Induction of apoptosis by abrogation of HSP70 expression in human oral cancer cells

Abstract

Oral squamous cell carcinoma (SCC) is the most common cancer among males and ranks among 5 common cancers in females in India (Gupta, 1993). The high incidence of oral cancer in the Indian subcontinent is causally associated with the widespread habit of tobacco and betel quid chewing. The etiology of oral SCC in the betel-and tobacco-abused Indian population is considerably different as compared with Western populations. Betel quid chewing induces physical abrasions, which might create a mitogenic environment. In addition, chronic exposure of the oral cavity to the mutagenic constituents of betel quid may cause mutations in cellular genes. Heat shock proteins (HSP) or stress proteins are molecular chaperones that are induced by various environmental and pathophysiological stimuli (Ashburner and Bonner, 1979). Members of the 70-kDa heat shock protein (HSP70) family are involved in the regulation of cell growth and transformation. Cell-cycle-related regulation of HSP70 levels has been shown in mammalian cells, suggesting a role for this protein in the control of mammalian cell growth (Ferris et al., 1988). HSP70 binds to p53 (mutant/wild-type) tumour-suppressor protein and, consequently, regulates p53 accumulation or subcellular localization and modulates its biological effects on cells (Davidoff et al., 1992).We have previously reported that elevation in the levels of p53 and HSP70 proteins are early events in the pathogenicity of human oral cancer (Kaur et al., 1994;Kaur and Ralhan, 1995). Differential expression of HSP70 was observed during oral tumorigenesis. A significant increase in HSP70 levels was observed as the tissues progressed from normal to dysplasia and towards carcinoma (p Ͻ 0.001) (Kaur and Ralhan, 1995). Furthermore, an intriguing feature was the unusual cell-surface localization of HSP70 protein in a subset of oral premalignant and malignant lesions, suggesting that HSP70 protein may be involved in tumour immunity (Kaur et al., 1998a). Furthermore, tumours exhibiting elevated HSP70 levels showed poor prognosis (Kaur et al., 1998b). These clinical results revealed that HSP70 may be implicated in oral tumorigenesis. However, the specific role of HSP70 in the genesis of oral cancer is not known. Hence, the present study was undertaken to determine the functional significance of HSP70 in oral oncogenesis by abrogation of its expression in oral cancer cells using antisense HSP70 oligonucleotides. MATERIAL AND METHODS Synthesis and purification of oligomersThe 15-mer phosphorothiolate oligodeoxynucleotides (antisense, sense and nonsense) were synthesized using an automated model 381 Applied Biosystems (Foster City, CA) oligonucleotide synthesizer and purified by high-pressure liquid chromatography and reverse-phase chromatography. HSP70 antisense oligomer (5Ј-CGCGGCTTTGGCCAT-3Ј) was complementary to the initiation codon and 4 downstream codons of human HSP70 mRNA. The corresponding sense oligomer (5Ј-ATGGCCAAAGCCGCG-3Ј) and nonsense oligomer (5Ј-CGGGTATGCTTCGCC-3Ј) were used as controls (Wei et al., 19...

Dietary low or excess levels of lipids reduced growth performance, and impaired immune function and structure of head kidney, spleen and skin in young grass carp (Ctenopharyngodon idella) under the infection of Aeromonas hydrophila

“…Furthermore, Carratelli et al [36] reported that lipids supplementation could up-regulate the protein levels of 70-kDa heat shock protein (hsp70) in mouse splenic lymphocytes. Studies indicate that up-regulating hsp70 could protect human liver cells from apoptosis [37]. Based on these results, we speculate that lipids may modulate antioxidant enzyme activities, GSH content, Nrf2 and Keap1 signalling molecules and apoptosis in fish immune organs, and the possibility is worthy of investigation.…”

Protein kinase WNK3 increases cell survival in a caspase-3-dependent pathway

“…Interestingly, expression of Hsp70 was reported to protect cells against death stimuli (Jaattela and Wissing, 1993;Mosser et al, 1997;Parcellier et al, 2003). Increased Hsp70 expression in tumours also correlates with evasion from apoptosis (Ciocca et al, 1993;Wei et al, 1995;Jaattela, 1999;Kaur et al, 2000). Hsp70 was further shown to inhibit the activation of procaspase-3, but not the activity of processed caspase-3 (Mosser et al, 1997;Li et al, 2000;Mosser et al, 2000;Saleh et al, 2000).…”

Selective depletion of inducible HSP70 enhances immunogenicity of rat colon cancer cells

“…The balance between immunogenic (Blachere et al, 1997;Udono and Srivastava, 1993) and anti-apoptotic (Beere et al, 2000;Jaattela et al, 1998;Saleh et al, 2000) e ects of this stress protein may account for the contradictory reports assessing a role for HSP70 expression in malignant cell tumorigenicity and immunogenicity (Jaattela, 1995;Kaur and Ralhan, 1995;Ralhan and Kaur, 1995;Seo et al, 1996;Volloch and Sherman, 1999;Wells and Malkovsky, 2000). Limited expression of the protein, below an antiapoptotic level, could contribute to tumor cell immunogenicity when being released from dying cells (Kaur and Ralhan, 2000;Nylandsted et al, 2000).…”