I try what you said but didn't work.
I set DisableUserNameVars=no and SetRemoteUser=yes in web agent configuration.
I got the following headers(No "REMOTE_USER"):
[Host, User-Agent, Accept, Accept-Language, Accept-Encoding, SM_TRANSACTIONID, SM_CLIENT_IP, SM_SDOMAIN, SM_REALM, SM_REALMOID, SM_AUTHTYPE, SM_AUTHREASON, SM_SESSIONDRIFT, SM_AUTHDIROID, SM_AUTHDIRNAME, SM_AUTHDIRSERVER, SM_AUTHDIRNAMESPACE, Cookie, SM_USER, SM_USERDN, SM_SERVERSESSIONID, SM_SERVERSESSIONSPEC, SM_TIMETOEXPIRE, SM_SERVERIDENTITYSPEC, x-forwarded-for, $WSIS, $WSSC, $WSPR, $WSRA, $WSRH, $WSRU, $WSSN, $WSSP, Surrogate-Capability, $WSFO, _WS_HAPRT_WLMVERSION]