Loss-of-Function but Not Gain-of-Function Properties of Mutant TP53 Are Critical for the Proliferation, Survival, and Metastasis of a Broad Range of Cancer Cells.

Mutations in the tumor suppressor TP53 cause cancer and impart poor chemotherapeutic responses, reportedly through loss-of-function, dominant-negative effects and gain-of-function (GOF) activities. The relative contributions of these attributes is unknown. We found that removal of 12 different TP53 mutants with reported GOFs by CRISPR/Cas9 did not impact proliferation and response to chemotherapeutics of 15 human cancer cell lines and colon cancer-derived organoids in culture. Moreover, removal of mutant TP53/TRP53 did not impair growth or metastasis of human cancers in immune-deficient mice or growth of murine cancers in immune-competent mice. DepMap mining revealed that removal of 158 different TP53 mutants had no impact on the growth of 391 human cancer cell lines. In contrast, CRISPR-mediated restoration of wild-type TP53 extinguished the growth of human cancer cells in vitro. These findings demonstrate that LOF but not GOF effects of mutant TP53/TRP53 are critical to sustain expansion of many tumor types. SIGNIFICANCE: This study provides evidence that removal of mutant TP53, thereby deleting its reported GOF activities, does not impact the survival, proliferation, metastasis, or chemotherapy responses of cancer cells. Thus, approaches that abrogate expression of mutant TP53 or target its reported GOF activities are unlikely to exert therapeutic impact in cancer. See related commentary by Lane, p. 211 . This article is featured in Selected Articles from This Issue, p. 201.

Mitochondrial E3 ubiquitin ligase MARCHF5 controls BAK apoptotic activity independently of BH3-only proteins.

Intrinsic apoptosis is principally governed by the BCL-2 family of proteins, but some non-BCL-2 proteins are also critical to control this process. To identify novel apoptosis regulators, we performed a genome-wide CRISPR-Cas9 library screen, and it identified the mitochondrial E3 ubiquitin ligase MARCHF5/MITOL/RNF153 as an important regulator of BAK apoptotic function. Deleting MARCHF5 in diverse cell lines dependent on BAK conferred profound resistance to BH3-mimetic drugs. The loss of MARCHF5 or its E3 ubiquitin ligase activity surprisingly drove BAK to adopt an activated conformation, with resistance to BH3-mimetics afforded by the formation of inhibitory complexes with pro-survival proteins MCL-1 and BCL-XL. Importantly, these changes to BAK conformation and pro-survival association occurred independently of BH3-only proteins and influence on pro-survival proteins. This study identifies a new mechanism by which MARCHF5 regulates apoptotic cell death by restraining BAK activating conformation change and provides new insight into how cancer cells respond to BH3-mimetic drugs. These data also highlight the emerging role of ubiquitin signalling in apoptosis that may be exploited therapeutically.

Interferon-γ primes macrophages for pathogen ligand-induced killing via a caspase-8 and mitochondrial cell death pathway.

Cell death plays an important role during pathogen infections. Here, we report that interferon-γ (IFNγ) sensitizes macrophages to Toll-like receptor (TLR)-induced death that requires macrophage-intrinsic death ligands and caspase-8 enzymatic activity, which trigger the mitochondrial apoptotic effectors, BAX and BAK. The pro-apoptotic caspase-8 substrate BID was dispensable for BAX and BAK activation. Instead, caspase-8 reduced pro-survival BCL-2 transcription and increased inducible nitric oxide synthase (iNOS), thus facilitating BAX and BAK signaling. IFNγ-primed, TLR-induced macrophage killing required iNOS, which licensed apoptotic caspase-8 activity and reduced the BAX and BAK inhibitors, A1 and MCL-1. The deletion of iNOS or caspase-8 limited SARS-CoV-2-induced disease in mice, while caspase-8 caused lethality independent of iNOS in a model of hemophagocytic lymphohistiocytosis. These findings reveal that iNOS selectively licenses programmed cell death, which may explain how nitric oxide impacts disease severity in SARS-CoV-2 infection and other iNOS-associated inflammatory conditions.

