Temozolomide resistance and tumor recurrence are two major complications that glioblastoma patients are faced with. Recent research has found that connexin-43, a gap junction protein highly expressed in glioblastoma tissue compared to normal tissue, confers temozolomide resistance in glioblastoma. Treatment of glioblastoma cells with αCT1, a selective inhibitor of connexin-43, sensitizes them to temozolomide. The Sheng lab also identified PIK3CB, a catalytic subunit of the PI3K complex, as a diagnostic marker for glioblastoma recurrence. Given the fact that connexin-43 activates PI3K and recurrent glioblastoma is temozolomide resistant, it is imperative to investigate whether combined inhibition of connexin-43 and PI3KCB, using αCT1 and TGX-221 respectively, will yield a synergistic effect on temozolomide sensitization.

Glioblastoma cell lines and primary cells were plated in 96-well plates and treated with vehicle (DMSO), TMZ (50 μmol/L), varying concentrations of TGX-221 or αCT1, or a combination of all three drugs. Cell viability was measured using the MTS assay and the optimal dose of the triple combination was determined. U87MG and SF295 cell lines were tested first, followed by primary glioblastoma cell lines VTC-001, VTC-003, VTC-004, VTC-005, VTC-037, and VTC-103. Normal human astrocytes were also tested to make sure there were no off-target effects.