Lease exit strategy

This is my 37th year in the lighting business in Salt Lake City. The economy has taken it's toll. I am in a commercial complex, and my rent went up $1200.00 a year as of December 1st '08. We are directly tied to the construction industry, which died last summer. With little new construction we are primarily entertaining walk in customers only, which does not give us the cash flow to stay current with our landlord or vendors. Last year our landlord allowed another lighting company to open in our same building, 2 doors away. With gas at $4.20 a gallon, customers could stop at one location and shop 2 lighting stores. I told our landlord I would renew our lease for another 3 years. When he came back with the paperwork, he filled it out for a 5 year lease. I felt intimidated, but signed it anyway. I am now 2-1/2 years into a 5 year lease. My main question is:
If I can sell this business would I be able to break my commercial lease? If I cannot sell it and have to close my business, does that vacate the balance of the years left on my lease if I have to close.

Thank You, Gary