Neoadjuvant chemotherapy for advanced stage endometrial cancer: A systematic review.

OBJECTIVE: While primary cytoreductive surgery (PCS) is considered the standard of care for women who present with stage IV endometrial cancer, neoadjuvant chemotherapy (NACT) followed by interval cytoreductive surgery (ICS) has emerged as an alternative treatment strategy. We summarized the literature and compared outcomes of PCS compared to NACT and ICS. METHODS: We conducted a systematic search on PubMed, Embase, Web of Science, and Scopus for articles published from January 1, 1990 to December 31, 2020. Key search terms included multiple descriptors of advanced disease status in combination with "endometrial cancer" and "neoadjuvant chemotherapy". Our review included studies that examined survival and surgical outcomes of patients with stage III or IV endometrial cancer treated with neoadjuvant chemotherapy followed by interval cytoreductive surgery versus those who received primary cytoreductive surgery. We excluded studies examining only patients with leiomyosarcomas, carcinosarcomas, and stromal sarcomas due to the biologic heterogeneity of these malignancies. RESULTS: The nine included studies encompassed 5,844 patients, of which 1,317 (22.5%) received NACT and 4,527 received PCS (77.5%). With the exception of a single study, all were retrospective observational studies or case series. Use of NACT in patients with stage IV EC increased from 16.0% in 2010 to 23.9% in 2015. Five studies analyzed median overall survival and all but one reported no significant difference between NACT + ICS vs. PCS. Optimal cytoreduction (<1 cm of residual disease) rates were similar across both treatment groups in three separate analyses, however pooled data suggest improved rates of optimal cytoreduction for NACT + ICS vs. PCS patients (81.9% vs. 51.5% respectively). Patients receiving NACT experienced significantly shorter hospital admissions and lower operative times compared to PCS counterparts. CONCLUSIONS: NACT followed by ICS reduces perioperative morbidity while offering similar overall survival.

Primary cytoreductive surgery for advanced stage endometrial cancer: a systematic review and meta-analysis.

OBJECTIVE: Endometrial cancer uncommonly presents at an advanced stage and little prospective evidence exists to guide the management thereof. We aimed to summarize the evidence about primary cytoreductive surgery in the treatment of advanced stage endometrial cancer. DATA SOURCES: MEDLINE, Embase, and Scopus databases were searched from inception to September 11, 2020, using search terms representing the themes "endometrial cancer," "advanced stage," and "primary cytoreductive surgery." STUDY ELIGIBILITY CRITERIA: We included full-text, English reports that included ≥10 patients undergoing primary cytoreductive surgery for advanced stage endometrial cancer and that reported on the outcomes of primary cytoreductive surgery and survival rates based on the residual disease burden. METHODS: Two reviewers independently screened the studies and with disagreements between the reviewers resolved by a third reviewer. Data were extracted using a standardized form. The percentage of cases reaching maximal (no gross residual disease) and optimal (<1 cm or <2 cm residual disease) cytoreduction were assessed by summing binomials proportions, and the association with survival was assessed using an inverse variance-weighted meta-analysis of logarithmic hazard ratios. RESULTS: From 1219 unique records identified, 34 studies were selected for inclusion. Studies consisted of single or multi-institutional cohorts of patients collected over a period of 6 to 24 years and included various mixes of histologies (endometrioid, serous, clear cell, and carcinosarcoma) and disease stages (III or IV). In a meta-analysis of the extent of residual disease after primary cytoreductive surgery, we found that 52.1% of cases reached no gross residual disease status (n=18 studies; 1329 patients) and 75% reached <1 cm residual disease status (n=27 studies; 2343 patients). The proportion of cytoreduction for both thresholds was lower for studies of stage IV vs stage III to IV disease (41.4% vs 69.8% for no gross residual disease; 63.2% vs 82.2% for <1 cm residual disease) but did not vary notably by histology. In a meta-analysis of the reported hazard ratios, submaximal (any gross residual disease vs no gross residual disease) and suboptimal (≥1 cm vs <1 cm) cytoreduction thresholds were associated with worse progression-free survival (submaximal hazard ratio, 2.16; 95% confidence interval, 1.45-3.21; I2=68%; suboptimal hazard ratio, 2.55; 95% confidence interval, 1.93-3.37; I2=63%) and overall survival rates (submaximal hazard ratio, 2.57; 95% confidence interval, 2.13-3.10; I2=1%; suboptimal hazard ratio, 2.62; 95% confidence interval, 2.20-3.11; I2=15%). Sensitivity analyses limited to high-quality studies demonstrated consistent results. CONCLUSION: Among cases of advanced stage endometrial cancer undergoing primary cytoreductive surgery, a significant proportion of patients are left with residual disease, which is associated with worse survival outcomes. Further investigations about the roles of neoadjuvant chemotherapy and primary cytoreductive surgery in prospective trials is warranted in this population.

