Fig 1.
ACE2 and TMPRSS2 gene expression data for 301 DSMZ human cell lines in the CCLE RNA-seq data set.
A: Expression of ACE2 and TMPRSS2 for selected disease entities. RNA-seq data were normalised and calculated to FPKM values. Gene expression for ACE2 and TMPRSS2 varies between and within the different tumour species. B: Expression of ACE2, TMPRSS2 and NRP1, cell lines sorted to ACE2 expression levels. Top 25 ACE2 expressing cell lines were selected for further studies, plus CALU-3 and two further neuronal cell lines with high NRP1 levels. FPKM—fragments per kilobase million: normalised gene expression data.
Fig 2.
Verified presence of ACE2 and TMPRSS2 in carcinoma cell lines determined by qRT-PCR and western blots.
A: Quantification of ACE2 and TMPRSS2 transcripts in the selected candidate cell lines by qRT-PCR (normalised to CAL-27 and CL-40). B: Western blot analysis was performed to assess the expression of proteins associated with SARS-CoV-2 cell entry.
Fig 3.
Susceptibility of tumour cell lines toward SARS-CoV-2 infection.
Virus titers in the supernatant of infected cell lines at 1–4 days postinfection (dpi) determined by plaque assay for the top 10 ACE2 expressing cell lines (A) and controls (B). The red dotted line indicates the initial inoculum (2000 pfu/ml); the blue dashed line specifies the minimal limit of detection LOD 33.3 pfu/ml. Number of replicates varied between 3–8. pfu: plaque-forming units; mean values with SEM. (C) Predominant productive virus production in highly permissive cell lines seen in the correlation between qRT-PCR measured viral nucleoprotein N mRNA and releasing virions tested by viral plaques. Eight replicates served for the means of the viral titers and one representative expression fold change of two biological replicates qRT-PCR with three technical replicates. Note the logarithmic scaling for both x and y-axis.
Table 1.
Permissive cell line characteristics.
Fig 4.
ACE2 and TMPRSS2 transcript variants for the cell lines.
A: Different exon usage of ACE2 for the top 10 ACE2 expressing cell lines plus CALU-3 (see S2 Fig for the top 25 cells). BFTC-905, CAL-33, CAL-27, M-07e, and MOLM-16 show reduced exon expression from exon 1–9 (blue rectangles). Cell lines are ordered alphabetically. ACE2 is reversely oriented. B: Missense variants in the coding regions of TMPRSS2 (V197M = rs12329760, G6V = rs75603675) for the selected cell lines. No mutations were found in the coding regions of ACE2. 0/1 denotes heterozygous and 1/1 homozygous mutations.