Targeting KRAS in metastatic colorectal cancer: current strategies and emerging opportunities

Abstract

Developing drugs that target KRAS, the most frequently mutated oncogene in cancer, has not been successful despite much concerted efforts dedicated towards it in the last thirty years. Considering the key role this driver oncogene plays, the pharmacological drugging of KRAS remains a key challenge for cancer research. In this review, we highlight the emerging experimental strategies for blocking KRAS function and signaling and its direct targeting. We also report on the results in this field of research produced by our group.

Fig. 1

Direct targeting of KRAS. ASOs: Antisense Oligonucleotides; GAP: GTP-ase Activating Proteins; GEF: Guanine Nucleotide Exchange Factor; G4: G-quadruplex; RTKs: Receptor Tyrosine Kinases

Fig. 2

EMICORON downregulates KRAS expression. a HCT116 colon cancer cells were treated with EMICORON at doses of 0.5 and 1 μM for 6, 12, 24 h. The DNA extracted was amplified by PCR. The histogram shows the relative optical density of KRAS. Histograms show the mean values ± SD. A representative picture of PCR products is shown. Densitometry was performed with ImageJ software version 1.40. b KRAS protein levels were detected by Western blotting. The total cell extracts of HCT116 cells treated with EMICORON 1 μM for 24 h, were prepared and immunoblotting was conducted by antibodies against KRAS (Santa Cruz) or Actin (Santa Cruz)

Fig. 3

EMICORON has antitumoral activity against CRC KRAS-mutated PDXs. PDXs were obtained by the implant in mice of tumor fragments from three CRC patients at IRCCS Regina Elena National Cancer Institute (Rome, Italy). Briefly, surgical specimens, not required for histopathologic analysis, were placed in medium supplemented with antibiotics, diced into 15–20 mm³ pieces, coated in Matrigel and implanted in NOD.SCID mice by a small incision and subcutaneous pocket made in one side of the lower back [50]. After mass formation in mice (Passage 0), tumors were passed in four mice (Passage 1) and afterwards expanded in further mice for the drug experimentation (Passage 2). When tumors reached a mass of 250–300 mm³, EMICORON was administered per os at 15 mg/kg for seven days. Tumor growth was followed by caliper measurements. The tumor weight in untreated or EMICORON-treated mice was reported at the nadir of the effect. PDX 1 experiment included six untreated and six EMICORON-treated mice; PDX 2 experiment included two untreated and four EMICORON-treated mice; PDX 3 experiment included two untreated and four EMICORON-treated mice. The use of human specimens was approved by the Ethics Committee of the IRCCS Regina Elena National Cancer Institute (N. 823/2016) and animal procedures were in compliance with the national and international directives (D.L. March 4, 2014, no. 26; directive 2010/63/EU of the European Parliament and of the council) and were approved by the Ethics Committee of the IRCCS Regina Elena National Cancer Institute (N. 823/2016) and by the Italian Ministry of Health (N. 183/2017-PR)