Impact of quality of care on racial disparities in survival for endometrial cancer.

BACKGROUND: Black women experience poorer survival compared with white women across all endometrial cancer stages and histologies. The incidence of endometrial cancer is 30% lower in black women compared with white women, yet mortality is 80% higher in black women. Differences in adherence to evidence-based guidelines have been proposed to be major contributors to this disparity. OBJECTIVES: We examined whether adherence to evidence-based treatment recommendations for endometrial cancer could mitigate survival disparities between black and white women. STUDY DESIGN: The National Cancer Database was used to identify women with endometrial cancer treated from 2004 through 2016. We established 5 evidence-based quality metrics based on review of primary literature and accepted guidelines: surgical treatment within 6 weeks of diagnosis (Q1), use of minimally invasive surgery (stage I-IIIC; Q2), pelvic nodal assessment (high-risk tumors; Q3), adjuvant radiation (high intermediate risk; Q4), and systemic chemotherapy (stage III-IV; Q5). The rates of 30 and 90 day mortality and 5 year survival were compared between black and white women. To determine the influence of quality on outcomes, we compared outcomes among perfectly adherent black and white women with stage I and III endometrial cancer. RESULTS: We identified 310,208 women including 35,035 (11.3%) black women and 275,173 (88.3%) white women. Black women were less likely than white women to receive Q1 (65.8 vs 75.6%), Q2 (58.5 vs 72.9%), Q3 (71.3 vs 74.2%), and Q5 (72.7 vs 73.2%) (P < .05 for all). Adherence to each quality metrics was associated with improved survival. Among women with stage I disease, perfect adherence to the relative quality metrics was seen in 53.1% of white and 41.5% of black women. Among perfectly adherent stage I patients, outcomes in black women improved relative to unselected black women; however, they still experienced higher risk of 30 day (adjusted relative risk, 2.25; 95% confidence interval, 1.30-3.90), 90 day (adjusted relative risk, 1.84; 95% confidence interval, 1.23-2.76), and 5 year mortality (adjusted hazard ratio, 1.42; 95% confidence interval, 1.26-1.59) compared with similar white women. Among women with stage III tumors, perfect adherence to the relative quality metrics was seen in 56.6% of white and 44.1% of black women. Perfectly adherent black women with stage III disease had improved outcomes but remained at increased risk of 30 day (adjusted relative risk, 1.86; 95% confidence interval, 1.01-3.44) and 5 year mortality (adjusted hazard ratio, 1.35; 95% confidence interval, 1.22-1.50) compared with white women. CONCLUSION: Black women are less likely than white women with endometrial cancer to receive evidence-based care. However, receipt of evidence-based care mitigates but does not eliminate racial disparities in outcomes and black women remain at greater risk of death from endometrial cancer.

MARCH5 requires MTCH2 to coordinate proteasomal turnover of the MCL1:NOXA complex.

