UBS's Global Wealth Management advises clients to be wary of bitcoin (BTC-USD) even as media reports suggest institutional money has entered in the margins with futures contracts, dedicated funds, and more mature know-your-customer processes."We remain unconvinced this surge is different from previous speculative bubbles," the GWM chief investment office said in a note.Bitcoin is up 1.1% today, recently trading ~$52.7K, still down from its high of $61.7K on March 13. Yesterday, the cryptocurrency dropped 10% in morning trading, possibly helped by the unwinding of bitcoin options.UBS warns that the same factors that drive crypto appreciation also boosts its volatility and risk."Bitcoin's limited and highly inelastic supply exacerbates its volatility."Also limited real-world use and its extreme volatility indicate buyers are seeking speculative gains."We think investors should maintain discipline and exercise extreme caution with regard to crypto speculation."Rather, UBS's GWM chief investment office suggests that select semiconductor shares may offer upside exposure to crypto-mining;