A non-catalytic role of choline kinase alpha is important in promoting cancer cell survival

Choline kinase alpha (ChoKα) is regarded as an attractive cancer target. The enzyme catalyses the formation of phosphocholine (PCho), an important precursor in the generation of phospholipids essential for cell growth. ChoKα has oncogenic properties and is critical for the survival of cancer cells. Overexpression of the ChoKα protein can transform noncancer cells into cells with a cancerous phenotype, and depletion of the ChoKα protein can result in cancer cell death. However, the mechanisms underlying the tumourigenic properties of ChoKα are not fully understood. ChoKα was recently demonstrated to associate with other oncogenic proteins, raising the possibility that a non-catalytic protein scaffolding function drives the tumourigenic properties of ChoKα rather than a catalytic function. In order to differentiate these two roles, we compared the impact on cancer cell survival using two tools specific for ChoKα: (1) small interfering RNA (siRNA) to knockdown the ChoKα protein levels; and (2) compound V-11-0711, a novel potent and selective ChoKα inhibitor (ChoKα IC₅₀ 20 nℳ), to impede the catalytic activity. Both treatments targeted the endogenous ChoKα protein in HeLa cells, as demonstrated by a substantial reduction in the PCho levels. siRNA knockdown of the ChoKα protein in HeLa cells resulted in significant cell death through apoptosis. In contrast, compound V-11-0711 caused a reversible growth arrest. This suggests that inhibition of ChoKα catalytic activity alone is not sufficient to kill cancer cells, and leads us to conclude that there is a role for the ChoKα protein in promoting cancer cell survival that is independent of its catalytic activity.

Characterization of a selective and potent antagonist of human P2X(7) receptors, AZ11645373

BACKGROUND AND PURPOSE

The ATP-gated P2X(7) receptor has been shown to play a role in several inflammatory processes, making it an attractive target for anti-inflammatory drug discovery. We have recently identified a novel set of cyclic imide compounds that inhibited P2X(7) receptor-mediated dye uptake in human macrophage THP-1 cells. In this study the actions and selectivity of one of these compounds, AZ11645373, were characterized.

EXPERIMENTAL APPROACH

We measured membrane currents, calcium influx, and YOPRO-1 uptake from HEK cells expressing individual P2X receptors, and YOPRO1 uptake and interleukin-1beta release from THP-1 cells in response to ATP and the ATP analogue benzoylbenzoyl ATP (BzATP).

KEY RESULTS

AZ11645373 up to 10 microM, had no agonist or antagonist actions on membrane currents due to P2X receptor activation at human P2X(1), rat P2X(2), human P2X(3), rat P2X(2/3), human P2X(4), or human P2X(5) receptors expressed in HEK cells. AZ11645373 inhibited human P2X(7) receptor responses in HEK cells in a non-surmountable manner with K (B) values ranging from 5 - 20 nM, with mean values not significantly different between assays. K (B) values were not altered by removing extracellular calcium and magnesium. ATP-evoked IL-1beta release from lipopolysaccharide-activated THP-1 cells was inhibited by AZ11645373, IC(50) = 90 nM. AZ11645373 was > 500-fold less effective at inhibiting rat P2X(7) receptor-mediated currents with less than 50% inhibition occurring at 10 microM.

CONCLUSIONS AND IMPLICATIONS

AZ11645373 is a highly selective and potent antagonist at human but not rat P2X(7) receptors and will have much practical value in studies of human cells.

Novel P2X7 receptor antagonists

The synthesis and pharmacological evaluation of a new series of potent P2X(7) receptor antagonists is disclosed. The compounds inhibit BzATP-mediated pore formation in THP-1 cells. The distribution of the P2X(7) receptor in inflammatory cells, most notably the macrophage, mast cell and lymphocyte, suggests that P2X(7) antagonists have a significant role to play in the treatment of inflammatory disease.

Biogenetically inspired approach to the Strychnos alkaloids. Concise syntheses of (+/-)-akuammicine and (+/-)-strychnine

A linear synthesis of the indole alkaloid (+/-)-akuammicine (2) was completed by a novel sequence of reactions requiring only 10 steps from commercially available starting materials. The approach features a tandem vinylogous Mannich addition and an intramolecular hetero Diels-Alder reaction to rapidly assemble the pentacyclic heteroyohimboid derivative 8 from the readily available hydrocarboline 6. Oxidation of the E ring of 8 gave the lactone 9 that was converted into deformylgeissoschizine (11). The subsequent elaboration of 11 into 2 was effected by a biomimetically patterned transformation that involved sequential oxidation and base-induced skeletal reorganization. A variation of these tactics was then applied to the synthesis of the C(18) hydroxylated akuammicine derivative 36. Because 36 had previously been converted into strychnine (1) in four steps, its preparation constitutes a concise, formal synthesis of this complex alkaloid.

