Targeting the Akt/mTOR pathway in Brca1-deficient cancers

The breast cancer susceptibility gene 1 (Brca1) has a key role in both hereditary and sporadic mammary tumorigenesis. However, the reasons why Brca1-deficiency leads to the development of cancer are not clearly understood. Activation of Akt kinase is one of the most common molecular alterations associated with human malignancy. Increased Akt kinase activity has been reported in most breast cancers. We previously found that downregulation of Brca1 expression or mutations of the Brca1 gene activate the Akt oncogenic pathway. To further investigate the role of Brca1/Akt in tumorigenesis, we analyzed Brca1/Akt expression in human breast cancer samples and found that reduced expression of Brca1 was highly correlated with increased phosphorylation of Akt. Consistent with the clinical data, knockdown of Akt1 by short-hairpin RNA inhibited cellular proliferation of Brca1 mutant cells. Importantly, depletion of Akt1 significantly reduced tumor formation induced by Brca1-deficiency in mice. The third generation inhibitor of mammalian target of rapamycin (mTOR), Palomid 529, significantly suppressed Brca1-deficient tumor growth in mice through inhibition of both Akt and mTOR signaling. Our results indicate that activation of Akt is involved in Brca1-deficiency mediated tumorigenesis and that the mTOR pathway can be used as a novel target for treatment of Brca1-deficient cancers.

Combretastatin A4 prodrug study of effect on the growth and the microvasculature of colorectal liver metastases in a murine model

Combretastatin A4P (CA4P) is a prodrug that, in active form, binds to tubulin microtubules of capillary endothelial cells. Studies to date indicate it has significant activity as a specific tumor vascular targeting agent. The goals were to assess the effects of CA4P on tumor growth and microvasculature of colorectal liver metastases in the mouse model, using stereological and histological methods to measure tumor growth, and vascular corrosion casting and laser doppler flowmetry to assess effect on the microvasculature. Continuous s.c. infusion of CA4P produced a major reduction in tumor growth. The percentage of the liver occupied by metastases decreased from 20.55 +/- 13.3% in controls to 7.46 +/- 5.99% in treated animals (P = 0.03). Ultrastructural study of tumor microvasculature after a single dose of CA4P revealed marked effects 1 h after treatment. There was loss of patent microvessels at the normal liver-tumor interface. Central microvascular density was reduced, with constriction and tapering of vessels. CA4P appeared to cause no damage to normal liver tissue or vasculature. Tumor blood flow decreased from 37.6 +/- 13.9% in controls to 24.4 +/- 6.1% in tumors >5 mm in diameter, 1 h after treatment with CA4P (P < 0.03). Quantitative histology of tissue at 6 and 24 h after CA4P treatment showed a significant increase in tumor necrosis (48.7 +/- 21% and 55.5 +/- 19% compared with controls, 20.6 +/- 8%; P = 0.01). Continuous infusion with CA4P causes marked reduction in tumor volume. A single dose of CA4P causes major changes of the tumor microvasculature, reduction of tumor blood flow, and increase in tumor necrosis. CA4P has a potential role in the management of patients with liver metastases.

Relationship of human papillomavirus to Schneiderian papillomas

OBJECTIVES/HYPOTHESIS

To classify a large group of Schneiderian papillomas (SPs) into their histologic subtypes and to determine the incidence of human papillomavirus (HPV) in each subtype.

STUDY DESIGN

Pathologic review and polymerase chain reaction-based (PCR-based) examination of archived tissue.

METHODS

Slides of 114 tumors diagnosed as Schneiderian, inverting, fungiform, or cylindric cell papillomas, or any associated carcinomas, were examined by a head and neck pathologist. Using PCR, consensus primers for the L1 region of HPV were used to determine the presence of HPV in the tumors. This was also performed on normal turbinate control specimens.

RESULTS

Eighty-two (78%) were the inverting subtype, 21 (20%) the fungiform subtype, and 2 (2%) the cylindric cell type. Nine tumors were diagnosed as either verrucous or squamous cell carcinoma. Eighty-eight percent of the tumors had DNA of sufficient quality to be amplified using PCR. Of these, 5 of 69 (6.8%) inverting, 17 of 17 (100%) fungiform, and 0 of 2 cylindric cell papillomas were positive for HPV. One of nine (11.1%) cancers was positive for HPV. No normal turbinate tissue contained HPV. HPV types 6b and 11 accounted for all cases of fungiform papillomas. Of the five HPV-positive inverting papillomas, three had HPV type 11 and two had HPV type 16. The single carcinoma containing HPV contained HPV type 18.

