What human cancer cell lines express p-glycoprotein which can be
detected with western/immunoblot analysis?
Do sw 480 and 620 cells express p-glycoprotein which can be detected
with western/immunoblot analysis?

Hving had a look at Pub med I've found the following info which may help.

Firstly from the asbtract "Cancer Res. 1992 Apr 1;52(7):1886-90.
Biochemical characterization of resistance to mitoxantrone and
adriamycin in Caco-2 human colon adenocarcinoma cells: a possible role
for glutathione S-transferases.
Peters WH, Roelofs HM." it appears that the two cell lines you have
mentioned do express PgP (170Kda) but that higher expression is noted
in CACO2 (another colorectal cell line).

Three other cell lines I found which express PgP are HK2 (human
proximal tubular cells) within which PgP expression can be induced
(ref :Effects of grapefruit juice on the multidrug transporter
P-glycoprotein in the human proximal tubular cell line HK-2.
Romiti N, Tramonti G, Donati A, Chieli E.
Life Sci. 2004 Dec 3;76(3):293-302) and the L-MDR1, P388/dx cell lines
(ref :In vitro and ex vivo evidence for modulation of P-glycoprotein
activity by progestins.
Frohlich M, Albermann N, Sauer A, Walter-Sack I, Haefeli WE, Weiss J.
Biochem Pharmacol. 2004 Dec 15;68(12):2409-2416)  these overexpress PgP.