Sporadic basal cell carcinoma (BCC) is the most common type of malignant cancer in fair-skinned adults. Familial BCCs and a fraction of sporadic BCCs have lost the function of Patched (Ptc), a Sonic hedgehog (Shh) receptor that acts negatively on this signalling pathway. Overexpression of Shh can induce BCCs in mice. Here we show that ectopic expression of the zinc-finger transcription factor Gli1 in the embryonic frog epidermis results in the development of tumours that express endogenous Gli1. We also show that Shh and the Gli genes are normally expressed in hair follicles, and that human sporadic BCCs consistently express Gli1 but not Shh or Gli3. Because Gli1, but not Gli3, acts as a target and mediator of Shh signalling, our results suggest that expression of Gli1 in basal cells induces BCC formation. Moreover, loss of Ptc or overexpression of Shh cannot be the sole causes of Gli1 induction and sporadic BCC formation, as they do not occur consistently. Thus any mutations leading to the expression of Gli1 in basal cells are predicted to induce BCC formation.

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WHEN I BEGAN TO PRACTICE CHEMOSURGERY nearly sixteen years ago, only one out of every five dermatologists and possibly one out of every twenty physicians of the rest of the medical community were aware that that technique of managing cutaneous cancers existed, even though Dr. Frederic Mohs had developed it 25 years earlier. At the time, fewer than 20 physicians, mostly dermatologists and a few general surgeons, were practicing chemosurgery , a mere handful compared to the number practicing it today. Nowadays more than one hundred physicians skilled in the method are members of the American College of Chemosurgery, and chemosurgery is almost a household word in medical circles. The entire dermatologic world and most of the surgical community recognize it as the most effective treatment for basal-and squamous-cell carcinomas.Thirteen years ago I introduced the first one-year comprehensive training program in chemosurgery , an expansion upon the one-and two-week programs that Dr. Mohs had established in Madison, Wisconsin. The program begun at the New York University Medical Center was the first in which qualified physicians could receive extensive training in chemosurgery and general dermatologic surgery. Upon completion of the program, those trained in chemosurgery (17 to date) have since started practices at several leading medical centers throughout the world, and these have multiplied many times the value and availability of this novel and highly effective technique. Eventually, word of it reached physicians of all specialties and has resulted in Dr.