CONCLUSIONS

The histologic subtype of SPs is important, as their etiologies appear to be different. HPV 6b and 11 appear to be involved in all cases of fungiform papillomas but are only rarely involved in cases of inverting or cylindric cell papillomas. HPV 16 may rarely play a role in cases of inverting papillomas, and HPV 16 and 18 may be involved in a subset of cases of carcinomas originating in an inverting papilloma.

Soluble CD16 in the treatment of murine lupus nephritis

To determine if soluble CD16 (sCD16) could alter the expression of lupus-like disease, groups of 10 female NZB/NZW mice (age 16-20 weeks) were given sCD16 three times a week for 5 weeks (control; 100 microg; 200 microg/dose) after onset of proteinuria. Results of this study indicate that the administration of sCD16 after onset of disease lowered anti-DNA levels, delayed the development of proteinuria, and significantly prolonged survival while the mice were on treatment. These results indicate that sCD16 alters the expression of autoantibodies and the progression of renal disease in NZB/NZW mice, suggesting that therapies directed at Fc receptors may be useful in the treatment of SLE.

Lipopolysaccharide (LPS) neutralizing peptides reveal a lipid A binding site of LPS binding protein

Endotoxic shock follows a cascade of events initiated by release of lipopolysaccharide during infection with Gram-negative organisms. Two overlapping 15-mer peptides were identified, corresponding to residues 91-108 of human lipopolysaccharide binding protein that specifically bound the lipid A moiety of lipopolysaccharide with high affinity. The peptides inhibited binding of lipopolysaccharide to lipopolysaccharide binding protein, inhibited the chromogenic Limulus amebocyte lysate reaction, and blocked release of tumor necrosis factor alpha following lipopolysaccharide challenge both in vitro and in vivo. These results suggest lipopolysaccharide binding protein residues 91-108 form at least part of the lipopolysaccharide binding site. Moreover, derivatives of lipopolysaccharide binding protein residues 91-108 might modulate lipopolysaccharide toxicity in the clinical setting.

Cytokines regulating human B cell growth and differentiation

Utilizing a model system of anti-CD3-stimulated T cells, we have identified a potent B cell differentiation factor (BCDF) in the supernatant of these cells. This factor, 446-BCDF, appears to act on SAC-activated B cells inducing a 10- to 100-fold increase in Ig secretion. 446-BCDF has an apparent MW of 32 kDa and a pI of 6.0. Its activity cannot be inhibited by an anti-IL-6 antiserum, and activity is enhanced after passage over an anti-IL-6 affinity column. 446-BCDF activity is detected in the 50 mM salt fraction eluted from a Mono Q column. This 50 mM fraction has the only activity detected after passage over an anti-IL-6 affinity column and migrates with an apparent pI of 6.0. Taken together these data suggest that 446-BCDF is a unique potent polyclonal human BCDF which may be a predominant factor regulating terminal B cell differentiation.

Correction of ulnar drift during silastic metacarpo-phalangeal joint arthroplasty

In previous published accounts of silastic replacement arthroplasty of the M.P. joint of the finger in rheumatoid disease, dynamic splintage has been used for up to six months after operation to ensure correction of ulnar drift. We have investigated two methods of surgical correction in a prospective trial in consecutive patients. No dynamic splintage was used. Both resulted in correction of ulnar drift from an average of 34 degrees (maximum 92 degrees) to 8 degrees (maximum 32 degrees) in 86 fingers. The two methods both corrected ulnar drift well, but crossed intrinsic transfer gave a better range of active movement and is recommended as an alternative to dynamic splintage.

