The Ubiquitin Ligase CHIP Integrates Proteostasis and Aging by Regulation of Insulin Receptor Turnover.

Aging is attended by a progressive decline in protein homeostasis (proteostasis), aggravating the risk for protein aggregation diseases. To understand the coordination between proteome imbalance and longevity, we addressed the mechanistic role of the quality-control ubiquitin ligase CHIP, which is a key regulator of proteostasis. We observed that CHIP deficiency leads to increased levels of the insulin receptor (INSR) and reduced lifespan of worms and flies. The membrane-bound INSR regulates the insulin and IGF1 signaling (IIS) pathway and thereby defines metabolism and aging. INSR is a direct target of CHIP, which triggers receptor monoubiquitylation and endocytic-lysosomal turnover to promote longevity. However, upon proteotoxic stress conditions and during aging, CHIP is recruited toward disposal of misfolded proteins, reducing its capacity to degrade the INSR. Our study indicates a competitive relationship between proteostasis and longevity regulation through CHIP-assisted proteolysis, providing a mechanistic concept for understanding the impact of proteome imbalance on aging.

Long-term experience with tepotinib in Japanese patients with MET exon 14 skipping NSCLC from the Phase II VISION study.

Tepotinib is a highly selective MET tyrosine kinase inhibitor (TKI) that has demonstrated robust and durable clinical activity in patients with MET exon 14 (METex14) skipping non-small-cell lung cancer (NSCLC). In the Phase II VISION study, patients received oral tepotinib 500 mg once daily. The primary endpoint was an objective response by an independent review committee (IRC) according to RECIST v1.1 criteria. The secondary endpoints included duration of response (DOR), progression-free survival (PFS), overall survival (OS), and safety. Here we report the analysis of the efficacy and safety of tepotinib in all Japanese patients with advanced METex14 skipping NSCLC from VISION (n = 38) with >18 months' follow-up. The median age of the Japanese patients was 73 years (range 63-88), 39.5% of patients were ≥75 years old, 68.4% were male, 55.3% had a history of smoking, 76.3% had adenocarcinoma, and 10.5% of patients had known brain metastases at baseline. Overall, the objective response rate (ORR) was 60.5% (95% confidence interval (CI): 43.4, 76.0) with a median DOR of 18.5 months (95% CI: 8.3, not estimable). ORR in treatment-naïve patients (n = 18) was 77.8% (95% CI: 52.4, 93.6), and in patients aged ≥75 years (n = 15), ORR was 73.3% (95% CI: 44.9, 92.2). The most common treatment-related adverse event (AE) with any grade was blood creatinine increase (65.8%), which resolved following tepotinib discontinuation. Other common treatment-related AEs were peripheral edema (60.5%), hypoalbuminemia (34.2%), diarrhea (28.9%), and nausea (15.8%). In summary, tepotinib demonstrated robust and durable clinical activity irrespective of age or therapy line, with a manageable safety profile in Japanese patients with METex14 skipping NSCLC enrolled in VISION.

INSIGHT 2: a phase II study of tepotinib plus osimertinib in MET-amplified NSCLC and first-line osimertinib resistance.

MET amplification (METamp), a mechanism of acquired resistance to EGFR tyrosine kinase inhibitors, occurs in up to 30% of patients with non-small-cell lung cancer (NSCLC) progressing on first-line osimertinib. Combining osimertinib with a MET inhibitor, such as tepotinib, an oral, highly selective, potent MET tyrosine kinase inhibitor, may overcome METamp-driven resistance. INSIGHT 2 (NCT03940703), an international, open-label, multicenter phase II trial, assesses tepotinib plus osimertinib in patients with advanced/metastatic EGFR-mutant NSCLC and acquired resistance to first-line osimertinib and METamp, determined centrally by fluorescence in situ hybridization (gene copy number ≥5 and/or MET/CEP7 ≥2) at time of progression. Patients will receive tepotinib 500 mg (450 mg active moiety) plus osimertinib 80 mg once-a-day. The primary end point is objective response, and secondary end points include duration of response, progression-free survival, overall survival and safety. Trial registration number: NCT03940703 (clinicaltrials.gov).

