c-Jun NH2-terminal kinase-mediated activation of interleukin-1beta converting enzyme/CED-3-like protease during anticancer drug-induced apoptosis.

Upon treatment with various anticancer drugs, myeloid leukemia U937 cells undergo apoptosis. In this study, we found that either etoposide (VP-16) or camptothecin (CPT) activated c-Jun N-terminal kinase 1/stress-activated protein kinase (JNK1/SAPK), transient c-jun expression, and ICE (interleukin-1beta converting enzyme)/CED-3-like proteases in U937 cells. Phorbol ester-resistant U937 variant, UT16 cells, displayed a decreased susceptibility to apoptosis induced by these drugs. The drugs did not cause JNK1 activation, c-jun expression, nor activation of ICE/CED-3-like proteases in UT16 cells. As reported previously, benzyloxycarbonyl-Asp-CH2OC(O)-2,6-dichlorobenzene (Z-Asp), a preferential inhibitor of ICE/CED-3-like proteases, blocked the apoptosis of U937 cells. Interestingly, however, Z-Asp did not inhibit JNK1 activation in either VP-16- or CPT-treated U937 cells. The JNK1 antisense oligonucleotides diminished protein expression of JNK1 and inhibited drug-induced apoptosis of U937 cells, whereas sense control oligonucleotides did not. Consistent with this observation, the antisense oligonucleotide-treated cells did not respond to VP-16 or CPT with Z-Asp-sensitive proteases. These results indicate that JNK1 triggers the DNA damaging drug-induced apoptosis of U937 cells by activating Z-Asp-sensitive ICE/CED-3-like proteases.

Phorbol ester-resistant monoblastoid leukemia cells with a functional mitogen-activated protein kinase cascade but without responsive protein tyrosine phosphatases.

Human monoblastoid leukemia U937 cells differentiate to monocyte/macrophage upon treatment with phorbol ester, 12-o-tetradecanoylphorbol-13-acetate (TPA). Previous studies, including our own, have demonstrated that drug-induced differentiation of leukemia cells is associated with genetic and enzymatic activations of protein tyrosine phosphatases (PTPases). In this study, to further investigate a relationship between PTPase activation and leukemic differentiation, we established TPA-resistant U937 variant UT16 cells. Unlike known TPA-resistant cells whose resistance is mainly due to lack or down modulation of protein kinase C (PKC), UT16 cells showed TPA-induced activation of PKC, Raf-1, and ERK/MAP kinases similar to the parental U937 cells. Interestingly, however, UT16 cells exhibited altered binding activity of AP-1 complexes, decreased ability to induce c-jun and c-fos gene expressions, and failure to differentiate to a monocytic lineage. Based on these observations, UT16 cells could be considered a novel type of TPA-resistant cell. Among UT16 cells, most of TPA-inducible PTPase genes, PTP-1C, PTP-MEG2, P19-PTP, HPTP epsilon, and PTP-U1, did not respond to TPA. Consistently, TPA increased PTPase enzymatic activity in U937 but not in UT16 cells. Taken together, activation of PTPases is well correlated with TPA-induced differentiation of U937 cells. These findings indicate that gene expression and enzymatic activity of some PTPase isozymes described here are regulated by a TPA-mediated signaling event and are likely to be used as biomarkers for the monocytic differentiation of myeloid leukemia cells.

[Immunohistochemical studies of the acne-like inflammatory model].

The acne-like inflammatory model was produced in the ears of male Sprague-Dawley rats by subcutaneous injection of 140 micrograms of heat killed Propionibacterium acnes (P. acnes). Ear thickness was measured as an index of inflammatory strength, using a micro indicator once every day for the first week, then every other day until the 35th day. Animals were sacrificed and ears were excised for histological study. The tissue was stained with Hematoxylin and Eosin to investigate the state of inflammation. At the same time, P. acnes was stained specifically by enzyme labelled antibody to study the localization of the injected bacteria body. When thickness of rat ears was measured, more than a doubling of control ear was observed with maximum swelling on the second day. The ear thickness decreased to 1.5 times control levels at 5th day, then remained with no change for 35 days. Histological study revealed remarkable inflammatory infiltration of lymphocytes and neutrophils at the swelling site. Polynucleocyte was major infiltrated cells until 24 hours, and then mononucleocyte was principal after 24 hours. In the tissue excised at 6 hours after injection, a temporary characteristic infiltration of eosinophils was observed. When the tissue at 35th day was stained by enzyme labelled antibody, it revealed that the antigen of P. acnes existed among the cells at the site of infiltration and in mononucleocytes. This inflammatory model is considered to be a valuable experimental animal model for acne vulagaris with granulomatous inflammation.