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The APOBEC cytidine deaminase enzyme family is linked to mutational signatures identified in cancer. While previous work has provided insights into the role of APOBEC3A and APOBEC3B in mutational processes in cancer, understanding of the mutational signatures induced by other APOBEC family members is limited. In this issue of Cancer Research, Liu and colleagues investigated the role of APOBEC3G (A3G) in bladder cancer. The authors revealed that transgenic expression of A3G in a murine bladder cancer model promotes tumorigenesis and induces a unique mutational signature distinct from previously identified APOBEC signatures. Expression of this A3G-related mutational signature correlated with significantly worse survival in patients with urothelial bladder carcinoma, and A3G expression was identified in 21 different cancer types. These findings suggest that different APOBEC3 enzymes induce unique mutation signatures and play distinct roles in cancer evolution. More complete understanding of the function of each APOBEC3 enzyme will improve anticancer therapy.See related article by Liu et al., p. 506

Environmental carcinogenic exposures are major contributors to global disease burden yet how they promote cancer is unclear. Over 70 years ago, the concept of tumour promoting agents driving latent clones to expand was first proposed. In support of this model, recent evidence suggests that human tissue contains a patchwork of mutant clones, some of which harbour oncogenic mutations, and many environmental carcinogens lack a clear mutational signature. We hypothesised that the environmental carcinogen

Introduction: Increasing our understanding of drivers of mutagenesis in lung cancer is critical in our efforts to prevent tumor reoccurrence and resistance. Results: Using the multi-region TRACERx lung cancer study, we uncovered that APOBEC3B is significantly upregulated when compared with other APOBEC family members in EGFR driven lung cancer and identified subclonal enrichment of APOBEC mutational signatures. To model APOBEC mutagenesis in lung cancer, several novel EGFR mutant mouse models containing a human APOBEC3B transgene were generated. Using these models, it was uncovered that APOBEC3B expression is detrimental at tumor initiation when expressed continuously in a p53 wildtype background. This detrimental effect is likely due to elevated chromosomal instability, which was observed to increase significantly with APOBEC3B expression in an EGFR mutant TP53 deficient mouse model. Induction of subclonal expression of APOBEC3B in an EGFR mutant mouse model with tyrosine kinase inhibitor (TKI) therapy resulted in a significant increase in resistant tumor development. Significant downregulation of the base excision repair gene uracil-DNA glycosylase (UNG) was also observed in APOBEC3B expressing mice, which paralleled findings in patient tumors and cell lines treated with TKI therapy. Finally, a mouse mutational signature was identified in APOBEC3B expressing cell lines, reinforcing the idea that APOBEC driven mutagenesis contributes to TKI resistance. Conclusion: This study demonstrates a unique principle by which targeted therapy induces changes within tumors ideal for APOBEC driven tumor evolution, fueling therapy resistance. Citation Format: Manasi Mayekar, Deborah Caswell, Natalie Vokes, Emily K. Law, Wei Wu, William Hill, Eva Gronroos, Andrew Rowan, Maise Al Bakir, Clare Weeden, Caroline E. McCoach, Collin M. Blakely, Nuri Alpay Temiz, Ai Nagano, Daniel L. Kerr, Julia K. Rotow, Oriol Pich, Franziska Haderk, Michelle Dietzen, Carlos Martinez Ruiz, Bruna Almeida, Lauren Cech, Beatrice Gini, Joanna Przewrocka, Chris Moore, Miguel Murillo, Bjorn Bakker, Brandon Rule, Cameron Durfee, Shigeki Nanj, Lisa Tan, Lindsay K. Larson, Prokopios P. Argyris, William L. Brown, Johnny Yu, Carlos Gomez, Philippe Gui, Rachel I. Vogel, Elizabeth A. Yu, Nicholas J. Thomas, Subramanian Venkatesan, Sebastijan Hobor, Su Kit Chew, Nicholas McGranahan, Nnennaya Kanu, Eliezer M. Van Allen, Julian Downward, Reuben S. Harris, Trever Bivona, Charles Swanton. Targeted cancer therapy induces APOBEC fueling the evolution of drug resistance [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 2197.

