Cascading proxy with apache

Hello,

I want apache to act as a proxy and to forward requests to another proxy.
Client -> Apache-proxy -> other-proxy -> Server

The problem is that Apache is changing headers and "consider" the
other-proxy as a web server, not a proxy.

I've tried ProxyPass, ReWriteRule and ProxyRemote directives without
success... Things like :
ProxyRemote * http://foo.bar.com:6060
or RewriteRule ^(.+)$ http://foo.bar.com:6060 [P]
or ProxyPass * http://foo.bar.com:6060

Thanks for any help !

Tran.