Early Australian experience with infliximab, a chimeric antibody against tumour necrosis factor-alpha, in the treatment of Crohn's disease: is its efficacy augmented by steroid-sparing immunosuppressive therapy? The Infliximab User Group

BACKGROUND

Tumour necrosis factor-alpha (TNF-alpha) plays an important role in the pathology of Crohn's disease. Infliximab, a chimeric antibody against TNF-alpha, has been shown in controlled clinical trials to be effective in two-thirds of patients with refractory or fistulating Crohn's disease. The factors that determine a clinical response in some patients but not others are unknown.

AIMS

To document the early Australian experience with infliximab treatment for Crohn's disease and to identify factors that may determine a beneficial clinical response.

METHODS

Gastroenterologists known to have used infliximab for Crohn's disease according to a compassionate use protocol were asked to complete a spreadsheet that included demographic information, Crohn's disease site, severity, other medical or surgical treatments and a global clinical assessment of Crohn's disease outcome, judged by participating physicians as complete and sustained (remission for the duration of the study), complete but unsustained (remission at 4 weeks but not for the whole study) or partial clinical improvement (sustained or unsustained).

RESULTS

Fifty-seven patients were able to be evaluated, with a median follow-up time of 16.4 (4-70) weeks, including 23 patients with fistulae. There were 21 adverse events, including four serious events. Fifty-one patients (89%) had a positive clinical response for a median duration (range) of 11 (2-70) weeks. Thirty patients (52%) had a remission at 4 weeks, 10 of whom had remission for longer than 12 weeks. Forty-two per cent of fistulae closed. Sustained remission (P = 0.065), remission at 4 weeks (P = 0.033) and a positive clinical response of any sort (P = 0.004) were more likely in patients on immunosuppressive therapy, despite there being more smokers in this group.

CONCLUSION

This review of the first Australian experience with infliximab corroborates the reported speed and efficacy of this treatment for Crohn's disease. The excellent response appears enhanced by the concomitant use of conventional steroid-sparing immunosuppressive therapy.

The haemochromatosis gene: a global perspective and implications for the Asia-Pacific region

Mutations in the haemochromatosis (HFE) gene cause most of the cases of hereditary haemochromatosis among people of Northern European ancestry while remaining a rare cause of iron overload among indigenous persons of the Asia-Pacific region. Advances in understanding of the role of the HFE protein product and other recently cloned iron transporters signify an exciting period, as previously unknown components of the iron metabolism pathway are revealed one by one. Epidemiological studies have shown that this gene is more widespread than its phenotypic expression would suggest and that the heterozygous state may be implicated in the expression of other diseases of the liver such as porphyria cutanea tarda, hepatitis C virus infection and non-alcoholic steatohepatitis. The diagnosis, management and ethical implications for clinical practice in the aftermath of this discovery are discussed.

Population growth and natural resource use: do we need to despair of Africa?

The authors make the case that population growth can lead to increases in agricultural output per head on a sustainable basis. This argument, originally developed by E. Boserup, is "illustrated by a study of Machakos District, Kenya during 1930-1960, which shows that, if policies are supportive, agricultural and non-farm incomes grow faster than even the rapid population growth rate experienced in Africa. Land use capability is not fixed, but can be transformed by investment, new technologies and good management. Lack of investment and consequent degradation are most likely at low population densities. While the study cannot foretell the future, Java illustrates a similar theme at even higher densities."

The structure of (+-)-21-oxoisopteropodine

Methyl (1'S*,3S*,4a'S*,5a'S*,10a'R*)- 3',4a',5a',6',7',8',10',10a'-octahydro-2-hydroxy-1'-methyl-10'- oxospiro[3H-indole-3,6'-[1'H]pyrano[3,4-f]indolizine-4'-carb oxylate, (1), C21H22N2O5, Mr = 382.42, monoclinic, P21/c, a = 12.920 (4), b = 10.342 c = 15.192 (8) A, beta = 105.68 (3) degrees, V = 1954.4 (14) A3, Z = 4, D chi = 1.30 g cm-3 (298 K), mu = 0.8738 cm-1, Mo K alpha radiation, lambda = 0.7107 A, F(000) = 808, T = 298 K, R = 0.0800 for 1000 reflections, F zero greater than or equal to 4 sigma(F zero). The indole NH group is hydrogen bonded to the amide oxygen, O15' (related by chi, 0.5 -y, -0.5 + z), of the indolizine moiety with relevant parameters: N...O 2.79 (2)A, H...O 2.02 (15) A, N-H...O 145 (14) degrees. A close, non-bonded contact of 2.28 (8) A is also observed between O15' and H7'A (related by -chi, 0.5 + y, 1.5 - z).