Metabolic and redox profile of breast tumor and adipose cells in premenopausal women: the relationship with obesity

[A. T. Kalezić]

125 str.

Biologija - Biologija ćelija i tkiva /

Incidenca premenopauzalnog karcinoma dojke i gojaznosti je u porastu, a veza između ovih oboljenja je izrazito kompleksna. Gojaznost pokazuje negativnu korelaciju sa incidencom premenopauzalnog karcinoma dojke, ali pozitivnu korelaciju sa stopom metastaza, terapijske rezistencije i smrtnosti. Metaboličko reprogramiranje i visoka plastičnost redoks homeostaze su fundamentalne karakteristike malignog fenotipa koje omogućavaju adaptivni odgovor na povišene energetske zahteve i selektivne pritiske poreklom iz tumorske mikrosredine. U karcinomu dojke adipociti su ključni konstituent tumorske mikrosredine, a dvosmerna komunikacija između kancerskih ćelija i adipocita doprinosi proliferativnom i invazivnom potencijalu kancerskih ćelija. Uprkos ovakvim nalazima, in vivo molekulski mehanizmi redoks-senzitivnog metaboličkog reprogramiranja su mahom nepoznati. Cilj ove doktorske disertacije bio je da se okarakteriše redoks i metabolički profil tumorskog i masnog tkiva normalno uhranjenih i gojaznih premenopauzalnih žena sa benignim, odnosno malignim tumorom dojke i identifikuju ključni metabolički putevi i transkripcioni faktori uključeni u redoks-senzitivno metaboličko reprogramiranje. Pokazana povećana ekspresija osnovnih enzima antioksidativne odbrane ukazuje da malignitet indukuje uspostavljanje nove redoks homeostaze, paralelno u tumorskom i masnom tkivu. Diferencijalna ekspresija enzima antioksidativne odbrane i master regulatora redoks homeostaze, nukleusnog faktora-eritroid faktor 2-zavisnog faktora 2 (Nrf2), između normalno uhranjenih i gojaznih žena, ukazuje da gojaznost utiče na uspostavljanje nove redoks homeostaze u tkivima dojke. Simultano sa redoks reprogramiranjem, povećana ekspresija AMP-aktivirane protein kinaze (AMPK), enzima glikolize i pentozofosfatnog puta ukazuje na uspostavljanje AMPK-zavisnog Varburgovog efekta. Posledično, metabolizam glukoze u tumorskom tkivu je usmeren ka glikolizi uz produkciju laktata i pentozofosfatnom putu, dok je u masnom tkivu usmeren prevashodno ka pentozofosfatnom putu, ističući tkivno specifičan karakter Varburgovog efekta. U skladu sa Varburgovim efektom, smanjena ekspresija enzima oksidativne dekarboksilacije piruvata i Krebsovog ciklusa, a povećana ekspresija enzima oksidativne fosforilacije ukazuju da se metabolizam mitohondrija u tumorskom tkivu održava zahvaljujući plastičnosti anaplerotskih puteva. Sa druge strane, povećan broj kopija mitohondrijske DNK, kao i povećana proteinska ekspresija enzima oksidativne dekarboksilacije piruvata, Krebsovog ciklusa i oksidativne fosforilacije ukazuju da je indukcija oksidativnog metabolizma u osnovi metaboličkog reprogramiranja masnog tkiva u malignitetu. Markantne razlike u ekspresiji enzima uključenih u mobilizaciju, β-oksidaciju i de novo sintezu masnih kiselina između normalno uhranjenih i gojaznih premenopauzalnih žena ukazuju da gojaznost utiče na smer metaboličkog reprogramiranja u tumorskom i masnom tkivu dojke. Rezultati ove doktorske disertacije su pokazali da u procesu neoplastične transformacije tumorsko i masno tkivo dojke čine kompleksan pseudo-organ u kome dolazi do uspostavljanja specifičnih redoks i metaboličkih profila u zavisnosti od sistemskih i lokalnih uticaja gojaznosti na tumorsku mikrosredinu u kojoj se razvija karcinom dojke.

The incidence of premenopausal breast cancer and obesity is rising, while accumulating evidence shows that the relationship between two diseases is highly complex. Obesity shows a negative correlation with the incidence of premenopausal breast cancer but a positive correlation with the rate of metastasis, therapeutic resistance, and mortality. Metabolic reprogramming and high redox homeostasis threshold are fundamental characteristics of the malignant phenotype that enable adaptive responses to increased energy demands and selective pressures imposed by the tumor microenvironment. In breast cancer, adipocytes represent a crucial component of the tumor microenvironment, where two-way communication between cancer cells and adipocytes contributes to cancer cell proliferation and invasion. Despite such findings, in vivo molecular mechanisms of redox-sensitive metabolic reprogramming remain mostly unknown. This doctoral dissertation aimed to characterize the redox and metabolic profile of tumor and adipose tissue of normalweight and obese premenopausal women with benign or malignant breast tumors and identify key metabolic pathways and transcription factors involved in redox-sensitive metabolic reprogramming. Increased expression of main antioxidant defense enzymes was shown, indicating that malignancy contributes to the establishment of new redox homeostasis, both in tumor and adipose tissue. Differential expression of antioxidant defense enzymes and the master regulator of redox hemostasis, the nuclear factor-erythroid factor 2-related factor 2 (Nrf2), between normal-weight and obese women indicates that obesity affects the establishment of new redox homeostasis. Simultaneously with redox reprogramming, increased expression of AMP-activated protein kinase (AMPK), glycolytic, and pentose phosphate pathway enzymes indicates the establishment of an AMPK-dependent Warburg effect. Consequently, glucose metabolism in tumor tissue is directed to glycolysis with lactate production and the pentose phosphate pathway, while in adipose tissue, it is directed primarily to the pentose phosphate pathway, emphasizing the tissue-specific character of the Warburg effect. Consistent with the Warburg effect, decreased expression of pyruvate decarboxylation and Krebs cycle enzymes and increased expression of oxidative phosphorylation enzymes indicate that mitochondrial metabolism in tumor tissue is maintained due to the plasticity of anaplerotic pathways. On the other hand, increased mitochondrial copy number, as well as protein expression of pyruvate decarboxylation, Krebs cycle, and oxidative phosphorylation enzymes indicate that the induction of oxidative metabolism underlies metabolic reprogramming of adipose tissue in malignancy. Striking differences in the expression of enzymes involved in mobilization, β-oxidation, and de novo synthesis of fatty acids between normal-weight and obese premenopausal women indicate that obesity affects the direction of metabolic reprogramming in breast tumor and adipose tissue. This doctoral dissertation showed that in the process of neoplastic transformation, breast tumor and adipose tissue behave as a complex pseudo-organ in which specific redox and metabolic profiles are established, in accordance with the systemic and local influences of obesity on the tumor microenvironment.

premenopauzalni karcinom dojke, masno tkivo, redoks homeostaza, metaboličko reprogramiranje, gojaznost

premenopausal breast cancer, adipose tissue, redox homeostasis, metabolic reprogramming, obesity

576.385.5:618.19-006.6(043.3)

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