BEIJING, June 16 (Reuters) - China shares dropped on Wednesday, led by losses in healthcare and material stocks, as investor concerns about lofty valuations as well as Sino-West tensions dented risk appetite. ** At the midday break, the Shanghai Composite index was down 0.77% at 3,529.11 points, while the blue-chip CSI300 index dropped 1.28%. ** Among the worst performing sectors, the healthcare sub-index and material sub-index slumped 2.52% and 2.49%, respectively. ** Analysts remained cautious, citing lack of factors for any upside momentum, and also noting lofty valuations in some parts of the market. The broader credit growth continue to slow as the central bank seeks to contain rising leverage ratio and local debt. ** Tensions between China and the West soured investor sentiment, which dragged down the mainland markets ever since trading resumed after a long weekend post the Dragon Boat Festival. ** China stocks ended lower on Tuesday after G7 leaders took the Asian nation to task over a range of issues, which Beijing called a gross interference in the country’s internal affairs. ** Shanghai shares of WuXi AppTec Co Ltd, one of the heavyweight stocks in the healthcare sub-index, fell 4.8% by the mid-day break after falling as much as 6.3%. ** Stocks slumped after WuXi received regulatory letter from the Shanghai Stock Exchange, as one of its shareholders cut stakes without proper information disclosure. ** The smaller Shenzhen index was down 1.82%, the start-up board ChiNext Composite index was weaker by 3.44%, and Shanghai’s tech-focused STAR50 index was down 2.64%. ** Chinese H-shares listed in Hong Kong fell 0.59% to 10,605.78, while the Hang Seng Index was down 0.23% at 28,573.35. ** The smaller Shenzhen index was down 1.82%, the start-up board ChiNext Composite index was weaker by 3.44% and Shanghai’s tech-focused STAR50 index was down 2.64%. ** Around the region, MSCI’s Asia ex-Japan stock index was weaker by 0.26% while Japan’s Nikkei index was down 0.41%. Reporting by Beijing Newsroom; Editing by Sherry Jacob-Phillips Our Standards: The Thomson Reuters Trust Principles.