Lance Armstrong stepped down as chairman of his Livestrong cancer-fighting charity today. As if that is not a big enough blow to the famed cyclist, we have also learned that his largest sponsor, Nike, has cut all ties with the athlete due to allegations that Armstrong used performance-enhancing drugs.

Armstrong announced his severance from Livestrong this morning. Immediately after, Nike made its own announcement: “due to the seemingly insurmountable evidence that Lance Armstrong participated in doping and misled Nike for more than a decade, it is with great sadness that we have terminated our contract with him.”

Last week, the U.S. Anti-Doping Agency released a detailed report setting forth allegations of widespread doping by Armstrong when he won the Tour de France seven consecutive times from 1999 to 2005.

Armstrong who denies the doping allegations said today, “This organization, its mission and its supporters are incredibly dear to my heart. Today therefore, to spare the foundation any negative effects as a result of controversy surrounding my cycling career, I will conclude my chairmanship.”

Armstrong who survived testicular cancer himself added, “As my cancer treatment was drawing to an end, I created a foundation to serve people affected by cancer. It has been a great privilege to help grow it from a dream into an organization that today has served 2.5 million people and helped spur a cultural shift in how the world views cancer survivors.”

Armstrong who will remain on the board vows: “My family and I have devoted our lives to the work of the foundation and that will not change. We plan to continue our service to the foundation and the cancer community. We will remain active advocates for cancer survivors and engaged supporters of the fight against cancer.”