Amino Acid-Starved Cancer Cells Utilize Macropinocytosis and Ubiquitin-Proteasome System for Nutrient Acquisition

To grow in nutrient-deprived tumor microenvironment, cancer cells often internalize and degrade extracellular proteins to refuel intracellular amino acids. However, the nutrient acquisition routes reported by previous studies are mainly restricted in autophagy-lysosomal pathway. It remains largely unknown if other protein degradation systems also contribute to the utilization of extracellular nutrients. Herein, it is demonstrated that under amino acid starvation, extracellular protein internalization through macropinocytosis and protein degradation through ubiquitin-proteasome system are activated as a nutrient supply route, sensitizing cancer cells to proteasome inhibition. By inhibiting both macropinocytosis and ubiquitin-proteasome system, an innovative approach to intensify amino acid starvation for cancer therapy is presented. To maximize therapeutic efficacy and minimize systemic side effects, a pH-responsive polymersome nanocarrier is developed to deliver therapeutic agents specifically to tumor tissues. This nanoparticle system provides an approach to exacerbate amino acid starvation for cancer therapy, which represents a promising strategy for cancer treatment.

[Survey on the cognition of the "undetectable equals untransmittable" concept among HIV-infected men who have sex with men receiving antiviral treatment]

Objective: To explore the cognition of the "undetectable equals untransmittable" ("U=U") concept and associated factors among HIV-infected men who have sex with men (MSM) receiving antiviral treatment (ART) in Shenzhen, and provide evidence for designing promotion and advocacy strategies for the "U=U" concept. Methods: We recruited HIV-infected MSM receiving ART using convenient sampling method combined with routine follow-up in Shenzhen through conducting observational survey. The sample size was estimated to be 475. A questionnaire was administered to collect socio-demographic characteristics, sexual behaviors, ART, viral load testing and the cognition towards "U=U" in HIV-infected MSM. Logistic regression was used to access factors associated with acceptance of "U=U". Results: A total of 490 HIV-infected MSM receiving ART were recruited. Of whom, 60.2% (295/490) were aware of "U=U" and 50.6% (248/490) accepted "U=U". Multiple logistic regression showed that participants who had an educational level of college or above (aOR=1.76,95%CI: 1.12-2.75) were more likely to accept "U=U". Those who had no local residency (aOR=0.51,95%CI: 0.29-0.92), had viral load >0 copies/ml in the last testing (aOR=0.61,95%CI: 0.38-0.98) and were unaware of "U=U" (aOR=0.13, 95%CI: 0.09-0.21), were less likely to accept "U=U". Conclusions: HIV-infected MSM receiving ART had a low cognition level of "U=U" in Shenzhen. Promotion and advocacy on this concept through healthcare workers should be enhanced in combination with routine follow-up in order to improve their ART adherence and outcome of treatment. Furthermore, developing related guidelines on "U=U" according to the characteristics of HIV-infected individuals is warranted to improve the normalization of promotion and advocacy on "U=U".