FBW7 mutations mediate resistance of colorectal cancer to targeted therapies by blocking Mcl-1 degradation.

Colorectal cancer (CRC), the second leading cause of cancer-related deaths in the US, has been treated with targeted therapies. However, the mechanisms of differential responses and resistance of CRCs to targeted therapies are not well understood. In this study, we found that genetic alterations of FBW7, an E3 ubiquitin ligase and a tumor suppressor frequently mutated in CRCs, contribute to resistance to targeted therapies. CRC cells containing FBW7-inactivating mutations are insensitive to clinically used multi-kinase inhibitors of RAS/RAF/MEK/ERK signaling, including regorafenib and sorafenib. In contrast, sensitivity to these agents is not affected by oncogenic mutations in KRAS, BRAF, PIK3CA or p53. These cells are defective in apoptosis owing to blocked degradation of Mcl-1, a pro-survival Bcl-2 family protein. Deleting FBW7 in FBW7-wild-type CRC cells abolishes Mcl-1 degradation and recapitulates the in vitro and in vivo drug-resistance phenotypes of FBW7-mutant cells. CRC cells selected for regorafenib resistance have progressive enrichment of pre-existing FBW7 hotspot mutations, and are cross-resistant to other targeted drugs that induce Mcl-1 degradation. Furthermore, a selective Mcl-1 inhibitor restores regorafenib sensitivity in CRC cells with intrinsic or acquired resistance. Together, our results demonstrate FBW7 mutational status as a key genetic determinant of CRC response to targeted therapies, and Mcl-1 as an attractive therapeutic target.

Molluscicidal activity of the plant Eupatorium adenophorum against Oncomelania hupensis, the intermediate host snail of Schistosoma japonicum.

The potential molluscicidal activities of aqueous extracts of Eupatorium adenophorum have recently been evaluated against Oncomelania hupensis, the intermediate host snail of Schistosoma japonicum. The snails were continuously exposed to extracts of the leaves, roots or stems [each at concentrations of 0.27%, 0.50% and 0.86% (w/v)], with survival recorded 6, 12, 24, 30, 36, 48, 52, 58, 70, 76, 82 and 96 h after the start of the exposure. Even at the lowest concentration tested (0.27%), the leaf extract caused mortality in excess of 50% after 58 h and 100% mortality after 82 h. This extract was significantly more effective against O. hupensis than the stem or root extract (P<0.05) but there was no statistically significant difference between the root and stem extracts in their molluscicidal effects (P>0.05). These preliminary results indicate that E. adenophorum may potentially provide a new molluscicide that could give effective and environmentally-friendly control of schistosomiasis in humans and livestock. The toxicity of E. adenophorum extracts, or molluscicidal compounds isolated from such extracts, to other snail hosts of human parasites and to non-target species of aquatic life will be investigated.

[Effects of Bay K8644 and nifedipine on L-type Ca2+ channels in hypothalamic neurons of rats].

To investigate the effects of Bay K8644 and nifedipine on L-type of Ca2+ channels in hypothalamic neurons, the cell-attached patch-clamp technique was used to record Ca2+ current from isolated neurons. The results showed that the averaged open time and NPo were markedly increased by Bay K8644, but had no effect on channel conductance. Nifedipine, on the contrary, had an inhibitory effect on the L-type Ca2+ channels.

[Effects of temperature on the open-channel density of delayed rectifier K+ channels in hypothalamic neurons].

AIM AND METHODS: To observe the effect of temperature on multi-order open of delayed rectifier K+ channels in hypothalamic-neurons by cell-attached mode of patch-clamp technique. RESULTS: With temperature raising, the probability of open-channel recording increased, multichannel open occurred. The density of open - channel on membrane of 32 degrees C, 37 degrees C and 39 degrees C was 0.71, 1.22 and 1.82 channels/microm2 respectively (P < 0.05). CONCLUSION: More Ik of hypothalamus opened with temperature raising, this benefited to the body temperature regulation of neurons in hypothalamus.

[Properties of single L-type Ca2+ channels in hypothalamic neurons of newborn rats].

AIM: To investigate the characteristics of single L-type Ca2+ channels in hypothalamic neurons. METHODS: The cell-attached patch-clamp technique and acute cell isolation technique were used. RESULTS: (1) L-type Ca2+ channels opened throughout an 768 ms long voltage pulse. (2) The averaged open-time constant was 0.28 ms(tau0), two closed-time constants were 2.91 (tau(c1)) and 53.22 ms(tau(c2)). (3) The conductance was (29.5 +/- 3.1) pS and (4) Bay K 8644 increased the open probability by prolonging the mean open time to 1.61 ms. CONCLUSION: L-type Ca2+ channel existed in hypothalamic neurons, with the similar properties to Ca2+ currents as previously reported, but showed its own peculiarity.

[Rectification of calcium-activated potassium channels in hypothalamic neurons].

AIM: To study the rectification of calcium-activated potassium channel in hypothalamic neurons. METHODS: Channels in inside-out patches are studied by patch-clamp technique. RESULTS: A big conductance calcium-activated K+ channel was observed, with symmetrical 140 mol/L [K+] across patches, in ward conductance was (171 +/- 12) pS and change little as different [Ca2+] was included in the bath solution. Outward conductance was regulated by [Ca2+] and was (76 +/- 14) pS with 500 micromol/L [Ca2+]. The higher level of [Ca2+] caused larger degree of rectification. Mg2+ only had a minor effect on rectification of this calcium-activated K+ channel. CONCLUSION: BK in hypothalamic neurons had rectification properties, it might play a role in neuronal excitation and stability.