Discriminating metastasised from non-metastasised seminoma based on transcriptional changes in primary tumours using NGS.

BACKGROUND

We aimed to better discriminate (occult) metastasised from non-metastasised seminoma based on transcriptional changes of small RNAs in the primary tumour.

METHODS

Total RNAs including small RNAs were isolated from five testicular tumours of each, lymphogenic, occult and non-metastasised patients. Next-generation sequencing (SOLID, Life Technologies) was used to examine transcriptional changes. Small RNAs showing ⩾50 reads and a significant ⩾2-fold difference using non-metastasised tumours as the reference group were examined in univariate logistic regression analysis and combinations of two small RNAs were further examined using support vector machines.

RESULTS

On average, 1.3 × 10(7), 1.4 × 10(7) and 1.7 × 10(7) small RNA reads were detectable in non-metastasised, occult and lymphogenic metastasised seminoma, respectively, of which 30-32% remained after trimming. Between 59 and 68% represented annotated reads and between 8.6 and 11% were annotated small RNA tags. Of them, 137 small RNAs showed>50 reads and a two-fold difference to the reference. In univariate analysis, 32-38 small RNAs significantly discriminated lymphogenic/occult from non-metastasised seminoma, and among these different comparisons, it were the same small RNAs in 51-88%. Many combinations of two of these small RNAs allowed a complete discrimination of metastasised from non-metastasised seminoma irrespective of the metastasis subtype.

CONCLUSIONS

Metastasised and non-metastasised seminoma can be completely discriminated with a combination of two small RNAs.