Expression of heat shock protein 20 inversely correlated with tumor progression in patients with ovarian cancer.

OBJECTIVE: To investigate a possible correlation between expression levels of heat shock protein 20 (HSP20) and tumor progression in patients with ovarian cancer. MATERIALS AND METHODS: The study included 34 patients with ovarian cancer who were to undergo surgery, seven patients with ovarian carcinoid tumors, and five patients with normal ovaries as a control group. Ovarian tissues were obtained from patients by surgical resection and then analyzed by western blot. RESULTS: Expression levels of HSP20 were inversely correlated with the grade of malignancy. CONCLUSION: The present findings suggest that HSP20 may play a protective role against the progression of ovarian cancer. Thus, HSP20 may represent a new target for the prediction and treatment of ovarian cancer.

Expression of small heat shock-related protein 20 (HSP20) in rat myometrium is markedly decreased during late pregnancy and labour.

The underlying mechanisms regulating uterine contractions during labour are still poorly understood. Heat shock protein 20 (HSP20) is known to be present at high levels in smooth muscle and implicated in muscle relaxation, but HSP20 expression in the myometrium is completely undetermined. Since HSP20 has been implicated in smooth muscle relaxation, we hypothesized that HSP20 would be highly expressed in the rat myometrium during early and mid-pregnancy when the myometrium is relatively quiescent. Northern blot analysis particularly demonstrated that HSP20 mRNA detection was significantly decreased from day (d) 22 of pregnancy to 1-day post-partum (PP) compared with d6 (P < 0.05). HSP20 mRNA detection was also significantly decreased from d22 to d23 of gestation compared with non-pregnant (NP) samples. Immunoblot analysis showed that detection of HSP20 was significantly decreased at d23 compared with d12 and d15 (P < 0.05). HSP20 detection also significantly decreased at PP compared with d15 (P < 0.05). Immunofluorescence analysis demonstrated that after d15, plasma membrane-associated localization of HSP20 decreased markedly in both circular and longitudinal muscle layers. In addition, HSP20 was detectable near cell membranes at much higher levels in the longitudinal muscle layer of progesterone-treated pregnant rats (delayed labour) at all gestational time points examined, compared with controls. Our results demonstrate that HSP20 mRNA and protein are highly expressed during early and mid-pregnancy and then the expression markedly decreases during late pregnancy and labour. The observed patterns of HSP20 expression are consistent with a potential role for HSP20 in facilitating myometrium quiescence during early and mid-pregnancy.

Expression levels of heat shock protein 20 decrease in parallel with tumor progression in patients with hepatocellular carcinoma.

Heat shock protein (HSP) 20, a low-molecular-weight HSP, is constitutively expressed in various tissues, such as smooth muscle, skeletal muscle, and liver. However, the characteristics and function of HSP20 have not been precisely understood. In the present study, we investigated correlations of expression levels of HSP20 in hepatocellular carcinoma (HCC) tissues and the surrounding tissues with clinical and pathologic characteristics in 53 resected HCC specimens. Although HSP20 was detected in all 53 HCC tissues, the expression levels were reduced compared with those in the adjacent non-tumor tissues. The expression levels of HSP20 were inversely correlated with tumor stage by TNM classification (p<0.01), presence of microvascular invasion (p<0.05), and tumor size (p<0.05). Our findings strongly suggest that HSP20 may play a role against the progression of human HCC.

Synthetic peptides of actin-tropomyosin binding region of troponin I and heat shock protein 20 modulate the relaxation process of skinned preparations of taenia caeci from guinea pig.

To explore the possible role of the thin filament-linked regulation of cross-bridge cycling in living smooth muscle contraction, we studied the effects of TnIp and HSP20p, a synthetic peptide originating from an actin tropomyosin binding region of rabbit cardiac troponin I (residues 136-147; GKFKRPTLRRVR), and that of human heat shock protein 20 (residues 110-121; GFVAREFHRRYR) on the relaxation of skinned (cell membrane ilized) preparations from guinea pig taenia caeci. An active stress of the skinned preparations, resulting from actin-myosin interaction, rapidly decayed following Ca(2+) removal (relaxation). TnIp accelerated the initial rapid phase and slowed the following slow phase of the relaxation. On the other hand, HSP20p only slowed the whole process of the relaxation. The relaxation time courses were well fitted in a double exponential manner, and the double exponential decay of the stress could be explained as a portion of fast-detaching cross bridges not to dissociate rapidly by Ca(2+) removal, but to transfer to latch bridges dissociating very slowly. Our present results suggested that (i) TnIp and HSP20p accelerated transferring from fast-detaching cross bridges to slow-detaching (latch) bridges, and (ii) TnIp accelerated dissociation of the fast-detaching cross bridges and the latch bridges, while HSP20p slowed dissociation the fast-detaching cross bridges. Since TnIp and HSP20p are thought to bind to actin and tropomyosin, but not to myosin, we concluded that through thin-filament-dependent mechanisms these peptides regulated the formation and/or deformation of latch bridges in smooth muscle. The thin-filament-dependent regulation might physiologically control the stress maintenance and relaxation in smooth muscle cells.