Characterization of lymphokines mediating B cell growth and differentiation from monoclonal anti-CD3 antibody-stimulated T cells

Addition of anti-CD3 mAb 147 (IgG1), 446 (IgG1), or 454 (IgG2a) to cultures of T plus non-T cells can result in both B cell growth and differentiation. To determine whether lymphokines mediating these activities were similar to those described from conventional mitogen-induced T cell activation, normal peripheral blood T cells were stimulated with anti-CD3 mAb for 48 h. The supernatants were assayed for factors inducing B cell growth or differentiation (BCDF). A marked increase in Ig secretion was observed when either EBV-transformed B cell lines or normal B cells, pre-activated with Staphylococcus aureus Cowan I strain, were cultured in the presence of mAb 446 (anti-CD3) stimulated T cell supernatant whereas no significant increase in Ig secretion was noted with either mAb 454- or 147-induced T cell supernatant despite equivalent T cell proliferative responses to these antibodies. In contrast, IL-2 secretion was detectable in T cell supernatants from T cells stimulated with either mAb 454 or 147 but not 446. Factors promoting B cell proliferation were detected in all antibody-stimulated T cell supernatants but, contrary to BCDF, appear to act only on non-activated B cells. To determine whether these effector activities were due to distinct lymphokines, supernatants were pooled and concentrated by ammonium sulfate precipitation. Superose 12 permeation chromatography revealed BCDF activity with an apparent Mr of approximately 30,000 Da. The growth factor activity eluted over a wider and higher molecular weight range which overlapped the differentiation factor activity. Fractions containing BCDF activity were pooled, dialyzed, applied to a Mono Q anion-exchange column, and eluted with a linear NaCl gradient. The growth factor activity came off in a single-peak while BCDF was found divided into two major areas. The growth factor eluted at an ionic strength between the two BCDF activities. BCDF has an apparent isoelectric point (pI) of 6, in contrast to the reported pI 5 for IL-6 and more acidic than the documented basic pI of IFN-gamma. Lastly, peaks with BCDF activity were not active in assays for either IL-2 or IL-4. In addition, a rabbit anti-IL-6 heteroantiserum failed to inhibit the pI 6 BCDF, suggesting non-identity between IL-6 and anti-CD3 induced BCDF. Thus, anti-CD3 activated T cells generate both growth factor activity and BCDF as separate molecular entities distinct from IFN-gamma, IL-2, IL-4, and conventional IL-6.

Endotoxemia elicits increased circulating beta 2-IFN/IL-6 in man

beta 2-IFN/hepatocyte stimulating factor/IL-6 is a cytokine secreted by monocytes, fibroblasts, and endothelial cells in cell culture that possesses diverse biologic activity including the stimulation of acute phase plasma protein synthesis and immunomodulation. The circulating levels of this cytokine in man in response to bacterial LPS (endotoxin) were studied. A single i.v. bolus of endotoxin (20 U/kg) produced a monophasic rise in circulating immunoreactive IFN-beta 2/IL-6 and IFN-beta 2/IL-6 bioactivity (hepatocyte stimulation and B cell differentiation assays) peaking 2 to 4 h after the endotoxin challenge. Peak IFN-beta 2/IL-6 levels ranged from 4.1 to 27.5 ng/ml. Associated with this was a rise in circulating C-reactive protein levels detected 20 h after the endotoxin bolus. Thus, IFN-beta 2/IL-6 is likely one of the endogenous mediators which is triggered in man during bacterial infection and likely participates in the metabolic and immune responses of the infected host.

Endotoxemia elicits increased circulating beta 2-IFN/IL-6 in man

beta 2-IFN/hepatocyte stimulating factor/IL-6 is a cytokine secreted by monocytes, fibroblasts, and endothelial cells in cell culture that possesses diverse biologic activity including the stimulation of acute phase plasma protein synthesis and immunomodulation. The circulating levels of this cytokine in man in response to bacterial LPS (endotoxin) were studied. A single i.v. bolus of endotoxin (20 U/kg) produced a monophasic rise in circulating immunoreactive IFN-beta 2/IL-6 and IFN-beta 2/IL-6 bioactivity (hepatocyte stimulation and B cell differentiation assays) peaking 2 to 4 h after the endotoxin challenge. Peak IFN-beta 2/IL-6 levels ranged from 4.1 to 27.5 ng/ml. Associated with this was a rise in circulating C-reactive protein levels detected 20 h after the endotoxin bolus. Thus, IFN-beta 2/IL-6 is likely one of the endogenous mediators which is triggered in man during bacterial infection and likely participates in the metabolic and immune responses of the infected host.

