The ability of p53 to induce apoptosis requires its sequence-specific DNA binding activity; however, the transactivation-deficient p53(Gln 22 -Ser 23 ) can still induce apoptosis. Previously, we have shown that the region between residues 23 and 97 in p53 is necessary for such activity. In an effort to more precisely map a domain necessary for apoptosis within the N terminus, we found that deletion of the N-terminal 23 amino acids compromises, but does not abolish, p53 induction of apoptosis. Surprisingly, p53(⌬1-42), which lacks the N-terminal 42 amino acids and the previously defined activation domain, retains the ability to induce apoptosis to an even higher level than wild-type p53. A more extensive deletion, which eliminates the N-terminal 63 amino acids, renders p53 completely inert in mediating apoptosis. In addition, we found that both p53(⌬1-42) and p53(Gln 22 -Ser 23 ) can activate a subset of cellular p53 targets. Furthermore, we showed that residues 53 and 54 are critical for the apoptotic and transcriptional activities of both p53(⌬1-42) and p53(Gln 22 -Ser 23 ). Taken together, these data suggest that within residues 43-63 lie an apoptotic domain as well as another transcriptional activation domain. We therefore postulate that the apoptotic activity in p53(Gln 22 -Ser 23) and p53(⌬1-42) is still transcription-dependent.

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Long non-coding RNAs play critical roles in tumour progression. Through analysis of publicly available genomic datasets, we found that MIR22HG, the host gene of microRNAs miR-22-3p and miR-22-5p, is ranked among the most dysregulated long non-coding RNAs in glioblastoma. The main purpose of this work was to determine the impact of MIR22HG on glioblastoma growth and invasion and to elucidate its mechanistic function. The MIR22HG/miR-22 axis was highly expressed in glioblastoma as well as in glioma stem-like cells compared to normal neural stem cells. In glioblastoma, increased expression of MIR22HG is associated with poor prognosis. Through a number of functional studies, we show that MIR22HG silencing inhibits the Wnt/β-catenin signalling pathway through loss of miR-22-3p and -5p. This leads to attenuated cell proliferation, invasion and in vivo tumour growth. We further show that two genes, SFRP2 and PCDH15, are direct targets of miR-22-3p and -5p and inhibit Wnt signalling in glioblastoma. Finally, based on the 3D structure of the pre-miR-22, we identified a specific small-molecule inhibitor, AC1L6JTK, that inhibits the enzyme Dicer to block processing of pre-miR-22 into mature miR-22. AC1L6JTK treatment caused an inhibition of tumour growth in vivo. Our findings show that MIR22HG is a critical inducer of the Wnt/β-catenin signalling pathway, and that its targeting may represent a novel therapeutic strategy in glioblastoma patients.

TNF antagonists may offer therapeutic potential in solid tumors, but patients who have high serum levels of TNF-a fail to respond to infliximab, suggesting consumption of the circulating antibody and loss of transmembrane TNF-a (tmTNF-a) on tumors by ectodomain shedding. Addressing this possibility, we developed a monoclonal antibody (mAb) that binds both full-length tmTNF-a and its N-terminal truncated fragment on the membrane after tmTNF-a processing but does not cross-react with soluble TNF-a. We documented high levels of tmTNF-a expression in primary breast cancers, lower levels in atypical hyperplasia or hyperplasia, but undetectable levels in normal breast tissue, consistent with the notion that tmTNF-a is a potential therapeutic target. Evaluations in vitro and in vivo further supported this assertion. tmTNF-a mAb triggered antibodydependent cell-mediated cytotoxicity against tmTNF-a-expressing cells but not to tmTNF-a-negative cells. In tumor-bearing mice, tmTNF-a mAb delayed tumor growth, eliciting complete tumor regressions in some mice. Moreover, tmTNF-a mAb inhibited metastasis and expression of CD44v6, a prometastatic molecule. However, the antibody did not activate tmTNF-a-mediated reverse signaling, which facilitates tumor survival and resistance to apoptosis, but instead inhibited NF-kB activation and Bcl-2 expression by decreasing tmTNF-a-positive cells. Overall, our results established that tmTNF-a mAb exerts effective antitumor activities and offers a promising candidate to treat tmTNF-a-positive tumors, particularly in patients that are nonresponders to TNF antagonists. Cancer Res; 73(13); 4061-74. Ó2013 AACR.