP and TMCO1 proteins is further validated in human colon tissues. Inhibition of iASPP-TMCO1 axis promotes cytosolic Ca²⁺ overload–induced apoptotic cell death, reducing tumor growth both in vitro and in vivo. Thus, iASPP-TMCO1 represents a promising anticancer treatment target by modulating Ca²⁺ homeostasis.

Blocking iASPP/Nrf2/M-CSF axis improves anti-cancer effect of chemotherapy-induced senescence by attenuating M2 polarization

The complex interaction between cancer cells and the immune microenvironment is a central regulator of tumor growth and the treatment response. Chemotherapy-induced senescence is accompanied by the senescence-associated secretion phenotype (SASP). However, the mechanisms underlying the regulation of the SASP remain the most poorly understood element of senescence. Here, we show that nuclear erythroid factor 2-like factor 2 (Nrf2), a master antioxidative transcription factor, accumulates upon doxorubicin-induced senescence. This is due to the increased cytoplasmic Inhibitor of Apoptosis Stimulating Protein of P53, iASPP, which binds with Keap1, interrupting Keap1/Nrf2 interaction and promoting Nrf2 stabilization and activation. Activated Nrf2 transactivates a novel target gene of SASP factor, macrophage colony-stimulating factor (M-CSF), which subsequently acts on macrophages and induces polarization from M1 to M2 via a paracrine mechanism. Genetic inhibition of iASPP-Nrf2 suppresses the growth of apoptosis-resistant xenografts, with further analysis revealing that M-CSF/M-CSFR-regulated macrophage polarization is critical for the functional outcomes delineated above. Overall, our data uncover a novel function of iASPP-Nrf2 in skewing the immune microenvironment under treatment-induced senescence. Targeting the iASPP-Nrf2 axis could be a powerful strategy for the implementation of new chemotherapy-based therapeutic opportunities.

Malignant transformation of human bronchial epithelial cells induced by benzo [a] pyrene suggests a negative feedback of TP53 to PPP1R13L via binding a possible enhancer element

Previous studies have shown that PPP1R13L as an inhibitor of apoptosis protease TP53 can lead to abnormal cell proliferation and carcinogenesis, however, the function of PPP1R13L was complicated and the interaction between TP53 and PPP1R13L needs to be further explored. In the present study, a malignant transformation model of human bronchial epithelial cells induced by benzo (a) pyrene-7,8-dihydrodiol-9,10-epoxide (BPDE) was established to observe the regulatory patterns between TP53 and PPP1R13L during carcinogenesis. In vitro experiments including CRISPR-Cas9 editing, RNA silence, Co-Immunoprecipitation and Chromatin Immunoprecipitation were applied to discuss their interactive effects. Additionally, TCGA data profile and our clinical samples of lung cancer were also used to analyze their relationship at the transcriptome level. Interestingly, we found that the mRNA and protein level of TP53 and PPP1R13L fluctuated as a wave in BPDE-induced malignant transformation under wild-type TP53 genetic background. Our results have also demonstrated that PPP1R13L acts as an inhibitor of TP53, while TP53 can regulate PPP1R13L via binding a possible enhancer of the first intron of PPP1R13L gene. Likewise, TCGA data and clinical samples have identified that in the case of TP53 mutation, TP53 expression was negatively correlated with PPP1R13L, while in the case of TP53 wild-type, TP53 expression was not correlated with PPP1R13L. It suggested that there existed a negative feedback of wild-type TP53 to PPP1R13L, which reminded a unique implication during chemical carcinogenesis.

Nuclear iASPP determines cell fate by selectively inhibiting either p53 or NF-κB

p53 and NF-κBp65 are essential transcription factors (TFs) in the cellular response to stress. Two signaling systems can often be entwined together and generally produce opposing biological outcomes in a cell context-dependent manner. Inhibitor of apoptosis-stimulating protein of p53 (iASPP) has the potential to inhibit both p53 and NF-κBp65, yet how such activities of iASPP are integrated with cancer remains unknown. Here, we utilized different cell models with diverse p53/NF-κBp65 activities. An iASPP(295–828) mutant, which is exclusively located in the nucleus and has been shown to be essential for its inhibitory effects on p53/NF-κBp65, was used to investigate the functional interaction between iASPP and the two TFs. The results showed that iASPP inhibits apoptosis under conditions when p53 is activated, while it can also elicit a proapoptotic effect when NF-κBp65 alone is activated. Furthermore, we demonstrated that iASPP inhibited the transcriptional activity of p53/NF-κBp65, but with a preference toward p53, thereby producing an antiapoptotic outcome when both TFs were simultaneously activated. This may be due to stronger binding between p53 and iASPP than NF-κBp65 and iASPP. Overall, these findings provide important insights into how the activities of p53 and NF-κBp65 are modulated by iASPP. Despite being a well-known oncogene, iASPP may have a proapoptotic role, which will guide the development of iASPP-targeted therapies to reach optimal outcomes in the future.

[A Review of Celluar Senescence and Tumor Treatment]

Cellular senescence is a permanent state of cell cycle arrest, combined with the acquisition of a variety of secretory phenotypes. In addition to apoptosis, the induction of cellular senescence is an important mechanism that chemo- and radiotherapies and some targeted therapies rely on to produce an anti-tumor effect. However, being a self-protective mechanism of cells, cellular senescence can produce both positive and negative effects in tumor treatment. It remains a challenge to effectively utilize the anti-tumor effect of cellular senescence while averting the pro-tumor effect. How to improve the sensitivity of tumor treatment and to prevent tumor recurrence and metastasis has become the bottleneck in cellular senescence research. We summarize in this review the "double-edged-sword" effect of cellular senescence in tumor treatment. We summarize and discuss the cell autonomous and non-autonomous mechanisms that senescent cells use to affect tumor treatment, hoping to provide information that will help improve the outcome of tumor treatment and promote further research in basic and clinical application of cellular senescence in tumor treatment.