Characterization of lymphokines mediating B cell growth and differentiation from monoclonal anti-CD3 antibody-stimulated T cells

Addition of anti-CD3 mAb 147 (IgG1), 446 (IgG1), or 454 (IgG2a) to cultures of T plus non-T cells can result in both B cell growth and differentiation. To determine whether lymphokines mediating these activities were similar to those described from conventional mitogen-induced T cell activation, normal peripheral blood T cells were stimulated with anti-CD3 mAb for 48 h. The supernatants were assayed for factors inducing B cell growth or differentiation (BCDF). A marked increase in Ig secretion was observed when either EBV-transformed B cell lines or normal B cells, pre-activated with Staphylococcus aureus Cowan I strain, were cultured in the presence of mAb 446 (anti-CD3) stimulated T cell supernatant whereas no significant increase in Ig secretion was noted with either mAb 454- or 147-induced T cell supernatant despite equivalent T cell proliferative responses to these antibodies. In contrast, IL-2 secretion was detectable in T cell supernatants from T cells stimulated with either mAb 454 or 147 but not 446. Factors promoting B cell proliferation were detected in all antibody-stimulated T cell supernatants but, contrary to BCDF, appear to act only on non-activated B cells. To determine whether these effector activities were due to distinct lymphokines, supernatants were pooled and concentrated by ammonium sulfate precipitation. Superose 12 permeation chromatography revealed BCDF activity with an apparent Mr of approximately 30,000 Da. The growth factor activity eluted over a wider and higher molecular weight range which overlapped the differentiation factor activity. Fractions containing BCDF activity were pooled, dialyzed, applied to a Mono Q anion-exchange column, and eluted with a linear NaCl gradient. The growth factor activity came off in a single-peak while BCDF was found divided into two major areas. The growth factor eluted at an ionic strength between the two BCDF activities. BCDF has an apparent isoelectric point (pI) of 6, in contrast to the reported pI 5 for IL-6 and more acidic than the documented basic pI of IFN-gamma. Lastly, peaks with BCDF activity were not active in assays for either IL-2 or IL-4. In addition, a rabbit anti-IL-6 heteroantiserum failed to inhibit the pI 6 BCDF, suggesting non-identity between IL-6 and anti-CD3 induced BCDF. Thus, anti-CD3 activated T cells generate both growth factor activity and BCDF as separate molecular entities distinct from IFN-gamma, IL-2, IL-4, and conventional IL-6.

Posttranslational processing of methyl-accepting chemotaxis proteins in Escherichia coli

Methyl-accepting chemotaxis proteins (MCPs) of Escherichia coli undergo changes in methylation state in response to chemical stimuli. The addition of methyl groups to MCP is dependent on cheR function; their removal is dependent on cheB function. This MCP methylation system is instrumental in establishing the unstimulated swimming pattern of E. coli and in enabling the cell to carry out sensory adaptation after a chemotactic response. We employed electrophoresis in sodium dodecyl sulfate-containing polyacrylamide gels to analyze MCP molecules synthesized in cheR deletion mutants lacking MCP-specific methyltransferase activity. MCP made under these conditions proved to be completely devoid of methyl groups. In the absence of cheB function as well, this unmethylated MCP is made in a form, designated 2(*), that exhibits several properties characteristic of methylated MCP. In the presence of cheB function, MCP 2(*) is processed to a form, designated 1(*), that no longer resembles methylated MCP. The rate of this conversion process is modulated by chemotactic stimuli. Both MCP 1(*) and MCP 2(*) are capable of initiating changes in flagellar rotation in response to stimuli, and, in the presence of cheR function, both forms can accept methyl groups. We suggest that MCP 2(*) is a normal intermediate in MCP synthesis in which one or more of the methyl-accepting glutamic acid residues carry a methyl-ester-like modification, which, like glutamic acid methyl esters, can be removed by cheB function. This cheB-dependent processing event does not appear to be reversible, but nevertheless it may play an important role in modulating the signaling behavior of newly synthesized MCP molecules.