Osimertinib is used to treat a type of lung cancer that has specific changes (mutations) in a gene called EGFR. Although tumors will usually shrink (respond) during treatment with osimertinib, they can stop responding, or become resistant, to osimertinib. A common cause of resistance is 'MET amplification', which describes when extra copies of a gene called MET are present. Lung cancer that is resistant to osimertinib due to MET amplification could be treated by combining osimertinib with a treatment that blocks MET, such as tepotinib. INSIGHT 2 is an ongoing study that is designed to learn about the effects and safety of tepotinib combined with osimertinib, in patients with lung cancer that has stopped responding to osimertinib because of MET amplification. A plain language version of this article is available and is published alongside the paper online: www.futuremedicine.com/doi/suppl/10.2217/fon-2021-1406.

Repression of Human Papillomavirus Oncogene Expression under Hypoxia Is Mediated by PI3K/mTORC2/AKT Signaling.

Hypoxia is linked to therapeutic resistance and poor clinical prognosis for many tumor entities, including human papillomavirus (HPV)-positive cancers. Notably, HPV-positive cancer cells can induce a dormant state under hypoxia, characterized by a reversible growth arrest and strong repression of viral E6/E7 oncogene expression, which could contribute to therapy resistance, immune evasion and tumor recurrence. The present work aimed to gain mechanistic insights into the pathway(s) underlying HPV oncogene repression under hypoxia. We show that E6/E7 downregulation is mediated by hypoxia-induced stimulation of AKT signaling. Ablating AKT function in hypoxic HPV-positive cancer cells by using chemical inhibitors efficiently counteracts E6/E7 repression. Isoform-specific activation or downregulation of AKT1 and AKT2 reveals that both AKT isoforms contribute to hypoxic E6/E7 repression and act in a functionally redundant manner. Hypoxic AKT activation and consecutive E6/E7 repression is dependent on the activities of the canonical upstream AKT regulators phosphoinositide 3-kinase (PI3K) and mechanistic target of rapamycin (mTOR) complex 2 (mTORC2). Hypoxic downregulation of E6/E7 occurs, at least in part, at the transcriptional level. Modulation of E6/E7 expression by the PI3K/mTORC2/AKT cascade is hypoxia specific and not observed in normoxic HPV-positive cancer cells. Quantitative proteome analyses identify additional factors as candidates to be involved in hypoxia-induced activation of the PI3K/mTORC2/AKT signaling cascade and in the AKT-dependent repression of the E6/E7 oncogenes under hypoxia. Collectively, these data uncover a functional key role of the PI3K/mTORC2/AKT signaling cascade for viral oncogene repression in hypoxic HPV-positive cancer cells and provide new insights into the poorly understood cross talk between oncogenic HPVs and their host cells under hypoxia.IMPORTANCE Oncogenic HPV types are major human carcinogens. Under hypoxia, HPV-positive cancer cells can repress the viral E6/E7 oncogenes and induce a reversible growth arrest. This response could contribute to therapy resistance, immune evasion, and tumor recurrence upon reoxygenation. Here, we uncover evidence that HPV oncogene repression is mediated by hypoxia-induced activation of canonical PI3K/mTORC2/AKT signaling. AKT-dependent downregulation of E6/E7 is only observed under hypoxia and occurs, at least in part, at the transcriptional level. Quantitative proteome analyses identify additional factors as candidates to be involved in AKT-dependent E6/E7 repression and/or hypoxic PI3K/mTORC2/AKT activation. These results connect PI3K/mTORC2/AKT signaling with HPV oncogene regulation, providing new mechanistic insights into the cross talk between oncogenic HPVs and their host cells.

Virus/Host Cell Crosstalk in Hypoxic HPV-Positive Cancer Cells.

Oncogenic types of human papillomaviruses (HPVs) are major human carcinogens. The expression of the viral E6/E7 oncogenes plays a key role for HPV-linked oncogenesis. It recently has been found that low oxygen concentrations ("hypoxia"), as present in sub-regions of HPV-positive cancers, strongly affect the interplay between the HPV oncogenes and their transformed host cell. As a result, a state of dormancy is induced in hypoxic HPV-positive cancer cells, which is characterized by a shutdown of viral oncogene expression and a proliferative arrest that can be reversed by reoxygenation. In this review, these findings are put into the context of the current concepts of both HPV-linked carcinogenesis and of the effects of hypoxia on tumor biology. Moreover, we discuss the consequences for the phenotype of HPV-positive cancer cells as well as for their clinical behavior and response towards established and prospective therapeutic strategies.