Colon cancer is the second leading cause of cancer deaths in the U.S. Polyps, the first stage In tumor development http://www.clevelandclinic.org/registries/inherited/fap.htm

One gene mutated in the progression to malignancy is K-ras Lodish et al. Fig. 24-6

This can be visualized in culture Oncogenes relieve contact inhibition. This can be visualized in culture by “focus formation” Transfect with H-ras Transfect with H-ras (close-up) J Biol Chem 2002 277:10813-23 Fiordalisi et al. J Virol 2000 74:1008-13 Yoshioka et al.

Isolation of the first oncogene Lodish et al. Fig. 24-4

Lipid modification of ras helps target it to the plasma membrane

Farnesyltransferase inhibitors offer a way of reducing ras activity

Farnesyltransferase inhibitors offer a way of reducing ras activity or lonafarnib Phase II trials: Leukemias (esp. AML/CML): Initial results promising (also Advanced Multiple Myeloma) Urothelial tract (with gemcitabine): in progress Pancreatic cancer (with gemcitabine): no improvement Colorectal cancer (with Irinotecan): just beginning Small cell lung cancer (with Taxol): Discontinued.

Ras encodes a GTPase that is active when bound to GTP Lodish et al. Fig. 20-5

Oncogenic Ras is stuck in the GTP-bound state Ras G12V Lodish et al. Fig. 20-5

The activity of Ras is regulated by GEFs and GAPs Lodish et al. Fig. 20-22

Ligand binding activates RTKs by dimerization Lodish et al. Fig. 20-21

The RTK-ras pathway: Part 1 Lodish et al. Fig. 20-23

SH2 domains allow “effector” proteins to bind activated receptors Alberts et al. Fig. 15-49

The RTK-ras pathway: Part 2 Lodish et al. Fig. 20-23

Ras activation triggers a kinase cascade Lodish et al. Fig. 20-28

RTK signaling ultimately leads to activation of a transcription factor Gilbert Fig. 6.14

The eye of a fly: Key to learning how Ras and RTKs work Lodish et al. Fig. 20-24

Did you say flies?

Did you say flies?

This is all I need to know

But wait--flies provided the Key to learning how Ras and RTKs work Lodish et al. Fig. 20-24

Each ommatidium is built by a series of cell-cell interactions

Sevenless is required to specify the R7 photoreceptor Wild-type sevenless mutant Lodish et al. Fig. 20-24

Sevenless encodes an RTK Lodish et al. Fig. 20-25

Looking for other players in the pathway using genetics R7 present sev pathway activity sev threshhold R7 absent wild type sev- sevts sevts sevts; enh*/+ 22.7o C 24.3o C 22.7o C Lecture slides of Gian Garriga, UC Berkeley

A number of genes were found that might function in the RTK pathway

A number of genes were found that might function in the RTK pathway Sos Ras

Ras acts downstream of the RTK Sevenless Lodish et al. Fig. 20-25

The signal transduction pathway should look familiar Alberts et al. Fig. 15-53

Flies were bad enough, but worms!?

Hermaphrodites do it by themselves

Cell ablations demonstrate that a signal From the anchor cell induces the vulva Alberts et al. Fig. 21-41

How can we figure out how to build a vulva?

How can we figure out how to build a vulva? GENETICS! Vul = “bag of worms” Normal vulva” Muv

The first two vul mutations identify the anchor cell signal and its receptor Alberts et al. Fig. 21-44

How can we figure out more about how to build a vulva? MORE GENETICS! Vul = “bag of worms” Normal vulva” Muv

The vul mutations define the RTK-Ras pathway Alberts et al. Fig. 21-44

Parallels in the RTK/ras pathways of humans, flies and worms

The RTK-Ras pathway offers drug targets for cancer treatment e.g., the Raf kinase inhibitor sorafenib (also inhibits the RTKs VEGFR, PDGFR, and Kit) Approved for treatment of advanced renal cell carcinoma (Jan. 2006) Increased survival in Phase III liver cancer trial and approved for inoperable form (Nov. 2007) In clinical trials for melanoma and lung cancer Alberts et al. Fig. 21-44