Semmelweis Egyetem, I. Patológiai és Kísérleti Rákkutató Intézet, Budapest
In most cases, the targeted therapy is able to produce clinical response, but after a certain interval it turns to be ineffective due to secondary resistance against the therapy. One of the most demanding challenge in treatment of cancer is to prevent or inhibit such resistance, which could have several forms, e.g. appearance of new driver activating mutations in the treated tumor, clon(s) existed in minority with different mutations (targets) can grow and replace the temporarely sensitive tumor cells (on the basis of tumor heterogeneity); another pathway takes over the role in cancer progression, etc.
Such problems are very common in the RAS-RAF-MEK-ERK pathway. These are very important proteins to collect extracellular signals in order to regular different cell functions, especially proliferation. With activating mutations make the RAS-pathway independent from the normal .regulation. To inhibit the consequence of the mutations is largely still an unsolved problem, with few exceptions (e.g. inhibition of BRAF mutations). Theoretically, the inhibition of the next steps of the pathway, MEK and ERK, may stop the pathologically activated signals, partly due to their inhibition, and party to effi ciently decrease the feedback inside the pathway. This review discusses aspects of this possibilities, especially to overcome resistance and prolong the effectiveness of therapy.