PIK3CB and neoplasm: However, it is interesting to note that while the presence of PIK3CA p.E545K and p. H1047R mutations has been shown to increase the sensitivity of tumour cells to dual PI3K/mTOR inhibitors [228], these hotspot mutations were not present in any of the 12 cell lines, indicating that they were not responsible for the increased sensitivity observed in some of the cell lines [227].