MCL1, a BCL2 relative, is critical for the survival of many cells. Its turnover is often tightly controlled through both ubiquitin-dependent and -independent mechanisms of proteasomal degradation. Several cell stress signals, including DNA damage and cell cycle arrest, are known to elicit distinct E3 ligases to ubiquitinate and degrade MCL1. Another trigger that drives MCL1 degradation is engagement by NOXA, one of its BH3-only protein ligands, but the mechanism responsible has remained unclear. From an unbiased genome-wide CRISPR-Cas9 screen, we discovered that the ubiquitin E3 ligase MARCH5, the ubiquitin E2 conjugating enzyme UBE2K, and the mitochondrial outer membrane protein MTCH2 co-operate to mark MCL1 for degradation by the proteasome-specifically when MCL1 is engaged by NOXA. This mechanism of degradation also required the MCL1 transmembrane domain and distinct MCL1 lysine residues to proceed, suggesting that the components likely act on the MCL1:NOXA complex by associating with it in a specific orientation within the mitochondrial outer membrane. MTCH2 has not previously been reported to regulate protein stability, but is known to influence the mitochondrial localization of certain key apoptosis regulators and to impact metabolism. We have now pinpointed an essential but previously unappreciated role for MTCH2 in turnover of the MCL1:NOXA complex by MARCH5, further strengthening its links to BCL2-regulated apoptosis.

A Thpok-Directed Transcriptional Circuitry Promotes Bcl6 and Maf Expression to Orchestrate T Follicular Helper Differentiation.

The generation of high-affinity neutralizing antibodies, the objective of most vaccine strategies, occurs in B cells within germinal centers (GCs) and requires rate-limiting "help" from follicular helper CD4+ T (Tfh) cells. Although Tfh differentiation is an attribute of MHC II-restricted CD4+ T cells, the transcription factors driving Tfh differentiation, notably Bcl6, are not restricted to CD4+ T cells. Here, we identified a requirement for the CD4+-specific transcription factor Thpok during Tfh cell differentiation, GC formation, and antibody maturation. Thpok promoted Bcl6 expression and bound to a Thpok-responsive region in the first intron of Bcl6. Thpok also promoted the expression of Bcl6-independent genes, including the transcription factor Maf, which cooperated with Bcl6 to mediate the effect of Thpok on Tfh cell differentiation. Our findings identify a transcriptional program that links the CD4+ lineage with Tfh differentiation, a limiting factor for efficient B cell responses, and suggest avenues to optimize vaccine generation.

The G protein-coupled estrogen receptor-1, GPER-1, promotes fibrillogenesis via a Shc-dependent pathway resulting in anchorage-independent growth.

The G protein-coupled estrogen receptor-1, GPER-1, coordinates fibronectin (FN) matrix assembly and release of heparan-bound epidermal growth factor (HB-EGF). This mechanism of action results in the recruitment of FN-engaged integrin α5ß1 to fibrillar adhesions and the formation of integrin α5ß1-Shc adaptor protein complexes. Here, we show that GPER-1 stimulation of murine 4 T1 or human SKBR3 breast cancer cells with 17ß-estradiol (E2ß) promotes the formation of focal adhesions and actin stress fibers and results in increased cellular adhesion and haptotaxis on FN, but not collagen. These actions are also induced by the xenoestrogen, bisphenol A, and the estrogen receptor (ER) antagonist, ICI 182, 780, but not the inactive stereoisomer, 17α-estradiol (E2α). In addition, we show that GPER-1 stimulation of breast cancer cells allows for FN-dependent, anchorage-independent growth and FN fibril formation in "hanging drop" assays, indicating that these GPER-1-mediated actions occur independently of adhesion to solid substrata. Stable expression of Shc mutant Y317F lacking its primary tyrosyl phosphorylation site disrupts E2ß-induced focal adhesion and actin stress fiber formation and abolishes E2ß-enhanced haptotaxis on FN and anchorage-dependent growth. Collectively, these data demonstrate that E2ß action via GPER-1 enhances cellular adhesivity and FN matrix assembly and allows for anchorage-independent growth, cellular events that may allow for cellular survival, and tumor progression.