Objective:

To investigate the proteomic changes and arsenic methylation status in human keratinocytes during arsenic-induced skin cancer development.

Approach:

• Arsenic Speciation Analysis: Conducted across primary, hTERT-immortalized, and spontaneously immortalized human keratinocyte cell lines to assess arsenic metabolism and expression of arsenite methyltransferase (AS3MT).
• Longitudinal Proteomic Profiling: Utilized tandem-mass tagging liquid chromatography-tandem mass spectrometry (TMT-LC-MS/MS) to analyze protein expression changes at pre-initiation, initiation, and fully transformed stages of HaCaT cells.
• Functional Enrichment Analysis: Performed pathway analysis to identify dysregulated cellular processes and networks associated with chronic iAsIII exposure, providing biological context from individual protein level data.

Key Findings:

• Chronic exposure to inorganic arsenic leads to significant proteomic alterations in human keratinocytes.
• HaCaT cells do not methylate inorganic arsenic, suggesting direct involvement of iAsIII in malignant transformation.
• Differential protein expression was observed at pre-initiation, initiation, and fully transformed stages of cSCC development.

Interpretation:

The study highlights the importance of understanding the proteomic landscape and arsenic metabolism in the context of skin cancer development due to arsenic exposure.

Limitations:

• Previous studies on proteomics were limited to single time points, hindering comprehensive understanding.
• The relevance of findings in HaCaT cells to other human keratinocytes remains to be fully established.

Conclusion:

Comprehensive longitudinal proteomic profiling is essential to elucidate the molecular mechanisms underlying arsenic-induced skin carcinogenesis.