In Vivo Validation of PAPSS1 (3'-phosphoadenosine 5'-phosphosulfate synthase 1) as a Cisplatin-Sensitizing Therapeutic Target

Introduction: Our previous screening efforts found that inhibition of PAPSS1 increases the potency of DNA damaging agents in non-small cell lung cancer (NSCLC) cell lines. Here, we explored the clinical relevance of PAPSS1 and further investigated it as a therapeutic target in pre-clinical model systems. Methods: PAPSS1 expression and cisplatin IC₅₀ values were assessed in 52 lung adenocarcinoma (LAC) cell lines. Effects of PAPSS1 inhibition on A549 cisplatin sensitivity under hypoxic and starvation conditions, in 3D spheroids, as well as in zebrafish and mouse xenografts, were evaluated. Finally, the association between PAPSS1 expression levels and survival in patients treated with standard chemotherapy was assessed. Results: Our results show a positive correlation between low PAPSS1 expression and increased cisplatin sensitivity in LAC. In vitro, the potentiation effect was greatest when A549 cells were serum-starved under hypoxic conditions. When treated with low-dose cisplatin, PAPSS1-deficient A549 spheroids showed a 58% reduction in size compared to control cells. In vivo, PAPSS1 suppression and low-dose cisplatin treatment inhibited proliferation of lung tumor cells in zebrafish xenografts and significantly delayed development of subcutaneous tumors in mice. Clinical data suggest that NSCLC and ovarian cancer patients with low PAPSS1 expression survive longer following platinum-based chemotherapy. Conclusions: These results suggest that PAPSS1 inhibition enhances cisplatin activity in multiple pre-clinical model systems and that low PAPSS1 expression may serve as a biomarker for platin sensitivity in cancer patients. Developing strategies to target PAPSS1 activity in conjunction with platinum-based chemotherapy may offer an approach to improving treatment outcomes.

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