Hypoxia as a modulator of cytochromes P450: Overexpression of the cytochromes CYP2S1 and CYP24A1 in human liver cancer cells in hypoxia

Abstract

Low levels of oxygen (hypoxia) have been reported in solid tumours. This hypoxic microenvironment modulates the expression of genes linked to a more aggressive disease. However, it is unclear if the expression of drug‐metabolizing enzymes as cytochromes P450 (CYPs) is affected by hypoxia in cancer. We aimed to define which cytochromes are affected by hypoxia using a liver cancer model in vitro. For this purpose, we assessed whole‐genome expression microarrays of HepG2 liver cancer cell line from free repository databases, looking for gene expression hypoxia‐associated profiles and selected those cytochromes with significant differences. Then, we corroborated their mRNA expression and protein levels by RT‐qPCR and western blot, respectively, as well as immunofluorescence. Based on microarray analysis, we found that the expression of CYP2S1 and CYP24A1 were up‐regulated with at least twice fold change compared with normoxia. The levels of mRNA and protein of CYP2S1 and CYP24A1 were increased significantly in hypoxic conditions (P < .05), and this tendency was also observed by immunofluorescence assays. Our data show that the expression of cytochromes CYP2S1 and CYP24A1 are induced in hypoxia, being the first time that CYP24A1 expression is associated with tumour hypoxia; which might have consequences in cancer progression and drug resistance. Significance of the study Hypoxia is among the most important factors for cellular adaptation to stress. Especially in cancer, a major public health issue, hypoxia plays a substantial role in angiogenesis, metastasis and resistance to therapy. Tumoral hypoxia has been described at least in the brain, breast, cervical, liver, renal, lung, pancreatic and renal cancer. However, the understanding of how hypoxia drives cancer progression is still a major challenge. One emerging question is the role of hypoxia over the expression of drug‐metabolizing enzymes, with a significant impact on drug treatment. In this context, our paper focus on the effect of hypoxia on CYPs, which is an essential group of drug‐metabolizing enzymes. We show that hypoxia induces the expression of two members of the CYPs family: CYP2S1 and CYP24A1. Importantly, CYP2S1 is a major metabolizer of carcinogenic substances being relevant that hypoxia could promote this function. Interestingly, CYP24A1 limits the action of the active form of vitamin D, which is an anti‐proliferative factor in cancer. Our evidence shows for the first time that hypoxia can induce CYP24A1 expression, with a potential effect on cancer progression. Our contribution clarifies a particular effect of tumoral hypoxia and the implications will be useful in the understanding of the progression of cancer, the resistance to treatment and the development of alternative therapies.

Circular RNA circ_0023404 serves as a miR‐636 sponge to promote malignant behaviors in cervical cancer cells through upregulation of CYP2S1

“…It has been reported that CYP2S1 serve as a carcinogenic factor in diverse cancer, such as thyroid cancer and liver cancer 21,22 . In this study, RT‐qPCR assay and western blot assay discovered that the upregulation of CYP2S1 in cervical tumor tissues and cells when compared with their respective controls (Figure 6A–D).…”

Vitamin D and Hypoxia: Points of Interplay in Cancer

“…Although these data indicate the great prospect of calcitriol as an anticancer agent, there are mainly two limiting factors that hinder its broader use: (i) its side effects when calcitriol is administered in high doses (oral calcitriol dose ranging from 0.5–2.5 μg/kg daily with a maximum tolerated dose being 1.5 μg or 2.5 μg depending on the study) [ 208 ], and (ii) the decreased availability of calcitriol due to its enzymatic deactivation by the calcitriol-induced CYP24A1 gene [ 32 ]. Concerning the latter, hypoxia induces CYP24A1 levels [ 20 , 209 ] and, at the same time, it was found that in breast cancers, CYP27B1 levels drop while CYP24A1 levels rise [ 210 ]. Moreover, tissue hypoxia (though not in cancer tissues) caused a drop in VDR, vitamin D binding protein (VDBP), and 25-hydroxylase (CYP2R1) levels while it increased CYP27B1 and CYP24A1 levels [ 211 ].…”

Efecto de la hipoxia sobre la expresión del citocromo P450 CYP2S1 en células de cáncer de hígado

“…Li et al, 2020). Existen algunos otros mecanismos además de la vía de señalización del AhR, que pudieran regular la expresión de CYP2S1, uno de ellos es la hipoxia que forma parte del microambiente de varios tumores (Cabrera-Cano et al, 2021;Rivera et al, 2007).…”

“…En tumores sólidos la hipoxia está relacionada con la resistencia a fármacos, la malignidad y progresión tumoral además de un mal pronóstico (Höckel & Vaupel, 2001;Samanta & Semenza, 2018;Semenza, 2008;Valencia-Cervantes et al, 2019). Los procesos antes mencionados podrían estar relacionados con la sobreexpresión del CYP2S1, ya que la hipoxia estimula la expresión de CYP2S1 (Cabrera-Cano et al, 2021;Rivera et al, 2007) Figura 8. Mecanismo de activación de HIF1-α.…”

“…Describieron que el gen de CYP2S1 en estas células tiene elementos de respuesta a hipoxia y observaron un efecto similar en células HepG2 sometidas a hipoxia (Rivera et al, 2007). En nuestro grupo de trabajo recientemente reportamos que en células HepG2, la hipoxia induce un aumento en la expresión del ARNm de CYP2S1 (Figura 9-A) y de la proteína también (Figura 9-B) (Cabrera-Cano et al, 2021).…”