SummaryDepending on endoplasmic reticulum (ER) stress levels, the ER transmembrane multidomain protein IRE1α promotes either adaptation or apoptosis. Unfolded ER proteins cause IRE1α lumenal domain homo-oligomerization, inducing trans autophosphorylation that further drives homo-oligomerization of its cytosolic kinase/endoribonuclease (RNase) domains to activate mRNA splicing of adaptive XBP1 transcription factor. However, under high/chronic ER stress, IRE1α surpasses an oligomerization threshold that expands RNase substrate repertoire to many ER-localized mRNAs, leading to apoptosis. To modulate these effects, we developed ATP-competitive IRE1α Kinase-Inhibiting RNase Attenuators—KIRAs—that allosterically inhibit IRE1α’s RNase by breaking oligomers. One optimized KIRA, KIRA6, inhibits IRE1α in vivo and promotes cell survival under ER stress. Intravitreally, KIRA6 preserves photoreceptor functional viability in rat models of ER stress-induced retinal degeneration. Systemically, KIRA6 preserves pancreatic β cells, increases insulin, and reduces hyperglycemia in Akita diabetic mice. Thus, IRE1α powerfully controls cell fate but can itself be controlled with small molecules to reduce cell degeneration.

Purpose: Contemporary treatment of abdominal aortic aneurysms (AAA) includes transabdominal (TA), retroperitoneal (RP), and endovascular (EV) repair. This study compares the cost and early (30-day) results of a consecutive series of AAA repair by means of these three methods in a single institution. Methods: A total of 125 consecutive AAA repairs between February 1993 and August 1997 were reviewed. Risk factors, 30-day morbidity and mortality rates, and hospital stay and cost were analyzed according to method of repair (TA, RP, EV). Cost was normalized by means of a conversion factor to maintain confidentiality. Cost analysis includes conversion to TA repair (intent to treat) in the EV group. Results: One hundred twenty-five AAA repairs were performed with the TA (n = 40), RP (n = 24), or EV (n = 61) approach. Risk factors among the groups (age, coronary artery disease, hypertension, diabetes, chronic obstructive pulmonary disease, and cigarette smoking) were not statistically different, and thus the groups were comparable. The average estimated blood loss was significantly lower for EV (300 mL) than for RP (700 mL) and TA (786 mL; P > .05). Statistically significant higher cost for TA and RP for pharmacy and clinical laboratories (likely related to increased length of stay [LOS]) and significantly higher cost for EV in supplies and radiology (significantly reducing cost savings in LOS) were revealed by means of an itemized cost analysis. Operating room cost was similar for EV, TA, and RP. There were six perigraft leaks (9.6%) and six conversions to TA (9.6%) in the EV group. Conclusion: There were no statistically significant differences in mortality rates among TA, RP, and EV. Respiratory failure was significantly more common after TA repair, compared with RP or EV, whereas wound complications were more common after RP. Overall cost was significantly higher for TA repair, with no significant difference in cost between EV and RP. EV repair significantly shortened hospital stay and intensive care unit (ICU) use and had a lower morbidity rate. Cost savings in LOS were significantly reduced in the EV group by the increased cost of supplies and radiology, accounting for a similar cost between EV and RP. Considering the increased resource use preoperatively and during follow-up for EV patients, the difference in cost between TA and EV may be insignificant. EV repair is unlikely to save money for the health care system; its use is likely to be driven by patient and physician preference, in view of a significant decrease in the morbidity rate and length of hospital stay. (J Vasc Surg 1999;30:59-67.)

Hay-Wells Syndrome is a rare genetic disorder characterized by ankyloblepharon, ectodermal dysplasia, and cleft palate. Recalcitrant scalp wounds with secondary infections are common. This case series describes the use of acoustic pressure wound therapy in 3-year-old fraternal twins (male and female) with HWS-associated scalp wounds. Present since infancy, the wounds were severe and extensive at presentation to the authors' wound clinic. Previous management consisted of standard topical treatments, including foam; oxidized, regenerated-cellulose/collagen with silver; calcium alginate; silver sulfadiazine cream; and biologic tissue matrix. Following admission to the authors' wound clinic, acoustic pressure wound therapy was administered one to three times weekly for 3 to 10 minutes for 7 months in addition to standard topical treatments to provide nonsurgical debridement and reduce wound bioburden without inflicting additional pain. Substantial improvements occurred during the first 5 weeks of consistent treatment. When treatments became sporadic due to health and family issues, wound deterioration occurred. After 7 months, wound sizes decreased by 31.3% in the boy and 1.1% in the girl, 70% of the wound surface in both children was covered with granulation tissue, and no clinical signs of infection were evident. The treatments were well tolerated. So far, the twins each received a total of 37 treatments. Consistent, long-term acoustic pressure wound therapy improved the status of severe, recalcitrant, Hay-Wells Syndrome-associated scalp wounds.

Nurses caring for patients undergoing liver transplants were surveyed to identify specific needs and concerns. Previously identified issues in regard to orthotopic liver transplantation also were addressed: high mortality rates, time-consuming care, emotional factors and ethical issues. Nurses need to be represented on selection and ethics committees and to participate in clinical decisions.