Lumacaftor/ Ivacaftor improves exercise tolerance in patients with Cystic Fibrosis and severe airflow obstruction.

BACKGROUND: Treatment of patients with Cystic Fibrosis homozygous for the Phe508del gene, with Lumacaftor /Ivacaftor (LUM/IVA) improves outcomes in patients with FEV1 > 40% predicted. We set out to observe the most sensitive clinical measure that would change with treatment in terms of exercise capacity or lung function in adults with severe lung disease as defined by an FEV1 < 40% predicted when clinically stable. METHODS: 10 adults homozygous for the Phe508del received LUM/IVA. We assessed; six minute walk test (6MWT), spirometry, gas transfer (DLCO), plethysmography, and nitrogen multiple breath washout (MBW) at baseline, 4, 12, 24 and 52 weeks. Comparison was made with 10 matched historical controls that had been observed over 12 months. RESULTS: There was a significant improvement in 6MWT by 4 weeks of treatment; with a mean increase of 78 m (SD 62.3) and this increased to 118.1 m (SD 80.9) (ANOVA p = 0.006) by 52 weeks. Significant improvements were also seen in the resting heart rate and the oxygen saturation (SaO2) after 6 min walking. A significant improvement was not seen in FEV1 though until 24 weeks, though this was maintained at 52 weeks (ANOVA, p = 0.0004). There were no significant differences seen in the MBW or DLCO. After 12 months treatment with LUM/IVA, in comparison to historical controls; the 6MWT increased by 118 m (SD 80.9), but fell in the controls - 61.3 m (SD 31.1). FEV1; LUM/IVA led to an increase of 0.398 L/min, compared to a fall in the controls - 0.18 (SD 0.2). CONCLUSION: In adults homozygous for Phe508del with severe disease, treatment with LUM/IVA results in a clinically significant improvement in 6MWT that was evident at 4 weeks and maintained at 52 weeks. Improvement in exercise tolerance is an important outcome to consider in those with more severe airways disease. TRIAL REGISTRATION: This was an observational trial conducted on individuals who became eligible to receive LUM/IVA. All investigations were carried out as part of routine clinical care. The trial was registered in retrospect on the 13/5/2019 on the Australian New Zealand Clinical Trials registry; ACTRN12619000708156 .

A randomised trial of hypertonic saline during hospitalisation for exacerbation of cystic fibrosis.

BACKGROUND: The mucoactive effects of hypertonic saline should promote exacerbation resolution in people with cystic fibrosis (CF). OBJECTIVES: To determine the effects of hypertonic saline inhalation during hospitalisation for exacerbation of CF on length of stay, lung function, symptoms, oxygenation, exercise tolerance, quality of life, bacterial load and time to next hospitalisation. METHODS: 132 adults with an exacerbation of CF were randomised to inhale three nebulised doses a day of either 4 mL 7% saline or a taste-masked control of 0.12% saline, throughout the hospital admission. The primary outcome measure was length of hospital stay. RESULTS: All participants tolerated their allocated saline solution. There was no significant difference in length of stay, which was 12 days in the hypertonic saline group and 13 days in controls, with a mean between-group difference (MD) of 1 day (95% CI 0 to 2). The likelihood of regaining pre-exacerbation FEV1 by discharge was significantly higher in the hypertonic saline group (75% vs 57%), and the number needed to treat was 6 (95% CI 3 to 65). On a 0-100 scale, the hypertonic saline group had significantly greater reduction in symptom severity than the control group at discharge in sleep (MD=13, 95% CI 4 to 23), congestion (MD=10, 95% CI 3 to 18) and dyspnoea (MD=8, 95% CI 1 to 16). No significant difference in time to next hospitalisation for a pulmonary exacerbation was detected between groups (HR=0.86 (CI 0.57 to 1.30), p=0.13). Other outcomes did not significantly differ. CONCLUSIONS: Addition of hypertonic saline to the management of a CF exacerbation did not reduce the length of hospital stay. Hypertonic saline speeds the resolution of exacerbation symptoms and allows patients to leave hospital with greater symptom resolution. TRIAL REGISTRATION NUMBER: ACTRN12605000780651.

Direct integrin alphavbeta6-ERK binding: implications for tumour growth.

Blockade of the mitogen-activated protein (MAP) kinase pathway suppresses growth of colon cancer in vivo. Here we demonstrate a direct link between the extracellular signal-regulated kinase ERK2 and the growth-promoting cell adhesion molecule, integrin alphavbeta6, in colon cancer cells. Down-regulation of beta6 integrin subunit expression inhibits tumour growth in vivo and MAP kinase activity in response to serum stimulation. In alphavbeta6-expressing cells ERK2 is bound only to the beta6 subunit. The increase in cytosolic MAP kinase activity upon epidermal growth factor stimulation is all accounted for by beta6-bound ERK. Deletion of the ERK2 binding site on the beta6 cytoplasmic domain inhibits tumour growth and leads to an association between ERK and the beta5 subunit. The physical interaction between integrin alphavbeta6 and ERK2 defines a novel paradigm of integrin-mediated signalling and provides a therapeutic target for cancer treatment.

Integrin expression in colon cancer cells is regulated by the cytoplasmic domain of the beta6 integrin subunit.

We have previously reported that the alphavbeta6 integrin upregulates its own expression in a protein kinase C-dependent manner with increasing cell density. The wild-type beta6 integrin subunit has also been shown to promote tumour growth in vivo and its growth-enhancing effect is regulated by both a MAP kinase binding motif on beta6 and the 11 amino acid C-terminal cytoplasmic extension unique to the beta6 subunit. Herein, we show that the 11 amino acid cytoplasmic extension is essential for the cell density-dependent increase in beta6 expression and that the 11 amino acid tail exerts a dominant negative effect on cell density- and PKC-mediated beta5 expression in alphavbeta6-expressing colon cancer cells. Cells that express beta6 lacking the 11 amino acid tail respond to PKC simulation with increased expression of only the beta5 subunit as seen for cells that lack constitutive alphavbeta6 expression. In contrast, loss of the ERK binding site on beta6 markedly impairs cell density- and PKC-dependent expression of either beta6 or beta5 in the presence or absence of the 11 amino acid tail, respectively. Our findings suggest that in alphavbeta6-expressing cells, a hierarchy of kinase signalling cascades exists and that the beta6-ERK2 interaction dominates over PKC-mediated signalling pathways responsible for integrin upregulation with cell confluence. Given the dominance of the beta6-ERK2 interaction over PKC-mediated expression of both beta5 and beta6 integrin subunits, targeting the beta6-ERK2 interaction may prove useful as an anticancer strategy in colon cancer.